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Network Working Group                                            M. KaatRequest for Comments: 2956                   SURFnet ExpertiseCentrum bvCategory: Informational                                     October 2000Overview of 1999 IAB Network Layer WorkshopStatus 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.Copyright Notice   Copyright (C) The Internet Society (2000).  All Rights Reserved.Abstract   This document is an overview of a workshop held by the Internet   Architecture Board (IAB) on the Internet Network Layer architecture   hosted by SURFnet in Utrecht, the Netherlands on 7-9 July 1999.  The   goal of the workshop was to understand the state of the network layer   and its impact on continued growth and usage of the Internet.   Different technical scenarios for the (foreseeable) future and the   impact of external influences were studied.  This report lists the   conclusions and recommendations to the Internet Engineering Task   Force (IETF) community.Table of Contents1. Introduction . . . . . . . . . . . . . . . . . . . . . . .22. Conclusions and Observations . . . . . . . . . . . . . . .32.1  Transparency. . . . . . . . . . . . . . . . . . . . . .32.2  NAT, Application Level Gateways & Firewalls . . . . . .42.3  Identification and Addressing . . . . . . . . . . . . .42.4  Observations on Address Space . . . . . . . . . . . . .52.5  Routing Issues. . . . . . . . . . . . . . . . . . . . .52.6  Observations on Mobility. . . . . . . . . . . . . . . .62.7  DNS Issues. . . . . . . . . . . . . . . . . . . . . . .72.8  NAT and RSIP. . . . . . . . . . . . . . . . . . . . . .72.9  NAT, RSIP and IPv6. . . . . . . . . . . . . . . . . . .82.10 Observations on IPv6. . . . . . . . . . . . . . . . . .93. Recommendations. . . . . . . . . . . . . . . . . . . . . .103.1 Recommendations on Namespace . . . . . . . . . . . . . .103.2 Recommendations on RSIP. . . . . . . . . . . . . . . . .103.3 Recommendations on IPv6. . . . . . . . . . . . . . . . .103.4 Recommendations on IPsec . . . . . . . . . . . . . . . .11Kaat                         Informational                      [Page 1]

RFC 2956            1999 IAB Network Layer Workshop         October 20003.5 Recommendations on DNS . . . . . . . . . . . . . . . . .113.6 Recommendations on Routing . . . . . . . . . . . . . . .123.7 Recommendations on Application Layer and APIs. . . . . .124. Security Considerations. . . . . . . . . . . . . . . . . .12   References. . . . . . . . . . . . . . . . . . . . . . . . . .13Appendix A. Participants. . . . . . . . . . . . . . . . . . .15   Author's Address. . . . . . . . . . . . . . . . . . . . . . .15   Full Copyright Statement  . . . . . . . . . . . . . . . . . .161. Introduction   From July 7 to July 9, 1999 the Internet Architecture Board (IAB)   held a workshop on the architecture of the Internet Network Layer.   The Network Layer is usually referred to as the IP layer.  The goal   of the workshop was to discuss the current state of the Network Layer   and the impact various currently deployed or future mechanisms and   technologies might have on the continued growth and usage of the   Internet.   The most important issues to be discussed were:   o  Status of IPv6 deployment and transition issues   o  Alternative technical strategies in case IPv6 is not adopted   o  Globally unique addresses and 32 bit address depletion   o  Global connectivity and reachability   o  Fragmentation of the Internet   o  End to end transparency and the progressive loss thereof   o  End to end security   o  Complications of address sharing mechanisms (NAT, RSIP)   o  Separation of identification and location in addressing   o  Architecture and scaling of the current routing system   The participants looked into several technical scenarios and   discussed the feasibility and probability of the deployment of each   scenario.  Among the scenarios were for example full migration to   IPv6, IPv6 deployment only in certain segments of the network, no   significant deployment of IPv6 and increased segmentation of the IPv4   address space due to the use of NAT devices.   Based on the discussion of these scenarios several trends and   external influences were identified which could have a large impact   on the status of the network layer, such as the deployment of   wireless network technologies, mobile networked devices and special   purpose IP devices.Kaat                         Informational                      [Page 2]

