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Network Working Group                                      B. Aboba, Ed.Request for Comment: 4924                                      E. DaviesCategory: Informational                      Internet Architecture Board                                                               July 2007Reflections on Internet TransparencyStatus 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 IETF Trust (2007).Abstract   This document provides a review of previous IAB statements on   Internet transparency, as well a discussion of new transparency   issues.  Far from having lessened in relevance, technical   implications of intentionally or inadvertently impeding network   transparency play a critical role in the Internet's ability to   support innovation and global communication.  This document provides   some specific illustrations of those potential impacts.Table of Contents1. Introduction ....................................................22. Additional Transparency Issues ..................................42.1. Application Restriction ....................................42.2. Quality of Service (QoS) ...................................62.3. Application Layer Gateways (ALGs) ..........................72.4. IPv6 Address Restrictions ..................................82.4.1. Allocation of IPv6 Addresses by Providers ...........82.4.2. IKEv2 ...............................................82.5. DNS Issues .................................................92.5.1. Unique Root .........................................92.5.2. Namespace Mangling ..................................92.6. Load Balancing and Redirection ............................103. Security Considerations ........................................114. References .....................................................114.1. Informative References ....................................11   Acknowledgments ...................................................13Appendix A - IAB Members at the Time of Approval ..................14Aboba & Davies               Informational                      [Page 1]

RFC 4924          Reflections on Internet Transparency         July 20071.  Introduction   In the past, the IAB has published a number of documents relating to   Internet transparency and the end-to-end principle, and other IETF   documents have also touched on these issues as well.  These documents   articulate the general principles on which the Internet architecture   is based, as well as the core values that the Internet community   seeks to protect going forward.  This document reaffirms those   principles, describes the concept of "oblivious transport" as   developed in the DARPA NewArch project [NewArch], and addresses a   number of new transparency issues.   A network that does not filter or transform the data that it carries   may be said to be "transparent" or "oblivious" to the content of   packets.  Networks that provide oblivious transport enable the   deployment of new services without requiring changes to the core.  It   is this flexibility that is perhaps both the Internet's most   essential characteristic as well as one of the most important   contributors to its success.   "Architectural Principles of the Internet"[RFC1958], Section 2   describes the core tenets of the Internet architecture:      However, in very general terms, the community believes that the      goal is connectivity, the tool is the Internet Protocol, and the      intelligence is end to end rather than hidden in the network.      The current exponential growth of the network seems to show that      connectivity is its own reward, and is more valuable than any      individual application such as mail or the World-Wide Web.  This      connectivity requires technical cooperation between service      providers, and flourishes in the increasingly liberal and      competitive commercial telecommunications environment.   "The Rise of the Middle and the Future of End-to-End:  Reflections on   the Evolution of the Internet Architecture"[RFC3724], Section 4.1.1   describes some of the desirable consequences of this approach:      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 counterargument - 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 forAboba & Davies               Informational                      [Page 2]

RFC 4924          Reflections on Internet Transparency         July 2007      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.   Yet, even while the Internet has greatly expanded both in size and in   application diversity, the degree of transparency has diminished.   "Internet Transparency" [RFC2775] notes some of the causes for the   loss of Internet transparency and analyzes their impact.  This   includes discussion of Network Address Translators (NATs), firewalls,   application level gateways (ALGs), relays, proxies, caches, split   Domain Name Service (DNS), load balancers, etc.  [RFC2775] also   analyzes potential future directions that could lead to the   restoration of transparency.Section 6 summarizes the conclusions:      Although the pure IPv6 scenario is the cleanest and simplest, it      is not straightforward to reach it.  The various scenarios without      use of IPv6 are all messy and ultimately seem to lead to dead ends      of one kind or another.  Partial deployment of IPv6, which is a      required step on the road to full deployment, is also messy but      avoids the dead ends.   While full restoration of Internet transparency through the   deployment of IPv6 remains a goal, the Internet's growing role in   society, the increasing diversity of applications, and the continued   growth in security threats has altered the balance between   transparency and security, and the disparate goals of interested   parties make these tradeoffs inherently complex.   While transparency provides great flexibility, it also makes it   easier to deliver unwanted as well as wanted traffic.  Unwanted   traffic is increasingly cited as a justification for limiting   transparency.  If taken to its logical conclusion, this argument will   lead to the development of ever more complex transparency barriers to   counter increasingly sophisticated security threats.  Transparency,   once lost, is hard to regain, so that such an approach, if   unsuccessful, would lead to an Internet that is both insecure and   lacking in transparency.  The alternative is to develop increasingly   sophisticated host-based security mechanisms; while such an approach   may also fail to keep up with increasingly sophisticated security   threats, it is less likely to sacrifice transparency in the process.   Since many of the fundamental forces that have led to a reduction in   the transparency of the IPv4 Internet also may play a role in the   IPv6 Internet, the transparency of the IPv6 Internet is not pre-Aboba & Davies               Informational                      [Page 3]

