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Internet Research Task Force (IRTF)                             A. DoriaRequest for Comments: 5772                                           LTUCategory: Historic                                             E. DaviesISSN: 2070-1721                                         Folly Consulting                                                           F. Kastenholz                                                        BBN Technologies                                                           February 2010A Set of Possible Requirements for a Future Routing ArchitectureAbstract   The requirements for routing architectures described in this document   were produced by two sub-groups under the IRTF Routing Research Group   (RRG) in 2001, with some editorial updates up to 2006.  The two sub-   groups worked independently, and the resulting requirements represent   two separate views of the problem and of what is required to fix the   problem.  This document may usefully serve as part of the recommended   reading for anyone who works on routing architecture designs for the   Internet in the future.   The document is published with the support of the IRTF RRG as a   record of the work completed at that time, but with the understanding   that it does not necessarily represent either the latest technical   understanding or the technical consensus of the research group at the   date of publication.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for the historical record.   This document defines a Historic Document for the Internet community.   This document is a product of the Internet Research Task Force   (IRTF).  The IRTF publishes the results of Internet-related research   and development activities.  These results might not be suitable for   deployment.  This RFC represents the individual opinion(s) of one or   more members of the Routing Research Group of the Internet Research   Task Force (IRTF).  Documents approved for publication by the IRSG   are not a candidate for any level of Internet Standard; seeSection 2   of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc5772.Doria, et al.                   Historic                        [Page 1]

RFC 5772                IRTF Routing Requirements          February 2010Copyright Notice   Copyright (c) 2010 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.Table of Contents1. Background ......................................................42. Results from Group A ............................................5      2.1. Group A - Requirements for a Next Generation Routing and           Addressing Architecture ....................................52.1.1. Architecture ........................................62.1.2. Separable Components ................................62.1.3. Scalable ............................................72.1.4. Lots of Interconnectivity ..........................102.1.5. Random Structure ...................................102.1.6. Multi-Homing .......................................112.1.7. Multi-Path .........................................112.1.8. Convergence ........................................122.1.9. Routing System Security ............................142.1.10. End Host Security .................................162.1.11. Rich Policy .......................................162.1.12. Incremental Deployment ............................192.1.13. Mobility ..........................................192.1.14. Address Portability ...............................202.1.15. Multi-Protocol ....................................202.1.16. Abstraction .......................................202.1.17. Simplicity ........................................212.1.18. Robustness ........................................212.1.19. Media Independence ................................222.1.20. Stand-Alone .......................................222.1.21. Safety of Configuration ...........................232.1.22. Renumbering .......................................232.1.23. Multi-Prefix ......................................232.1.24. Cooperative Anarchy ...............................232.1.25. Network-Layer Protocols and Forwarding Model ......232.1.26. Routing Algorithm .................................232.1.27. Positive Benefit ..................................242.1.28. Administrative Entities and the IGP/EGP Split .....242.2. Non-Requirements ..........................................252.2.1. Forwarding Table Optimization ......................25Doria, et al.                   Historic                        [Page 2]

RFC 5772                IRTF Routing Requirements          February 20102.2.2. Traffic Engineering ................................252.2.3. Multicast ..........................................252.2.4. Quality of Service (QoS) ...........................262.2.5. IP Prefix Aggregation ..............................262.2.6. Perfect Safety .....................................262.2.7. Dynamic Load Balancing .............................272.2.8. Renumbering of Hosts and Routers ...................272.2.9. Host Mobility ......................................272.2.10. Backward Compatibility ............................273. Requirements from Group B ......................................273.1. Group B - Future Domain Routing Requirements ..............283.2. Underlying Principles .....................................283.2.1. Inter-Domain and Intra-Domain ......................293.2.2. Influences on a Changing Network ...................293.2.3. High-Level Goals ...................................313.3. High-Level User Requirements ..............................353.3.1. Organizational Users ...............................353.3.2. Individual Users ...................................373.4. Mandated Constraints ......................................383.4.1. The Federated Environment ..........................393.4.2. Working with Different Sorts of Networks ...........393.4.3. Delivering Resilient Service .......................393.4.4. When Will the New Solution Be Required? ............403.5. Assumptions ...............................................403.6. Functional Requirements ...................................423.6.1. Topology ...........................................433.6.2. Distribution .......................................443.6.3. Addressing .........................................483.6.4. Statistics Support .................................503.6.5. Management Requirements ............................503.6.6. Provability ........................................513.6.7. Traffic Engineering ................................523.6.8. Support for Middleboxes ............................543.7. Performance Requirements ..................................543.8. Backward Compatibility (Cutover) and Maintainability ......553.9. Security Requirements .....................................563.10. Debatable Issues .........................................573.10.1. Network Modeling ..................................583.10.2. System Modeling ...................................583.10.3. One, Two, or Many Protocols .......................593.10.4. Class of Protocol .................................593.10.5. Map Abstraction ...................................593.10.6. Clear Identification for All Entities .............603.10.7. Robustness and Redundancy .........................603.10.8. Hierarchy .........................................603.10.9. Control Theory ....................................613.10.10. Byzantium ........................................613.10.11. VPN Support ......................................61Doria, et al.                   Historic                        [Page 3]

RFC 5772                IRTF Routing Requirements          February 20103.10.12. End-to-End Reliability ...........................623.10.13. End-to-End Transparency ..........................624. Security Considerations ........................................625. IANA Considerations ............................................636. Acknowledgments ................................................637. Informative References .........................................651.  Background   In 2001, the IRTF Routing Research Group (IRTF RRG) chairs, Abha   Ahuja and Sean Doran, decided to establish a sub-group to look at   requirements for inter-domain routing (IDR).  A group of well-known   routing experts was assembled to develop requirements for a new   routing architecture.  Their mandate was to approach the problem   starting from a blank slate.  This group was free to take any   approach, including a revolutionary approach, in developing   requirements for solving the problems they saw in inter-domain   routing.   Simultaneously, an independent effort was started in Sweden with a   similar goal.  A team, calling itself Babylon, with participation   from vendors, service providers, and academia assembled to understand   the history of inter-domain routing, to research the problems seen by   the service providers, and to develop a proposal of requirements for   a follow-on to the current routing architecture.  This group's remit   required an evolutionary approach starting from current routing   architecture and practice.  In other words, the group limited itself   to developing an evolutionary strategy.  The Babylon group was later   folded into the IRTF RRG as Sub-Group B to distinguish it from the   original RRG Sub-Group A.   One of the questions that arose while the groups were working in   isolation was whether there would be many similarities between their   sets of requirements.  That is, would the requirements that grew from   a blank sheet of paper resemble those that started with the   evolutionary approach?  As can be seen from reading the two sets of   requirements, there were many areas of fundamental agreement but some   areas of disagreement.   There were suggestions within the RRG that the two teams should work   together to create a single set of requirements.  Since these   requirements are only guidelines to future work, however, some felt   that doing so would risk losing content without gaining any   particular advantage.  It is not as if any group, for example, the   IRTF RRG or the IETF Routing Area, was expected to use these   requirements as written and to create an architecture that met these   requirements.  Rather, the requirements were in practice strongDoria, et al.                   Historic                        [Page 4]

RFC 5772                IRTF Routing Requirements          February 2010   recommendations for a way to proceed in creating a new routing   architecture.  In the end, the decision was made to include the   results of both efforts, side by side, in one document.   This document contains the two requirement sets produced by the   teams.  The text has received only editorial modifications; the   requirements themselves have been left unaltered.  Whenever the   editors felt that conditions had changed in the few years since the   text was written, an editors' note has been added to the text.   In reading this document, it is important to keep in mind that all of   these requirements are suggestions, which are laid out to assist   those interested in developing new routing architectures.  It is also   important to remember that, while the people working on these   suggestions have done their best to make intelligent suggestions,   there are no guarantees.  So a reader of this document should not   treat what it says as absolute, nor treat every suggestion as   necessary.  No architecture is expected to fulfill every   "requirement".  Hopefully, though, future architectures will consider   what is offered in this document.   The IRTF RRG supported publication of this document as a historical   record of the work completed on the understanding that it does not   necessarily represent either the latest technical understanding or   the technical consensus of the research group at the time of   publication.  The document has had substantial review by members of   the two teams, other members of the IRTF RRG, and additional experts   over the years.   Finally, this document does not make any claims that it is possible   to have a practical solution that meets all the listed requirements.2.  Results from Group A   This section presents the results of the work done by Sub-Group A of   the IRTF RRG during 2001-2002.  The work originally appeared under   the title: "Requirements For a Next Generation Routing and Addressing   Architecture" and was edited by Frank Kastenholz.2.1.  Group A - Requirements for a Next Generation Routing and      Addressing Architecture   The requirements presented in this section are not presented in any   particular order.Doria, et al.                   Historic                        [Page 5]

RFC 5772                IRTF Routing Requirements          February 20102.1.1.  Architecture   The new routing and addressing protocols, data structures, and   algorithms need to be developed from a clear, well thought-out, and   documented architecture.   The new routing and addressing system must have an architectural   specification that describes all of the routing and addressing   elements, their interactions, what functions the system performs, and   how it goes about performing them.  The architectural specification   does not go into issues such as protocol and data structure design.   The architecture should be agnostic with regard to specific   algorithms and protocols.   Doing architecture before doing detailed protocol design is good   engineering practice.  This allows the architecture to be reviewed   and commented upon, with changes made as necessary, when it is still   easy to do so.  Also, by producing an architecture, the eventual   users of the protocols (the operations community) will have a better   understanding of how the designers of the protocols meant them to be   used.2.1.2.  Separable Components   The architecture must place different functions into separate   components.   Separating functions, capabilities, and so forth into individual   components and making each component "stand alone" is generally   considered by system architects to be "A Good Thing".  It allows   individual elements of the system to be designed and tuned to do   their jobs "very well".  It also allows for piecemeal replacement and   upgrading of elements as new technologies and algorithms become   available.   The architecture must have the ability to replace or upgrade existing   components and to add new ones, without disrupting the remaining   parts of the system.  Operators must be able to roll out these   changes and additions incrementally (i.e., no "flag days").  These   abilities are needed to allow the architecture to evolve as the   Internet changes.   The architecture specification shall define each of these components,   their jobs, and their interactions.Doria, et al.                   Historic                        [Page 6]

RFC 5772                IRTF Routing Requirements          February 2010   Some thoughts to consider along these lines are:   o  Making topology and addressing separate subsystems.  This may      allow highly optimized topology management and discovery without      constraining the addressing structure or physical topology in      unacceptable ways.   o  Separate "fault detection and healing" from basic topology.  From      Mike O'Dell:         Historically the same machinery is used for both.  While         attractive for many reasons, the availability of exogenous         topology information (i.e., the intended topology) should, it         seems, make some tasks easier than the general case of starting         with zero knowledge.  It certainly helps with recovery in the         case of constraint satisfaction.  In fact, the intended         topology is a powerful way to state certain kinds of policy.         [ODell01]   o  Making policy definition and application a separate subsystem,      layered over the others.   The architecture should also separate topology, routing, and   addressing from the application that uses those components.  This   implies that applications such as policy definition, forwarding, and   circuit and tunnel management are separate subsystems layered on top   of the basic topology, routing, and addressing systems.2.1.3.  Scalable   Scaling is the primary problem facing the routing and addressing   architecture today.  This problem must be solved and it must be   solved for the long term.   The architecture must support a large and complex network.  Ideally,   it will serve our needs for the next 20 years.  Unfortunately:   1.  we do not know how big the Internet will grow over that time, and   2.  the architecture developed from these requirements may change the       fundamental structure of the Internet and therefore its growth       patterns.  This change makes it difficult to predict future       growth patterns of the Internet.   As a result, we can't quantify the requirement in any meaningful way.   Using today's architectural elements as a mechanism for describing   things, we believe that the network could grow to:Doria, et al.                   Historic                        [Page 7]

RFC 5772                IRTF Routing Requirements          February 2010   1.  tens of thousands of ASs          Editors' Note: As of 2005, this level had already been          reached.   2.  tens to hundreds of millions of prefixes, during the lifetime of       this architecture.   These sizes are given as a "flavor" for how we expect the Internet to   grow.  We fully believe that any new architecture may eliminate some   current architectural elements and introduce new ones.   A new routing and addressing architecture designed for a specific   network size would be inappropriate.  First, the cost of routing   calculations is based only in part on the number of ASs or prefixes   in the network.  The number and locations of the links in the network   are also significant factors.  Second, past predictions of Internet   growth and topology patterns have proven to be wildly inaccurate, so   developing an architecture to a specific size goal would at best be   shortsighted.      Editors' Note: At the time of these meetings, the BGP statistics      kept at sites such as www.routeviews.org either did not exist or      had been running for only a few months.  After 5 years of      recording public Internet data trends in AS growth, routing table      growth can be observed (past) with some short-term prediction.  As      each year of data collection continues, the ability to observe and      predict trends improves.  This architecture work pointed out the      need for such statistics to improve future routing designs.   Therefore, we will not make the scaling requirement based on a   specific network size.  Instead, the new routing and addressing   architecture should have the ability to constrain the increase in   load (CPU, memory space and bandwidth, and network bandwidth) on ANY   SINGLE ROUTER to be less than these specific functions:   1.  The computational power and memory sizes required to execute the       routing protocol software and to contain the tables must grow       more slowly than hardware capabilities described by Moore's Law,       doubling every 18 months.  Other observations indicate that       memory sizes double every 2 years or so.   2.  Network bandwidth and latency are some key constraints on how       fast routing protocol updates can be disseminated (and therefore       how fast the routing system can adapt to changes).  Raw network       bandwidth seems to quadruple every 3 years or so.  However, it       seems that there are some serious physics problems in going       faster than 40 Gbit/s (OC768); we should not expect raw networkDoria, et al.                   Historic                        [Page 8]