RFC 2956            1999 IAB Network Layer Workshop         October 2000   The following technical issues were identified to be important goals:   o  Deployment of end to end security   o  Deployment of end to end transport   o  Global connectivity and reachability should be maintained   o  It should be easy to deploy new applications   o  It should be easy to connect new hosts and networks to the      Internet ("plug and ping")   By the notion "deployment of end to end transport" it is meant that   it is a goal to be able to deploy new applications that span from any   host to any other host without intermediaries, and this requires   transport protocols with similar span (see also [1]).   This document summarizes the conclusions and recommendations made by   the workshop.  It should be noted that not all participants agreed   with all of the statements, and it was not clear whether anyone   agreed with all of them.  The recommendations made however are based   on strong consensus among the participants.2. Conclusions and Observations   The participants came to a number of conclusions and observations on   several of the issues mentioned insection 1.  In the following   sections2.1-2.10 these conclusions will be described.2.1 Transparency   In the discussions transparency was referred to as the original   Internet concept of a single universal logical addressing scheme and   the mechanisms by which packets may flow from source to destination   essentially unaltered [1].  This traditional end to end transparency   has been lost in the current Internet, specifically the assumption   that IPv4 addresses are globally unique or invariant is no longer   true.   There are multiple causes for the loss of transparency, for example   the deployment of network address translation devices, the use of   private addresses, firewalls and application level gateways, proxies   and caches.  These mechanisms increase fragmentation of the network   layer, which causes problems for many applications on the Internet.   It adds up to complexity in applications design and inhibits the   deployment of new applications.  In particular, it has a severe   effect on the deployment of end to end IP security.Kaat                         Informational                      [Page 3]

RFC 2956            1999 IAB Network Layer Workshop         October 2000   Another consequence of fragmentation is the deployment of "split DNS"   or "two faced DNS", which means that the correspondence between a   given FQDN and an IPv4 address is no longer universal and stable over   long periods (seesection 2.7).   End to end transparency will probably not be restored due to the fact   that some of the mechanisms have an intrinsic value (e.g. firewalls,   caches and proxies) and the loss of transparency may be considered by   some as a security feature.  It was however concluded that end to end   transparency is desirable and an important issue to pursue.   Transparency is further explored in [1].2.2 NAT, Application Level Gateways & Firewalls   The previous section indicated that the deployment of NAT (Network   Address Translation), Application Level Gateways and firewalls causes   loss of network transparency.  Each of them is incompatible with   certain applications because they interfere with the assumption of   end to end transparency.  NAT especially complicates setting up   servers, peer to peer communications and "always-on" hosts as the   endpoint identifiers, i.e. IP addresses, used to set up connections   are globally ambiguous and not stable (see [2]).   NAT, application level gateways and firewalls however are being   increasingly widely deployed as there are also advantages to each,   either real or perceived.  Increased deployment causes a further   decline of network transparency and this inhibits the deployment of   new applications.  Many new applications will require specialized   Application Level Gateways (ALGs) to be added to NAT devices, before   those applications will work correctly when running through a NAT   device.  However, some applications cannot operate effectively with   NAT even with an ALG.2.3 Identification and Addressing   In the original IPv4 network architecture hosts are globally,   permanently and uniquely identified by an IPv4 address.  Such an IP   address is used for identification of the node as well as for   locating the node on the network.  IPv4 in fact mingles the semantics   of node identity with the mechanism used to deliver packets to the   node.  The deployment of mechanisms that separate the network into   multiple address spaces breaks the assumption that a host can be   uniquely identified by a single IP address.  Besides that, hosts may   wish to move to a different location in the network but keep their   identity the same.  The lack of differentiation between the identity   and the location of a host leads to a number of problems in the   current architecture.Kaat                         Informational                      [Page 4]

