James Kempf Internet Draft Rob Austein Document: draft-iab-e2e-futures-03.txt IAB Expires: October 2003 April 2003 The Rise of the Middle and the Future of End to End: Reflections on the Evolution of the Internet Architecture Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract The end to end principle is the core architectural guidline of the Internet. In this document, we briefly examine the development of the end to end principle as it has been applied to the Internet architecture over the years. We discuss current trends in the evolution of the Internet architecture in relation to the end to end principle, and try to draw some conclusion about the evolution of the end to end principle, and thus for the Internet architecture which it supports, in light of these current trends. Table of Contents 1.0 Introduction..........................................................2 2.0 A Brief History of the End to End Principle...........................2 3.0 Trends Opposed to the End to End Principle............................4 4.0 Whither the End to End Principle?.....................................7 5.0 Internet Standards as an Arena for Conflict...........................9 6.0 Conclusions..........................................................10 7.0 Acknowledgements.....................................................10 8.0 References...........................................................10 9.0 Security Considerations..............................................11 10.0 IANA Considerations................................................11 Kempf and Austein Expires October 2003 [Page 1] Internet Draft Future of End to End April, 2003 11.0 Author Information.................................................11 12.0 Full Copyright Statement...........................................12 1.0 Introduction One of the key architectural guidelines of the Internet is the end to end principle in the papers by Saltzer, Reed, and Clark .[1][2]. The end to end principle was originally articulated as a question of where best not to put functions in a communication system. Yet, in the ensuing years, it has evolved to address concerns of maintaining openness, increasing reliability and robustness, and preserving the properties of user choice and ease of new service development as discussed by Blumenthal and Clark in .[3]; concerns that were not part of the original articulation of the end to end principle. In this document, we examine how the interpretation of the end to end principle has evolved over the years, and where it stands currently. We examine trends in the development of the Internet that have led to pressure to define services in the network, a topic that has already received some amount of attention from the IAB in RFC 3238 [4]. We describe some considerations about how the end to end principle might evolve in light of these trends. Discussion of this draft should be directed to: end2end-interest@postel.org subscribe through: http://www.postel.org/mailman/listinfo/end2end-interest. 2.0 A Brief History of the End to End Principle 2.1 In the Beginnning... The end to end principle was originally articulated as a question of where best not to put functions in a communication system: The function in question can completely and correctly be implemented only with the knowledge and help of the application standing at the end points of the communication system. Therefore, providing that questioned function as a feature of the communication system itself is not possible. (Sometimes an incomplete version of the function provided by the communication system may be useful as a performance enhancement.) [1]. The specific examples given in [1] and other references at the time [2] primarily involve transmission of data packets: data integrity, delivery guarantees, duplicate message suppression, per packet encryption, and transaction management. From the viewpoint of today's Internet architecture, we would view most of these as transport layer functions (data integrity, delivery guarantees, duplicate message suppression, and perhaps transaction management), others as network layer functions with support at other layers where necessary (for example, packet encryption), and not application layer functions. Kempf and Austein Expires October 2003 [Page 2] Internet Draft Future of End to End April, 2003 Interestingly, the expression of the end to end principle cited above is phrased as a negative: what *cannot* be fully provided in a communication system rather than what can be provided. Much of the wider applicability later attributed to the end to end principle, outside of the original application to the transport of packets, derives from this phrasing. 2.2 ...In the Middle... As the Internet developed, the end to end principle gradually widened to concerns about where best to put the state associated with applications in the Internet: in the network or at end nodes. The best example is the description in RFC 1958 [5]: This principle has important consequences if we require applications to survive partial network failures. An end-to-end protocol design should not rely on the maintenance of state (i.e. information about the state of the end-to-end communication) inside the network. Such state should be maintained only in the endpoints, in such a way that the state can only be destroyed when the endpoint itself breaks (known as fate-sharing). An immediate consequence of this is that datagrams are better than classical virtual circuits. The network's job is to transmit datagrams as efficiently and flexibly as possible. Everything else should be done at the fringes. The original articulation of the end to end principle as where not to define functions