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Network Working Group                                      D. Meyer, Ed.Request for Comments: 4984                                 L. Zhang, Ed.Category: Informational                                     K. Fall, Ed.                                                          September 2007Report from the IAB Workshop on Routing and AddressingStatus of This Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Abstract   This document reports the outcome of the Routing and Addressing   Workshop that was held by the Internet Architecture Board (IAB) on   October 18-19, 2006, in Amsterdam, Netherlands.  The primary goal of   the workshop was to develop a shared understanding of the problems   that the large backbone operators are facing regarding the   scalability of today's Internet routing system.  The key workshop   findings include an analysis of the major factors that are driving   routing table growth, constraints in router technology, and the   limitations of today's Internet addressing architecture.  It is hoped   that these findings will serve as input to the IETF community and   help identify next steps towards effective solutions.   Note that this document is a report on the proceedings of the   workshop.  The views and positions documented in this report are   those of the workshop participants and not of the IAB.  Furthermore,   note that work on issues related to this workshop report is   continuing, and this document does not intend to reflect the   increased understanding of issues nor to discuss the range of   potential solutions that may be the outcome of this ongoing work.Meyer, et al.                Informational                      [Page 1]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007Table of Contents1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .32.  Key Findings from the Workshop . . . . . . . . . . . . . . . .42.1.  Problem #1: The Scalability of the Routing System  . . . .42.1.1.  Implications of DFZ RIB Growth . . . . . . . . . . . .52.1.2.  Implications of DFZ FIB Growth . . . . . . . . . . . .62.2.  Problem #2: The Overloading of IP Address Semantics  . . .62.3.  Other Concerns . . . . . . . . . . . . . . . . . . . . . .72.4.  How Urgent Are These Problems? . . . . . . . . . . . . . .83.  Current Stresses on the Routing and Addressing System  . . . .83.1.  Major Factors Driving Routing Table Growth . . . . . . . .83.1.1.  Avoiding Renumbering  . . . . . . . . . . . . . . . . .93.1.2.  Multihoming  . . . . . . . . . . . . . . . . . . . . .103.1.3.  Traffic Engineering  . . . . . . . . . . . . . . . . .103.2.  IPv6 and Its Potential Impact on Routing Table Size  . . .114.  Implications of Moore's Law on the Scaling Problem . . . . . .114.1.  Moore's Law  . . . . . . . . . . . . . . . . . . . . . . .124.1.1.  DRAM . . . . . . . . . . . . . . . . . . . . . . . . .134.1.2.  Off-chip SRAM  . . . . . . . . . . . . . . . . . . . .134.2.  Forwarding Engines . . . . . . . . . . . . . . . . . . . .134.3.  Chip Costs . . . . . . . . . . . . . . . . . . . . . . . .144.4.  Heat and Power . . . . . . . . . . . . . . . . . . . . . .144.5.  Summary  . . . . . . . . . . . . . . . . . . . . . . . . .155.  What Is on the Horizon . . . . . . . . . . . . . . . . . . . .155.1.  Continual Growth . . . . . . . . . . . . . . . . . . . . .155.2.  Large Numbers of Mobile Networks . . . . . . . . . . . . .165.3.  Orders of Magnitude Increase in Mobile Edge Devices  . . .166.  What Approaches Have Been Investigated . . . . . . . . . . . .176.1.  Lessons from MULTI6  . . . . . . . . . . . . . . . . . . .176.2.  SHIM6: Pros and Cons . . . . . . . . . . . . . . . . . . .186.3.  GSE/Indirection Solutions: Costs and Benefits  . . . . . .196.4.  Future for Indirection . . . . . . . . . . . . . . . . . .207.  Problem Statements . . . . . . . . . . . . . . . . . . . . . .217.1.  Problem #1: Routing Scalability  . . . . . . . . . . . . .217.2.  Problem #2: The Overloading of IP Address Semantics  . . .227.2.1.  Definition of Locator and Identifier . . . . . . . . .227.2.2.  Consequence of Locator and Identifier Overloading  . .23       7.2.3.  Traffic Engineering and IP Address Semantics               Overload . . . . . . . . . . . . . . . . . . . . . . .247.3.  Additional Issues  . . . . . . . . . . . . . . . . . . . .247.3.1.  Routing Convergence  . . . . . . . . . . . . . . . . .247.3.2.  Misaligned Costs and Benefits  . . . . . . . . . . . .257.3.3.  Other Concerns . . . . . . . . . . . . . . . . . . . .257.4.  Problem Recognition  . . . . . . . . . . . . . . . . . . .268.  Criteria for Solution Development  . . . . . . . . . . . . . .268.1.  Criteria on Scalability  . . . . . . . . . . . . . . . . .268.2.  Criteria on Incentives and Economics . . . . . . . . . . .27Meyer, et al.                Informational                      [Page 2]

RFC 4984          IAB Workshop on Routing & Addressing    September 20078.3.  Criteria on Timing . . . . . . . . . . . . . . . . . . . .288.4.  Consideration on Existing Systems  . . . . . . . . . . . .288.5.  Consideration on Security  . . . . . . . . . . . . . . . .298.6.  Other Criteria . . . . . . . . . . . . . . . . . . . . . .298.7.  Understanding the Tradeoff . . . . . . . . . . . . . . . .299.  Workshop Recommendations . . . . . . . . . . . . . . . . . . .3010. Security Considerations  . . . . . . . . . . . . . . . . . . .3111. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .3112. Informative References . . . . . . . . . . . . . . . . . . . .31Appendix A.  Suggestions for Specific Steps  . . . . . . . . . . .35Appendix B.  Workshop Participants . . . . . . . . . . . . . . . .35Appendix C.  Workshop Agenda . . . . . . . . . . . . . . . . . . .36Appendix D.  Presentations . . . . . . . . . . . . . . . . . . . .371.  Introduction   It is commonly recognized that today's Internet routing and   addressing system is facing serious scaling problems.  The ever-   increasing user population, as well as multiple other factors   including multi-homing, traffic engineering, and policy routing, have   been driving the growth of the Default Free Zone (DFZ) routing table   size at an increasing and potentially alarming rate [DFZ][BGT04].   While it has been long recognized that the existing routing   architecture may have serious scalability problems, effective   solutions have yet to be identified, developed, and deployed.   As a first step towards tackling these long-standing concerns, the   IAB held a "Routing and Addressing Workshop" in Amsterdam,   Netherlands on October 18-19, 2006.  The main objectives of the   workshop were to identify existing and potential factors that have   major impacts on routing scalability, and to develop a concise   problem statement that may serve as input to a set of follow-on   activities.  This document reports on the outcome from that workshop.   The remainder of the document is organized as follows:Section 2   provides an executive summary of the workshop findings.Section 3   describes the sources of stress in the current global routing and   addressing system.Section 4 discusses the relationship between   Moore's law and our ability to build large routers.Section 5   describes a few foreseeable factors that may exacerbate the current   problems outlined inSection 2.Section 6 describes previous work in   this area.Section 7 describes the problem statements in more   detail, andSection 8 discusses the criteria that constrain the   solution space.  Finally,Section 9 summarizes the recommendations   made by the workshop participants.Meyer, et al.                Informational                      [Page 3]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   The workshop participant list is attached inAppendix B.  The agenda   can be found inAppendix C, andAppendix D provides pointers to the   presentations from the workshop.   Finally, note that this document is a report on the outcome of the   workshop, not an official document of the IAB.  Any opinions   expressed are those of the workshop participants and not of the IAB.2.  Key Findings from the Workshop   This section provides a concise summary of the key findings from the   workshop.  While many other aspects of a routing and addressing   system were discussed, the first two problems described in this   section were deemed the most important ones by the workshop   participants.   The clear, highest-priority takeaway from the workshop is the need to   devise a scalable routing and addressing system, one that is scalable   in the face of multihoming, and that facilitates a wide spectrum of   traffic engineering (TE) requirements.  Several scalability problems   of the current routing and addressing systems were discussed, most   related to the size of the DFZ routing table (frequently referred to   as the Routing Information Base, or RIB) and its implications.  Those   implications included (but were not limited to) the sizes of the DFZ   RIB and FIB (the Forwarding Information Base), the cost of   recomputing the FIB, concerns about the BGP convergence times in the   presence of growing RIB and FIB sizes, and the costs and power (and   hence heat dissipation) properties of the hardware needed to route   traffic in the core of the Internet.2.1.  Problem #1: The Scalability of the Routing System   The shape of the growth curve of the DFZ RIB has been the topic of   much research and discussion since the early days of the Internet   [H03].  There have been various hypotheses regarding the sources of   this growth.  The workshop identified the following factors as the   main driving forces behind the rapid growth of the DFZ RIB:   o  Multihoming,   o  Traffic engineering,   o  Non-aggregatable address allocations (a big portion of which is      inherited from historical allocations), and   o  Business events, such as mergers and acquisitions.Meyer, et al.                Informational                      [Page 4]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   All of the above factors can lead to prefix de-aggregation and/or the   injection of unaggregatable prefixes into the DFZ RIB.  Prefix de-   aggregation leads to an uncontrolled DFZ RIB growth because, absent   some non-topologically based routing technology (for example, Routing   On Flat Labels [ROFL] or any name-independent compact routing   algorithm, e.g., [CNIR]), topological aggregation is the only known   practical approach to control the growth of the DFZ RIB.  The   following section reviews the workshop discussion of the implications   of the growth of the DFZ RIB.2.1.1.  Implications of DFZ RIB Growth   Presentations made at the workshop showed that the DFZ RIB has been   growing at greater than linear rates for several years [DFZ].  While   this has the obvious effects on the requirements for RIB and FIB   memory sizes, the growth driven by prefix de-aggregation also exposes   the core of the network to the dynamic nature of the edges, i.e., the   de-aggregation leads to an increased number of BGP UPDATE messages   injected into the DFZ (frequently referred to as "UPDATE churn").   Consequently, additional processing is required to maintain state for   the longer prefixes and to update the FIB.  Note that, although the   size of the RIB is bounded by the given address space size and the   number of reachable hosts (i.e., O(m*2^32) for IPv4, where <m> is the   average number of peers each BGP router may have), the amount of   protocol activity required to distribute dynamic topological changes   is not.  That is, the amount of BGP UPDATE churn that the network can   experience is essentially unbounded.  It was also noted that the   UPDATE churn, as currently measured, is heavy-tailed [ATNAC2006].   That is, a relatively small number of Autonomous Systems (ASs) or   prefixes are responsible for a disproportionately large fraction of   the UPDATE churn that we observe today.  Furthermore, much of the   churn may turn out to be unnecessary information, possibly due to   instability of edge ASs being injected into the global routing system   [DynPrefix], or arbitrage of some bandwidth pricing model (see [GIH],   for example, or the discussion of the behavior of AS 9121 in   [BGP2005]).   Finally, it was noted by the workshop participants that the UPDATE   churn situation may be exacerbated by the current Regional Internet   Registry (RIR) policy in which end sites are allocated Provider-   Independent (PI) addresses.  These addresses are not topologically   aggregatable, and as such, bring the churn problem described above   into the core routing system.  Of course, as noted by several   participants, the RIRs have no real choice in this matter, as many   enterprises demand PI addresses that allow them to multihome without   the "provider lock" that Provider-Allocated (PA) [PIPA] address space   creates.  Some enterprises also find the renumbering cost associated   with PA address assignments unacceptable.Meyer, et al.                Informational                      [Page 5]