RFC 5772                IRTF Routing Requirements          February 2010       link speed to grow much beyond OC768.  On the other hand, for       economic reasons, large swathes of the core of the Internet will       still operate at lower speeds, possibly as slow as DS3.          Editors' Note: Technology is running ahead of imagination and          higher speeds are already common.       Furthermore, in some sections of the Internet, even lower speed       links are found.  Corporate access links are often T1, or slower.       Low-speed radio links exist.  Intra-domain links may be T1 or       fractional-T1 (or slower).       Therefore, the architecture must not make assumptions about the       bandwidth available.   3.  The speeds of high-speed RAMs (Static RAMs (SRAMs), used for       caches and the like) are growing, though slowly.  Because of       their use in caches and other very specific applications, these       RAMs tend to be small, a few megabits, and the size of these RAMs       is not increasing very rapidly.       On the other hand, the speed of "large" memories (Dynamic RAMs       (DRAMs)) is increasing even slower than that for the high-speed       RAMs.  This is because the development of these RAMs is driven by       the PC market, where size is very important, and low speed can be       made up for by better caches.       Memory access rates should not be expected to increase       significantly.          Editors' Note: Various techniques have significantly increased          memory bandwidth. 800 MHz is now possible, compared with less          than 100 MHz in the year 2000.  This does not, however,          contradict the next paragraph, but rather just extends the          timescales somewhat.   The growth in resources available to any one router will eventually   slow down.  It may even stop.  Even so, the network will continue to   grow.  The routing and addressing architecture must continue to scale   in even this extreme condition.  We cannot continue to add more   computing power to routers forever.  Other strategies must be   available.  Some possible strategies are hierarchy, abstraction, and   aggregation of topology information.Doria, et al.                   Historic                        [Page 9]

RFC 5772                IRTF Routing Requirements          February 20102.1.4.  Lots of Interconnectivity   The new routing and addressing architecture must be able to cope with   a high degree of interconnectivity in the Internet.  That is, there   are large numbers of alternate paths and routes among the various   elements.  Mechanisms are required to prevent this interconnectivity   (and continued growth in interconnectivity) from causing tables,   compute time, and routing protocol traffic to grow without bound.   The "cost" to the routing system of an increase in complexity must be   limited in scope; sections of the network that do not see, or do not   care about, the complexity ought not pay the cost of that complexity.   Over the past several years, the Internet has seen an increase in   interconnectivity.  Individual end sites (companies, customers,   etc.), ISPs, exchange points, and so on, all are connecting to more   "other things".  Companies multi-home to multiple ISPs, ISPs peer   with more ISPs, and so on.  These connections are made for many   reasons, such as getting more bandwidth, increased reliability and   availability, policy, and so on.  However, this increased   interconnectivity has a price.  It leads to more scaling problems as   it increases the number of AS paths in the networks.   Any new architecture must assume that the Internet will become a   denser mesh.  It must not assume, nor can it dictate, certain   patterns or limits on how various elements of the network   interconnect.   Another facet of this requirement is that there may be multiple   valid, loop-free paths available to a destination.  SeeSection 2.1.7   for a further discussion.   We wryly note that one of the original design goals of IP was to   support a large, heavily interconnected network, which would be   highly survivable (such as in the face of a nuclear war).2.1.5.  Random Structure   The routing and addressing architecture must not place any   constraints on or make assumptions about the topology or   connectedness of the elements comprising the Internet.  The routing   and addressing architecture must not presume any particular network   structure.  The network does not have a "nice" structure.  In the   past, we used to believe that there was this nice "backbone/tier-1/   tier-2/end-site" sort of hierarchy.  This is not so.  Therefore, any   new architecture must not presume any such structure.Doria, et al.                   Historic                       [Page 10]

RFC 5772                IRTF Routing Requirements          February 2010   Some have proposed that a geographic addressing scheme be used,   requiring exchange points to be situated within each geographic   "region".  There are many reasons why we believe this to be a bad   approach, but those arguments are irrelevant.  The main issue is that   the routing architecture should not presume a specific network   structure.2.1.6.  Multi-Homing   The architecture must provide multi-homing for all elements of the   Internet.  That is, multi-homing of hosts, subnetworks, end-sites,   "low-level" ISPs, and backbones (i.e., lots of redundant   interconnections) must be supported.  Among the reasons to multi-home   are reliability, load sharing, and performance tuning.   The term "multi-homing" may be interpreted in its broadest sense --   one "place" has multiple connections or links to another "place".   The architecture must not limit the number of alternate paths to a   multi-homed site.   When multi-homing is used, it must be possible to use one, some (more   than one but less than all), or all of the available paths to the   multi-homed site.  The multi-homed site must have the ability to   declare which path(s) are used and under what conditions (for   example, one path may be declared "primary" and the other "backup"   and to be used only when the primary fails).   A current problem in the Internet is that multi-homing leads to undue   increases in the size of the BGP routing tables.  The new   architecture must support multi-homing without undue routing table   growth.2.1.7.  Multi-Path   As a corollary to multi-homing, the architecture must allow for   multiple paths from a source to a destination to be active at the   same time.  These paths need not have the same attributes.  Policies   are to be used to disseminate the attributes and to classify traffic   for the different paths.   There must be a rich "language" for specifying the rules for   classifying the traffic and assigning classes of traffic to different   paths (or prohibiting it from certain paths).  The rules should allow   traffic to be classified based upon, at least, the following:Doria, et al.                   Historic                       [Page 11]

RFC 5772                IRTF Routing Requirements          February 2010   o  IPv6 FlowIDs,   o  Diffserv Code Point (DSCP) values,   o  source and/or destination prefixes, or   o  random selections at some probability.   A mechanism is needed that allows operators to plan and manage the   traffic load on the various paths.  To start, this mechanism can be   semi-automatic or even manual.  Eventually, it ought to become fully   automatic.   When multi-path forwarding is used, options must be available to   preserve packet ordering where appropriate (such as for individual   TCP connections).   Please refer toSection 2.2.7 for a discussion of dynamic load-   balancing and management over multiple paths.2.1.8.  Convergence   The speed of convergence (also called the "stabilization time") is   the time it takes for a router's routing processes to reach a new,   stable, "solution" (i.e., forwarding information base) after a change   someplace in the network.  In effect, what happens is that the output   of the routing calculations stabilizes -- the Nth iteration of the   software produces the same results as the N-1th iteration.   The speed of convergence is generally considered to be a function of   the number of subnetworks in the network and the amount of   connections between those networks.  As either number grows, the time   it takes to converge increases.   In addition, a change can "ripple" back and forth through the system.   One change can go through the system, causing some other router to   change its advertised connectivity, causing a new change to ripple   through.  These oscillations can take a while to work their way out   of the network.  It is also possible that these ripples never die   out.  In this situation, the routing and addressing system is   unstable; it never converges.   Finally, it is more than likely that the routers comprising the   Internet never converge simply because the Internet is so large and   complex.  Assume it takes S seconds for the routers to stabilize on a   solution for any one change to the network.  Also, assume that   changes occur, on average, every C seconds.  Because of the size and   complexity of the Internet, C is now less than S.  Therefore, if aDoria, et al.                   Historic                       [Page 12]

RFC 5772                IRTF Routing Requirements          February 2010   change, C1, occurs at time T, the routing system would stabilize at   time T+S, but a new change, C2, will occur at time T+C, which is   before T+S.  The system will start processing the new change before   it's done with the old.   This is not to say that all routers are constantly processing   changes.  The effects of changes are like ripples in a pond.  They   spread outward from where they occur.  Some routers will be   processing just C1, others C2, others both C1 and C2, and others   neither.   We have two separate scopes over which we can set requirements with   respect to convergence:   1.  Single Change: In this requirement, a single change of any type       (link addition or deletion, router failure or restart, etc.) is       introduced into a stabilized system.  No additional changes are       introduced.  The system must re-stabilize within some measure of       bounded time.  This requirement is a fairly abstract one as it       would be impossible to test in a real network.  Definition of the       time constraints remains an open research issue.   2.  System-Wide: Defining a single target for maximum convergence       time for the real Internet is absurd.  As we mentioned earlier,       the Internet is large enough and diverse enough so that it is       quite likely that new changes are introduced somewhere before the       system fully digests old ones.   So, the first requirement here is that there must be mechanisms to   limit the scope of any one change's visibility and effects.  The   number of routers that have to perform calculations in response to a   change is kept small, as is the settling time.   The second requirement is based on the following assumptions:   -  the scope of a change's visibility and impact can be limited.      That is, routers within that scope know of the change and      recalculate their tables based on the change.  Routers outside of      the scope don't see it at all.   -  Within any scope, S, network changes are constantly occurring and      the average inter-change interval is Tc seconds.   -  There are Rs routers within scope S.   -  A subset of the destinations known to the routers in S, Ds, are      impacted by a given change.Doria, et al.                   Historic                       [Page 13]

RFC 5772                IRTF Routing Requirements          February 2010   -  We can state that for Z% of the changes, within Y% of Tc seconds      after a change, C, X% of the Rs routers have their routes to Ds      settled to a useful answer (useful meaning that packets can get to      Ds, though perhaps not by the optimal path -- this allows some      "hunting" for the optimal solution).      X, Y, and Z are yet to be defined.  Their definition remains a      research issue.   This requirement implies that the scopes can be kept relatively small   in order to minimize Rs and maximize Tc.   The growth rate of the convergence time must not be related to the   growth rate of the Internet as a whole.  This implies that the   convergence time either:   1.  not be a function of basic network elements (such as prefixes and       links/paths), and/or   2.  that the Internet be continuously divisible into chunks that       limit the scope and effect of a change, thereby limiting the       number of routers, prefixes, links, and so on, involved in the       new calculations.2.1.9.  Routing System Security   The security of the Internet's routing system is paramount.  If the   routing system is compromised or attacked, the entire Internet can   fail.  This is unacceptable.  Any new architecture must be secure.   Architectures by themselves are not secure.  It is the implementation   of an architecture, its protocols, algorithms, and data structures   that are secure.  These requirements apply primarily to the   implementation.  The architecture must provide the elements that the   implementation needs to meet these security requirements.  Also, the   architecture must not prevent these security requirements from being   met.   Security means different things to different people.  In order for   this requirement to be useful, we must define what we mean by   security.  We do this by identifying the attackers and threats we   wish to protect against.  They are:Doria, et al.                   Historic                       [Page 14]

RFC 5772                IRTF Routing Requirements          February 2010   Masquerading         The system, including its protocols, must be secure against         intruders adopting the identity of other known, trusted         elements of the routing system and then using that position of         trust for carrying out other attacks.  Protocols must use         cryptographically strong authentication.   Denial-of-Service (DoS) Attacks         The architecture and protocols should be secure against DoS         attacks directed at the routers.         The new architecture and protocols should provide as much         information as it can to allow administrators to track down         sources of DoS and Distributed DOS (DDoS) attacks.   No Bad Data         Any new architecture and protocols must provide protection         against the introduction of bad, erroneous, or misleading data         by attackers.  Of particular importance, an attacker must not         be able to redirect traffic flows, with the intent of:         o  directing legitimate traffic away from a target, causing a            denial-of-service attack by preventing legitimate data from            reaching its destination,         o  directing additional traffic (going to other destinations            that are "innocent bystanders") to a target, causing the            target to be overloaded, or         o  directing traffic addressed to the target to a place where            the attacker can copy, snoop, alter, or otherwise affect the            traffic.   Topology Hiding         Any new architecture and protocols must provide mechanisms to         allow network owners to hide the details of their internal         topologies, while maintaining the desired levels of service         connectivity and reachability.   Privacy         By "privacy" we mean privacy of the routing protocol exchanges         between routers.         When the routers are on point-to-point links, with routers at         each end, there may not be any need to encrypt the routing         protocol traffic as the possibility of a third partyDoria, et al.                   Historic                       [Page 15]

RFC 5772                IRTF Routing Requirements          February 2010         intercepting the traffic is limited, though not impossible.  We         do believe, however, that it is important to have the ability         to protect routing protocol traffic in two cases:         1.  When the routers are on a shared network, it is possible             that there are hosts on the network that have been             compromised.  These hosts could surreptitiously monitor the             protocol traffic.         2.  When two routers are exchanging information "at a distance"             (over intervening routers and, possibly, across             administrative domain boundaries).  In this case, the             security of the intervening routers, links, and so on,             cannot be assured.  Thus, the ability to encrypt this             traffic is important.         Therefore, we believe that the option to encrypt routing         protocol traffic is required.   Data Consistency         A router should be able to detect and recover from any data         that is received from other routers that is inconsistent.  That         is, it must not be possible for data from multiple routers,         none of which is malicious, to "break" another router.   Where security mechanisms are provided, they must use methods that   are considered to be cryptographically secure (e.g., using   cryptographically strong encryption and signatures -- no cleartext   passwords!).   Use of security features should not be optional (except as required   above).  This may be "social engineering" on our part, but we believe   it to be necessary.  If a security feature is optional, the   implementation of the feature must default to the "secure" setting.2.1.10.  End Host Security   The architecture must not prevent individual host-to-host   communications sessions from being secured (i.e., it cannot interfere   with things like IPsec).2.1.11.  Rich Policy   Before setting out policy requirements, we need to define the term.   Like "security", "policy" means different things to different people.   For our purposes, "policy" is the set of administrative influences   that alter the path determination and next-hop selection procedures   of the routing software.Doria, et al.                   Historic                       [Page 16]

RFC 5772                IRTF Routing Requirements          February 2010   The main motivators for influencing path and next-hop selection seem   to be transit rules, business decisions, and load management.   The new architecture must support rich policy mechanisms.   Furthermore, the policy definition and dissemination mechanisms   should be separated from the network topology and connectivity   dissemination mechanisms.  Policy provides input to and controls the   generation of the forwarding table and the abstraction, filtering,   aggregation, and dissemination of topology information.   Note that if the architecture is properly divided into subsystems,   then at a later time, new policy subsystems that include new features   and capabilities could be developed and installed as needed.   We divide the general area of policy into two sub-categories: routing   information and traffic control.  Routing Information Policies   control what routing information is disseminated or accepted, how it   is disseminated, and how routers determine paths and next-hops from   the received information.  Traffic Control Policies determine how   traffic is classified and assigned to routes.2.1.11.1.  Routing Information Policies   There must be mechanisms to allow network administrators, operators,   and designers to control receipt and dissemination of routing   information.  These controls include, but are not limited to:   -  Selecting to which other routers routing information will be      transmitted.   -  Specifying the "granularity" and type of transmitted information.      The length of IPv4 prefixes is an example of granularity.   -  Selection and filtering of topology and service information that      is transmitted.  This gives different "views" of internal      structure and topology to different peers.   -  Selecting the level of security and authenticity for transmitted      information.   -  Being able to cause the level of detail that is visible for some      portion of the network to reduce the farther you get from that      part of the network.   -  Selecting from whom routing information will be accepted.  This      control should be "provisional" in the sense of "accept routes      from "foo" only if there are no others available".Doria, et al.                   Historic                       [Page 17]