in a communication system took a while to percolate through the engineering community, and had evolved by this point to a broad architectural statement about what belongs in the network and what doesn't. RFC 1958 uses the term "application" to mean the entire network stack on the end node, including network, transport, and application layers, in contrast to the earlier articulation of the end to end principle as being about the communication system itself. "Fate-sharing" describes this quite clearly: the fate of a conversation between two applications is only shared between the two applications; the fate does not depend on anything in the network, except for the network's ability to get packets from one application to the other. The end to end principle in this formulation is specifically about what kind of state is maintained where: To perform its services, the network maintains some state information: routes, QoS guarantees that it makes, session information where that is used in header compression, compression histories for data compression, and the like. This state must be self-healing; adaptive procedures or protocols must exist to derive and maintain that state, and change it when the topology or activity of the network changes. The volume of this state must be minimized, and the loss of the state must not result in more than a temporary denial of service given that connectivity exists. Manually configured state must be kept to an absolute minimum.[5] In this formulation of the end to end principle, state involved in getting packets from one end of the network to the other is maintained in the network. The state is "soft state," in the sense that it can be quickly dropped and reconstructed (or even required to be periodically renewed) as the network topology changes due to routers and switches going on and off line. "Hard Kempf and Austein Expires October 2003 [Page 3] Internet Draft Future of End to End April, 2003 state", state upon which the proper functioning of the application depends, is only maintained in the end nodes. In summary, the general awareness both of the principle itself and of its implications for how unavoidable state should be handled grew over time to become a (if not the) foundation principle of the Internet architecture. 2.3 ...And Now. An interesting example of how the end to end principle continues to influence the technical debate in the Internet community is IP mobility. While the existing Internet routing architecture imposes some severe constraints on how closely IP mobility can match the end to end principle, the Mobile IPv6 standard, described in the Mobile IPv6 draft by Johnson, Perkins, and Arkko [6], tries to strike a balance. Mobile IPv6 has eliminated the local routing proxy (the Foreign Agent), which was a feature of the older Mobile IPv4 design that compromised end to end routing. The end node now handles its own routing identifier, the care of address. In addition, Mobile IPv6 includes secure mechanisms for optimizing routing to allow end to end routing between the mobile end node and the correspondent node, removing the need to route through the global routing proxy at the home agent. These features are all based on end to end considerations. However, the need for the global routing proxy in the home agent in Mobile IPv6 is determined by the aliasing of the global node identifier with the routing identifier in the Internet routing architecture, a topic that was discussed in an IAB workshop and reported in RFC 2956 [8], and that hasn't changed in IPv6. Despite this constraint, the vision emerging out of the IETF working groups developing standards for mobile networking is of a largely autonomous mobile node with multiple wireless link options, among which the mobile node picks and chooses. The end node is therefore responsible for maintaining the integrity of the communication, as the end to end principle implies. This kind of innovative application of the end to end principle derives from the same basic considerations of reliability and robustness (wireless link integrity, changes in connectivity and service availability with movement, etc.) that motivated the original development of the end to end principle. While the basic reliability of wired links and routing and switching equipment has improved considerably since the end to end principle was formalized 15 years ago, the reliability or unreliability of wireless links is governed more strongly by the basic physics of the medium and the instantaneous radio propagation conditions. It therefore seems likely that despite the inclusion of link mechanisms to mitigate unreliability in wireless links, the end to end principle will play an increasingly important role in IP wireless networking technology. 3.0 Trends Opposed to the End to End Principle While the end to end principle continues to provide a solid foundation for much IETF design work, the specific application of the end to end principle described in RFC 1958 has increasingly come into question from various directions. The IAB has been concerned about trends opposing the end to end principle for some time, for example RFC 2956 [8] and RFC 2775 [11]. The primary focus of concern in these documents is the reduction in transparency due to the introduction of NATs and other address translation mechanisms in the Internet, and the consequences to the end to end principle of various scenarios Kempf and Austein Expires October 2003 [Page 4] Internet Draft Future of End to End April, 2003 involving full, partial, or no deployment of IPv6. More recently, the topic of concern has shifted to the consequences of service deployment in the network. The IAB opinion on Open Pluggable Edge