RFC 2956            1999 IAB Network Layer Workshop         October 2000   Several technologies at this moment use tunneling techniques to   overcome the problem or cannot be deployed in the case of separate   address spaces.  If a node could have some sort of a unique   identifier or endpoint name this would help in solving a number of   problems.   It was concluded that it may be desirable on theoretical grounds to   separate the node identity from the node locator.  This is especially   true for IPsec, since IP addresses are used (in transport mode) as   identifiers which are cryptographically protected and hence MUST   remain unchanged during transport.  However, such a separation of   identity and location will not be available as a near-term solution,   and will probably require changes to transport level protocols.   However, the current specification of IPsec does allow to use some   other identifier than an IP address.2.4 Observations on Address Space   There is a significant risk that a single 32 bit global address space   is insufficient for foreseeable needs or desires.  The participants'   opinions about the time scale over which new IPv4 addresses will   still be available for assignment ranged from 2 to 20 years.   However, there is no doubt that at the present time, users cannot   obtain as much IPv4 address space as they desire.  This is partly a   result of the current stewardship policies of the Regional Internet   Registries (RIRs).   It was concluded that it ought to be possible for anybody to have   global addresses when required or desired.  The absence of this   inhibits the deployment of some types of applications.  It should   however be noted that there will always be administrative boundaries,   firewalls and intranets, because of the need for security and the   implementation of policies.  NAT is seen as a significant   complication on these boundaries.  It is often perceived as a   security feature because people are confusing NATs with firewalls.2.5 Routing Issues   A number of concerns were raised regarding the scaling of the current   routing system.  With current technology, the number of prefixes that   can be used is limited by the time taken for the routing algorithm to   converge, rather than by memory size, lookup time, or some other   factor.  The limit is unknown, but there is some speculation, of   extremely unclear validity, that it is on the order of a few hundred   thousand prefixes.  Besides the computational load of calculating   routing tables, the time it takes to distribute routing updates   across the network, the robustness and security of the current   routing system are also important issues.  The only known addressingKaat                         Informational                      [Page 5]

RFC 2956            1999 IAB Network Layer Workshop         October 2000   scheme which produces scalable routing mechanisms depends on   topologically aggregated addresses, which requires that sites   renumber when their position in the global topology changes.   Renumbering remains operationally difficult and expensive ([3], [4]).   It is not clear whether the deployment of IPv6 would solve the   current routing problems, but it should do so if it makes renumbering   easier.   At least one backbone operator has concerns about the convergence   time of internetwork-wide routing during a failover.  This operator   believes that current convergence times are on the order of half a   minute, and possibly getting worse.  Others in the routing community   did not believe that the convergence times are a current issue. Some,   who believe that real-time applications (e.g. telephony) require   sub-second convergence, are concerned about the implications of   convergence times of a half minute on such applications.   Further research is needed on routing mechanisms that might help   palliate the current entropy in the routing tables, and can help   reduce the convergence time of routing computations.   The workshop discussed global routing in a hypothetical scenario with   no distinguished root global address space.  Nobody had an idea how   to make such a system work.  There is currently no well-defined   proposal for a new routing system that could solve such a problem.   For IPv6 routing in particular, the GSE/8+8 proposal and IPNG WG   analysis of this proposal ([5]) are still being examined by the IESG.   There is no consensus in the workshop whether this proposal could be   made deployable.2.6 Observations on Mobility   Mobility and roaming require a globally unique identifier. This does   not have to be an IP address.  Mobile nodes must have a widely usable   identifier for their location on the network, which is an issue if   private IP addresses are used or the IP address is ambiguous (see   alsosection 2.3).  Currently tunnels are used to route traffic to a   mobile node.  Another option would be to maintain state information   at intermediate points in the network if changes are made to the   packets.  This however reduces the flexibility and it breaks the end   to end model of the network.  Keeping state in the network is usually   considered a bad thing.  Tunnels on the other hand reduce the MTU   size.  Mobility was not discussed in detail as a separate IAB   workshop is planned on this topic.Kaat                         Informational                      [Page 6]