RFC 5772                IRTF Routing Requirements          February 2010   -  Accepting or rejecting routing information based on the path the      information traveled (using the current system as an example, this      would be filtering routes based on an AS appearing anywhere in the      AS path).  This control should be "use only if there are no other      paths available".   -  Selecting the desired level of granularity for received routing      information (this would include, but is not limited to, things      similar in nature to the prefix-length filters widely used in the      current routing and addressing system).   -  Selecting the level of security and authenticity of received      information in order for that information to be accepted.   -  Determining the treatment of received routing information based on      attributes supplied with the information.   -  Applying attributes to routing information that is to be      transmitted and then determining treatment of information (e.g.,      sending it "here" but not "there") based on those tags.   -  Selection and filtering of topology and service information that      is received.2.1.11.2.  Traffic Control Policies   The architecture should provide mechanisms that allow network   operators to manage and control the flow of traffic.  The traffic   controls should include, but are not limited to:   -  The ability to detect and eliminate congestion points in the      network (by redirecting traffic around those points).   -  The ability to develop multiple paths through the network with      different attributes and then assign traffic to those paths based      on some discriminators within the packets (discriminators include,      but are not limited to, IP addresses or prefixes, IPv6 flow ID,      DSCP values, and MPLS labels).   -  The ability to find and use multiple, equivalent paths through the      network (i.e., they would have the "same" attributes) and allocate      traffic across the paths.   -  The ability to accept or refuse traffic based on some traffic      classification (providing, in effect, transit policies).Doria, et al.                   Historic                       [Page 18]

RFC 5772                IRTF Routing Requirements          February 2010      Traffic classification must at least include the source and      destination IP addresses (prefixes) and the DSCP value.  Other      fields may be supported, such as:      *  Protocol and port-based functions,      *  DSCP/QoS (Quality of Service) tuple (such as ports),      *  Per-host operations (i.e., /32 s for IPv4 and /128 s for IPv6),         and      *  Traffic matrices (e.g., traffic from prefix X and to prefix Y).2.1.12.  Incremental Deployment   The reality of the Internet is that there can be no Internet-wide   cutover from one architecture and protocol to another.  This means   that any new architecture and protocol must be incrementally   deployable; ISPs must be able to set up small sections of the new   architecture, check it out, and then slowly grow the sections.   Eventually, these sections will "touch" and "squeeze out" the old   architecture.   The protocols that implement the architecture must be able to   interoperate at "production levels" with currently existing routing   protocols.  Furthermore, the protocol specifications must define how   the interoperability is done.   We also believe that sections of the Internet will never convert over   to the new architecture.  Thus, it is important that the new   architecture and its protocols be able to interoperate with "old   architecture" regions of the network indefinitely.   The architecture's addressing system must not force existing address   allocations to be redone: no renumbering!2.1.13.  Mobility   There are two kinds of mobility: host mobility and network mobility.   Host mobility is when an individual host moves from where it was to   where it is.  Network mobility is when an entire network (or   subnetwork) moves.   The architecture must support network-level mobility.  Please refer   toSection 2.2.9 for a discussion of host mobility.Doria, et al.                   Historic                       [Page 19]

RFC 5772                IRTF Routing Requirements          February 2010      Editors' Note: Since the time of this work, the Network Mobility      (NEMO) extensions to Mobile-IP [RFC3963] to accommodate mobile      networks have been developed.2.1.14.  Address Portability   One of the big "hot items" in the current Internet political climate   is portability of IP addresses (both v4 and v6).  The short   explanation is that people do not like to renumber when changing   connection point or provider and do not trust automated renumbering   tools.   The architecture must provide complete address portability.2.1.15.  Multi-Protocol   The Internet is expected to be "multi-protocol" for at least the next   several years.  IPv4 and IPv6 will co-exist in many different ways   during a transition period.  The architecture must be able to handle   both IPv4 and IPv6 addresses.  Furthermore, protocols that supplant   IPv4 and IPv6 may be developed and deployed during the lifetime of   the architecture.  The architecture must be flexible and extensible   enough to handle new protocols as they arise.   Furthermore, the architecture must not assume any given relationships   between a topological element's IPv4 address and its IPv6 address.   The architecture must not assume that all topological elements have   IPv4 addresses/prefixes, nor can it assume that they have IPv6   addresses/prefixes.   The architecture should allow different paths to the same destination   to be used for different protocols, even if all paths can carry all   protocols.   In addition to the addressing technology, the architecture need not   be restricted to only packet-based multiplexing/demultiplexing   technology (such as IP); support for other multiplexing/   demultiplexing technologies may be added.2.1.16.  Abstraction   The architecture must provide mechanisms for network designers and   operators to:   o  Group elements together for administrative control purposes,   o  Hide the internal structure and topology of those groupings for      administrative and security reasons,Doria, et al.                   Historic                       [Page 20]

RFC 5772                IRTF Routing Requirements          February 2010   o  Limit the amount of topology information that is exported from the      groupings in order to control the load placed on external routers,   o  Define rules for traffic transiting or terminating in the      grouping.   The architecture must allow the current Autonomous System structure   to be mapped into any new abstraction schemes.   Mapping mechanisms, algorithms, and techniques must be specified.2.1.17.  Simplicity   The architecture must be simple enough so that someone who is   extremely knowledgeable in routing and who is skilled at creating   straightforward and simple explanations can explain all the important   concepts in less than an hour.   This criterion has been chosen since developing an objective measure   of complexity for an architecture can be very difficult and is out of   scope for this document.   The requirement is that the routing architecture be kept as simple as   possible.  This requires careful evaluation of possible features and   functions with a merciless weeding out of those that "might be nice"   but are not necessary.   By keeping the architecture simple, the protocols and software used   to implement the architecture are simpler.  This simplicity in turn   leads to:   1.  Faster implementation of the protocols.  If there are fewer bells       and whistles, then there are fewer things that need to be       implemented.   2.  More reliable implementations.  With fewer components, there is       less code, reducing bug counts, and fewer interactions between       components that could lead to unforeseen and incorrect behavior.2.1.18.  Robustness   The architecture, and the protocols implementing it, should be   robust.  Robustness comes in many different flavors.  Some   considerations with regard to robustness include (but are not limited   to):   o  Continued correct operation in the face of:Doria, et al.                   Historic                       [Page 21]

RFC 5772                IRTF Routing Requirements          February 2010      *  Defective (even malicious) trusted routers.      *  Network failures.  Whenever possible, valid alternate paths are         to be found and used.   o  Failures must be localized.  That is, the architecture must limit      the "spread" of any adverse effects of a misconfiguration or      failure.  Badness must not spread.   Of course, the general robustness principle of being liberal in   what's accepted and conservative in what's sent must also be applied.      Original Editor's Note: Some of the contributors to this section      have argued that robustness is an aspect of security.  I have      exercised editor's discretion by making it a separate section.      The reason for this is that to too many people "security" means      "protection from break-ins" and "authenticating and encrypting      data".  This requirement goes beyond those views.2.1.19.  Media Independence   While it is an article of faith that IP operates over a wide variety   of media (such as Ethernet, X.25, ATM, and so on), IP routing must   take an agnostic view toward any "routing" or "topology" services   that are offered by the medium over which IP is operating.  That is,   the new architecture must not be designed to integrate with any   media-specific topology management or routing scheme.   The routing architecture must assume, and must work over, the   simplest possible media.   The routing and addressing architecture can certainly make use of   lower-layer information and services, when and where available, and   to the extent that IP routing wishes.2.1.20.  Stand-Alone   The routing architecture and protocols must not rely on other   components of the Internet (such as DNS) for their correct operation.   Routing is the fundamental process by which data "finds its way   around the Internet" and most, if not all, of those other components   rely on routing to properly forward their data.  Thus, routing cannot   rely on any Internet systems, services, or capabilities that in turn   rely on routing.  If it did, a dependency loop would result.Doria, et al.                   Historic                       [Page 22]

RFC 5772                IRTF Routing Requirements          February 20102.1.21.  Safety of Configuration   The architecture, protocols, and standard implementation defaults   must be such that a router installed "out of the box" with no   configuration, etc., by the operators will not cause "bad things" to   happen to the rest of the routing system (e.g., no dial-up customers   advertising routes to 18/8!).2.1.22.  Renumbering   The routing system must allow topological entities to be renumbered.2.1.23.  Multi-Prefix   The architecture must allow topological entities to have multiple   prefixes (or the equivalent under the new architecture).2.1.24.  Cooperative Anarchy   AsRFC 1726[RFC1726] states:      A major contributor to the Internet's success is the fact that      there is no single, centralized, point of control or promulgator      of policy for the entire network.  This allows individual      constituents of the network to tailor their own networks,      environments, and policies to suit their own needs.  The      individual constituents must cooperate only to the degree      necessary to ensure that they interoperate.   This decentralization, called "cooperative anarchy", is still a key   feature of the Internet today.  The new routing architecture must   retain this feature.  There can be no centralized point of control or   promulgator of policy for the entire Internet.2.1.25.  Network-Layer Protocols and Forwarding Model   For the purposes of backward compatibility, any new routing and   addressing architecture and protocols must work with IPv4 and IPv6   using the traditional "hop-by-hop" forwarding and packet-based   multiplex/demultiplex models.  However, the architecture need not be   restricted to these models.  Additional forwarding and multiplex/   demultiplex models may be added.2.1.26.  Routing Algorithm   The architecture should not require a particular routing algorithm   family.  That is to say, the architecture should be agnostic about   link-state, distance-vector, or path-vector routing algorithms.Doria, et al.                   Historic                       [Page 23]

RFC 5772                IRTF Routing Requirements          February 20102.1.27.  Positive Benefit   Finally, the architecture must show benefits in terms of increased   stability, decreased operational costs, and increased functionality   and lifetime, over the current schemes.  This benefit must remain   even after the inevitable costs of developing and debugging the new   protocols, enduring the inevitable instabilities as things get shaken   out, and so on.2.1.28.  Administrative Entities and the IGP/EGP Split   We explicitly recognize that the Internet consists of resources under   control of multiple administrative entities.  Each entity must be   able to manage its own portion of the Internet as it sees fit.   Moreover, the constraints that can be imposed on routing and   addressing on the portion of the Internet under the control of one   administration may not be feasibly extended to cover multiple   administrations.  Therefore, we recognize a natural and inevitable   split between routing and addressing that is under a single   administrative control and routing and addressing that involves   multiple administrative entities.  Moreover, while there may be   multiple administrative authorities, the administrative authority   boundaries may be complex and overlapping, rather than being a strict   hierarchy.   Furthermore, there may be multiple levels of administration, each   with its own level of policy and control.  For example, a large   network might have "continental-level" administrations covering its   European and Asian operations, respectively.  There would also be   that network's "inter-continental" administration covering the   Europe-to-Asia links.  Finally, there would be the "Internet" level   in the administrative structure (analogous to the "exterior" concept   in the current routing architecture).   Thus, we believe that the administrative structure of the Internet   must be extensible to many levels (more than the two provided by the   current IGP/EGP split).  The interior/exterior property is not   absolute.  The interior/exterior property of any point in the network   is relative; a point on the network is interior with respect to some   points on the network and exterior with respect to others.   Administrative entities may not trust each other; some may be almost   actively hostile toward each other.  The architecture must   accommodate these models.  Furthermore, the architecture must not   require any particular level of trust among administrative entities.Doria, et al.                   Historic                       [Page 24]

RFC 5772                IRTF Routing Requirements          February 20102.2.  Non-Requirements   The following are not required or are non-goals.  This should not be   taken to mean that these issues must not be addressed by a new   architecture.  Rather, addressing these issues or not is purely an   optional matter for the architects.2.2.1.  Forwarding Table Optimization   We believe that it is not necessary for the architecture to minimize   the size of the forwarding tables (FIBs).  Current memory sizes,   speeds, and prices, along with processor and Application-specific   Integrated Circuit (ASIC) capabilities allow forwarding tables to be   very large, O(E6), and allow fast (100 M lookups/second) tables to be   built with little difficulty.2.2.2.  Traffic Engineering   "Traffic engineering" is one of those terms that has become terribly   overloaded.  If one asks N people what traffic engineering is, one   would get something like N! disjoint answers.  Therefore, we elect   not to require "traffic engineering", per se.  Instead, we have   endeavored to determine what the ultimate intent is when operators   "traffic engineer" their networks and then make those capabilities an   inherent part of the system.2.2.3.  Multicast   The new architecture is not designed explicitly to be an inter-domain   multicast routing architecture.  However, given the notable lack of a   viable, robust, and widely deployed inter-domain multicast routing   architecture, the architecture should not hinder the development and   deployment of inter-domain multicast routing without an adverse   effect on meeting the other requirements.   We do note however that one respected network sage [Clark91] has said   (roughly):      When you see a bunch of engineers standing around congratulating      themselves for solving some particularly ugly problem in      networking, go up to them, whisper "multicast", jump back, and      watch the fun begin...Doria, et al.                   Historic                       [Page 25]