RFC 4984          IAB Workshop on Routing & Addressing    September 20072.1.2.  Implications of DFZ FIB Growth   One surprising outcome of the workshop was the observation made by   Tony Li about the relationship between "Moore's Law" [ML] and our   ability to build cost-effective, high-performance routers (seeAppendix D).  "Moore's Law" is the empirical observation that the   transistor density of integrated circuits, with respect to minimum   component cost, doubles roughly every 24 months.  A commonly held   wisdom is that Moore's law would save the day by ensuring that   technology will continue to scale at historical rates that surpass   the growth rate of routing information handled by core router   hardware.  However, Li pointed out that Moore's Law does not apply to   building high-end routers as far as the cost is concerned.   Moore's Law applies specifically to the high-volume portion of the   semiconductor industry, while the low-volume, customized silicon used   in core routing is well off Moore's Law's cost curve.  In particular,   off-chip SRAM is commonly used for storing FIB data, and the driver   for low-latency, high-capacity SRAM used to be PC cache memory.   However, recently cache memory has been migrating directly onto the   processor die, and cell phones are now the primary driver for off-   chip SRAM.  Given cell phones require low-power, small-capacity parts   that are not applicable to high-end routers, the SRAMs that are   favored for router design are not volume parts and do not track with   Moore's law.2.2.  Problem #2: The Overloading of IP Address Semantics   One of the fundamental assumptions underlying the scalability of   routing systems was eloquently stated by Yakov Rekhter (and is   sometimes referred to as "Rekhter's Law"), namely:        "Addressing can follow topology or topology can follow         addressing. Choose one."   The same idea was expressed by Mike O'Dell's design of an alternate   address architecture for ipv6 [GSE], where the address structure was   designed specifically to enable "aggressive topological aggregation"   to scale the routing system.  Noel Chiappa has also written   extensively on this topic (see, e.g., [EID]).   There is, however, a difficulty in creating (and maintaining) the   kind of congruence envisioned by Rekhter's Law in today's Internet.   The difficulty arises from the overloading of addressing with the   semantics of both "who" (endpoint identifier, as used by transport   layer) and "where" (locators for the routing system); some might also   add that IP addresses are also overloaded with "how" [GIH].  In anyMeyer, et al.                Informational                      [Page 6]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   event, this kind of overloading is felt to have had deep implications   for the scalability of the global routing system.   A refinement to Rekhter's Law, then, is that for the Internet routing   system to scale, an IP address must be assigned in such a way that it   is congruent with the Internet's topology.  However, identifiers are   typically assigned based upon organizational (not topological)   structure and have stability as a desirable property, a "natural   incongruence" arises.  As a result, it is difficult (if not   impossible) to make a single number space serve both purposes   efficiently.   Following the logic of the previous paragraphs, workshop participants   concluded that the so-called "locator/identifier overload" of the IP   address semantics is one of the causes of the routing scalability   problem as we see today.  Thus, a "split" seems necessary to scale   the routing system, although how to actually architect and implement   such a split was not explored in detail.2.3.  Other Concerns   In addition to the issues described inSection 2.1 andSection 2.2,   the workshop participants also identified the following three   pressing, but "second tier", issues.   The first one is a general concern with IPv6 deployment.  It is   commonly believed that the IPv4 address space has put an effective   constraint on the IPv4 RIB growth.  Once this constraint is lifted by   the deployment of IPv6, and in the absence of a scalable routing   strategy, the rapid DFZ RIB size growth problem today can potentially   be exacerbated by IPv6's much larger address space.  The only routing   paradigm available today for IPv6 is a combination of Classless   Inter-Domain Routing (CIDR) [RFC4632] and Provider-Independent (PI)   address allocation strategies [PIPA] (and possibly SHIM6 [SHIM6] when   that technology is developed and deployed).  Thus, the opportunity   exists to create a "swamp" (unaggregatable address space) that can be   many orders of magnitude larger than what we faced with IPv4.  In   short, the advent of IPv6 and its larger address space further   underscores both the concerns raised inSection 2.1, and the   importance of resolving the architectural issue raised inSection 2.2.   The second issue is slow routing convergence.  In particular, the   concern was that growth in the number of routes that service   providers must carry will cause routing convergence to become a   significant problem.Meyer, et al.                Informational                      [Page 7]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   The third issue is the misalignment of costs and benefits in today's   routing system.  While the IETF does not typically consider the   "business model" impacts of various technology choices, many   participants felt that perhaps the time has come to review that   philosophy.2.4.  How Urgent Are These Problems?   There was a fairly universal agreement among the workshop   participants that the problems outlined inSection 2.1 andSection 2.2 need immediate attention.  This need was not because the   participants perceived a looming, well-defined "hit the wall" date,   but rather because these are difficult problems that to date have   resisted solution, are likely to get more unwieldy as IPv6 deployment   proceeds, and the development and deployment of an effective solution   will necessarily take at least a few years.3.  Current Stresses on the Routing and Addressing System   The primary concern voiced by the workshop participants regarding the   state of the current Internet routing system was the rapid growth of   the DFZ RIB.  The number of entries in 2005 ranged from about 150,000   entries to 175,000 entries [BGP2005]; this number has reached 200,000   as of October 2006 [CIDRRPT], and is projected to increase to 370,000   or more within 5 years [Fuller].  Some workshop participants   projected that the DFZ could reach 2 million entries within 15 years,   and there might be as many as 10 million multihomed sites by 2050.   Another related concern was the number of prefixes changed, added,   and withdrawn as a function of time (i.e., BGP UPDATE churn).  This   has a detrimental impact on routing convergence, since UPDATEs   frequently necessitate a re-computation and download of the FIB.  For   example, a BGP router may observe up to 500,000 BGP updates in a   single day [DynPrefix], with the peak arrival rates over 1000 updates   per second.  Such UPDATE churn problems are not limited to DFZ   routes; indeed, the number of internal routes carried by large ISPs   also threatens convergence times, given that such internal routes   include more specifics, Virtual Private Network (VPN) routes, and   other routes that do not appear in the DFZ [ATNAC2006].3.1.  Major Factors Driving Routing Table Growth   The growth of the DFZ RIB results from the addition of more prefixes   to the table.  Although some of this growth is organic (i.e., results   simply from growth of the Internet), a large portion of the growth   results from de-aggregation of address prefixes (i.e., more specificMeyer, et al.                Informational                      [Page 8]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   prefixes).  In this section, we discuss in more detail why this trend   is accelerating and may be cause for concern.   An increasing fraction of the more-specific prefixes found in the DFZ   are due to deliberate action on the part of operators [ATNAC2006].   Motivations to advertise these more-specifics include:   o  Traffic Engineering, where load is balanced across multiple links      through selective advertisement of more-specific routes on      different links to adjust the amount of traffic received on each;      and   o  Attempts to prevent prefix-hijacking by other operators who might      advertise more-specifics to steer traffic toward them; there are      several known instances of this behavior today [BHB06].3.1.1.  Avoiding Renumbering   The workshop participants noted that customers generally prefer to   have PI address space.  Doing so gives them additional agility in   selecting ISPs and helps them avoid the need to renumber.  Many end-   systems use DHCP to assign addresses, so a cursory analysis might   suggest renumbering might involve modification of a modest number of   routers and servers (perhaps rather than end hosts) at a site that   was forced to renumber.   In reality, however, renumbering can be more cumbersome because IP   addresses are often used for other purposes such as access control   lists.  They are also sometimes hard-coded into applications used in   environments where failure of the DNS would be catastrophic (e.g.,   some remote monitoring applications).  Although renumbering may be a   mild inconvenience for some sites and guidelines have been developed   for renumbering a network without a flag day [RFC4192], for others,   the necessary changes are sufficiently difficult so as to make   renumbering effectively impossible.   For these reasons, PI address space is sought by a growing number of   customers.  Current RIR policy reflects this trend, and their policy   is to allocate PI prefixes to all customers who claim a need.   Routing PI prefixes requires additional entries in the DFZ routing   and forwarding tables.  At present, ISPs do not typically charge to   route PI prefixes.  Therefore, the "costs" of the additional   prefixes, in terms of routing table entries and processing overhead,   is born by the global routing system as a whole, rather than directly   by the users of PI space.  The workshop participants observed that no   strong disincentive exists to discourage the increasing use of PI   address space.Meyer, et al.                Informational                      [Page 9]