RFC 4924          Reflections on Internet Transparency         July 2007   ordained, but rather represents an ideal whose maintenance will   require significant ongoing effort.   As noted in [NewArch], the technical cooperation that once   characterized the development of the Internet has increasingly given   way to a tussle between the interests of subscribers, vendors,   providers, and society at large.  Oblivious transport may be desired   by developers seeking to deploy new services; providers may desire to   block unwanted traffic in the core before it impacts subscribers;   vendors and providers may wish to enable delivery of "value added"   services in the network that enable them to differentiate their   offerings; subscribers may be sympathetic to either point of view,   depending on their interests; society at large may wish to block   "offensive" material and monitor traffic that shows malicious intent.   While there is no architectural "fix" that can restore oblivious   transport while satisfying the interests of all parties, it is   possible for providers to provide subscribers with information about   the nature of the services being provided.  Subscribers need to be   aware of whether they are receiving oblivious transport, and if not,   how the service affects their traffic.   Since the publication of the previously cited IAB statements, new   technologies have been developed, and views on existing technology   have changed.  In some cases, these new technologies impact oblivious   transport, and subscribers need to be aware of the implications for   their service.2.  Additional Transparency Issues2.1.  Application Restriction   Since one of the virtues of the Internet architecture is the ease   with which new applications can be deployed, practices that restrict   the ability to deploy new applications have the potential to reduce   innovation.   One such practice is filtering designed to block or restrict   application usage, implemented without customer consent.  This   includes Internet, Transport, and Application layer filtering   designed to block or restrict traffic associated with one or more   applications.   While provider filtering may be useful to address security issues   such as attacks on provider infrastructure or denial of service   attacks, greater flexibility is provided by allowing filtering to be   determined by the customer.  Typically, this would be implemented at   the edges, such as within provider access routers (e.g., outsourcedAboba & Davies               Informational                      [Page 4]

RFC 4924          Reflections on Internet Transparency         July 2007   firewall services), customer premise equipment (e.g., access   firewalls), or on hosts (e.g., host firewalls).  Deployment of   filtering at the edges provides customers with the flexibility to   choose which applications they wish to block or restrict, whereas   filtering in the core may not permit hosts to communicate, even when   the communication would conform to the appropriate use policies of   the administrative domains to which those hosts belong.   In practice, filtering intended to block or restrict application   usage is difficult to successfully implement without customer   consent, since over time developers will tend to re-engineer filtered   protocols so as to avoid the filters.  Thus over time, filtering is   likely to result in interoperability issues or unnecessary   complexity.  These costs come without the benefit of effective   filtering since many application protocols began to use HTTP as a   transport protocol after application developers observed that   firewalls allow HTTP traffic while dropping packets for unknown   protocols.   In addition to architectural concerns, filtering to block or restrict   application usage also raises issues of disclosure and end-user   consent.  As pointed out in "Terminology for Describing Internet   Connectivity" [RFC4084], services advertised as providing "Internet   connectivity" differ considerably in their capabilities, leading to   confusion.  The document defines terminology relating to Internet   connectivity, including "Web connectivity", "Client connectivity   only, without a public address", "Client only, public address",   "Firewalled Internet Connectivity", and "Full Internet Connectivity".   With respect to "Full Internet Connectivity"[RFC4084], Section 2   notes:      Filtering Web proxies, interception proxies, NAT, and other      provider-imposed restrictions on inbound or outbound ports and      traffic are incompatible with this type of service.  Servers ...      are typically considered normal.  The only compatible restrictions      are bandwidth limitations and prohibitions against network abuse      or illegal activities.[RFC4084], Section 4 describes disclosure obligations that apply to   all forms of service limitation, whether applied on outbound or   inbound traffic:      More generally, the provider should identify any actions of the      service to block, restrict, or alter the destination of, the      outbound use (i.e., the use of services not supplied by the      provider or on the provider's network) of applications services.Aboba & Davies               Informational                      [Page 5]