RFC 5772                IRTF Routing Requirements          February 20102.2.4.  Quality of Service (QoS)   The architecture concerns itself primarily with disseminating network   topology information so that routers may select paths to destinations   and build appropriate forwarding tables.  Quality of Service (QoS) is   not a part of this function and we make no requirements with respect   to QoS.   However, QoS is an area of great and evolving interest.  It is   reasonable to expect that in the not too distant future,   sophisticated QoS facilities will be deployed in the Internet.  Any   new architecture and protocols should be developed with an eye toward   these future evolutions.  Extensibility mechanisms, allowing future   QoS routing and signaling protocols to "piggy-back" on top of the   basic routing system are desired.   We do require the ability to assign attributes to entities and then   do path generation and selection based on those attributes.  Some may   call this QoS.2.2.5.  IP Prefix Aggregation   There is no specific requirement that CIDR-style (Classless Inter-   Domain Routing) IP prefix aggregation be done by the new   architecture.  Address allocation policies, societal pressure, and   the random growth and structure of the Internet have all conspired to   make prefix aggregation extraordinarily difficult, if not impossible.   This means that large numbers of prefixes will be sloshing about in   the routing system and that forwarding tables will grow quite big.   This is a cost that we believe must be borne.   Nothing in this non-requirement should be interpreted as saying that   prefix aggregation is explicitly prohibited.  CIDR-style IP prefix   aggregation might be used as a mechanism to meet other requirements,   such as scaling.2.2.6.  Perfect Safety   Making the system impossible to misconfigure is, we believe, not   required.  The checking, constraints, and controls necessary to   achieve this could, we believe, prevent operators from performing   necessary tasks in the face of unforeseen circumstances.   However, safety is always a "good thing", and any results from   research in this area should certainly be taken into consideration   and, where practical, incorporated into the new routing architecture.Doria, et al.                   Historic                       [Page 26]

RFC 5772                IRTF Routing Requirements          February 20102.2.7.  Dynamic Load Balancing   History has shown that using the routing system to perform highly   dynamic load balancing among multiple more-or-less-equal paths   usually ends up causing all kinds of instability, etc., in the   network.  Thus, we do not require such a capability.   However, this is an area that is ripe for additional research, and   some believe that the capability will be necessary in the future.   Thus, the architecture and protocols should be "malleable" enough to   allow development and deployment of dynamic load-balancing   capabilities, should we ever figure out how to do it.2.2.8.  Renumbering of Hosts and Routers   We believe that the routing system is not required to "do   renumbering" of hosts and routers.  That's an IP issue.   Of course, the routing and addressing architecture must be able to   deal with renumbering when it happens.2.2.9.  Host Mobility   In the Internet architecture, host mobility is handled on a per-host   basis by a dedicated, Mobile-IP protocol [RFC3344].  Traffic destined   for a mobile-host is explicitly forwarded by dedicated relay agents.   Mobile-IP [RFC3344] adequately solves the host-mobility problem and   we do not see a need for any additional requirements in this area.   Of course, the new architecture must not impede or conflict with   Mobile-IP.2.2.10.  Backward Compatibility   For the purposes of development of the architecture, we assume that   there is a "clean slate".  Unless specified inSection 2.1, there are   no explicit requirements that elements, concepts, or mechanisms of   the current routing architecture be carried forward into the new one.3.  Requirements from Group B   The following is the result of the work done by Sub-Group B of the   IRTF RRG in 2001-2002.  It was originally released under the title:   "Future Domain Routing Requirements" and was edited by Avri Doria and   Elwyn Davies.Doria, et al.                   Historic                       [Page 27]

RFC 5772                IRTF Routing Requirements          February 20103.1.  Group B - Future Domain Routing Requirements   It is generally accepted that there are major shortcomings in the   inter-domain routing of the Internet today and that these may result   in meltdown within an unspecified period of time.  Remedying these   shortcomings will require extensive research to tie down the exact   failure modes that lead to these shortcomings and identify the best   techniques to remedy the situation.      Reviewer's Note: Even in 2001, there was a wide difference of      opinion across the community regarding the shortcomings of inter-      domain routing.  In the years between writing and publication,      further analysis, changes in operational practice, alterations to      the demands made on inter-domain routing, modifications made to      BGP, and a recognition of the difficulty of finding a replacement      may have altered the views of some members of the community.   Changes in the nature and quality of the services that users want   from the Internet are difficult to provide within the current   framework, as they impose requirements never foreseen by the original   architects of the Internet routing system.   The kind of radical changes that have to be accommodated are   epitomized by the advent of IPv6 and the application of IP mechanisms   to private commercial networks that offer specific service guarantees   beyond the best-effort services of the public Internet.  Major   changes to the inter-domain routing system are inevitable to provide   an efficient underpinning for the radically changed and increasingly   commercially-based networks that rely on the IP protocol suite.3.2.  Underlying Principles   Although inter-domain routing is seen as the major source of   problems, the interactions with intra-domain routing, and the   constraints that confining changes to the inter-domain arena would   impose, mean that we should consider the whole area of routing as an   integrated system.  This is done for two reasons:   -  Requirements should not presuppose the solution.  A continued      commitment to the current definitions and split between inter-      domain and intra-domain routing would constitute such a      presupposition.  Therefore, this part of the document uses the      name Future Domain Routing (FDR).   -  It is necessary to understand the degree to which inter-domain and      intra-domain routing are related within today's routing      architecture.Doria, et al.                   Historic                       [Page 28]

RFC 5772                IRTF Routing Requirements          February 2010   We are aware that using the term "domain routing" is already fraught   with danger because of possible misinterpretation due to prior usage.   The meaning of "domain routing" will be developed implicitly   throughout the document, but a little advance explicit definition of   the word "domain" is required, as well as some explanation on the   scope of "routing".   This document uses "domain" in a very broad sense, to mean any   collection of systems or domains that come under a common authority   that determines the attributes defining, and the policies   controlling, that collection.  The use of "domain" in this manner is   very similar to the concept of region that was put forth by John   Wroclawski in his Metanet model [Wroclawski95].  The idea includes   the notion that certain attributes will characterize the behavior of   the systems within a domain and that there will be borders between   domains.  The idea of domain presented here does not presuppose that   two domains will have the same behavior.  Nor does it presuppose   anything about the hierarchical nature of domains.  Finally, it does   not place restrictions on the nature of the attributes that might be   used to determine membership in a domain.  Since today's routing   domains are an example of the concept of domains in this document,   there has been no attempt to create a new term.   Current practice in routing-system design stresses the need to   separate the concerns of the control plane and the forwarding plane   in a router.  This document will follow this practice, but we still   use the term "routing" as a global portmanteau to cover all aspects   of the system.  Specifically, however, "routing" will be used to mean   the process of discovering, interpreting, and distributing   information about the logical and topological structure of the   network.3.2.1.  Inter-Domain and Intra-Domain   Throughout this section, the terms "intra-domain" and "inter-domain"   will be used.  These should be understood as relative terms.  In all   cases of domains, there will be a set of network systems that are   within that domain; routing between these systems will be termed   "intra-domain".  In some cases there will be routing between domains,   which will be termed "inter-domain".  It is possible that the routing   exchange between two network systems can be viewed as intra-domain   from one perspective and as inter-domain from another perspective.3.2.2.  Influences on a Changing Network   The development of the Internet is likely to be driven by a number of   changes that will affect the organization and the usage of the   network, including:Doria, et al.                   Historic                       [Page 29]

RFC 5772                IRTF Routing Requirements          February 2010   -  Ongoing evolution of the commercial relationships between      (connectivity) service providers, leading to changes in the way in      which peering between providers is organized and the way in which      transit traffic is routed.   -  Requirements for traffic engineering within and between domains      including coping with multiple paths between domains.   -  Addition of a second IP addressing technique, in the form of IPv6.   -  The use of VPNs and private address space with IPv4 and IPv6.   -  Evolution of the end-to-end principle to deal with the expanded      role of the Internet, as discussed in [Blumenthal01]: this paper      discusses the possibility that the range of new requirements,      especially the social and techno-political ones that are being      placed on the future, may compromise the Internet's original      design principles.  This might cause the Internet to lose some of      its key features, in particular, its ability to support new and      unanticipated applications.  This discussion is linked to the rise      of new stakeholders in the Internet, especially ISPs; new      government interests; the changing motivations of the ever growing      user base; and the tension between the demand for trustworthy      overall operation and the inability to trust the behavior of      individual users.   -  Incorporation of alternative forwarding techniques such as the      explicit routing (pipes) supplied by the MPLS [RFC3031] and GMPLS      [RFC3471] environments.   -  Integration of additional constraints into route determination      from interactions with other layers (e.g., Shared Risk Link Groups      [InferenceSRLG]).  This includes the concern that redundant routes      should not fate-share, e.g., because they physically run in the      same trench.   -  Support for alternative and multiple routing techniques that are      better suited to delivering types of content organized in ways      other than into IP-addressed packets.   Philosophically, the Internet has the mission of transferring   information from one place to another.  Conceptually, this   information is rarely organized into conveniently sized, IP-addressed   packets, and the FDR needs to consider how the information (content)   to be carried is identified, named, and addressed.  Routing   techniques can then be adapted to handle the expected types of   content.Doria, et al.                   Historic                       [Page 30]

RFC 5772                IRTF Routing Requirements          February 20103.2.3.  High-Level Goals   This section attempts to answer two questions:   -  What are we trying to achieve in a new architecture?   -  Why should the Internet community care?   There is a third question that needs to be answered as well, but that   has seldom been explicitly discussed:   -  How will we know when we have succeeded?3.2.3.1.  Providing a Routing System Matched to Domain Organization   Many of today's routing problems are caused by a routing system that   is not well matched to the organization and policies that it is   trying to support.  Our goal is to develop a routing architecture   where even a domain organization that is not envisioned today can be   served by a routing architecture that matches its requirements.  We   will know when this goal is achieved when the desired policies,   rules, and organization can be mapped into the routing system in a   natural, consistent, and easily understood way.3.2.3.2.  Supporting a Range of Different Communication Services   Today's routing protocols only support a single data forwarding   service that is typically used to deliver a best-effort service in   the public Internet.  On the other hand, Diffserv for example, can   construct a number of different bit transport services within the   network.  Using some of the per-domain behaviors (PDB)s that have   been discussed in the IETF, it is possible to construct services such   as Virtual Wire [DiffservVW] and Assured Rate [DiffservAR].   Providers today offer rudimentary promises about traffic handling in   the network, for example, delay and long-term packet loss guarantees.   As time goes on, this becomes even more relevant.  Communicating the   service characteristics of paths in routing protocols will be   necessary in the near future, and it will be necessary to be able to   route packets according to their service requirements.   Thus, a goal of this architecture is to allow adequate information   about path service characteristics to be passed between domains and   consequently, to allow the delivery of bit transport services other   than the best-effort datagram connectivity service that is the   current common denominator.Doria, et al.                   Historic                       [Page 31]

RFC 5772                IRTF Routing Requirements          February 20103.2.3.3.  Scalable Well Beyond Current Predictable Needs   Any proposed FDR system should scale beyond the size and performance   we can foresee for the next ten years.  The previous IDR proposal as   implemented by BGP, has, with some massaging, held up for over ten   years.  In that time the Internet has grown far beyond the   predictions that were implied by the original requirements.   Unfortunately, we will only know if we have succeeded in this goal if   the FDR system survives beyond its design lifetime without serious   massaging.  Failure will be much easier to spot!3.2.3.4.  Alternative Forwarding Mechanisms   With the advent of circuit-based technologies (e.g., MPLS [RFC3031]   and GMPLS [RFC3471]) managed by IP routers there are forwarding   mechanisms other than the datagram service that need to be supported   by the routing architecture.   An explicit goal of this architecture is to add support for   forwarding mechanisms other then the current hop-by-hop datagram   forwarding service driven by globally unique IP addresses.3.2.3.5.  Separation of Topology Map from Connectivity Service   It is envisioned that an organization can support multiple services   within a single network.  These services can, for example, be of   different quality, of different connectivity type, or of different   protocols (e.g., IPv4 and IPv6).  For all these services, there may   be common domain topology, even though the policies controlling the   routing of information might differ from service to service.  Thus, a   goal with this architecture is to support separation between creation   of a domain (or organization) topology map and service creation.3.2.3.6.  Separation between Routing and Forwarding   The architecture of a router is composed of two main separable parts:   control and forwarding.  These components, while inter-dependent,   perform functions that are largely independent of each other.   Control (routing, signaling, and management) is typically done in   software while forwarding typically is done with specialized ASICs or   network processors.   The nature of an IP-based network today is that control and data   protocols share the same network and forwarding regime.  This may not   always be the case in future networks, and we should be careful to   avoid building in this sharing as an assumption in the FDR.Doria, et al.                   Historic                       [Page 32]

RFC 5772                IRTF Routing Requirements          February 2010   A goal of this architecture is to support full separation of control   and forwarding, and to consider what additional concerns might be   properly considered separately (e.g., adjacency management).3.2.3.7.  Different Routing Paradigms in Different Areas of the Same          Network   A number of routing paradigms have been used or researched, in   addition to the conventional shortest-path-by-hop-count paradigm that   is the current mainstay of the Internet.  In particular, differences   in underlying transport networks may mean that other kinds of routing   are more relevant, and the perceived need for traffic engineering   will certainly alter the routing chosen in various domains.   Explicitly, one of these routing paradigms should be the current   routing paradigm, so that the new paradigms will inter-operate in a   backward-compatible way with today's system.  This will facilitate a   migration strategy that avoids flag days.3.2.3.8.  Protection against Denial-of-Service and Other Security          Attacks   Currently, existence of a route to a destination effectively implies   that anybody who can get a packet onto the network is entitled to use   that route.  While there are limitations to this generalization, this   is a clear invitation to denial-of-service attacks.  A goal of the   FDR system should be to allow traffic to be specifically linked to   whole or partial routes so that a destination or link resources can   be protected from unauthorized use.      Editors' Note: When sections like this one and the previous ones      on quality differentiation were written, the idea of separating      traffic for security or quality was considered an unqualified      advantage.  Today, however, in the midst of active discussions on      Network Neutrality, it is clear that such issues have a crucial      policy component that also needs to be understood.  These, and      other similar issues, are open to further research.3.2.3.9.  Provable Convergence with Verifiable Policy Interaction   It has been shown both analytically, by Griffin, et al. (see   [Griffin99]), and practically (see [RFC3345]) that BGP will not   converge stably or is only meta-stable (i.e., will not re-converge in   the face of a single failure) when certain types of policy constraint   are applied to categories of network topology.  The addition of   policy to the basic distance-vector algorithm invalidates the proofs   of convergence that could be applied to a policy-free implementation.Doria, et al.                   Historic                       [Page 33]