RFC 4984          IAB Workshop on Routing & Addressing    September 20073.1.2.  Multihoming   Multihoming refers generically to the case in which a site is served   by more than one ISP [RFC4116].  There are several reasons for the   observed increase in multihoming, including the increased reliance on   the Internet for mission- and business-critical applications and the   general decrease in cost to obtain Internet connectivity.   Multihoming provides backup routing -- Internet connection   redundancy; in some circumstances, multihoming is mandatory due to   contract or law.  Multihoming can be accomplished using either PI or   PA address space, and multihomed sites generally have their own AS   numbers (although some do not; this generally occurs when such   customers are statically routed).   A multihomed site using PI address space has its prefixes present in   the forwarding and routing tables of each of its providers.  For PA   space, each prefix allocated from one provider's address allocation   will be aggregatable for that provider but not the others.  If the   addresses are allocated from a 'primary' ISP (i.e., one that the site   uses for routing unless a failure occurs), then the additional   routing table entries only appear during path failures to that   primary ISP.  A problem with multihoming arises when a customer's PA   IP prefixes are advertised by AS(es) other than their 'primary'   ISP's.  Because of the longest-matching prefix forwarding rule, in   this case, the customer's traffic will be directed through the non-   primary AS(s).  In response, the primary ISP is forced to de-   aggregate the customer's prefix in order to keep the customer's   traffic flowing through it instead of the non-primary AS(s).3.1.3.  Traffic Engineering   Traffic engineering (TE) is the act of arranging for certain Internet   traffic to use or avoid certain network paths (that is, TE puts   traffic where capacity exists, or where some set of parameters of the   path is more favorable to the traffic being placed there).  TE is   performed by both ISPs and customer networks, for three primary   reasons:   o  First, as mentioned above, to match traffic with network capacity,      or to spread the traffic load across multiple links (frequently      referred to as "load balancing").   o  Second, to reduce costs by shifting traffic to lower cost paths or      by balancing the incoming and outgoing traffic volume to maintain      appropriate peering relations.Meyer, et al.                Informational                     [Page 10]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   o  Finally, TE is sometimes deployed to enforce certain forms of      policy (e.g., Canadian government traffic may not be permitted to      transit through the United States).   Few tools exist for inter-domain traffic engineering today.  Network   operators usually achieve traffic engineering by "tweaking" the   processing of routing protocols to achieve desired results.  At the   BGP level, if the address range requiring TE is a portion of a larger   PA address aggregate, network operators implementing TE are forced to   de-aggregate otherwise aggregatable prefixes in order to steer the   traffic of the particular address range to specific paths.   In today's highly competitive environment, providers require TE to   maintain good performance and low cost in their networks.  However,   the current practice of TE deployment results in an increase of the   DFZ RIB; although individual operators may have a certain gain from   doing TE, it leads to an overall increased cost for the Internet   routing infrastructure as a whole.3.2.  IPv6 and Its Potential Impact on Routing Table Size   Due to the increased IPv6 address size over IPv4, a full immediate   transition to IPv6 is estimated to lead to the RIB and FIB sizes   increasing by a factor of about four.  The size of the routing table   based on a more realistic assumption, that of parallel IPv4 and IPv6   routing for many years, is less clear.  An increasing amount of   allocated IPv6 address prefixes is in PI space.  ARIN [ARIN] has   relaxed its policy for allocation of such space and has been   allocating /48 prefixes when customers request PI prefixes.  Thus,   the same pressures affecting IPv4 address allocations also affect   IPv6 allocations.4.  Implications of Moore's Law on the Scaling Problem   [Editor's note: The information in this section is gathered from   presentations given at the workshop.  The presentation slides can be   retrieved from the pointer provided inAppendix D.  It is worth   noting that this information has generated quite a bit of discussion   since the workshop, and as such requires further community input.]   The workshop heard from Tony Li about the relationship between   Moore's law and the ability to build cost-effective, high-performance   routers.  The scalability of the current routing subsystem manifests   itself in the forwarding table (FIB) and routing table (RIB) of the   routers in the core of the Internet.  The implementation choices for   FIB storage are on-chip SRAM, off-chip SRAM, or DRAM.  DRAM is   commonly used in lower end devices.  RIB storage is done via DRAM.Meyer, et al.                Informational                     [Page 11]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   [Editor's note: The exact implementation of a high-performance   router's RIB and FIB memories is the subject of much debate; it is   also possible that alternative designs may appear in the future.]   The scalability question then becomes whether these memory   technologies can scale faster than the size of the full routing   table.  Intrinsic in this statement is the assumption that core   routers will be continually and indefinitely upgraded on a periodic   basis to keep up with the technology curve and that the costs of   those upgrades will be passed along to the general Internet   community.4.1.  Moore's Law   In 1965, Gordon Moore projected that the density of transistors in   integrated circuits could double every two years, with respect to   minimum component cost.  The period was subsequently adjusted to be   between 18-24 months and this conjecture became known as Moore's Law   [ML].  The semiconductor industry has been following this density   trend for the last 40 or so years.   The commonly held wisdom is that Moore's law will save the day by   ensuring that technology will continue to scale at the historical   rate that will surpass the growth rate of routing information.   However, it is vital to understand that Moore's law comes out of the   high-volume portion of the semiconductor industry, where the costs of   silicon are dominated by the actual fabrication costs.  The   customized silicon used in core routers is produced in far lower   volume, typically in the 1,000-10,000 parts per year, whereas   microprocessors are running in the tens of millions per year.  This   places the router silicon well off the cost curve, where the   economies of scale are not directly inherited, and yield improvements   are not directly inherited from the best current practices.  Thus,   router silicon benefits from the technological advances made in   semiconductors, but does not follow Moore's law from a cost   perspective.   To date, this cost difference has not shown clearly.  However, the   growth in bandwidth of the Internet and the steady climb of the speed   of individual links has forced router manufacturers to apply more   sophisticated silicon technology continuously.  There has been a new   generation of router hardware that has grown at about 4x the   bandwidth every three years, and increases in routing table size have   been absorbed by the new generations of hardware.  Now that router   hardware is nearing the practical limits of per-lambda bandwidth, it   is possible that upgrades solely for meeting the forwarding table   scaling will become more visible.Meyer, et al.                Informational                     [Page 12]

RFC 4984          IAB Workshop on Routing & Addressing    September 20074.1.1.  DRAM   In routers, DRAM is used for storing the RIB and, in lower-end   routers, is also used for storing the FIB.  Historically, DRAM   capacity grows at about 4x every 3.3 years.  This translates to 2.4x   every 2 years, so DRAM capacity actually grows faster than Moore's   law would suggest.  DRAM speed, however, only grows about 10% per   year, or 1.2x every 2 years [DRAM] [Molinero].  This is an issue   because BGP convergence time is limited by DRAM access speeds.  In   processing a BGP update, a BGP speaker receives a path and must   compare it to all of the other paths it has stored for the prefix.   It then iterates over all of the prefixes in the update stream.  This   results in a memory access pattern that has proven to limit the   effectiveness of processor caching.  As a result, BGP convergence   time degrades at the routing table growth rate, divided by the speed   improvement rate of DRAM.  In the long run, this is likely to become   a significant issue.4.1.2.  Off-chip SRAM   Storing the FIB in off-chip SRAM is a popular design decision.  For   high-speed interfaces, this requires low-latency, high-capacity   parts.  The driver for this type of SRAM was formerly PC cache   memory.  However, this cache memory has recently been migrating   directly onto the processor die, so that the volumes of cache memory   have fallen off.  Today, the primary driver for off-chip SRAM is cell   phones, which require low-power, small-capacity parts that are not   applicable to high-end router design.  As a result, the SRAMs that   are favored for router design are not volume parts.  They have fallen   off the cost curve and do not track with Moore's law.4.2.  Forwarding Engines   For many years, router companies have been building special-purpose   silicon to provide high-speed packet-forwarding capabilities.  This   has been necessary because the architectural limitations of general   purpose CPUs make them incapable of providing the high-bandwidth, low   latency, low-jitter I/O interface for making high speed forwarding   decisions.   As a result, the forwarding engines being built for high-end routers   are some of the most sophisticated Application-specific Integrated   Circuits (ASICs) being built, and are currently only one   technological step behind general-purpose CPUs.  This has been   largely driven by the growth in bandwidth and has already pushed the   technology well beyond the knee in the price/performance curve.   