RFC 2956            1999 IAB Network Layer Workshop         October 20002.7 DNS issues   If IPv6 is widely deployed, the current line of thinking is that site   renumbering will be significantly more frequent than today.  This   will have an impact on DNS updates.  It is not clear what the scale   of DNS updates might be, but in the most aggressive models it could   be millions a day.  Deployment of the A6 record type which is defined   to map a domain name to an IPv6 address, with the provision for   indirection for leading prefix bits, could make this possible ([6]).   Another issue is the security aspect of frequent updates, as they   would have to been done dynamically.  Unless we have fully secured   DNS, it could increase security risks.  Cached TTL values might   introduce problems as the cached records of renumbered hosts will not   be updated in time.  This will become especially a problem if rapid   renumbering is needed.   Another already mentioned issue is the deployment of split DNS (seesection 2.1).  This concept is widely used in the Intranet model,   where the DNS provides different information to inside and outside   queries.  This does not necessarily depend on whether private   addresses are used on the inside, as firewalls and policies may also   make this desirable.  The use of split DNS seems inevitable as   Intranets will remain widely deployed.  But operating a split DNS   raises a lot of management and administrative issues.  As a work   around, a DNS Application Level Gateway ([7]) (perhaps as an   extension to a NAT device) may be deployed, which intercepts DNS   messages and modifies the contents to provide the appropriate   answers.  This has the disadvantage that it interferes with the use   of DNSSEC ([8]).   The deployment of split DNS, or more generally the existence of   separate name spaces, makes the use of Fully Qualified Domain Names   (FQDNs) as endpoint identifiers more complex.2.8 NAT and RSIP   Realm-Specific IP (RSIP), a mechanism for use with IPv4, is a work   item of the IETF NAT WG.  It is intended as an alternative (or as a   complement) to network address translation (NAT) for IPv4, but other   uses are possible (for example, allowing end to end traffic across   firewalls).  It is similar to NAT, in that it allows sharing a small   number of external IPv4 addresses among a number of hosts in a local   address domain (called a 'realm').  However, it differs from NAT in   that the hosts know that different externally-visible IPv4 addresses   are being used to refer to them outside their local realm, and theyKaat                         Informational                      [Page 7]

RFC 2956            1999 IAB Network Layer Workshop         October 2000   know what their temporary external address is.  The addresses and   other information are obtained from an RSIP server, and the packets   are tunneled across the first routing realm ([9], [10]).   The difference between NAT and RSIP - that an RSIP client is aware of   the fact that it uses an IP address from another address space, while   with NAT, neither endpoint is aware that the addresses in the packets   are being translated - is significant.  Unlike NAT, RSIP has the   potential to work with protocols that require IP addresses to remain   unmodified between the source and destination.  For example, whereas   NAT gateways preclude the use of IPsec across them, RSIP servers can   allow it [11].   The addition of RSIP to NATs may allow them to support some   applications that cannot work with traditional NAT ([12]), but it   does require that hosts be modified to act as RSIP clients.  It   requires changes to the host's TCP/IP stack, any layer-three protocol   that needs to be made RSIP-aware will have to be modified (e.g. ICMP)   and certain applications may have to be changed.  The exact changes   needed to host or application software are not quite well known at   this moment and further research into RSIP is required.   Both NAT and RSIP assume that the Internet retains a core of global   address space with a coherent DNS.  There is no fully prepared model   for NAT or RSIP without such a core; therefore NAT and RSIP face an   uncertain future whenever the IPv4 address space is finally exhausted   (seesection 2.4).  Thus it is also a widely held view that in the   longer term the complications caused by the lack of globally unique   addresses, in both NAT and RSIP, might be a serious handicap ([1]).   If optimistic assumptions are made about RSIP (it is still being   defined and a number of features have not been implemented yet), the   combination of NAT and RSIP seems to work in most cases.  Whether   RSIP introduces specific new problems, as well as removing some of   the NAT issues, remains to be determined.   Both NAT and RSIP may have trouble with the future killer   application, especially when this needs QoS features, security and/or   multicast.  And if it needs peer to peer communication (i.e. there   would be no clear distinction between a server and a client) or   assumes "always-on" systems, this would probably be complex with both   NAT and RSIP (see alsosection 2.2).2.9 NAT, RSIP and IPv6   Assuming IPv6 is going to be widely deployed, network address   translation techniques could play an important role in the transition   process from IPv4 to IPv6 ([13]).  The impact of adding RSIP supportKaat                         Informational                      [Page 8]