Services (OPES) in RFC 3238 [4] is intended to assess the architectural desirability of defining services in the network and to raise questions about how such services might result in compromises of privacy, security, and end-to-end data integrity. Clark, et al. in [9] and Carpenter in RFC 3234 [10] also take up the topic of service definition in the network. Perhaps the best review of the forces militating against the end to end principle is by Blumenthal and Clark in [3]. The authors make the point that the Internet originally developed among a community of like-minded technical professionals who trusted each other, and was administered by academic and government institutions who enforced a policy of no commercial use. The major stakeholders in the Internet are quite different today. As a consequence, new requirements have evolved over the last decade. Examples of these requirements are discussed in the following subsections. Other discussions about pressures on the end to end principle in today's Internet can be found in the discussion by Reed [12] and Moors' paper in the 2002 IEEE International Communications Conference [13]. 3.1 Lack of Trust Perhaps the single most important change from the Internet of 15 years ago is the lack of trust between end nodes. Because the end users in the Internet of 15 years ago were few, and were largely dedicated to using the Internet as a tool for academic research and communicating research results (explict commercial use of the Internet was forbidden when it was run by the US government), trust between end users (and thus between the end nodes that they use) and between network operators and their users was simply not an issue in general. Today, the motivations of some individuals using the Internet are not always entirely ethical, and, even if they are, the assumption that end nodes will always co-operate to achieve some mutually beneficial action, as implied by the end to end principle, is not always accurate. In addition, the growth in users who are either not technologically sophisticated enough or simply uninterested in maintaining their own security has required network operators to become more proactive in deploying measures to prevent naive or uninterested users from inadvertently or intentionally generating security problems. While the end to end principle does not require that end nodes implicitly trust each other, the lack of trust in the Internet today requires that application and system designers make a choice about how to handle lack of trust, whereas that choice was rarely apparent 15 years ago. One of the most common examples of network elements interposing between end hosts are those dedicated to security: firewalls, VPN tunnel endpoints, certificate servers, etc. These intermediaries are designed to protect the network from unimpeded attack or to allow two end nodes that may have no inherent reason to trust each other to achieve some level of trust; but, at the same time, they act as impediments for end to end communications. Third party trust intermediaries are not a requirement for security, as end to end security mechanisms, such at PGP [14], can be used instead. Even if third parties are involved, ultimately it is up to the endpoints to determine which third parties they trust. Kempf and Austein Expires October 2003 [Page 5] Internet Draft Future of End to End April, 2003 3.2 New Service Models New service models inspired by new applications require achieving the proper performance level as a fundamental part of the delivered service. These service models are a significant change from the original best effort service model. Email, file transfer, and even Web access aren't perceived as failing if performance degrades, though the user may become frustrated at the time required to complete the transaction. However, for streaming audio and video, to say nothing of real time bidirectional voice and video, achieving the proper performance level, whatever that might mean for an acceptable user experience of the service, is part of delivering the service, and a customer contracting for the service has a right to expect the level of performance for which they have contracted. For example, content distributors sometimes release content via content distribution servers that are spread around the Internet at various locations to avoid delays in delivery if the server is topologically far away from the client. Retail broadband and multimedia services are a new service model for many service providers. 3.3 Rise of the Third Party Academic and government institutions ran the Internet of 10 years ago. These institutions did not expect to make a profit from their investment in networking technology. In contrast, the network operator with which most Internet users deal today is the commercial ISP. Commercial ISPs run their networks as a business, and expect to make a profit (or at least not lose much) on their investment in the network. While this radical change in business model is not an excuse for modifying an architectural principle that has exhibited its value over time, it does put a certain amount of pressure on the end to end principle. In particular, the standard retail dialup bit pipe account with email and shell access has become a commodity service, resulting in low profit margins. While many ISPs are happy with this business model and are able to survive on it, others would like to deploy different service models that have a higher profit potential and provide the customer with more or different services. An example is retail broadband bit pipe access via cable or DSL coupled with streaming multimedia. Some ISPs that offer broadband access also deploy content distribution