Given that this level of technology is already a requirement to meet   the performance goals, using on-chip SRAM is an interesting designMeyer, et al.                Informational                     [Page 13]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   alternative.  If this choice is selected, then growth in the   available FIB is tightly coupled to process technology improvements,   which are driven by the general-purpose CPU market.  While this   growth rate should suffice, in general, the forwarding engine market   is decidedly off the high-volume price curve, resulting in spiraling   costs to support basic forwarding.   Moreover, if there is any change in Moore's law or decrease in the   rate of processor technology evolution, the forwarding engine could   quickly become the technological leader of silicon technology.  This   would rapidly result in forwarding technology becoming prohibitively   expensive.4.3.  Chip Costs   Each process technology step in chip development has come at   increasing cost.  The milestone of sending a completed chip design to   a fabricator for manufacturing is known as 'tapeout', and is the   point where the designer pays for the fixed overhead of putting the   chip into production.  The costs of taping out a chip have been   rising about 1.5x every 2 years, driven by new process technology.   The actual design and development costs have been rising similarly,   because each new generation of technology increases the device count   by roughly a factor of 2.  This allows new features and chip   architectures, which inevitably lead to an increase in complexity and   labor costs.  If new chip development was driven solely by the need   to scale up memory, and if memory structures scaled, then we would   expect labor costs to remain fixed.  Unfortunately, memory structures   typically do not seem to scale linearly.  Individual memory   controllers have a non-negligible cost, leading to the design for an   internal on-chip interconnect of memories.  The net result is that we   can expect that chip development costs to continue to escalate   roughly in line with the increases in tapeout costs, leading to an   ongoing cost curve of about 1.5x every 2 years.  Since each   technology step roughly doubles memory, that implies that if demand   grows faster than about (2x/1.5x) = 1.3x per year, then technology   refresh will not be able to remain on a constant cost curve.4.4.  Heat and Power   Transistors consume power both when idle ("leakage current") and when   switching.  The smaller and hotter the transistors, the larger the   leakage current.  The overall power consumption is not linear with   the density increase.  Thus, as the need for more powerful routers   increases, cooling technology grows more taxed.  At present, the   existing air cooling system is starting to be a limiting factor for   scaling high-performance routers.Meyer, et al.                Informational                     [Page 14]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   A key metric for system evaluation is now the unit of forwarding   bandwidth per Watt-- [(Mb/s)/W].  About 60% of the power goes to the   forwarding engine circuits, with the rest divided between the   memories, route processors, and interconnect.  Using parallelization   to achieve higher bandwidths can aggravate the situation, due to   increased power and cooling demands.   [Editor's note: Many in the community have commented that heat, power   consumption, and the attendant heat dissipation, along with size   limitations of fabrication processes for high speed parallel I/O   interfaces, are the current limiting factors.]4.5.  Summary   Given the uncontrolled nature of its growth rate, there is some   concern about the long-term prospects for the health and cost of the   routing subsystem of the Internet.  The ongoing growth will force   periodic technology refreshes.  However, the growth rate can possibly   exceed the rate that can be supported at constant cost based on the   development costs seen in the router industry.  Since high-end   routing is based on low-volume technology, the cost advantages that   the bulk of the broader computing industry see, based on Moore's law,   are not directly inherited.  This leads to a sustainable growth rate   of 1.3x/2yrs for the forwarding table and 1.2x/2yrs for the routing   table.  Given that the current baseline growth is at 1.3x/2yrs   [CIDRRPT], with bursts that even exceed Moore's law, the trend is for   the costs of technology refresh to continue to grow, indefinitely,   even in constant dollars.5.  What Is on the Horizon   Routing and addressing are two fundamental pieces of the Internet   architecture, thus any changes to them will likely impact almost all   of the "IP stack", from applications to packet forwarding.  In   resolving the routing scalability problems, as agreed upon by the   workshop attendees, we should aim at a long-term solution.  This   requires a clear understanding of various trends in the foreseeable   future: the growth in Internet user population, the applications, and   the technology.5.1.  Continual Growth   The backbone operators expect that the current Internet user   population base will continue to expand, as measured by the traffic   volume, the number of hosts connected to the Internet, the number of   customer networks, and the number of regional providers.Meyer, et al.                Informational                     [Page 15]

RFC 4984          IAB Workshop on Routing & Addressing    September 20075.2.  Large Numbers of Mobile Networks   Boeing's Connexion service pioneered the deployment of commercial   mobile networks that may change their attachment points to the   Internet on a global scale.  It is believed that such in-flight   Internet connectivity would likely become commonplace in the not-too-   distant future.  When that happens, there can be multiple thousands   of airplane networks in the air at any given time.   Given that today's DFZ RIB already handles over 200,000 prefixes   [CIDRRPT], several thousands of mobile networks, each represented by   a single prefix announcement, may not necessarily raise serious   routing scalability or stability concerns.  However, there is an open   question regarding whether this number can become substantially   larger if other types of mobile networks, such as networks on trains   or ships, come into play.  If such mobile networks become   commonplace, then their impact on the global routing system needs to   be assessed.5.3.  Orders of Magnitude Increase in Mobile Edge Devices   Today's technology trend indicates that billions of hand-held gadgets   may come online in the next several years.  There were different   opinions regarding whether this would, or would not, have a   significant impact on global routing scalability.  The current   solutions for mobile hosts, namely Mobile IP (e.g., [RFC3775]),   handle the mobility by one level of indirection through home agents;   mobile hosts do not appear any different, from a routing perspective,   than stationary hosts.  If we follow the same approach, new mobile   devices should not present challenges beyond the increase in the size   of the host population.   The workshop participants recognized that the increase in the number   of mobile devices can be significant, and that if a scalable routing   system supporting generic identity-locator separation were developed   and introduced, billions of mobile gadgets could be supported without   bringing undue impact on global routing scalability and stability.   Further investigation is needed to gain a complete understanding of   the implications on the global routing system of connecting many new   mobile hand-held devices (including mobile sensor networks) to the   Internet.Meyer, et al.                Informational                     [Page 16]

RFC 4984          IAB Workshop on Routing & Addressing    September 20076.  What Approaches Have Been Investigated   Over the years, there have been many efforts designed to investigate   scalable inter-domain routing for the Internet [IDR-REQS].  To   benefit from the insights obtained from these past results, the   workshop reviewed several major previous and ongoing IETF efforts:   1.  The MULTI6 working group's exploration of the solution space and       the lessons learned,   2.  The solution to multihoming being developed by the SHIM6 Working       Group, and its pros and cons,   3.  The GSE proposal made by O'Dell in 1997, and its pros and cons,       and   4.  Map-and-Encap [RFC1955], a general indirection-based solution to       scalable multihoming support.6.1.  Lessons from MULTI6   The MULTI6 working group was chartered to explore the solution space   for scalable support of IPv6 multihoming.  The numerous proposals   collected by MULTI6 working group generally fell into one of two   major categories: resolving the above-mentioned conflict by using   provider-independent address assignments, or by assigning multiple   address prefixes to multihomed sites, one for each of its providers,   so that all the addresses can be topologically aggregatable.   The first category includes proposals of (1) simply allocating   provider-independent address space, which is effectively the current   practice, and (2) assigning IP addresses based on customers'   geographical locations.  The first approach does not scale; the   second approach represents a fundamental change to the Internet   routing system and its economic model, and imposes undue constraints   on ISPs.  These proposals were found to be incomplete, as they   offered no solutions to the new problems they introduced.   The majority of the proposals fell into the second category--   assigning multiple address blocks per site.  Because IP addresses   have been used as identifiers by higher-level protocols and   applications, these proposals face a fundamental design decision   regarding which layer should be responsible for mapping the multiple   locators (i.e., the multiple addresses received from ISPs) to an   identifier.  A related question involves which nodes are responsible   for handling multiple addresses.  One can implement a multi-address   scheme at either each individual host or at edge routers of a site,   or even both.  Handling multiple addresses by edge routers providesMeyer, et al.                Informational                     [Page 17]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   the ability to control the traffic flow of the entire site.   Conversely, handling multiple addresses by individual hosts offers   each host the flexibility to choose different policies for selecting   a provider; it also implies changes to all the hosts of a multihomed   site.   During the process of evaluating all the proposals, two major lessons   were learned:   o  Changing anything in the current practice is hard: for example,      inserting an additional header into the protocol would impact IP      fragmentation processing, and the current congestion control      assumes that each TCP connection follows a single routing path.      In addition, operators ask for the ability to perform traffic      engineering on a per-site basis, and specification of site policy      is often interdependent with the IP address structure.   