RFC 2956            1999 IAB Network Layer Workshop         October 2000   to hosts is not quite clear at this moment, but it is less than   adding IPv6 support since most applications probably don't need to be   changed.  And RSIP needs no changes to the routing infrastructure,   but techniques such as automatic tunneling ([14]) and 6to4 ([15])   would also allow IPv6 traffic to be passed over the existing IPv4   routing infrastructure.  While RSIP is principally a tool for   extending the life of IPv4, it is not a roadblock for the transition   to IPv6.  The development of RSIP is behind that of IPv6, and more   study into RSIP is required to determine what the issues with RSIP   might be.2.10 Observations on IPv6   An important issue in the workshop was whether the deployment of IPv6   is feasible and probable.  It was concluded that the transition to   IPv6 is plausible modulo certain issues.  For example applications   need to be ported to IPv6, and production protocol stacks and   production IPv6 routers should be released.  The core protocols are   finished, but other standards need to be pushed forward (e.g. MIBs).   A search through all RFCs for dependencies on IPv4 should be made, as   was done for the Y2K problem, and if problems are found they must be   resolved.  As there are serious costs in implementing IPv6 code, good   business arguments are needed to promote IPv6.   One important question was whether IPv6 could help solve the current   problems in the routing system and make the Internet scale better.   It was concluded that "automatic" renumbering is really important   when prefixes are to be changed periodically to get the addressing   topology and routing optimized.  This also means that any IP layer   and configuration dependencies in protocols and applications will   have to be removed ([3]).  One example that was mentioned is the use   of IP addresses in the PKI (IKE).  There might also be security   issues with "automatic" renumbering as DNS records have to be updated   dynamically (see alsosection 2.7).   Realistically, because of the dependencies mentioned, IPv6   renumbering cannot be truly automatic or instantaneous, but it has   the potential to be much simpler operationally than IPv4 renumbering,   and this is critical to market and ISP acceptance of IPv6.   Another issue is whether existing TCP connections (using the old   address(es)) should be maintained across renumbering.  This would   make things much more complex and it is foreseen that old and new   addresses would normally overlap for a long time.   There was no consensus on how often renumbering would take place or   how automatic it can be in practice; there is not much experience   with renumbering (maybe only for small sites).Kaat                         Informational                      [Page 9]

RFC 2956            1999 IAB Network Layer Workshop         October 20003. Recommendations3.1 Recommendation on Namespace   The workshop recommends the IAB to appoint a panel to make specific   recommendations to the IETF about:      i) whether we should encourage more parts of the stack to adopt a         namespace for end to end interactions, so that a) NAT works         'better', and b) we have a little more independence between the         internetwork and transport and above layers;     ii) if so, whether we should have a single system-wide namespace         for this function, or whether it makes more sense to allow         various subsystems to chose the namespace that makes sense for         them;    iii) and also, what namespace(s) [depending on the output of the         point above] that ought to be.3.2 Recommendations on RSIP   RSIP is an interesting idea, but it needs further refinement and   study.  It does not break the end to end network model in the same   way as NAT, because an RSIP host has explicit knowledge of its   temporary global address.  Therefore, RSIP could solve some of the   issues with NAT.  However, it is premature to recommend it as a   mainstream direction at this time.   It is recommended that the IETF should actively work on RSIP, develop   the details and study the issues.3.3 Recommendations on IPv63.3.1   The current model of TLA-based addressing and routing should be   actively pursued.  However, straightforward site renumbering using   TLA addresses is really needed, should be as nearly automatic as   possible, and should be shown to be real and credible by the IPv6   community.3.3.2   Network address translation techniques, in addition to their   immediate use in pure IPv4 environments, should also be viewed as   part of the starting point for migration to IPv6.  Also RSIP, if   successful, can be a starting point for IPv6 transition.Kaat                         Informational                     [Page 10]