networks to increase the performance of streaming media. These services are typically deployed so that they are only accessible within the ISP's network, and as a result, they do not contribute to open, end to end service. ISPs are not the only third party intermediary that has appeared within the last 10 years. Unlike the previous involvement of corporations and governments in running the Internet, corporate network administrators, and governmental officials have become increasingly demanding of opportunities to interpose between two parties in an end to end conversation. A benign motivation for this involvement is to mitigate the lack of trust, so the third party acts as a trust anchor or enforcer of good behavior between the two ends. A less benign motivation is for the third parties to insert policy for their own reasons, perhaps taxation or even censorship. The requirements of third parties often have little or nothing to do with technical concerns, but rather derive from particular social and legal considerations. Kempf and Austein Expires October 2003 [Page 6] Internet Draft Future of End to End April, 2003 3.4 The Consumer as the Primary User The original users of the Internet were technologists who understood how it worked and had no reservations about tinkering with the software or hardware on their end hosts. The users of today are primarily non-technical consumers who buy packaged hardware and software from vendors and contract with ISPs for service. They expect their Internet service to function smoothly like any other product they buy, without much involvement on their part in keeping the product functional. This development matches closely the development of other technologies, for example the automobile, that have become mainstream. This pressure to simplify the user experience has resulted in a corresponding pressure to reduce the amount of installation, configuration, maintenance, and upgrade on end nodes. Requiring user involvement in the deployment of new software or hardware on the end nodes, in order to deploy new services, runs directly counter to this trend. One response has been the tendency to move deployment of new services to servers running an existing protocol, such as HTTP, or downloadable code, such as Java or browser plug-ins, which don't require any user involvement to install. Utilizing existing protocols such as HTTP also simplifies deployment from the network operator's perspective, since the network operator does not need to open a new hole in the firewall. Another response has been network intermediaries to provide the service. Typically, these intermediaries don't interpose on a flow between a client and a server, but they may act more like DNS, in that the intermediary is required in order to get access to the service. A further development of this trend would be to move much of the context and configuration for a user into a node in the network, where it can be upgraded without any user involvement. This development would remove the end host as the definitive location for the application and spread it out between the network and the end host. 4.0 Whither the End to End Principle? Given the pressures on the end to end principle discussed in the previous section, a question arises about the future of the end to end principle. Does the end to end principle have a future in the Internet architecture or not? If it does have a future, how should it be applied? Clearly, an unproductive approach to answering this question is to insist upon the end to end principle as a fundamentalist principle that allows no compromise. The pressures described above are real and powerful, and if the current Internet technical community chooses to ignore these pressures, the likely result is that a market opportunity will be created for a new technical community that does not ignore these pressures but which may not understand the implications of their design choices. A more productive approach is to return to first principles and re- examine what the end to end principle is trying to accomplish, and then update our definition and exposition of the end to end principle given the complexities of the Internet today. 4.1 Consequences of the End to End Principle In this section, we consider the two primary desirable consequences of the end to end principle: protection of innovation and provision of reliability and robustness. Kempf and Austein Expires October 2003 [Page 7] Internet Draft Future of End to End April, 2003 4.1.1 Protection of Innovation One desirable consequence of the end to end principle is protection of innovation. Requiring modification in the network in order to deploy new services is still typically more difficult than modifying end nodes. The lack of widespread deployment of multicast in public service providers is an example, since it is impossible to deploy without touching the network. The counterargument in Section 3 - that many end nodes are now essentially closed boxes which are not updatable and that most users don't want to update them anyway - does not apply to all nodes and all users. Many end nodes are still user configurable and a sizable percentage of users are "early adopters," who are willing to put up with a certain amount of technological grief in order to try out a new idea. And, even for the closed boxes and uninvolved users, downloadable code that abides by the end to end principle can provide fast service innovation. Requiring someone with a new idea for a service to convince a bunch of ISPs or corporate network administrators to modify their networks is much more difficult than simply putting up a Web page with some downloadable software implementing the service. 