o  The IP address has been used as an identifier and has been      codified into many Internet applications that manipulate IP      addresses directly or include IP addresses within the application      layer data stream.  IP addresses have also been used as      identifiers in configuring network policies.  Changing the      semantics of an IP address, for example, using only the last 64-      bit as identifiers as proposed by GSE, would require changes to      all such applications and network devices.6.2.  SHIM6: Pros and Cons   The SHIM6 working group took the second approach from the MULTI6   working group's investigation, i.e., supporting multihoming through   the use of multiple addresses.  SHIM6 adopted a host-based approach,   where the host IP stack includes a "shim" that presents a stable   "upper layer identifier" (ULID) to the upper layer protocols, but may   rewrite the IP packets sent and received so that a currently working   IP address is used in the transmitted packets.  When needed, a SHIM6   header is also included in the packet itself, to signal to the remote   stack.   With SHIM6, protocols above the IP layer use the ULID to identify   endpoints (e.g., for TCP connections).  The current design suggests   choosing one of the locators as the ULID (borrowing a locator to be   used as an identifier).  This approach makes the implementation   compatible with existing IPv6 upper layer protocol implementations   and applications.  Many of these applications have inherited the long   time practice of using IP addresses as identifiers.   SHIM6 is able to isolate upper layer protocols from multiple IP layer   addresses.  This enables a multihomed site to use provider-allocatedMeyer, et al.                Informational                     [Page 18]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   prefixes, one from each of its multiple providers, to facilitate   provider-based prefix aggregation.  However, this gain comes with   several significant costs.  First, SHIM6 requires modifications to   all host stack implementations to support the shim processing.   Second, the shim layer must maintain the mapping between the   identifier and the multiple locators returned from IPv6 AAAA name   resolution, and must take the responsibility to try multiple locators   if failures ever occur during the end-to-end communication.  At this   time, the host has little information to determine the order of   locators it should use in reaching a multihomed destination, however,   there is ongoing effort in addressing this issue.   Furthermore, as a host-based approach, SHIM6 provides little control   to the service provider for effective traffic engineering.  At the   same time, it also imposes additional state information on the host   regarding the multiple locators of the remote communication end.   Such state information may not be a significant issue for individual   user hosts, but can lead to larger resource demands on large   application servers that handle hundreds of thousands of simultaneous   TCP connections.   Yet another major issue with the SHIM6 solution is the need for   renumbering when a site changes providers.  Although a multihomed   site is assigned multiple address blocks, none of them can be treated   as a persistent identifier for the site.  When the site changes one   of its providers, it must purge the address block of that provider   from the entire site.  The current practice of using the IP address   as both an identifier and a locator has been strengthened by the use   of IP addresses in access control lists present in various types of   policy-enforcement devices (e.g., firewalls).  If SHIM6's ULIDs are   to be used for policy enforcement, a change of providers may   necessitate the re-configuration of many such devices.6.3.  GSE/Indirection Solutions: Costs and Benefits   The use of indirection for scalable multihoming was discussed at the   workshop, including the GSE [GSE] and indirection approaches, such as   Map-and-Encap [RFC1955], in general.  The GSE proposal changes the   IPv6 address structure to bear the semantics of both an identifier   and a locator.  The first n bytes of the 16-byte IPv6 address are   called the Routing Goop (RG), and are used by the routing system   exclusively as a locator.  The last 8 bytes of the IPv6 address   specify an interface on an end-system.  The middle (16 - n - 8) bytes   are used to identify site local topology.  The border routers of a   site re-write the source RG of each outgoing packet to make the   source address part of the source provider's address aggregation;   they also re-write the destination RG of each incoming packet to hide   the site's RG from all the internal routers and hosts.  Although GSEMeyer, et al.                Informational                     [Page 19]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   designates the lower 8 bytes of the IPv6 address as identifiers, the   extent to which GSE could be made compatible with increasingly-   popular cryptographically-generated addresses (CGA) remains to be   determined [dGSE].   All identifier/locator split proposals require a mapping service that   can return a set of locators corresponding to a given identifier.  In   addition, these proposals must also address the problem of detecting   locator failures and redirecting data flows to remaining locators for   a multihomed site.  The Map-and-Encap proposal did not address these   issues.  GSE proposed to use DNS for providing the mapping service,   but it did not offer an effective means for locator failure recovery.   GSE also requires host stack modifications, as the upper layers and   applications are only allowed to use the lower 8-bytes, rather than   the entire, IPv6 address.6.4.  Future for Indirection   As the saying goes, "There is no problem in computer science that   cannot be solved by an extra level of indirection".  The GSE proposal   can be considered a specific instantiation of a class of indirection-   based solutions to scalable multihoming.  Map-and-Encap [RFC1955]   represents a more general form of this indirection solution, which   uses tunneling, instead of locator rewriting, to cross the DFZ and   support provider-based prefix aggregation.  This class of solutions   avoids the provider and customer conflicts regarding PA and PI   prefixes by putting each in a separate name space, so that ISPs can   use topologically aggregatable addresses while customers can have   their globally unique and provider-independent identifiers.  Thus, it   supports scalable multihoming, and requires no changes to the end   systems when the encapsulation is performed by the border routers of   a site.  It also requires no changes to the current practice of both   applications as well as backbone operations.   However, all gains of an effective solution are accompanied with   certain associated costs.  As stated earlier in this section, a   mapping service must be provided.  This mapping service not only   brings with it the associated complexity and cost, but it also adds   another point of failure and could also be a potential target for   malicious attacks.  Any solution to routing scalability is   necessarily a cost/benefit tradeoff.  Given the high potential of its   gains, this indirection approach deserves special attention in our   search for scalable routing solutions.Meyer, et al.                Informational                     [Page 20]

RFC 4984          IAB Workshop on Routing & Addressing    September 20077.  Problem Statements   The fundamental goal of this workshop was to develop a prioritized   problem statement regarding routing and addressing problems facing us   today, and the workshop spent a considerable amount of time on   reaching that goal.  This section provides a description of the   prioritized problem statement, together with elaborations on both the   rationale and open issues.   The workshop participants noted that there exist different classes of   stakeholders in the Internet community who view today's global   routing system from different angles, and assign different priorities   to different aspects of the problem set.  The prioritized problem   statement in this section is the consensus of the participants in   this workshop, representing primarily large network operators and a   few router vendors.  It is likely that a different group of   participants would produce a different list, or with different   priorities.  For example, freedom to change providers without   renumbering might make the top of the priority list assembled by a   workshop of end users and enterprise network operators.7.1.  Problem #1: Routing Scalability   The workshop participants believe that routing scalability is the   most important problem facing the Internet today and must be solved,   although the time frame in which these problems need solutions was   not directly specified.  The routing scalability problem includes the   size of the DFZ RIB and FIB, the implications of the growth of the   RIB and FIB on routing convergence times, and the cost, power (and   hence, heat dissipation) and ASIC real estate requirements of core   router hardware.   It is commonly believed that the IPv4 RIB growth has been constrained   by the limited IPv4 address space.  However, even under this   constraint, the DFZ IPv4 RIB has been growing at what appears to be   an accelerating rate [DFZ].  Given that the IPv6 routing architecture   is the same as the IPv4 architecture (with substantially larger   address space), if/when IPv6 becomes widely deployed, it is natural   to predict that routing table growth for IPv6 will only exacerbate   the situation.   The increasing deployment of Virtual Private Network/Virtual Routing   and Forwarding (VPN/VRF) is considered another major factor driving   the routing system growth.  However, there are different views   regarding whether this factor has, or does not have, a direct impact   to the DFZ RIB.  A common practice is to delegate specific routers to   handle VPN connections, thus backbone routers do not necessarily holdMeyer, et al.                Informational                     [Page 21]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   state for individual VPNs.  Nevertheless, VPNs do represent   scalability challenges in network operations.7.2.  Problem #2: The Overloading of IP Address Semantics   As we have reported inSection 3, multihoming, along with traffic   engineering, appear to be the major factors driving the growth of the   DFZ RIB.  Below, we elaborate their impact on the DFZ RIB.7.2.1.  Definition of Locator and Identifier   Roughly speaking, the Internet comprises a large number of transit   networks and a much larger number of customer networks containing   hosts that are attached to the backbone.  Viewing the Internet as a   graph, transit networks have branches and customer networks with   hosts hang at the edges as leaves.   As its name suggests, locators identify locations in the topology,   and a network's or host's locator should be topologically constrained   by its present position.  Identifiers, in principle, should be   network-topology independent.  That is, even though a network or host   may need to change its locator when it is moved to a different set of   attachment points in the Internet, its identifier should remain   constant.   From an ISP's viewpoint, identifiers identify customer networks and   customer hosts.  Note that the word "identifier" used here is defined   in the context of the Internet routing system; the definition may   well be different when the word "identifier" is used in other   contexts.  As an example, a non-routable, provider-independent IP   prefix for an enterprise network could serve as an identifier for   that enterprise.  This block of IP addresses can be used to route   packets inside the enterprise network.  However, they are independent   from the DFZ topology, which is why they are not globally routable on   the Internet.   Note that in cases such as the last example, the definition of   locators and identifiers can be context-dependent.  Following the   example further, a PI address may be routable in an enterprise but   not the global network.  If allowed to be visible in the global   network, such addresses might act as identifiers from a backbone   operator's point of view but locators from an enterprise operator's   point of view.Meyer, et al.                Informational                     [Page 22]