RFC 5772                IRTF Routing Requirements          February 2010   It has also been argued that global convergence may no longer be a   necessary goal and that local convergence may be all that is   required.   A goal of the FDR should be to achieve provable convergence of the   protocols used that may involve constraining the topologies and   domains subject to convergence.  This will also require vetting the   policies imposed to ensure that they are compatible across domain   boundaries and result in a consistent policy set.      Editors' Note: This requirement is very optimistic in that it      implies that it is possible to get operators to cooperate even it      is seen by them to be against their business practices.  Though      perhaps Utopian, this is a good goal.3.2.3.10.  Robustness Despite Errors and Failures   From time to time in the history of the Internet, there have been   occurrences where misconfigured routers have destroyed global   connectivity.   A goal of the FDR is to be more robust to configuration errors and   failures.  This should probably involve ensuring that the effects of   misconfiguration and failure can be confined to some suitable   locality of the failure or misconfiguration.3.2.3.11.  Simplicity in Management   The policy work ([rap-charter02], [snmpconf-charter02], and   [policy-charter02]) that has been done at IETF provides an   architecture that standardizes and simplifies management of QoS.   This kind of simplicity is needed in a Future Domain Routing   architecture and its protocols.   A goal of this architecture is to make configuration and management   of inter-domain routing as simple as possible.      Editors' Note: Snmpconf and rap are the hopes of the past.  Today,      configuration and policy hope is focused on netconf      [netconf-charter].3.2.3.12.  The Legacy ofRFC 1126RFC 1126 outlined a set of requirements that were used to guide the   development of BGP.  While the network has changed in the years since   1989, many of the same requirements remain.  A future domain routing   solution has to support, as its base requirement, the level of   function that is available today.  A detailed discussion ofRFC 1126Doria, et al.                   Historic                       [Page 34]

RFC 5772                IRTF Routing Requirements          February 2010   and its requirements can be found in [RFC5773].  Those requirements,   while specifically spelled out in that document, are subsumed by the   requirements in this document.3.3.  High-Level User Requirements   This section considers the requirements imposed by the target   audience of the FDR both in terms of organizations that might own   networks that would use FDR, and the human users who will have to   interact with the FDR.3.3.1.  Organizational Users   The organizations that own networks connected to the Internet have   become much more diverse sinceRFC 1126 [RFC1126] was published.  In   particular, major parts of the network are now owned by commercial   service provider organizations in the business of making profits from   carrying data traffic.3.3.1.1.  Commercial Service Providers   The routing system must take into account the commercial service   provider's need for secrecy and security, as well as allowing them to   organize their business as flexibly as possible.   Service providers will often wish to conceal the details of the   network from other connected networks.  So far as is possible, the   routing system should not require the service providers to expose   more details of the topology and capability of their networks than is   strictly necessary.   Many service providers will offer contracts to their customers in the   form of Service Level Agreements (SLAs).  The routing system must   allow the providers to support these SLAs through traffic engineering   and load balancing as well as multi-homing, providing the degree of   resilience and robustness that is needed.   Service providers can be categorized as:   -  Global Service Providers (GSPs) whose networks have a global      reach.  GSPs may, and usually will, wish to constrain traffic      between their customers to run entirely on their networks.  GSPs      will interchange traffic at multiple peering points with other      GSPs, and they will need extensive policy-based controls to      control the interchange of traffic.  Peering may be through the      use of dedicated private lines between the partners or,      increasingly, through Internet Exchange Points.Doria, et al.                   Historic                       [Page 35]

RFC 5772                IRTF Routing Requirements          February 2010   -  National, or regional, Service Providers (NSPs) that are similar      to GSPs but typically cover one country.  NSPs may operate as a      federation that provides similar reach to a GSP and may wish to be      able to steer traffic preferentially to other federation members      to achieve global reach.   -  Local Internet Service Providers (ISPs) operate regionally.  They      will typically purchase transit capacity from NSPs or GSPs to      provide global connectivity, but they may also peer with      neighboring, and sometimes distant, ISPs.   The routing system should be sufficiently flexible to accommodate the   continually changing business relationships of the providers and the   various levels of trustworthiness that they apply to customers and   partners.   Service providers will need to be involved in accounting for Internet   usage and monitoring the traffic.  They may be involved in government   action to tax the usage of the Internet, enforce social mores and   intellectual property rules, or apply surveillance to the traffic to   detect or prevent crime.3.3.1.2.  Enterprises   The leaves of the network domain graph are in many cases networks   supporting a single enterprise.  Such networks cover an enormous   range of complexity.  Some multi-national companies own networks that   rival the complexity and reach of a GSP, whereas many fall into the   Small Office-Home Office (SOHO) category.  The routing system should   allow simple and robust configuration and operation for the SOHO   category, while effectively supporting the larger enterprise.   Enterprises are particularly likely to lack the capability to   configure and manage a complex routing system, and every effort   should be made to provide simple configuration and operation for such   networks.   Enterprises will also need to be able to change their service   provider with ease.  While this is predominantly a naming and   addressing issue, the routing system must be able to support seamless   changeover; for example, if the changeover requires a change of   address prefix, the routing system must be able to cope with a period   when both sets of addresses are in use.   Enterprises will wish to be able to multi-home to one or more   providers as one possible means of enhancing the resilience of their   network.Doria, et al.                   Historic                       [Page 36]

RFC 5772                IRTF Routing Requirements          February 2010   Enterprises will also frequently need to control the trust that they   place both in workers and external connections through firewalls and   similar mid-boxes placed at their external connections.3.3.1.3.  Domestic Networks   Increasingly domestic, i.e., non-business home, networks are likely   to be 'always on' and will resemble SOHO enterprises networks with no   special requirements on the routing system.   The routing system must also continue to support dial-up users.3.3.1.4.  Internet Exchange Points   Peering of service providers, academic networks, and larger   enterprises is happening increasingly at specific Internet Exchange   Points where many networks are linked together in a relatively small   physical area.  The resources of the exchange may be owned by a   trusted third party or owned jointly by the connecting networks.  The   routing systems should support such exchange points without requiring   the exchange point to either operate as a superior entity with every   connected network logically inferior to it or by requiring the   exchange point to be a member of one (or all) connected networks.   The connecting networks have to delegate a certain amount of trust to   the exchange point operator.3.3.1.5.  Content Providers   Content providers are at one level a special class of enterprise, but   the desire to deliver content efficiently means that a content   provider may provide multiple replicated origin servers or caches   across a network.  These may also be provided by a separate content   delivery service.  The routing system should facilitate delivering   content from the most efficient location.3.3.2.  Individual Users   This section covers the most important human users of the FDR and   their expected interactions with the system.3.3.2.1.  All End Users   The routing system must continue to deliver the current global   connectivity service (i.e., any unique address to any other unique   address, subject to policy constraints) that has always been the   basic aim of the Internet.Doria, et al.                   Historic                       [Page 37]

RFC 5772                IRTF Routing Requirements          February 2010   End user applications should be able to request, or have requested on   their behalf by agents and policy mechanisms, end-to-end   communication services with QoS characteristics different from the   best-effort service that is the foundation of today's Internet.  It   should be possible to request both a single service channel and a   bundle of service channels delivered as a single entity.3.3.2.2.  Network Planners   The routing system should allow network planners to plan and   implement a network that can be proved to be stable and will meet   their traffic engineering requirements.3.3.2.3.  Network Operators   The routing system should, so far as is possible, be simple to   configure, operate and troubleshoot, behave in a predictable and   stable fashion, and deliver appropriate statistics and events to   allow the network to be managed and upgraded in an efficient and   timely fashion.3.3.2.4.  Mobile End Users   The routing system must support mobile end users.  It is clear that   mobility is becoming a predominant mode for network access.3.4.  Mandated Constraints   While many of the requirements to which the protocol must respond are   technical, some aren't.  These mandated constraints are those that   are determined by conditions of the world around us.  Understanding   these requirements requires an analysis of the world in which these   systems will be deployed.  The constraints include those that are   determined by:   -  environmental factors,   -  geography,   -  political boundaries and considerations, and   -  technological factors such as the prevalence of different levels      of technology in the developed world compared to those in the      developing or undeveloped world.Doria, et al.                   Historic                       [Page 38]

RFC 5772                IRTF Routing Requirements          February 20103.4.1.  The Federated Environment   The graph of the Internet network, with routers and other control   boxes as the nodes and communication links as the edges, is today   partitioned administratively into a large number of disjoint domains.   A common administration may have responsibility for one or more   domains that may or may not be adjacent in the graph.   Commercial and policy constraints affecting the routing system will   typically be exercised at the boundaries of these domains where   traffic is exchanged between the domains.   The perceived need for commercial confidentiality will seek to   minimize the control information transferred across these boundaries,   leading to requirements for aggregated information, abstracted maps   of connectivity exported from domains, and mistrust of supplied   information.   The perceived desire for anonymity may require the use of zero-   knowledge security protocols to allow users to access resources   without exposing their identity.   The requirements should provide the ability for groups of peering   domains to be treated as a complex domain.  These complex domains   could have a common administrative policy.3.4.2.  Working with Different Sorts of Networks   The diverse Layer 2 networks, over which the Layer 3 routing system   is implemented, have typically been operated totally independently   from the Layer 3 network and often with their own routing mechanisms.   Consideration needs to be given to the desirable degree and nature of   interchange of information between the layers.  In particular, the   need for guaranteed robustness through diverse routing layers implies   knowledge of the underlying networks.   Mobile access networks may also impose extra requirements on Layer 3   routing.3.4.3.  Delivering Resilient Service   The routing system operates at Layer 3 in the network.  To achieve   robustness and resilience at this layer requires that, where multiple   diverse routes are employed as part of delivering the resilience, the   routing system at Layer 3 needs to be assured that the Layer 2 and   lower routes are really diverse.  The "diamond problem" is theDoria, et al.                   Historic                       [Page 39]

RFC 5772                IRTF Routing Requirements          February 2010   simplest form of this problem -- a Layer 3 provider attempting to   provide diversity buys Layer 2 services from two separate providers   who in turn buy Layer 1 services from the same provider:                             Layer 3 service                              /           \                             /             \                         Layer 2         Layer 2                       Provider A      Provider B                             \             /                              \           /                             Layer 1 Provider   Now, when the backhoe cuts the trench, the Layer 3 provider has no   resilience unless he had taken special steps to verify that the   trench wasn't common.  The routing system should facilitate avoidance   of this kind of trap.   Some work is going on to understand the sort of problems that stem   from this requirement, such as the work on Shared Risk Link Groups   [InferenceSRLG].  Unfortunately, the full generality of the problem   requires diversity be maintained over time between an arbitrarily   large set of mutually distrustful providers.  For some cases, it may   be sufficient for diversity to be checked at provisioning or route   instantiation time, but this remains a hard problem requiring   research work.3.4.4.   When Will the New Solution Be Required?   There is a full range of opinion on this subject.  An informal survey   indicates that the range varies from 2 to 6 years.  And while there   are those, possibly outliers, who think there is no need for a new   routing architecture as well as those who think a new architecture   was needed years ago, the median seems to lie at around 4 years.  As   in all projections of the future, this is not provable at this time.      Editors' Note: The paragraph above was written in 2002, yet could      be written without change in 2006.  As with many technical      predictions and schedules, the horizon has remained fixed through      this interval.3.5.  Assumptions   In projecting the requirements for the Future Domain Routing, a   number of assumptions have been made.  The requirements set out   should be consistent with these assumptions, but there are doubtless   a number of other assumptions that are not explicitly articulated   here:Doria, et al.                   Historic                       [Page 40]

RFC 5772                IRTF Routing Requirements          February 2010   1.   The number of hosts today is somewhere in the area of 100        million.  With dial-in, NATs, and the universal deployment of        IPv6, this is likely to become up to 500 million users (see        [CIDR]).  In a number of years, with wireless accesses and        different appliances attaching to the Internet, we are likely to        see a couple of billion (10^9) "users" on the Internet.  The        number of globally addressable hosts is very much dependent on        how common NATs will be in the future.   2.   NATs, firewalls, and other middle-boxes exist, and we cannot        assume that they will cease being a presence in the networks.   3.   The number of operators in the Internet will probably not grow        very much, as there is a likelihood that operators will tend to        merge.  However, as Internet-connectivity expands to new        countries, new operators will emerge and then merge again.   4.   At the beginning of 2002, there are around 12000 registered ASs.        With current use of ASs (e.g., multi-homing) the number of ASs        could be expected to grow to 25000 in about 10 years [Broido02].        This is down from a previously reported growth rate of 51% per        year [RFC3221].  Future growth rates are difficult to predict.           Editors' Note: In the routing report table of August 2006,           the total number of ASs present in the Internet Routing Table           was 23000.  In 4 years, this is substantial progress on the           prediction of 25000 ASs.  Also, there are significantly more           ASs registered than are visibly active, i.e., in excess of           42000 in mid-2006.  It is possible, however, that many are           being used internally.   5.   In contrast to the number of operators, the number of domains is        likely to grow significantly.  Today, each operator has        different domains within an AS, but this also shows in SLAs and        policies internal to the operator.  Making this globally visible        would create a number of domains; 10-100 times the number of        ASs, i.e., between 100,000 and 1,000,000.   6.   With more and more capacity at the edge of the network, the IP        network will expand.  Today, there are operators with several        thousands of routers, but this is likely to be increased.  Some        domains will probably contain tens of thousands of routers.   7.   The speed of connections in the (fixed) access will technically        be (almost) unconstrained.  However, the cost for the links will        not be negligible so that the apparent speed will be effectively        bounded.  Within a number of years, some will have multi-gigabit        speed in the access.Doria, et al.                   Historic                       [Page 41]