RFC 4924          Reflections on Internet Transparency         July 2007   In essence, [RFC4084] calls for providers to declare the ways in   which the service provided departs from oblivious transport.  Since   the lack of oblivious transport within transit networks will also   affect transparency, this also applies to providers over whose   network the subscriber's traffic may travel.2.2.  Quality of Service (QoS)   While [RFC4084] notes that bandwidth limitations are compatible with   "Full Internet Connectivity", in some cases QoS restrictions may go   beyond simple average or peak bandwidth limitations.  When used to   restrict the ability to deploy new applications, QoS mechanisms are   incompatible with "Full Internet Connectivity" as defined in   [RFC4084].  The disclosure and consent obligations referred to in[RFC4084], Section 4 also apply to QoS mechanisms.   Deployment of QoS technology has potential implications for Internet   transparency, since the QoS experienced by a flow can make the   Internet more or less oblivious to that flow.  While QoS support is   highly desirable in order for real-time services to coexist with   elastic services, it is not without impact on packet delivery.   Specifically, QoS classes such as "default" [RFC2474] or "lower   effort" [RFC3662] may experience higher random-loss rates than others   such as "assured forwarding" [RFC2597].  Conversely, bandwidth-   limited QoS classes such as "expedited forwarding" [RFC3246] may   experience systematic packet loss if they exceed their assigned   bandwidth.  Other QoS mechanisms such as load balancing may have   side-effects such as re-ordering of packets, which may have a serious   impact on perceived performance.   QoS implementations that reduce the ability to deploy new   applications on the Internet are similar in effect to other   transparency barriers.  Since arbitrary or severe bandwidth   limitations can make an application unusable, the introduction of   application-specific bandwidth limitations is equivalent to   application blocking or restriction from a user's standpoint.   Using QoS mechanisms to discriminate against traffic not matching a   set of services or addresses has a similar effect to deployment of a   highly restrictive firewall.  Requiring an authenticated RSVP   reservation [RFC2747][RFC3182] for a flow to avoid severe packet loss   has a similar effect to deployment of authenticated firewall   traversal.Aboba & Davies               Informational                      [Page 6]

RFC 4924          Reflections on Internet Transparency         July 2007   As with filtering, there may be valid uses for customer-imposed QoS   restrictions.  For example, a customer may wish to limit the   bandwidth consumed by peer-to-peer file sharing services, so as to   limit the impact on mission-critical applications.2.3.  Application Layer Gateways (ALGs)   The IAB has devoted considerable attention to Network Address   Translation (NAT), so that there is little need to repeat that   discussion here.  However, with the passage of time, it has become   apparent that there are problems inherent in the deployment of   Application Layer Gateways (ALGs) (frequently embedded within   firewalls and devices implementing NAT).[RFC2775], Section 3.5 states:      If the full range of Internet applications is to be used, NATs      have to be coupled with application level gateways (ALGs) or      proxies.  Furthermore, the ALG or proxy must be updated whenever a      new address-dependent application comes along.  In practice, NAT      functionality is built into many firewall products, and all useful      NATs have associated ALGs, so it is difficult to disentangle their      various impacts.   With the passage of time and development of NAT traversal   technologies such as IKE NAT-T [RFC3947], Teredo [RFC4380], and STUN   [RFC3489], it has become apparent that ALGs represent an additional   barrier to transparency.  In addition to posing barriers to the   deployment of new applications not yet supported by ALGs, ALGs may   create difficulties in the deployment of existing applications as   well as updated versions.  For example, in the development of IKE   NAT-T, additional difficulties were presented by "IPsec Helper" ALGs   embedded within NATs.   It should be stressed that these difficulties are inherent in the   architecture of ALGs, rather than merely an artifact of poor   implementations.  No matter how well an ALG is implemented, barriers   to transparency will emerge over time, so that the notion of a   "transparent ALG" is a contradiction in terms.   In particular, DNS ALGs present a host of issues, including   incompatibilities with DNSSEC that prevent deployment of a secure   naming infrastructure even if all the endpoints are upgraded.  For   details, see "Reasons to Move the Network Address Translator -   Protocol Translator (NAT-PT) to Historic Status" [RFC4966],Section3.Aboba & Davies               Informational                      [Page 7]