RFC 4984          IAB Workshop on Routing & Addressing    September 20077.2.2.  Consequence of Locator and Identifier Overloading   In today's Internet architecture, IP addresses have been used as both   locators and identifiers.  Combined with the use of CIDR to perform   route aggregation, a problem arises for either providers or customers   (or both).   Consider, for example, a campus network C that received prefix   x.y.z/24 from provider P1.  When C multihomes with a second provider   P2, both P1 and P2 must announce x.y.z/24 so that C can be reached   through both providers.  In this example, the prefix x.y.z/24 serves   both as an identifier for C, as well as a (non-aggregatable) locator   for C's two attachment points to the transit system.   As far as the DFZ RIB is concerned, the above example shows that   customer multihoming blurs the distinction between PA and PI   prefixes.  Although C received a PA prefix x.y.z/24 from P1, C's   multihoming forced this prefix to be announced globally (equivalent   to a PI prefix), and forced the prefix's original owner, provider P1,   to de-aggregate.  As a result, today's multihoming practice leads to   a growth of the routing table size in proportion to the number of   multihomed customers.  The only practical way to scale a routing   system today is topological aggregation, which gets destroyed by   customer multihoming.   Although multihoming may blur the PA/PI distinction, there exists a   big difference between PA and PI prefixes when a customer changes its   provider(s).  If the customer has used a PA prefix from a former   provider P1, the prefix is supposed to be returned to P1 upon   completion of the change.  The customer is supposed to get a new   prefix from its new provider, i.e., renumbering its network.  It is   necessary for providers to reclaim their PA prefixes from former   customers in order to keep the topological aggregatiblity of their   prefixes.  On the other hand, renumbering is considered very painful,   if not impossible, by many Internet users, especially large   enterprise customers.  It is not uncommon for IP addresses in such   enterprises to penetrate deeply into various parts of the networking   infrastructure, ranging from applications to network management   (e.g., policy databases, firewall configurations, etc.).  This shows   how fragile the system becomes due to the overloading of IP addresses   as both locators and identifiers; significant enterprise operations   could be disrupted due to the otherwise simple operation of switching   IP address prefix assignment.Meyer, et al.                Informational                     [Page 23]

RFC 4984          IAB Workshop on Routing & Addressing    September 20077.2.3.  Traffic Engineering and IP Address Semantics Overload   In today's practice, traffic engineering (TE) is achieved by de-   aggregating IP prefixes.  One can effectively adjust the traffic   volume along specific routing paths by adjusting the prefix lengths   and the number of prefixes announced through those paths.  Thus, the   very means of TE practice directly conflicts with constraining the   routing table growth.   On the surface, traffic engineering induced prefix de-aggregation   seems orthogonal to the locator-identifier overloading problem.   However, this may not necessarily be true.  Had all the IP prefixes   been topologically aggregatable to start with, it would make re-   aggregation possible or easier, when the finer granularity prefix   announcements propagate further away from their origins.7.3.  Additional Issues7.3.1.  Routing Convergence   There are two kinds of routing convergence issues, eBGP (global   routing) convergence and IGP (enterprise or provider) routing   convergence.  Upon isolated topological events, eBGP convergence does   not suffer from extensive path explorations in most cases [PathExp],   and convergence delay is largely determined by the minimum route   advertisement interval (MRAI) timer [RFC4098], except those cases   when a route is withdrawn.  Route withdrawals tend to suffer from   path explorations and hence slow convergence; one participant's   experience suggests that the withdrawal delays often last up to a   couple of minutes.  One may argue that, if the destination becomes   unreachable, a long convergence delay would not bring further damage   to applications.  However, there are often cases where a more   specific route (a longer prefix) has failed, yet the destination can   still be reached through an aggregated route (a shorter prefix).  In   these cases, the long convergence delay does impact application   performance.   While IGPs are designed to and do converge more quickly than BGP   might, the workshop participants were concerned that, in addition to   the various special purpose routes that IGPs must carry, the rapid   growth of the DFZ RIB size can effectively slow down IGP convergence.   The IGP convergence delay can be due to multiple factors, including   1.  Delays in detecting physical failures,   2.  The delay in loading updated information into the FIB, andMeyer, et al.                Informational                     [Page 24]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   3.  The large size of the internal RIB, often twice as big as the DFZ       RIB, which can lead to both longer route computation time and       longer FIB loading time.   The workshop participants hold different views regarding (1) the   severity of the routing convergence problem; and (2) whether it is an   architectural problem, or an implementation issue.  However, people   generally agree that if we solve the routing scalability problem,   that will certainly help reduce the convergence delay or make the   problem a much easier one to handle because of the reduced number of   routes to process.7.3.2.  Misaligned Costs and Benefits   Today's rapid growth of the DFZ RIB is driven by a few major factors,   including multihoming and traffic engineering, in addition to the   organic growth of the Internet's user base.  There is a powerful   incentive to deploy each of the above features, as they bring direct   benefits to the parties who make use of them.  However, the   beneficiaries may not bear the direct costs of the resulting routing   table size increase, and there is no measurable or enforceable   constraint to limit such increase.   For example, suppose that a service provider has two bandwidth-   constrained transoceanic links and wants to split its prefix   announcements in order to fully load each link.  The origin AS   benefits from performing the de-aggregation.  However, if the de-   aggregated announcements propagate globally, the cost is born by all   other ASs.  That is, the costs of this type of TE practice are not   contained to the beneficiaries.  Multihoming provides a similar   example (in this case, the multihomed site achieves a benefit, but   the global Internet incurs the cost of carrying the additional   prefix(es)).   The misalignment of cost and benefit in the current routing system   has been a driver for acceleration of the routing system size growth.7.3.3.  Other Concerns   Mobility was among the most frequently mentioned issues at the   workshop.  It is expected that billions of mobile gadgets may be   connected to the Internet in the near future.  There was also a   discussion on network mobility as deployed in the Connexion service   provided by Boeing over the last few years.  However, at this time it   seems unclear (1) whether the Boeing-like network mobility support   would cause a scaling issue in the routing system, and (2) exactly   what would be the impact of billions of mobile hosts on the globalMeyer, et al.                Informational                     [Page 25]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   routing system.  These discussions were covered inSection 5 of this   report.   Routing security is another issue that was brought up a number of   times during the workshop.  The consensus from the workshop   participants was that, however important routing security may be, it   was out of scope for this workshop, whose main goal was to produce a   problem statement about addressing and routing scalability.  It was   duly considered that security must be one of the top design goals   when we get to a solution development stage.  It was also noted that,   if we continue to allow the routing table to grow indefinitely, then   it may be impossible to add security enhancements in the future.7.4.  Problem Recognition   The first step in solving a problem is recognizing its existence as   well as its importance.  However, recognizing the severity of the   routing scaling issue can be a challenge by itself, because there   does not exist a specific hard limit on routing system scalability   that can be easily demonstrated, nor is there any specific answer to   the question of how much time we may have in developing a solution.   Nevertheless, a general consensus among the workshop participants is   that we seem to be running out of time.  The current RIB scaling   leads to both accelerated hardware cost increases, as explained inSection 4, as well as pressure for shorter depreciation cycles, which   in turn also translates to cost increases.8.  Criteria for Solution Development   Any common problem statement may admit multiple different solutions.   This section provides a set of considerations, as identified from the   workshop discussion, over the solution space.  Given the   heterogeneity among customers and providers of the global Internet,   and the elasticity of the problem, none of these considerations   should inherently preclude any specific solution.  Consequently,   although the following considerations were initially deemed as   constraints on solutions, we have instead opted to adopt the term   'criteria' to be used in guiding solution evaluations.8.1.  Criteria on Scalability   Clearly, any proposed solution must solve the problem at hand, and   our number one problem concerns the scalability of the Internet's   routing and addressing system(s) as outlined in previous sections.   