RFC 5772                IRTF Routing Requirements          February 2010   8.   At the same time, the bandwidth of wireless access still has a        strict upper-bound.  Within the foreseeable future each user        will have only a tiny amount of resources available compared to        fixed accesses (10 kbps to 2 Mbps for a Universal Mobile        Telecommunications System (UMTS) with only a few achieving the        higher figure as the bandwidth is shared between the active        users in a cell and only small cells can actually reach this        speed, but 11 Mbps or more for wireless LAN connections).  There        may also be requirements for effective use of bandwidth as low        as 2.4 Kbps or lower, in some applications.   9.   Assumptions 7 and 8 taken together suggest a minimum span of        bandwidth between 2.4 kbps to 10 Gbps.   10.  The speed in the backbone has grown rapidly, and there is no        evidence that the growth will stop in the coming years.        Terabit-speed is likely to be the minimum backbone speed in a        couple of years.  The range of bandwidths that need to be        represented will require consideration on how to represent the        values in the protocols.   11.  There have been discussions as to whether Moore's Law will        continue to hold for processor speed.  If Moore's Law does not        hold, then communication circuits might play a more important        role in the future.  Also, optical routing is based on circuit        technology, which is the main reason for taking "circuits" into        account when designing an FDR.   12.  However, the datagram model still remains the fundamental model        for the Internet.   13.  The number of peering points in the network is likely to grow,        as multi-homing becomes important.  Also, traffic will become        more locally distributed, which will drive the demand for local        peering.           Editors' Note: On the other hand, peer-to-peer networking may           shift the balance in demand for local peering.   14.  The FDR will achieve the same degree of ubiquity as the current        Internet and IP routing.3.6.  Functional Requirements   This section includes a detailed discussion of new requirements for a   Future Domain Routing architecture.  The nth requirement carries the   label "R(n)".  As discussed inSection 3.2.3.12, a new architectureDoria, et al.                   Historic                       [Page 42]

RFC 5772                IRTF Routing Requirements          February 2010   must build upon the requirements of the past routing framework and   must not reduce the functionality of the network.  A discussion and   analysis of theRFC 1126 requirements can be found in [RFC5773].3.6.1.  Topology3.6.1.1.  Routers Should Be Able to Learn and to Exploit the Domain          Topology   R(1)  Routers must be able to acquire and hold sufficient information         on the underlying topology of the domain to allow the         establishment of routes on that topology.   R(2)  Routers must have the ability to control the establishment of         routes on the underlying topology.   R(3)  Routers must be able, where appropriate, to control Sub-IP         mechanisms to support the establishment of routes.   The OSI Inter-Domain Routing Protocol (IDRP) [ISO10747] allowed a   collection of topologically related domains to be replaced by an   aggregate domain object, in a similar way to the Nimrod [Chiappa02]   domain hierarchies.  This allowed a route to be more compactly   represented by a single collection instead of a sequence of   individual domains.   R(4)  Routers must, where appropriate, be able to construct         abstractions of the topology that represent an aggregation of         the topological features of some area of the topology.3.6.1.2.  The Same Topology Information Should Support Different Path          Selection Ideas   The same topology information needs to provide the more flexible   spectrum of path selection methods that we might expect to find in a   future Internet, including distributed techniques such as hop-by-hop,   shortest path, local optimization constraint-based, class of service,   source address routing, and destination address routing, as well as   the centralized, global optimization constraint-based "traffic   engineering" type.  Allowing different path selection techniques will   produce a much more predictable and comprehensible result than the   "clever tricks" that are currently needed to achieve the same   results.  Traffic engineering functions need to be combined.   R(5)  Routers must be capable of supporting a small number of         different path selection algorithms.Doria, et al.                   Historic                       [Page 43]

RFC 5772                IRTF Routing Requirements          February 20103.6.1.3.  Separation of the Routing Information Topology from the Data          Transport Topology   R(6)  The controlling network may be logically separate from the         controlled network.   The two functional "planes" may physically reside in the same nodes   and share the same links, but this is not the only possibility, and   other options may sometimes be necessary.  An example is a pure   circuit switch (that cannot see individual IP packets) combined with   an external controller.  Another example may be multiple links   between two routers, where all the links are used for data forwarding   but only one is used for carrying the routing session.3.6.2.  Distribution3.6.2.1.  Distribution Mechanisms   R(7)  Relevant changes in the state of the network, including         modifications to the topology and changes in the values of         dynamic capabilities, must be distributed to every entity in         the network that needs them, in a reliable and trusted way, at         the earliest appropriate time after the changes have occurred.   R(8)  Information must not be distributed outside areas where it is         needed, or believed to be needed, for the operation of the         routing system.   R(9)  Information must be distributed in such a way that it minimizes         the load on the network, consistent with the required response         time of the network to changes.3.6.2.2.  Path Advertisement   R(10)  The router must be able to acquire and store additional static          and dynamic information that relates to the capabilities of          the topology and its component nodes and links and that can          subsequently be used by path selection methods.   The inter-domain routing system must be able to advertise more kinds   of information than just connectivity and domain paths.   R(11)  The routing system must support service specifications, e.g.,          the Service Level Specifications (SLSs) developed by the          Differentiated Services working group [RFC3260].Doria, et al.                   Historic                       [Page 44]

RFC 5772                IRTF Routing Requirements          February 2010   Careful attention should be paid to ensuring that the distribution of   additional information with path advertisements remains scalable as   domains and the Internet get larger, more numerous, and more   diversified.   R(12)  The distribution mechanism used for distributing network state          information must be scalable with respect to the expected size          of domains and the volume and rate of change of dynamic state          that can be expected.   The combination of R(9) and R(12) may result in a compromise between   the responsiveness of the network to change and the overhead of   distributing change notifications.  Attempts to respond to very rapid   changes may damage the stability of the routing system.   Possible examples of additional capability information that might be   carried include:   -  QoS information      To allow an ISP to sell predictable end-to-end QoS service to any      destination, the routing system should have information about the      end-to-end QoS.  This means that:   R(13)  The routing system must be able to support different paths for          different services.   R(14)  The routing system must be able to forward traffic on the path          appropriate for the service selected for the traffic, either          according to an explicit marking in each packet (e.g., MPLS          labels, Diffserv Per-Hop Behaviors (PHBs) or DSCP values) or          implicitly (e.g., the physical or logical port on which the          traffic arrives).   R(15)  The routing system should also be able to carry information          about the expected (or actually, promised) characteristics of          the entire path and the price for the service.      (If such information is exchanged at all between network operators      today, it is through bilateral management interfaces, and not      through the routing protocols.)      This would allow for the operator to optimize the choice of path      based on a price/performance trade-off.      In addition to providing dynamic QoS information, the system      should be able to use static class-of-service information.Doria, et al.                   Historic                       [Page 45]

RFC 5772                IRTF Routing Requirements          February 2010   -  Security information      Security characteristics of other domains referred to by      advertisements can allow the routing entity to make routing      decisions based on political concerns.  The information itself is      assumed to be secure so that it can be trusted.   -  Usage and cost information      Usage and cost information can be used for billing and traffic      engineering.  In order to support cost-based routing policies for      customers (i.e., peer ISPs), information such as "traffic on this      link or path costs XXX per Gigabyte" needs to be advertised, so      that the customer can choose a more or a less expensive route.   -  Monitored performance      Performance information such as delay and drop frequency can be      carried.  (This may only be suitable inside a domain because of      trust considerations.)  This should support at least the kind of      delay-bound contractual terms that are currently being offered by      service providers.  Note that these values refer to the outcome of      carrying bits on the path, whereas the QoS information refers to      the proposed behavior that results in this outcome.   -  Multicast information   R(16)  The routing system must provide information needed to create          multicast distribution trees.  This information must be          provided for one-to-many distribution trees and should be          provided for many-to-many distribution trees.      The actual construction of distribution trees is not necessarily      done by the routing system.3.6.2.3.  Stability of Routing Information   R(17)  The new network architecture must be stable without needing          global convergence, i.e., convergence is a local property.   The degree to which this is possible and the definition of "local"   remain research topics.  Restricting the requirement for convergence   to localities will have an effect on all of the other requirements in   this section.Doria, et al.                   Historic                       [Page 46]

RFC 5772                IRTF Routing Requirements          February 2010   R(18)  The distribution and the rate of distribution of changes must          not affect the stability of the routing information.  For          example, commencing redistribution of a change before the          previous one has settled must not cause instability.3.6.2.3.1.  Avoiding Routing Oscillations   R(19)  The routing system must minimize oscillations in route          advertisements.3.6.2.3.2.  Providing Loop-Free Routing and Forwarding   In line with the separation of routing and forwarding concerns:   R(20)  The distribution of routing information must be, so far as is          possible, loop-free.   R(21)  The forwarding information created from this routing          information must seek to minimize persistent loops in the          data-forwarding paths.   It is accepted that transient loops may occur during convergence of   the protocol and that there are trade-offs between loop avoidance and   global scalability.3.6.2.3.3.  Detection, Notification, and Repair of Failures   R(22)  The routing system must provide means for detecting failures          of node equipment or communication links.   R(23)  The routing system should be able to coordinate failure          indications from Layer 3 mechanisms, from nodal mechanisms          built into the routing system, and from lower-layer mechanisms          that propagate up to Layer 3 in order to determine the root          cause of the failure.  This will allow the routing system to          react correctly to the failure by activating appropriate          mitigation and repair mechanisms if required, while ensuring          that it does not react if lower-layer repair mechanisms are          able to repair or mitigate the fault.   Most Layer 3 routing protocols have utilized keepalives or "hello"   protocols as a means of detecting failures at Layer 3.  The keepalive   mechanisms are often complemented by analog mechanisms (e.g., laser-   light detection) and hardware mechanisms (e.g., hardware/software   watchdogs) that are built into routing nodes and communication links.   Great care must be taken to make the best possible use of the various   failure repair methods available while ensuring that only one repair   mechanism at a time is allowed to repair any given fault.Doria, et al.                   Historic                       [Page 47]

RFC 5772                IRTF Routing Requirements          February 2010   Interactions between, for example, fast reroute mechanisms at Layer 3   and Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/   SDH) repair at Layer 1 are highly undesirable and are likely to cause   problems in the network.   R(24)  Where a network topology and routing system contains multiple          fault repair mechanisms, the responses of these systems to a          detected failure should be coordinated so that the fault is          repaired by the most appropriate means, and no extra repairs          are initiated.   R(25)  Where specialized packet exchange mechanisms (e.g., Layer 3          keepalive or "hello" protocol mechanisms) are used to detect          failures, the routing system must allow the configuration of          the rate of transmission of these keepalives.  This must          include the capability to turn them off altogether for links          that are deliberately broken when no real user or control          traffic is present (e.g., ISDN links).   This will allow the operator to compromise between the speed of   failure detection and the proportion of link bandwidth dedicated to   failure detection.3.6.3.  Addressing3.6.3.1.  Support Mix of IPv4, IPv6, and Other Types of Addresses   R(26)  The routing system must support a mix of different kinds of          addresses.   This mix will include at least IPv4 and IPv6 addresses, and   preferably various types of non-IP addresses, too.  For instance,   networks like SDH/SONET and Wavelength Division Multiplexing (WDM)   may prefer to use non-IP addresses.  It may also be necessary to   support multiple sets of "private" (e.g.,RFC 1918) addresses when   dealing with multiple customer VPNs.   R(27)  The routing system should support the use of a single topology          representation to generate routing and forwarding tables for          multiple address families on the same network.   This capability would minimize the protocol overhead when exchanging   routes.Doria, et al.                   Historic                       [Page 48]

RFC 5772                IRTF Routing Requirements          February 20103.6.3.2.  Support for Domain Renumbering/Readdressing   R(28)  If a domain is subject to address reassignment that would          cause forwarding interruption, then the routing system should          support readdressing (e.g., when a new prefix is given to an          old network, and the change is known in advance) by          maintaining routing during the changeover period [RFC2071]          [RFC2072].3.6.3.3.  Multicast and Anycast   R(29)  The routing system must support multicast addressing, both          within a domain and across multiple domains.   R(30)  The routing system should support anycast addressing within a          domain.  The routing system may support anycast addressing          across domains.   An open question is whether it is possible or useful to support   anycast addressing between cooperating domains.3.6.3.4.  Address Scoping   R(31)  The routing system must support scoping of unicast addresses,          and it should support scoping of multicast and anycast address          types.   The unicast address scoping that is being designed for IPv6 does not   seem to cause any special problems for routing.  IPv6 inter-domain   routing handles only IPv6 global addresses, while intra-domain   routing also needs to be aware of the scope of private addresses.      Editors' Note: the original reference was to site-local addresses,      but these have been deprecated by the IETF.  Link-local addresses      are never routed at all.   More study may be needed to identify the requirements and solutions   for scoping in a more general sense and for scoping of multicast and   anycast addresses.3.6.3.5.  Mobility Support   R(32)  The routing system must support system mobility.  The term          "system" includes anything from an end system to an entire          domain.Doria, et al.                   Historic                       [Page 49]

RFC 5772                IRTF Routing Requirements          February 2010   We observe that the existing solutions based on renumbering and/or   tunneling are designed to work with the current routing, so they do   not add any new requirements to future routing.  But the requirement   is general, and future solutions may not be restricted to the ones we   have today.3.6.4.  Statistics Support   R(33)  Both the routing and forwarding parts of the routing system          must maintain statistical information about the performance of          their functions.3.6.5.  Management Requirements   While the tools of management are outside the scope of routing, the   mechanisms to support the routing architecture and protocols are   within scope.   R(34)  Mechanisms to support Operational, Administrative, and          Management control of the routing architecture and protocols          must be designed into the original fabric of the architecture.3.6.5.1.  Simple Policy Management   The basic aims of this specification are:   -  to require less manual configuration than today, and   -  to satisfy the requirements for both easy handling and maximum      control.  That is:      -  All the information should be available,      -  but should not be visible except for when necessary.      -  Policies themselves should be advertised and not only the         result of policy, and      -  policy-conflict resolution must be provided.   R(35)  The routing system must provide management of the system by          means of policies.  For example, policies that can be          expressed in terms of the business and services implemented on          the network and reflect the operation of the network in terms          of the services affected.Doria, et al.                   Historic                       [Page 50]