4.1.2 Reliability and Robustness The second desirable consequence of the end to end principle is an increase in the reliability and robustness of the exchange between the two parties in the conversation. During the early development of the Internet, the basic reliability of the hardware and software was fairly low, so involving additional network elements between the two ends could radically decrease the reliability of the overall connection. Technical reliability has improved considerably, but reliability due to involvement of network elements is still a concern [4]. In particular, as discussed in Section 2, wireless links suffer from an inherent unreliability that can only be partially mitigated by costly measures at the link layer, and new software upgrades still suffer from unexpected bugs, despite the increased quality control applied by vendors. These sources of unreliability in network elements are likely to remain for the near term future. 4.1.3 Reliability and Trust Of more concern today, however, is the decrease in reliability and robustness that results from deliberate, active attacks on the network infrastructure and end nodes. While the original developers of the Internet were concerned by large-scale system failures, attacks of the subtlety and variety that the Internet experiences today were not a problem during the original development of the Internet. By and large, the end to end principle was not addressed to the decrease in reliability resulting from attacks deliberately engineered to take advantage of subtle flaws in software. These attacks are part of the larger issue of the trust breakdown discussed in Section 3. Thus, the issue of the trust breakdown can be considered another forcing function on the Internet architecture. The immediate reaction to this trust breakdown has been to try to back fit security into existing protocols. While this effort is necessary, it is not sufficient. The issue of trust must become as firm an architectural principle in protocol design for the future as the end to end principle is today. Trust isn't simply a matter of adding some cryptographic protection to a protocol Kempf and Austein Expires October 2003 [Page 8] Internet Draft Future of End to End April, 2003 after it is designed. Rather, prior to designing the protocol, the trust relationships between the network elements involved in the protocol must be defined, and boundaries must be drawn between those network elements that share a trust relationship. The trust boundaries should be used to determine what type of communication occurs between the network elements involved in the protocol and which network elements signal each other. When communication occurs across a trust boundary, cryptographic or other security protection of some sort may be necessary. Additional measures may be necessary to secure the protocol when communicating network elements do not share a trust relationship. For example, a protocol might need to minimize state in the recipient prior to establishing the validity of the credentials from the sender in order to avoid a memory depletion DoS attack. 4.2 Unbundling the End to End Principle One way to approach the end to end principle given the complexities of today's Internet is to, in a sense, unbundle it into its components of innovation protection and reliability and robustness, and apply these individually. Consider, for example, a distributed application running as an applet on an Internet appliance, like a cell phone or a pager. Provisioning of the appliance is a consequence of an end to end process, such as downloading the code for the applet from a Web, thus preserving rapid innovation. But in the operation of a distributed application, the end to end principle is not the only consideration for increasing reliability and robustness. For example, reliability and robustness can be increased with replication. An applet communicates with a server that then communicates with several databases or other applications that provide replicated services, and so on. The applet itself may have little or no knowledge of the services utilized by the server, but replication in those services may provide more reliability and robustness than if the end node running the applet had to manage the services, and at a considerable reduction in complexity. The entire application achieves robustness through distribution and replication of state and the possibility of failover maintained by the individual pieces of the application, while the end to end principle applies to each individual connection in the distributed application. 5.0 Internet Standards as an Arena for Conflict Internet standards have increasingly become an arena for conflict [9]. ISPs have certain concerns, businesses and government have others, and vendors of networking hardware and software still others. Often, these concerns conflict, and sometimes they conflict with the concerns of the end users. For example, ISPs are reluctant to deploy interdomain QoS services because, among other reasons, every known instance creates a significant and easily exploited DoS/DDoS vulnerability. However, some end users would like to have end-to-end, Diffserv or Intserv-style QoS available to improve support for voice and video multimedia applications between end nodes in different domains, as discussed by Huston in RFC 2990 [15]. In this case, the security, robustness and reliability concerns of the ISP conflict with the desire of users for a different type of service. These conflicts will inevitably be reflected in the Internet architecture going forward. Some of these conflicts are impossible to resolve on a technical level, nor would it even be desirable, because they involve social and legal Kempf and Austein Expires October 2003 [Page 9] Internet Draft Future of End to End April, 2003 choices that the IETF is not empowered to make (for a counter argument in the area of privacy, see Goldberg, et al. [16]). But for those conflicts that do involve technical choices, the important properties of user choice and empowerment, reliability and integrity of end to end service, supporting trust and "good network citizen behavior," and fostering innovation in services should be the basis upon which resolution is made. The conflict will then play out on the field of the resulting architecture. 