RFC 2956            1999 IAB Network Layer Workshop         October 2000   While the basic concepts of the IPv4 specific mechanisms NAT and RSIP   are also being used in elements of the proposed migration path to   IPv6 (in NAT-PT for NAT, and SIIT and AIIH for RSIP), NAT and RSIP   for IPv4 are not directly part of a documented transition path to   IPv6.   The exact implications, for transition to IPv6, of having NAT and   RSIP for IPv4 deployed, are not well understood.  Strategies for   transition to IPv6, for use in IPv4 domains using NAT and RSIP for   IPv4, should be worked out and documented by the IETF.3.3.3   The draft analysis of the 8+8/GSE proposal should be evaluated by the   IESG and accepted or rejected, without disturbing ongoing IPv6   deployment work.  The IESG should use broad expertise, including   liaison with the endpoint namespace panel (seesection 3.1) in their   evaluation.3.4 Recommendations on IPsec   It is urgent that we implement and deploy IPsec using some other   identifier than 32-bit IP addresses (seesection 2.3).  The current   IPsec specifications support the use of several different Identity   types (e.g. Domain Name, User@Domain Name).  The IETF should promote   implementation and deployment of non-address Identities with IPsec.   We strongly urge the IETF to completely deprecate the use of the   binary 32-bit IP addresses within IPsec, except in certain very   limited circumstances, such as router to router tunnels; in   particular any IP address dependencies should be eliminated from   ISAKMP and IKE.   Ubiquitous deployment of the Secure DNS Extensions ([8]) should be   strongly encouraged to facilitate widespread deployment of IPsec   (including IKE) without address-based Identity types.3.5 Recommendations on DNS   Operational stability of DNS is paramount, especially during a   transition of the network layer, and both IPv6 and some network   address translation techniques place a heavier burden on DNS.  It is   therefore recommended to the IETF that, except for those changes that   are already in progress and will support easier renumbering of   networks and improved security, no fundamental changes or additions   to the DNS be made for the foreseeable future.   In order to encourage widespread deployment of IPsec, rapid   deployment of DNSSEC is recommended to the operational community.Kaat                         Informational                     [Page 11]

RFC 2956            1999 IAB Network Layer Workshop         October 20003.6 Recommendations on Routing   The only known addressing scheme which produces scalable routing   mechanisms depends on topologically aggregated addresses, which   requires that sites renumber when their position in the global   topology changes.  Thus recommendation 3.3.1 is vital for routing   IPv6.   Although the same argument applies to IPv4, the installed base is   simply too large and the PIER working group showed that little can be   done to improve renumbering procedures for IPv4.  However, NAT and/or   RSIP may help.   In the absence of a new addressing model to replace topological   aggregation, and of clear and substantial demand from the user   community for a new routing architecture (i.e. path-selection   mechanism) there is no reason to start work on standards for a "next   generation" routing system in the IETF.  Therefore, we recommend that   work should continue in the IRTF Routing Research Group.3.7 Recommendations on Application layer and APIs   Most current APIs such as sockets are an obstacle to migration to a   new network layer of any kind, since they expose network layer   internal details such as addresses.   It is therefore recommended, as originally recommended inRFC 1900   [3], that IETF protocols, and third-party applications, avoid any   explicit awareness of IP addresses, when efficient operation of the   protocol or application is feasible in the absence of such awareness.   Some applications and services may continue to need to be aware of IP   addresses.  Until we once again have a uniform address space for the   Internet, such applications and services will necessarily have   limited deployability, and/or require ALG support in NATs.   Also we recommend an effort in the IETF to generalize APIs to offer   abstraction from all network layer dependencies, perhaps as a side-   effect of the namespace study ofsection 3.1.4. Security Considerations   The workshop did not address security as a separate topic, but the   role of firewalls, and the desirability of end to end deployment of   IPsec, were underlying assumptions.  Specific recommendations on   security are covered in sections3.4 and3.5.Kaat                         Informational                     [Page 12]