RFC 5772                IRTF Routing Requirements          February 2010                Editors' Note: This requirement is optimistic in that it                implies that it is possible to get operators to                cooperate even if it is seen by them to be against their                business practices.   R(36)  The distribution of policies must be amenable to scoping to          protect proprietary policies that are not relevant beyond the          local set of domains.3.6.5.2.  Startup and Maintenance of Routers   A major problem in today's networks is the need to perform initial   configuration on routers from a local interface before a remote   management system can take over.  It is not clear that this imposes   any requirements on the routing architecture beyond what is needed   for a ZeroConf host.   Similarly, maintenance and upgrade of routers can cause major   disruptions to the network routing because the routing system and   management of routers is not organized to minimize such disruption.   Some improvements have been made, such as graceful restart mechanisms   in protocols, but more needs to be done.   R(37)  The routing system and routers should provide mechanisms that          minimize the disruption to the network caused by maintenance          and upgrades of software and hardware.  This requirement          recognizes that some of the capabilities needed are outside          the scope of the routing architecture (e.g., minimum impact          software upgrade).3.6.6.  Provability   R(38)  The routing system and its component protocols must be          demonstrated to be locally convergent under the permitted          range of parameter settings and policy options that the          operator(s) can select.   There are various methods for demonstration and proof that include,   but are not limited to: mathematical proof, heuristic, and pattern   recognition.  No requirement is made on the method used for   demonstrating local convergence properties.   R(39)  Routing protocols employed by the routing system and the          overall routing system should be resistant to bad routing          policy decisions made by operators.Doria, et al.                   Historic                       [Page 51]

RFC 5772                IRTF Routing Requirements          February 2010   Tools are needed to check compatibility of routing policies.  While   these tools are not part of the routing architecture, the mechanisms   to support such tools are.   Routing policies are compatible if their interaction does not cause   instability.  A domain or group of domains in a system is defined as   being convergent, either locally or globally, if and only if, after   an exchange of routing information, routing tables reach a stable   state that does not change until the routing policies or the topology   changes again.   To achieve the above-mentioned goals:   R(40)  The routing system must provide a mechanism to publish and          communicate policies so that operational coordination and          fault isolation are possible.   Tools are required that verify the stability characteristics of the   routing system in specified parts of the Internet.  The tools should   be efficient (fast) and have a broad scope of operation (check large   portions of Internet).  While these tools are not part of the   architecture, developing them is in the interest of the architecture   and should be defined as a Routing Research Group activity while   research on the architecture is in progress.   Tools analyzing routing policies can be applied statically or   (preferably) dynamically.  A dynamic solution requires tools that can   be used for run time checking for oscillations that arise from policy   conflicts.  Research is needed to find an efficient solution to the   dynamic checking of oscillations.3.6.7.  Traffic Engineering   The ability to do traffic engineering and to get the feedback from   the network to enable traffic engineering should be included in the   future domain architecture.  Though traffic engineering has many   definitions, it is, at base, another alternative or extension for the   path selection mechanisms of the routing system.  No fundamental   changes to the requirements are needed, but the iterative processes   involved in traffic engineering may require some additional   capabilities and state in the network.   Traffic engineering typically involves a combination of off-line   network planning and administrative control functions in which the   expected and measured traffic flows are examined, resulting in   changes to static configurations and policies in the routing system.Doria, et al.                   Historic                       [Page 52]

RFC 5772                IRTF Routing Requirements          February 2010   During operations, these configurations control the actual flow of   traffic and affect the dynamic path selection mechanisms; the results   are measured and fed back into further rounds of network planning.3.6.7.1.  Support for, and Provision of, Traffic Engineering Tools   At present, there is an almost total lack of effective traffic   engineering tools, whether in real time for network control or off-   line for network planning.  The routing system should encourage the   provision of such tools.   R(41)  The routing system must generate statistical and accounting          information in such a way that traffic engineering and network          planning tools can be used in both real-time and off-line          planning and management.3.6.7.2.  Support of Multiple Parallel Paths   R(42)  The routing system must support the controlled distribution          over multiple links or paths of traffic toward the same          destination.  This applies to domains with two or more          connections to the same neighbor domain, and to domains with          connections to more than one neighbor domain.  The paths need          not have the same metric.   R(43)  The routing system must support forwarding over multiple          parallel paths when available.  This support should extend to          cases where the offered traffic is known to exceed the          available capacity of a single link, and to the cases where          load is to be shared over paths for cost or resiliency          reasons.   R(44)  Where traffic is forwarded over multiple parallel paths, the          routing system must, so far as is possible, avoid the          reordering of packets in individual micro-flows.   R(45)  The routing system must have mechanisms to allow the traffic          to be reallocated back onto a single path when multiple paths          are not needed.3.6.7.3.  Peering Support   R(46)  The routing system must support peer-level connectivity as          well as hierarchical connections between domains.Doria, et al.                   Historic                       [Page 53]

RFC 5772                IRTF Routing Requirements          February 2010   The network is becoming increasingly complex, with private peering   arrangements set up between providers at every level of the hierarchy   of service providers and even by certain large enterprises, in the   form of dedicated extranets.   R(47)  The routing system must facilitate traffic engineering of peer          routes so that traffic can be readily constrained to travel as          the network operators desire, allowing optimal use of the          available connectivity.3.6.8.  Support for Middleboxes   One of our assumptions is that NATs and other middle-boxes such as   firewalls, web proxies, and address family translators (e.g., IPv4 to   IPv6) are here to stay.   R(48)  The routing system should work in conjunction with middle-          boxes, e.g., NAT, to aid in bi-directional connectivity          without compromising the additional opacity and privacy that          the middle-boxes offer.   This problem is closely analogous to the abstraction problem, which   is already under discussion for the interchange of routing   information between domains.3.7.  Performance Requirements   Over the past several years, the performance of the routing system   has frequently been discussed.  The requirements that derive from   those discussions are listed below.  The specific values for these   performance requirements are left for further discussion.   R(49)  The routing system must support domains of at least N systems.          A system is taken to mean either an individual router or a          domain.   R(50)  Local convergence should occur within T units of time.   R(51)  The routing system must be measurably reliable.  The measure          of reliability remains a research question.   R(52)  The routing system must be locally stable to a measured          degree.  The degree of measurability remains a research issue.   R(53)  The routing system must be globally stable to a measured          degree.  The degree of measurability remains a research issue.Doria, et al.                   Historic                       [Page 54]

RFC 5772                IRTF Routing Requirements          February 2010   R(54)  The routing system should scale to an indefinitely large          number of domains.   There has been very little data or statistical evidence for many of   the performance claims made in the past.  In recent years, several   efforts have been initiated to gather data and do the analyses   required to make scientific assessments of performance issues and   requirements.  In order to complete this section of the requirements   analysis, the data and analyses from these studies needs to be   gathered and collated into this document.  This work has been started   but has yet to be completed.      Editors' Note: This work was never completed due to corporate      reorganizations.3.8.  Backward Compatibility (Cutover) and Maintainability   This area poses a dilemma.  On one hand, it is an absolute   requirement that:   R(55)  The introduction of the routing system must not require any          flag days.   R(56)  The network currently in place must continue to run at least          as well as it does now while the new network is being          installed around it.   However, at the same time, it is also an requirement that:   R(57)  The new architecture must not be limited by the restrictions          that plague today's network.   It has to be admitted that R(57) is not a well-defined requirement,   because we have not fully articulated what the restrictions might be.   Some of these restrictions can be derived by reading the discussions   for the positive requirements above.  It would be a useful exercise   to explicitly list all the restrictions and irritations with which we   wish to do away.  Further, it would be useful to determine if these   restrictions can currently be removed at a reasonable cost or whether   we are actually condemned to live with them.   Those restrictions cannot be allowed to become permanent baggage on   the new architecture.  If they do, the effort to create a new system   will come to naught.  It may, however, be necessary to live with some   of them temporarily for practical reasons while providing an   architecture that will eventually allow them to be removed.  The last   three requirements have significance not only for the transitionDoria, et al.                   Historic                       [Page 55]

RFC 5772                IRTF Routing Requirements          February 2010   strategy but also for the architecture itself.  They imply that it   must be possible for an internet such as today's BGP-controlled   network, or one of its ASs, to exist as a domain within the new FDR.3.9.  Security Requirements   As previously discussed, one of the major changes that has overtaken   the Internet since its inception is the erosion of trust between end   users making use of the net, between those users and the suppliers of   services, and between the multiplicity of providers.  Hence,   security, in all its aspects, will be much more important in the FDR.   It must be possible to secure the routing communication.   R(58)  The communicating entities must be able to identify who sent          and who received the information (authentication).   R(59)  The communicating entities must be able to verify that the          information has not been changed on the way (integrity).   Security is more important in inter-domain routing where the operator   has no control over the other domains, than in intra-domain routing   where all the links and the nodes are under the administration of the   operator and can be expected to share a trust relationship.  This   property of intra-domain trust, however, should not be taken for   granted:   R(60)  Routing communications must be secured by default, but an          operator must have the option to relax this requirement within          a domain where analysis indicates that other means (such as          physical security) provide an acceptable alternative.   R(61)  The routing communication mechanism must be robust against          denial-of-service attacks.   R(62)  It should be possible to verify that the originator of the          information was authorized to generate the information.   Further considerations that may impose further requirements include:   -  whether no one else but the intended recipient is able to access      (privacy) or understand (confidentiality) the information,   -  whether it is possible to verify that all the information has been      received and that the two parties agree on what was sent      (validation and non-repudiation),Doria, et al.                   Historic                       [Page 56]

RFC 5772                IRTF Routing Requirements          February 2010   -  whether there is a need to separate security of routing from      security of forwarding, and   -  whether traffic flow security is needed (i.e., whether there is      value in concealing who can connect to whom, and what volumes of      data are exchanged).   Securing the BGP session, as done today, only secures the exchange of   messages from the peering domain, not the content of the information.   In other words, we can confirm that the information we got is what   our neighbor really sent us, but we do not know whether or not this   information (that originated in some remote domain) is true.   A decision has to be made on whether to rely on chains of trust (we   trust our peers who trust their peers who..), or whether we also need   authentication and integrity of the information end-to-end.  This   information includes both routes and addresses.  There has been   interest in having digital signatures on originated routes as well as   countersignatures by address authorities to confirm that the   originator has authority to advertise the prefix.  Even understanding   who can confirm the authority is non-trivial, as it might be the   provider who delegated the prefix (with a whole chain of authority   back to ICANN) or it may be an address registry.  Where a prefix   delegated by a provider is being advertised through another provider   as in multi-homing, both may have to be involved to confirm that the   prefix may be advertised through the provider who doesn't have any   interest in the prefix!   R(63)  The routing system must cooperate with the security policies          of middle-boxes whenever possible.   This is likely to involve further requirements for abstraction of   information.  For example, a firewall that is seeking to minimize   interchange of information that could lead to a security breach.  The   effect of such changes on the end-to-end principle should be   carefully considered as discussed in [Blumenthal01].   R(64)  The routing system must be capable of complying with local          legal requirements for interception of communication.3.10.  Debatable Issues   This section covers issues that need to be considered and resolved in   deciding on a Future Domain Routing architecture.  While they can't   be described as requirements, they do affect the types of solution   that are acceptable.  The discussions included below are very open-   ended.Doria, et al.                   Historic                       [Page 57]

RFC 5772                IRTF Routing Requirements          February 20103.10.1.  Network Modeling   The mathematical model that underlies today's routing system uses a   graph representation of the network.  Hosts, routers, and other   processing boxes are represented by nodes and communications links by   arcs.  This is a topological model in that routing does not need to   directly model the physical length of the links or the position of   the nodes; the model can be transformed to provide a convenient   picture of the network by adjusting the lengths of the arcs and the   layout of the nodes.  The connectivity is preserved and routing is   unaffected by this transformation.   The routing algorithms in traditional routing protocols utilize a   small number of results from graph theory.  It is only recently that   additional results have been employed to support constraint-based   routing for traffic engineering.   The naturalness of this network model and the "fit" of the graph   theoretical methods may have tended to blind us to alternative   representations and inhibited us from seeking alternative strands of   theoretical thinking that might provide improved results.   We should not allow this habitual behavior to stop us from looking   for alternative representations and algorithms; topological   revolutions are possible and allowed, at least in theory.3.10.2.  System Modeling   The assumption that object modeling of a system is an essential first   step to creating a new system is still novel in this context.   Frequently, the object modeling effort becomes an end in itself and   does not lead to system creation.  But there is a balance, and a lot   that can be discovered in an ongoing effort to model a system such as   the Future Domain Routing system.  It is recommended that this   process be included in the requirements.  It should not, however, be   a gating event to all other work.   Some of the most important realizations will occur during the process   of determining the following:   -  Object classification   -  Relationships and containment   -  Roles and RulesDoria, et al.                   Historic                       [Page 58]

RFC 5772                IRTF Routing Requirements          February 20103.10.3.  One, Two, or Many Protocols   There has been a lot of discussion of whether the FDR protocol   solution should consist of one (probably new) protocol, two (intra-   and inter-domain) protocols, or many protocols.  While it might be   best to have one protocol that handles all situations, this seems   improbable.  On the other hand, maintaining the "strict" division   evident in the network today between the IGP and EGP may be too   restrictive an approach.  Given this, and the fact that there are   already many routing protocols in use, the only possible answer seems   to be that the architecture should support many protocols.  It   remains an open issue, one for the solution, to determine if a new   protocol needs to be designed in order to support the highest goals   of this architecture.  The expectation is that a new protocol will be   needed.3.10.4.  Class of Protocol   If a new protocol is required to support the FDR architecture, the   question remains open as to what kind of protocol this ought to be.   It is our expectation that a map distribution protocol will be   required to augment the current path-vector protocol and shortest   path first protocols.3.10.5.  Map Abstraction   Assuming that a map distribution protocol, as defined in [RFC1992] is   required, what are the requirements on this protocol?  If every   detail is advertised throughout the Internet, there will be a lot of   information.  Scalable solutions require abstraction.   -  If we summarize too much, some information will be lost on the      way.   -  If we summarize too little, then more information than required is      available, contributing to scaling limitations.   -  One can allow more summarization, if there also is a mechanism to      query for more details within policy limits.   -  The basic requirement is not that the information shall be      advertised, but rather that the information shall be available to      those who need it.  We should not presuppose a solution where      advertising is the only possible mechanism.Doria, et al.                   Historic                       [Page 59]