Under the assumption of continued growth of the Internet user   population, continued increases of multihoming andRFC 2547 VPN   [RFC2547] deployment, the solution must enable the routing system to   scale gracefully, as measured by the number ofMeyer, et al.                Informational                     [Page 26]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   o  DFZ Internet routes, and   o  Internal routes.   In addition, scalable support for traffic engineering (TE) must be   considered as a business necessity, not an option.  Capacity planning   involves placing circuits based on traffic demand over a relatively   long time scale, while TE must work more immediately to match the   traffic load to the existing capacity and to match the routing policy   requirements.   It was recognized that different parties in the Internet may have   different specific TE requirements.  For example,   o  End site TE: based on locally determined performance or cost      policies, end sites may wish to control the traffic volume exiting      to, or entering from specific providers.   o  Small ISP to transit ISP TE: operators may face tight resource      constraints and wish to influence the volume of entering traffic      from both customers and providers along specific routing paths to      best utilize the limited resources.   o  Large ISP TE: given the densely connected nature of the Internet      topology, a given destination normally can be reached through      different routing paths.  An operator may wish to be able to      adjust the traffic volume sent to each of its peers based on      business relations with its neighbor ASs.   At this time, it remains an open issue whether a scalable TE solution   would be necessarily inside the routing protocol, or can be   accomplished through means that are external to the routing system.8.2.  Criteria on Incentives and Economics   The workshop attendees concluded that one important reason for   uncontrolled routing growth was the misalignment of incentives.  New   entries are added to the routing system to provide benefit to   specific parties, while the cost is born by everyone in the global   routing system.  The consensus of the workshop was that any proposed   solutions should strive to provide incentives to reward practices   that reduce the overall system cost, and punish the "bad" behavior   that imposes undue burden on the global system.   Given the global scale and distributed nature of the Internet, there   can no longer (ever) be a flag day on the Internet.  To bootstrap the   deployment of new solutions, the solutions should provide incentives   to first movers.  That is, even when a single party starts to deployMeyer, et al.                Informational                     [Page 27]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   the new solution, there should be measurable benefits to balance the   costs.   Independent of what kind of solutions the IETF develops, if any, it   is unlikely that the resulting routing system would stay constant in   size.  Instead, the workshop participants believed the routing system   will continue to grow, and that ISPs will continue to go through   system and hardware upgrade cycles.  Many attendees expressed a   desire that the scaling properties of the system can allow the   hardware to keep up with the Internet growth at a rate that is   comparable to the current costs, for example, allowing one to keep a   5-year hardware depreciation cycle, as opposed to a situation where   scaling leads to accelerated cost increases.8.3.  Criteria on Timing   Although there does not exist a specific hard deadline, the unanimous   consensus among the workshop participants is that the solution   development must start now.  If one assumes that the solution   specification can get ready within a 1 - 2 year time frame, that will   be followed by another 2-year certification cycle.  As a result, even   in the best case scenario, we are facing a 3 - 5 year time frame in   getting the solutions deployed.8.4.  Consideration on Existing Systems   The routing scalability problem is a shared one between IPv4 and   IPv6, as IPv6 simply inherited IPv4's CIDR-style "Provider-based   Addressing".  The proposed solutions should, and are also expected   to, solve the problem for both IPv4 and IPv6.   Backwards compatibility with the existing IPv4 and IPv6 protocol   stack is a necessity.  Although a wide deployment of IPv6 is yet to   happen, there has been substantial investment into IPv6   implementation and deployment by various parties.  IPv6 is considered   a legacy with shipped code.  Thus, a highly desired feature of any   proposed solution is to avoid imposing backwards-incompatible changes   on end hosts (either IPv4 or IPv6).   In the routing system itself, the solutions must allow incremental   changes from the current operational Internet.  The solutions should   be backward compatible with the routing protocols in use today,   including BGP, OSPF, IS-IS, and others, possibly with incremental   enhancements.   The above backward-compatibility considerations should not constrain   the exploration of the solution space.  We need to first find right   solutions, and look into their backward-compatibility issues afterMeyer, et al.                Informational                     [Page 28]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   that.  This way enables us to gain a full understanding of the   tradeoffs, and what potential gains, if any, that we may achieve by   relaxing the backward-compatibility concerns.   As a rule of thumb for successful deployment, for any new design, its   chance of success is higher if it makes fewer changes to the existing   system.8.5.  Consideration on Security   Security should be considered from day one of solution development.   If nothing else, the solutions must not make securing the routing   system any worse than the situation today.  It is highly desirable to   have a solution that makes it more difficult to inject false routing   information, and makes it easier to filter out DoS traffic.   However, securing the routing system is not considered a requirement   for the solution development.  Security is important; having a   working system in the first place is even more important.8.6.  Other Criteria   A number of other criteria were also raised that fall into various   different categories.  They are summarized below.   o  Site renumbering forced by the routing system should be avoided.   o  Site reconfiguration driven by the routing system should be      minimized.   o  The solutions should not force ISPs to reveal internal topology.   o  Routing convergence delay must be under control.   o  End-to-end data delivery paths should be stable enough for good      Voice over IP (VoIP) performance.8.7.  Understanding the Tradeoff   As the old saying goes, every coin has two sides.  If we let the   routing table continue to grow at its present rate, rapid hardware   and software upgrade and replacement cycles for deployed core routing   equipment may become cost prohibitive.  In the worst case, the   routing table growth may exceed our ability to engineer the global   routing system in a cost-effective way.  On the other hand, solutions   for stopping or substantially slowing down the growth in the Internet   routing table will necessarily bring their own costs, perhaps showing   up elsewhere and in different forms.  Examples of such tradeoffs areMeyer, et al.                Informational                     [Page 29]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   presented inSection 6, where we examined the gains and costs of a   few different approaches to scalable multihoming support (SHIM6, GSE,   and a general tunneling approach).  A major task in the solution   development is to understand who may have to give up what, and   whether that makes a worthy tradeoff.   Before ending this discussion on the solution criteria, it is worth   mentioning the shortest presentation at the workshop, which was made   by Tony Li (the presentation slides can be found fromAppendix D).   He asked a fundamental question: what is at stake?  It is the   Internet itself.  If the routing system does not scale with the   continued growth of the Internet, eventually the costs might spiral   out of control, the digital divide widen, and the Internet growth   slow down, stop, or retreat.  Compared to this problem, he considered   that none of the criteria mentioned so far (except solving the   problem) was important enough to block the development and deployment   of an effective solution.9.  Workshop Recommendations   The workshop attendees would like to make the following   recommendations:   First of all, the workshop participants would like to reiterate the   importance of solving the routing scalability problem.  They noted   that the concern over the scalability and flexibility of the routing   and addressing system has been with us for a very long time, and the   current growth rate of the DFZ RIB is exceeding our ability to   engineer the routing infrastructure in an economically feasible way.   We need to start developing a long-term solution that can last for   the foreseeable future.   Second, because the participants of this workshop consisted of mostly   large service providers and major router vendors, the workshop   participants recommend that IAB/IESG organize additional workshops or   use other venues of communication to reach out to other stakeholders,   such as content providers, retail providers, and enterprise   operators, both to communicate to them the outcome of this workshop,   and to solicit the routing/addressing problems they are facing today,   and their requirements on the solution development.   Third, the workshop participants recommend conducting the solution   development in an open, transparent way, with broad-ranging   participation from the larger networking community.  A majority of   the participants indicated their willingness to commit resources   toward developing a solution.  We must also invite the participation   from the research community in this process.  The locator-identifier   split represents a fundamental architectural issue, and the IABMeyer, et al.                Informational                     [Page 30]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   should lead the investigation into understanding of both how to make   this architectural change and the overall impact of the change.   Fourth, given the goal of developing a long-term solution, and the   fact that development and deployment cycles will necessarily take   some time, it may be helpful (or even necessary) to buy some time   through engineering feasible short- or intermediate-term solutions   (e.g., FIB compression).   Fifth, the workshop participants believe the next step is to develop   a roadmap from here to the solution deployment.  The IAB and IESG are   expected to take on the leadership role in this roadmap development,   and to leverage on the momentum from this successful workshop to move   forward quickly.  The roadmap should provide clearly defined short-,   medium-, and long-term objectives to guide the solution development   process, so that the community as a whole can proceed in an   orchestrated way, seeing exactly where we are going when engineering   necessary short-term fixes.   