RFC 2956            1999 IAB Network Layer Workshop         October 2000References   [1]   Carpenter, B., "Internet Transparency",RFC 2775, February         2000.   [2]   Hain, T.,"Architectural Implications of NAT", Work in         Progress.   [3]   Carpenter, B. and Y. Rekhter, "Renumbering Needs Work",RFC1900, February 1996.   [4]   Ferguson, P and H. Berkowitz, "Network Renumbering Overview:         Why would I want it and what is it anyway?",RFC 2071, January         1997.   [5]   M. Crawford, A. Mankin, T. Narten, J.W. Stewart, III, L. Zhang,         "Separating Identifiers and Locators in Addresses: An Analysis         of the GSE Proposal for IPv6", Work in Progress.   [6]   Crawford, M., and C. Huitema, "DNS Extensions to Support IPv6         Address Aggregation and Renumbering",RFC 2874, July 2000.   [7]   Srisuresh, P., Tsirtsis, G., Akkiraju, P. and A. Heffernan,         "DNS extensions to Network Address Translators (DNS_ALG)",RFC2694, September 1999.   [8]   Eastlake, D., "Domain Name System Security Extensions",RFC2535, March 1999.   [9]   M. Borella, D. Grabelsky, J. Lo, K. Tuniguchi "Realm Specific         IP: Protocol Specification", Work in Progress.   [10]  M. Borella, J. Lo, D. Grabelsky, G. Montenegro "Realm Specific         IP: Framework", Work in Progress.   [11]  G. Montenegro, M. Borella,"RSIP Support for End-to-end IPsec",         Work in Progress.   [12]  M. Holdrege, P. Srisuresh, "Protocol Complications with the IP         Network Address Translator", Work in Progress.   [13]  Tsirtsis, G. and P. Srisuresh, "Network Address Translation -         Protocol Translation (NAT-PT)",RFC 2766, February 2000.Kaat                         Informational                     [Page 13]

RFC 2956            1999 IAB Network Layer Workshop         October 2000   [14]  Gilligan, R. and E. Nordmark, "Transition Mechanisms for IPv6         Hosts and Routers",RFC 2893, August 2000.   [15]  B. Carpenter, K. Moore, "Connection of IPv6 Domains via IPv4         Clouds", Work in Progress.Kaat                         Informational                     [Page 14]

RFC 2956            1999 IAB Network Layer Workshop         October 2000Appendix A. Participants   Harald Alvestrand           harald@alvestrand.no   Ran Atkinson                rja@corp.home.net   Rob Austein                 sra@hactrn.net   Steve Bellovin              smb@research.att.com   Randy Bush                  randy@psg.com   Brian E Carpenter           brian@hursley.ibm.com   Vint Cerf                   vcerf@MCI.NET   Noel Chiappa                jnc@lcs.mit.edu   Matt Crawford               crawdad@fnal.gov   Robert Elz                  kre@munnari.OZ.AU   Tony Hain                   tonyhain@microsoft.com   Matt Holdrege               matt@ipverse.com   Erik Huizer                 huizer@cs.utwente.nl   Geoff Huston                gih@telstra.net   Van Jacobson                van@cisco.com   Marijke Kaat                Marijke.Kaat@surfnet.nl   Daniel Karrenberg           Daniel.Karrenberg@ripe.net   John Klensin                klensin@jck.com   Peter Lothberg              roll@Stupi.SE   Olivier H. Martin           Olivier.Martin@cern.ch   Gabriel Montenegro          gab@sun.com   Keith Moore                 moore@cs.utk.edu   Robert (Bob) Moskowitz      rgm@htt-consult.com   Philip J. Nesser II         pjnesser@nesser.com   Kathleen Nichols            kmn@cisco.com   Erik Nordmark               nordmark@eng.sun.com   Dave Oran                   oran@cisco.com   Yakov Rekhter               yakov@cisco.com   Bill Sommerfeld             sommerfeld@alum.mit.edu   Bert Wijnen                 wijnen@vnet.ibm.com   Lixia Zhang                 lixia@cs.ucla.eduAuthor's Address   Marijke Kaat   SURFnet ExpertiseCentrum bv   P.O. Box 19115   3501 DC  Utrecht   The Netherlands   Phone: +31 30 230 5305   Fax: +31 30 230 5329   EMail: Marijke.Kaat@surfnet.nlKaat                         Informational                     [Page 15]

RFC 2956            1999 IAB Network Layer Workshop         October 2000Full Copyright Statement   Copyright (C) The Internet Society (2000).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS 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.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Kaat                         Informational                     [Page 16]