RFC 4924          Reflections on Internet Transparency         July 20072.4.  IPv6 Address Restrictions[RFC2775], Section 5.1 states:      Note that it is a basic assumption of IPv6 that no artificial      constraints will be placed on the supply of addresses, given that      there are so many of them.  Current practices by which some ISPs      strongly limit the number of IPv4 addresses per client will have      no reason to exist for IPv6.   Constraints on the supply of IPv6 addresses provide an incentive for   the deployment of NAT with IPv6.  The introduction of NAT for IPv6   would represent a barrier to transparency, and therefore is to be   avoided if at all possible.2.4.1.  Allocation of IPv6 Addresses by Providers   In order to encourage deployments of IPv6 to provide oblivious   transport, it is important that IPv6 networks of all sizes be   supplied with a prefix sufficient to enable allocation of addresses   and sub-networks for all the hosts and links within their network.   Initial address allocation policy suggested allocating a /48 prefix   to "small" sites, which should handle typical requirements.  Any   changes to allocation policy should take into account the   transparency reduction that will result from further restriction.   For example, provider provisioning of a single /64 without support   for prefix delegation or (worse still) a longer prefix (prohibited by[RFC4291], Section 2.5.4 for non-000/3 unicast prefixes) would   represent a restriction on the availability of IPv6 addresses that   could represent a barrier to transparency.2.4.2.  IKEv2   Issues with IPv6 address assignment mechanisms in IKEv2 [RFC4306] are   described in [RFC4718]:      IKEv2 also defines configuration payloads for IPv6.  However, they      are based on the corresponding IPv4 payloads, and do not fully      follow the "normal IPv6 way of doing things"...  In particular,      IPv6 stateless autoconfiguration or router advertisement messages      are not used; neither is neighbor discovery.   IKEv2 provides for the assignment of a single IPv6 address, using the   INTERNAL_IP6_ADDRESS attribute.  If this is the only attribute   supported for IPv6 address assignment, then only a single IPv6   address will be available.  The INTERNAL_IP6_SUBNET attribute enables   the host to determine the sub-networks accessible directly through   the secure tunnel created; it could potentially be used to assign oneAboba & Davies               Informational                      [Page 8]