RFC 5772                IRTF Routing Requirements          February 20103.10.6.  Clear Identification for All Entities   As in all other fields, the words used to refer to concepts and to   describe operations about routing are important.  Rather than   describe concepts using terms that are inaccurate or rarely used in   the real world of networking, it is necessary to make an effort to   use the correct words.  Many networking terms are used casually, and   the result is a partial or incorrect understanding of the underlying   concept.  Entities such as nodes, interfaces, subnetworks, tunnels,   and the grouping concepts such as ASs, domains, areas, and regions,   need to be clearly identified and defined to avoid confusion.   There is also a need to separate identifiers (what or who) from   locators (where) from routes (how to reach).      Editors' Note: Work was undertaken in the shim6 working group of      the IETF on this sort of separation.  This work needs to be taken      into account in any new routing architecture.3.10.7.  Robustness and Redundancy   The routing association between two domains should survive even if   some individual connection between two routers goes down.   The "session" should operate between logical "routing entities" on   each domain side, and not necessarily be bound to individual routers   or addresses.  Such a logical entity can be physically distributed   over multiple network elements.  Or, it can reside in a single   router, which would default to the current situation.3.10.8.  Hierarchy   A more flexible hierarchy with more levels and recursive groupings in   both upward and downward directions allows more structured routing.   The consequence is that no single level will get too big for routers   to handle.   On the other hand, it appears that the real-world Internet is   becoming less hierarchical, so that it will be increasingly difficult   to use hierarchy to control scaling.   Note that groupings can look different depending on which aspect we   use to define them.  A Diffserv area, an MPLS domain, a trusted   domain, a QoS area, a multicast domain, etc., do not always coincide;   nor are they strict hierarchical subsets of each other.  The basic   distinction at each level is "this grouping versus everything   outside".Doria, et al.                   Historic                       [Page 60]

RFC 5772                IRTF Routing Requirements          February 20103.10.9.  Control Theory   Is it possible to apply a control theory framework to analyze the   stability of the control system of the whole network domain, with   regard to, e.g., convergence speed and the frequency response, and   then use the results from that analysis to set the timers and other   protocol parameters?   Control theory could also play a part in QoS routing, by modifying   current link-state protocols with link costs dependent on load and   feedback.  Control theory is often used to increase the stability of   dynamic systems.   It might be possible to construct a new, totally dynamic routing   protocol solely on a control theoretic basis, as opposed to the   current protocols that are based in graph theory and static in   nature.3.10.10.  Byzantium   Is solving the Byzantine Generals problem a requirement?  This is the   problem of reaching a consensus among distributed units if some of   them give misleading answers.  The current intra-domain routing   system is, at one level, totally intolerant of misleading   information.  However, the effect of different sorts of misleading or   incorrect information has vastly varying results, from total collapse   to purely local disconnection of a single domain.  This sort of   behavior is not very desirable.   There are, possibly, other network robustness issues that must be   researched and resolved.3.10.11.  VPN Support   Today, BGP is also used for VPNs, for example, as described inRFC4364 [RFC4364].   Internet routing and VPN routing have different purposes and most   often exchange different information between different devices.  Most   Internet routers do not need to know VPN-specific information.  The   concepts should be clearly separated.   But when it comes to the mechanisms, VPN routing can share the same   protocol as ordinary Internet routing; it can use a separate instance   of the same protocol or it can use a different protocol.  All   variants are possible and have their own merits.  These requirements   are silent on this issue.Doria, et al.                   Historic                       [Page 61]

RFC 5772                IRTF Routing Requirements          February 20103.10.12.  End-to-End Reliability   The existing Internet architecture neither requires nor provides end-   to-end reliability of control information dissemination.  There is,   however, already a requirement for end-to-end reliability of control   information distribution, i.e., the ends of the VPN established need   to have an acknowledgment of the success in setting up the VPN.   While it is not necessarily the function of a routing architecture to   provide end-to-end reliability for this kind of purpose, we must be   clear that end-to-end reliability becomes a requirement if the   network has to support such reliable control signaling.  There may be   other requirements that derive from requiring the FDR to support   reliable control signaling.3.10.13.  End-to-End Transparency   The introduction of private addressing schemes, Network Address   Translators, and firewalls has significantly reduced the end-to-end   transparency of the network.  In many cases, the network is also no   longer symmetric, so that communication between two addresses is   possible if the communication session originates from one end but not   from the other.  This impedes the deployment of new peer-to-peer   services and some "push" services where the server in a client-   server arrangement originates the communication session.  Whether a   new routing system either can or should seek to restore this   transparency is an open issue.   A related issue is the extent to which end-user applications should   seek to control the routing of communications to the rest of the   network.4.  Security Considerations   We address security issues in the individual requirements.  We do   require that the architecture and protocols developed against this   set of requirements be "secure".  Discussion of specific security   issues can be found in the following sections:   o  Group A: Routing System Security -Section 2.1.9   o  Group A: End Host Security -Section 2.1.10   o  Group A: Routing Information Policies -Section 2.1.11.1   o  Group A: Abstraction -Section 2.1.16   o  Group A: Robustness -Section 2.1.18Doria, et al.                   Historic                       [Page 62]

RFC 5772                IRTF Routing Requirements          February 2010   o  Group B: Protection against Denial-of-Service and Other Security      Attacks -Section 3.2.3.8   o  Group B: Commercial Service Providers -Section 3.3.1.1   o  Group B: The Federated Environment -Section 3.4.1   o  Group B: Path Advertisement -Section 3.6.2.2   o  Group B: Security Requirements -Section 3.95.  IANA Considerations   This document is a set of requirements from which a new routing and   addressing architecture may be developed.  From that architecture, a   new protocol, or set of protocols, may be developed.   While this note poses no new tasks for IANA, the architecture and   protocols developed from this document probably will have issues to   be dealt with by IANA.6.  Acknowledgments   This document is the combined effort of two groups in the IRTF.   Group A, which was formed by the IRTF Routing Research chairs, and   Group B, which was self-formed and later was folded into the IRTF   Routing Research Group.  Each group has it own set of   acknowledgments.   Group A Acknowledgments      This originated in the IRTF Routing Research Group's sub-group on      Inter-domain routing requirements.  The members of the group were:           Abha Ahuja                      Danny McPherson           J. Noel Chiappa                 David Meyer           Sean Doran                      Mike O'Dell           JJ Garcia-Luna-Aceves           Andrew Partan           Susan Hares                     Radia Perlman           Geoff Huston                    Yakov Rehkter           Frank Kastenholz                John Scudder           Dave Katz                       Curtis Villamizar           Tony Li                         Dave Ward      We also appreciate the comments and review received from Ran      Atkinson, Howard Berkowitz, Randy Bush, Avri Doria, Jeffery Haas,      Dmitri Krioukov, Russ White, and Alex Zinin.  Special thanks to      Yakov Rehkter for contributing text and to Noel Chiappa.Doria, et al.                   Historic                       [Page 63]

RFC 5772                IRTF Routing Requirements          February 2010   Group B Acknowledgments      The document is derived from work originally produced by Babylon.      Babylon was a loose association of individuals from academia,      service providers, and vendors whose goal was to discuss issues in      Internet routing with the intention of finding solutions for those      problems.      The individual members who contributed materially to this document      are: Anders Bergsten, Howard Berkowitz, Malin Carlzon, Lenka Carr      Motyckova, Elwyn Davies, Avri Doria, Pierre Fransson, Yong Jiang,      Dmitri Krioukov, Tove Madsen, Olle Pers, and Olov Schelen.      Thanks also go to the members of Babylon and others who did      substantial reviews of this material.  Specifically, we would like      to acknowledge the helpful comments and suggestions of the      following individuals: Loa Andersson, Tomas Ahlstrom, Erik Aman,      Thomas Eriksson, Niklas Borg, Nigel Bragg, Thomas Chmara, Krister      Edlund, Owe Grafford, Torbjorn Lundberg, Jeremy Mineweaser,      Jasminko Mulahusic, Florian-Daniel Otel, Bernhard Stockman, Tom      Worster, and Roberto Zamparo.      In addition, the authors are indebted to the folks who wrote all      the references we have consulted in putting this paper together.      This includes not only the references explicitly listed below, but      also those who contributed to the mailing lists we have been      participating in for years.      The editors thank Lixia Zhang, as IRSG document shepherd, for her      help and her perseverance, without which this document would never      have been published.      Finally, it is the editors who are responsible for any lack of      clarity, any errors, glaring omissions or misunderstandings.Doria, et al.                   Historic                       [Page 64]

RFC 5772                IRTF Routing Requirements          February 20107.  Informative References   [Blumenthal01]              Blumenthal, M. and D. Clark, "Rethinking the design of the              Internet: The end to end arguments vs. the brave new              world", May 2001,              <http://dspace.mit.edu/handle/1721.1/1519>.   [Broido02]              Broido, A., Nemeth, E., Claffy, K., and C. Elves,              "Internet Expansion, Refinement and Churn", February 2002.   [CIDR]     Telcordia Technologies, "CIDR Report",              <http://www.cidr-report.org/>.   [Chiappa02]              Chiappa, N., "A New IP Routing and Addressing              Architecture", July 1991,              <http://ana-3.lcs.mit.edu/~jnc/nimrod/overview.txt>.   [Clark91]  Clark, D., "Quote reportedly from IETF Plenary              discussion", 1991.   [DiffservAR]              Seddigh, N., Nandy, B., and J. Heinanen, "An Assured Rate              Per-Domain Behaviour for Differentiated Services", Work              in Progress, July 2001.   [DiffservVW]              Jacobson, V., Nichols, K., and K. Poduri, "The 'Virtual              Wire' Per-Domain Behavior", Work in Progress, July 2000.   [Griffin99]              Griffin, T. and G. Wilfong, "An Analysis of BGP              Convergence Properties", SIGCOMM 1999.   [ISO10747]              ISO/IEC, "Protocol for Exchange of Inter-Domain Routeing              Information among Intermediate Systems to Support              Forwarding of ISO 8473 PDUs", International Standard              10747 ISO/IEC JTC 1, Switzerland, 1993.   [InferenceSRLG]              Papadimitriou, D., Poppe, F., J. Jones, J., S.              Venkatachalam, S., S. Dharanikota, S., Jain, R., Hartani,              R., and D. Griffith, "Inference of Shared Risk Link              Groups", Work in Progress, November 2001.Doria, et al.                   Historic                       [Page 65]

RFC 5772                IRTF Routing Requirements          February 2010   [ODell01]  O'Dell, M., "Private Communication", 2001.   [RFC1126]  Little, M., "Goals and functional requirements for inter-              autonomous system routing",RFC 1126, October 1989.   [RFC1726]  Partridge, C. and F. Kastenholz, "Technical Criteria for              Choosing IP The Next Generation (IPng)",RFC 1726,              Dec 1994.   [RFC1992]  Castineyra, I., Chiappa, N., and M. Steenstrup, "The              Nimrod Routing Architecture",RFC 1992, August 1996.   [RFC2071]  Ferguson, P. and H. Berkowitz, "Network Renumbering              Overview: Why would I want it and what is it anyway?",RFC 2071, January 1997.   [RFC2072]  Berkowitz, H., "Router Renumbering Guide",RFC 2072,              January 1997.   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol              Label Switching Architecture",RFC 3031, January 2001.   [RFC3221]  Huston, G., "Commentary on Inter-Domain Routing in the              Internet",RFC 3221, December 2001.   [RFC3260]  Grossman, D., "New Terminology and Clarifications for              Diffserv",RFC 3260, April 2002.   [RFC3344]  Perkins, C., "IP Mobility Support.",RFC 3344,              August 2002.   [RFC3345]  McPherson, D., Gill, V., Walton, D., and A. Retana,              "Border Gateway Protocol (BGP) Persistent Route              Oscillation Condition",RFC 3345, August 2002.   [RFC3471]  Berger, L., "Generalized Multi-Protocol Label Switching              (GMPLS) Signaling Functional Description",RFC 3471,              January 2003.   [RFC3963]  Devarapalli, V., Wakikawa, R., Petrescu, A., and P.              Thubert, "Network Mobility (NEMO) Basic Support Protocol",RFC 3963, January 2005.   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private              Networks (VPNs)",RFC 4364, February 2006.   [RFC5773]  Davies, E. and A. Doria, "Analysis of Inter-Domain Routing              Requirements and History",RFC 5773, February 2010.Doria, et al.                   Historic                       [Page 66]

RFC 5772                IRTF Routing Requirements          February 2010   [Wroclawski95]              Wroclowski, J., "The Metanet White Paper - Workshop on              Research Directions for the Next Generation Internet",              1995.   [netconf-charter]              Internet Engineering Task Force, "IETF Network              Configuration working group", 2005,              <http://www.ietf.org/html.charters/netconf-charter.html>.   [policy-charter02]              Internet Engineering Task Force, "IETF Policy working              group", 2002, <http://www.ietf.org/html.charters/OLD/policy-charter.html>.   [rap-charter02]              Internet Engineering Task Force, "IETF Resource Allocation              Protocol working group", 2002,              <http://www.ietf.org/html.charters/OLD/rap-charter.html>.   [snmpconf-charter02]              Internet Engineering Task Force, "IETF Configuration              management with SNMP working group", 2002, <http://www.ietf.org/html.charters/OLD/snmpconf-charter.html>.Doria, et al.                   Historic                       [Page 67]

RFC 5772                IRTF Routing Requirements          February 2010Authors' Addresses   Avri Doria   LTU   Lulea  971 87   Sweden   Phone: +46 73 277 1788   EMail: avri@ltu.se   Elwyn B. Davies   Folly Consulting   Soham, Cambs   UK   Phone: +44 7889 488 335   EMail: elwynd@dial.pipex.com   Frank Kastenholz   BBN Technologies   10 Moulton St.   Cambridge, MA  02183   USA   Phone: +1 617 873 8047   EMail: frank@bbn.comDoria, et al.                   Historic                       [Page 68]