6.0 Conclusions The end to end principle continues to guide technical development of Internet standards, and remains as important today for the Internet architecture as in the past. In many cases, unbundling of the end to end principle into its consequences leads to a distributed approach in which the end to end principle applies to interactions between the individual pieces of the application, while the unbundled consequences, protection of innovation and reliability and robustness, apply to the entire application. While the end to end principle originated as a focused argument about where best not to put functions in a communication system, particular properties developed by the Internet as a result of the end to end principle have come to be recognized as being as important, if not more so, than the principle itself. End user choice and empowerment, integrity of service, support for trust, and "good network citizen behavior" are all properties that have developed as a consequence of the end to end principle. Recognizing these properties in a particular proposal for modifications to the Internet has become more important than before as the pressures to incorporate services into the network have increased. Any proposal to incorporate services in the network should be weighed against these properties before proceeding. 7.0 Acknowledgements Many of the ideas presented here originally appeared in the works of Dave Clark, John Wroclawski, Bob Braden, Karen Sollins, Marjory Blumenthal, and Dave Reed on forces currently influencing the evolution of the Internet. The authors would particularly like to single out the work of Dave Clark, who was the original articulator of the end to end principle and who continues to inspire and guide the evolution of the Internet architecture, and John Wroclawski, with whom conversations during the development of this paper helped to clarify issues involving tussle and the Internet. 8.0 References [1] Saltzer, J.H., Reed, D.P., and Clark, D.D., "End to End Arguments in System Design," Communications Policy in Transition: The Internet and Beyond, B. Compaine and S. Greenstein, eds. MIT Press, September 2001. [2] Clark, D., "The Design Philosophy of the DARPA Internet Protocols," Proc SIGCOMM 88, ACM CCR Vol 18, Number 4, August 1988, pp. 106-114. [3] Blumenthal, M., Clark, D.D., "Rethinking the design of the Internet: The end to end arguments vs. the brave new world", ACM Transactions on Internet Technology, Vol. 1, No. 1, August 2001, pp 70-109. [4] Floyd, S., and Daigle, L., "IAB Architectural and Policy Considerations for Open Pluggable Edge Services", RFC 3238, January 2002. Kempf and Austein Expires October 2003 [Page 10] Internet Draft Future of End to End April, 2003 [5] Carpenter, B., "Architectural Principles of the Internet," RFC 1958, June, 1996. [6] Johnson, D., Perkins, C., and Arkko, J., "Mobility Support in IPv6," draft-ietf-mobileip-ipv6-20.txt, a work in progress. [7] Perkins, C., editor, "Mobility Support in IPv4", RFC 3220, August, 2002. [8] Kaat, M., "Overview of 1999 IAB Network Layer Workshop," RFC 2956, October, 2000. [9] Clark, D.D., Wroclawski, J., Sollins, K., and Braden, B., "Tussle in Cyberspace: Defining Tommorow's Internet", Proceedings of Sigcomm 2002. [10] Carpenter, B., and Brim, S., "Middleboxes: Taxonomy and Issues," RFC 3234, February, 2002. [11] Carpenter, B., "Internet Transparency," RFC 2775, February, 2000. [12] Reed, D., "The End of the End-to-End Argument?", http://www.reed.com/dprframeweb/dprframe.asp?section=paper&fn=endofendt oend.html, April, 2000. [13] Moors, T., "A Critical Review of End-to-end Arguments in System Design," Proc. 2000 IEEE International Conference on Communications, pp. 1214-1219, April, 2002. [14] Atkins, D., Stallings, W., and Zimmerman, P., "PGP Message Formats", RFC 1991, August, 1996. [15] Huston, G., "Next Steps for the IP QoS Architecture", RFC 2990, November, 2000. [16] Goldberg, I., Wagner, D., and Brewer, E., "Privacy-enhancing technologies for the Internet," Proceedings of IEEE COMPCON 97, pp. 103-109, 1997. 9.0 Security Considerations This document does not propose any new protocols, and therefore does not involve any security considerations in that sense. However, throughout this document there are discussions of the privacy and integrity issues and the architectural requirements created by those issues. 10.0 IANA Considerations There are no IANA considerations regarding this document. 11.0 Author Information Internet Architecture Board EMail: iab@iab.org IAB Membership at time this document was completed: Bernard Aboba Harald Alvestrand Rob Austein Leslie Daigle Patrik F„ltstr÷m Sally Floyd Jun-ichiro Itojun Hagino Kempf and Austein Expires October 2003 [Page 11] Internet Draft Future of End to End April, 2003 Mark Handley Geoff Huston Charlie Kaufman James Kempf Eric Rescorla Mike St. Johns This draft was created in April 2003. 12.0 Full Copyright Statement Copyright (C) The Internet Society (2003). 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. 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