Finally, the workshop participants also made a number of suggestions   that the IETF might consider when examining the solution space.   These suggestions are captured inAppendix A.10.  Security Considerations   While the security of the routing system is of great concern, this   document introduces no new protocol or protocol usage and as such   presents no new security issues.11.  Acknowledgments   Jari Arkko, Vince Fuller, Darrel Lewis, Tony Li, Eric Rescorla, and   Ted Seely made many insightful comments on earlier versions of this   document.  Finally, many thanks to Wouter Wijngaards for the fine   notes he took during the workshop.12.  Informative References   [RFC1955]    Hinden, R., "New Scheme for Internet Routing and                Addressing (ENCAPS) for IPNG",RFC 1955, June 1996.   [RFC2547]    Rosen, E. and Y. Rekhter, "BGP/MPLS VPNs",RFC 2547,                March 1999.   [RFC3775]    Johnson, D., Perkins, C., and J. Arkko, "Mobility                Support in IPv6",RFC 3775, June 2004.Meyer, et al.                Informational                     [Page 31]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   [RFC4098]    Berkowitz, H., Davies, E., Hares, S., Krishnaswamy, P.,                and M. Lepp, "Terminology for Benchmarking BGP Device                Convergence in the Control Plane",RFC 4098, June 2005.   [RFC4116]    Abley, J., Lindqvist, K., Davies, E., Black, B., and V.                Gill, "IPv4 Multihoming Practices and Limitations",RFC 4116, July 2005.   [RFC4192]    Baker, F., Lear, E., and R. Droms, "Procedures for                Renumbering an IPv6 Network without a Flag Day",RFC 4192, September 2005.   [RFC4632]    Fuller, V. and T. Li, "Classless Inter-domain Routing                (CIDR): The Internet Address Assignment and Aggregation                Plan",BCP 122,RFC 4632, August 2006.   [IDR-REQS]   Doria, A. and E. Davies, "Analysis of IDR requirements                and History", Work in Progress, February 2007.   [ARIN]       "American Registry for Internet Numbers",http://www.arin.net/index.shtml.   [PIPA]       Karrenberg, D., "IPv4 Address Allocation and Assignment                Policies for the RIPE NCC Service Region",                RIPE-387http://www.ripe.net/docs/ipv4-policies.html,                2006.   [SHIM6]      "Site Multihoming by IPv6 Intermediation (shim6)",http://www.ietf.org/html.charters/shim6-charter.html.   [EID]        Chiappa, J., "Endpoints and Endpoint Names: A Proposed                Enhancement to the Internet Architecture",http://www.chiappa.net/~jnc/tech/endpoints.txt, 1999.   [GSE]        O'Dell, M., "GSE - An Alternate Addressing Architecture                for IPv6", Work in Progress, 1997.   [dGSE]       Zhang, L., "An Overview of Multihoming and Open Issues                in GSE", IETF Journal,http://www.isoc.org/tools/blogs/ietfjournal/?p=98#more-98, 2006.   [PathExp]    Oliveira, R. and et. al., "Quantifying Path Exploration                in the Internet", Internet Measurement Conference (IMC)                2006,http://www.cs.ucla.edu/~rveloso/papers/imc175f-oliveira.pdf.Meyer, et al.                Informational                     [Page 32]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   [DynPrefix]  Oliveira, R. and et. al., "Measurement of Highly Active                Prefixes in BGP", IEEE GLOBECOM 2005http://www.cs.ucla.edu/~rveloso/papers/activity.pdf.   [BHB06]      Boothe, P., Hielbert, J., and R. Bush, "Short-Lived                Prefix Hijacking on the Internet", NANOG 36http://www.nanog.org/mtg-0602/pdf/boothe.pdf, 2006.   [ROFL]       Caesar, M. and et. al., "ROFL: Routing on Flat Labels",                SIGCOMM 2006,http://www.sigcomm.org/sigcomm2006/discussion/showpaper.php?paper_id=34, 2006.   [CNIR]       Abraham, I. and et. al., "Compact Name-Independent                Routing with Minimum Stretch", ACM Symposium on Parallel                Algorithms and Architectures,http://citeseer.ist.psu.edu/710757.html, 2004.   [BGT04]      Bu, T., Gao, L., and D. Towsley, "On Characterizing BGP                Routing Table Growth", J. Computer and Telecomm                Networking V45N1, 2004.   [Fuller]     Fuller, V., "Scaling issues with ipv6 routing+                multihoming",http://www.iab.org/about/workshops/routingandaddressing/vaf-iab-raws.pdf, 2006.   [H03]        Huston, G., "Analyzing the Internet's BGP Routing                Table",http://www.potaroo.net/papers/ipj/2001-v4-n1-bgp/bgp.pdf, 2003.   [BGP2005]    Huston, G., "2005 -- A BGP Year in Review",http://www.apnic.net/meetings/21/docs/sigs/routing/                routing-pres-huston-routing-update.pdf.   [DFZ]        Huston, G., "Growth of the BGP Table - 1994 to Present",http://bgp.potaroo.net, 2006.   [GIH]        Huston, G., "Wither Routing?",http://www.potaroo.net/ispcol/2006-11/raw.html, 2006.   [ATNAC2006]  Huston, G. and G. Armitage, "Projecting Future IPv4                Router Requirements from Trends in Dynamic BGP                Behaviour",http://www.potaroo.net/papers/phd/atnac-2006/bgp-atnac2006.pdf, 2006.   [CIDRRPT]    "The CIDR Report",http://www.cidr-report.org.Meyer, et al.                Informational                     [Page 33]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   [ML]         "Moore's Law",                Wikipediahttp://en.wikipedia.org/wiki/Moore's_law,                2006.   [Molinero]   Molinero-Fernandez, P., "Technology trends in routers                and switches", PhD thesis, Stanford Universityhttp://klamath.stanford.edu/~molinero/thesis/html/                pmf_thesis_node5.html, 2005.   [DRAM]       Landler, P., "DRAM Productivity and Capacity/Demand                Model", Global Economic Workshophttp://www.sematech.org/meetings/archives/GES/19990514/docs/                07_econ.pdf, 1999.Meyer, et al.                Informational                     [Page 34]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007Appendix A.  Suggestions for Specific Steps   At the end of the workshop there was a lively round-table discussion   regarding specific steps that IETF may consider undertaking towards a   quick solution development, as well as potential issues to avoid.   Those steps included:   o  Finding a home (mailing list) to continue the discussion started      from the workshop with wider participation.  [Editor's note: Done      -- This action has been completed.  The list is ram@iab.org.]   o  Considering a special process to expedite solution development,      avoiding the lengthy protocol standardization cycles.  For      example, IESG may charter special design teams for the solution      investigation.   o  If a working group is to be formed, care must be taken to ensure      that the scope of the charter is narrow and specific enough to      allow quick progress, and that the WG chair be forceful enough to      keep the WG activity focused.  There was also a discussion on      which area this new WG should belong to; both routing area ADs and      Internet area ADs are willing to host it.   o  It is desirable that the solutions be developed in an open      environment and free from any Intellectual Property Right claims.   Finally, given the perceived severity of the problem at hand, the   workshop participants trust that IAB/IESG/IETF will take prompt   actions.  However, if that were not to happen, operators and vendors   would be most likely to act on their own and get a solution deployed.Appendix B.  Workshop Participants   Loa Anderson (IAB)   Jari Arkko (IESG)   Ron Bonica   Ross Callon (IESG)   Brian Carpenter (IAB)   David Conrad (IANA)   Leslie Daigle (IAB Chair)   Elwyn Davies (IAB)   Terry Davis   Weisi Dong   Aaron Falk (IRTF Chair)   Kevin Fall (IAB)   Dino Farinacci   Vince Fuller   Vijay GillMeyer, et al.                Informational                     [Page 35]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   Russ Housley (IESG)   Geoff Huston   Daniel Karrenberg   Dorian Kim   Olaf Kolkman (IAB)   Darrel Lewis   Tony Li   Kurtis Lindqvist (IAB)   Peter Lothberg   David Meyer (IAB)   Christopher Morrow   Dave Oran (IAB)   Phil Roberts (IAB Executive Director)   Jason Schiller   Peter Schoenmaker   Ted Seely   Mark Townsley (IESG)   Iljitsch van Beijnum   Ruediger Volk   Magnus Westerlund (IESG)   Lixia Zhang (IAB)Appendix C.  Workshop Agenda   IAB Routing and Addressing Workshop Agenda               October 18-19            Amsterdam, Netherlands   DAY 1: the proposed goal is to collect, as complete as possible, a   set of scalability problems in the routing and addressing area facing   the Internet today.   0815-0900: Welcome, framing up for the 2 days              Moderator: Leslie Daigle   0900-1200: Morning session              Moderator: Elwyn Davies              Strawman topics for the morning session:              - Scalability              - Multihoming support              - Traffic Engineering              - Routing Table Size: Rate of growth, Dynamics                (this is not limited to DFZ, include iBGP)              - Causes of the growth              - Pains from the growth                (perhaps "Impact on routers" can come here?)              - How big a problem is BGP slow convergence?Meyer, et al.                Informational                     [Page 36]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007   1015-1030: Coffee Break   1200-1300: Lunch   1330-1730: Afternoon session: What are the top 3 routing problems              in your network?              Moderator: Kurt Erik Lindqvist   1500-1530: Coffee Break   Dinner at Indrapura (http://www.indrapura.nl), sponsored by Cisco   ---------   DAY 2: The proposed goal is to formulate a problem statement   0800-0830: Welcome   0830-1000: Morning session: What's on the table              Moderator: Elwyn Davies              - shim6              - GSE   1000-1030: Coffee Break   1030-1200: Problem Statement session #1: document the problems              Moderator: David Meyer   1200-1300: Lunch   1300-1500: Problem Statement session # 2, cont;              Moderator: Dino Farinacci               - Constraints on solutions   1500-1530: Coffee Break   1530-1730: Summary and Wrap-up              Moderator: Leslie DaigleAppendix D.  Presentations   The presentations from the workshop can be found onhttp://www.iab.org/about/workshops/routingandaddressingMeyer, et al.                Informational                     [Page 37]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007Authors' Addresses   David Meyer (editor)   EMail: dmm@1-4-5.net   Lixia Zhang (editor)   EMail: lixia@cs.ucla.edu   Kevin Fall (editor)   EMail: kfall@intel.comMeyer, et al.                Informational                     [Page 38]

RFC 4984          IAB Workshop on Routing & Addressing    September 2007Full Copyright Statement   Copyright (C) The IETF Trust (2007).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND   THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS   OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF   THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat and any   assurances of licenses to be made available, or the result of an   attempt made to obtain a general license or permission for the use of   such proprietary rights by implementers or users of this   specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Meyer, et al.                Informational                     [Page 39]