RFC 4924          Reflections on Internet Transparency         July 2007   or more prefixes to the IKEv2 initiator that could be used for   address creation.   However, this does not enable the host to obtain prefixes that can be   delegated.  The INTERNAL_IP6_DHCP attribute provides the address of a   DHCPv6 server, potentially enabling use of DHCPv6 prefix delegation   [RFC3633] to obtain additional prefixes.  However, in order for   implementers to utilize these options in an interoperable way,   clarifications to the IKEv2 specification appear to be needed.2.5.  DNS Issues2.5.1.  Unique Root   In "IAB Technical Comment on the Unique DNS Root" [RFC2826], the   technical arguments for a unique root were presented.   One of the premises in [RFC2826] is that a common namespace and   common semantics applied to these names is needed for effective   communication between two parties.  The document argues that this   principle can only be met when one unique root is being used and when   the domains are maintained by single owners or maintainers.   Because [RFC4084] targets only IP service terms and does not talk   about namespace issues, it does not refer to [RFC2826].  We stress   that the use of a unique root for the DNS namespace is essential for   proper IP service.2.5.2.  Namespace Mangling   Since the publication of [RFC2826], there have been reports of   providers implementing recursive nameservers and/or DNS forwarders   that replace answers that indicate that a name does not exist in the   DNS hierarchy with a name and an address record that hosts a Web   service that is supposed to be useful for end-users.   The effect of this modification is similar to placement of a wildcard   in top-level domains.  Although wildcard labels in top-level domains   lead to problems that are described elsewhere (such as "The Role of   Wildcards in the Domain Name System" [RFC4592]), they do not strictly   violate the DNS protocol.  This is not the case where modification of   answers takes place in the middle of the path between authoritative   servers and the stub resolvers that provide the answers to   applications.Aboba & Davies               Informational                      [Page 9]

RFC 4924          Reflections on Internet Transparency         July 2007   [RFC2826]section 1.3 states:      Both the design and implementations of the DNS protocol are      heavily based on the assumption that there is a single owner or      maintainer for every domain, and that any set of resources records      associated with a domain is modified in a single-copy serializable      fashion.   In particular, the DNSSEC protocol described in "Protocol   Modifications for the DNS Security Extensions" [RFC4035] has been   designed to verify that DNS information has not been modified between   the moment they have been published on an authoritative server and   the moment the validation takes place.  Since that verification can   take place at the application level, any modification by a recursive   forwarder or other intermediary will cause validation failures,   disabling the improved security that DNSSEC is intended to provide.2.6.  Load Balancing and Redirection   In order to provide information that is adapted to the locale from   which a request is made or to provide a speedier service, techniques   have been deployed that result in packets being redirected or taking   a different path depending on where the request originates.  For   example, requests may be distributed among servers using "reverse   NAT" (which modifies the destination rather than the source address);   responses to DNS requests may be altered; HTTP "gets" may be re-   directed; or specific packets may be diverted onto overlay networks.   Provided that these services are well-implemented, they can provide   value; however, transparency reduction or service disruption can also   result:   [1] The use of "reverse NAT" to balance load among servers supporting       IPv6 would adversely affect the transparency of the IPv6       Internet.   [2] DNS re-direction is typically based on the source address of the       query, which may not provide information on the location of the       host originating the query.  As a result, a host configured with       the address of a distant DNS server could find itself pointed to       a server near the DNS server, rather than a server near the host.       HTTP re-direction does not encounter this issue.   [3] If the packet filters that divert packets onto overlay networks       are misconfigured, this can lead to packets being misdirected       onto the overlay and delayed or lost if the far end cannot return       them to the global Internet.Aboba & Davies               Informational                     [Page 10]

RFC 4924          Reflections on Internet Transparency         July 2007   [4] The use of anycast needs to be carefully thought out so that       service can be maintained in the face of routing changes.3.  Security Considerations   Several transparency issues discussed in this document (NATs,   transparent proxies, DNS namespace mangling) weaken existing end-to-   end security guarantees and interfere with the deployment of   protocols that would strengthen end-to-end security.[RFC2775], Section 7 states:      The loss of transparency at the Intranet/Internet boundary may be      considered a security feature, since it provides a well defined      point at which to apply restrictions.  This form of security is      subject to the "crunchy outside, soft inside" risk, whereby any      successful penetration of the boundary exposes the entire Intranet      to trivial attack.  The lack of end-to-end security applied within      the Intranet also ignores insider threats.   Today, malware has evolved to increasingly take advantage of the   application-layer as a rich and financially attractive source of   security vulnerabilities, as well as a mechanism for penetration of   the Intranet/Internet boundary.  This has lessened the security value   of existing transparency barriers and made it increasingly difficult   to prevent the propagation of malware without imposing restrictions   on application behavior.  However, as with other approaches to   application restriction (seeSection 2.1), these limitations are most   flexibly imposed at the edge.4.  References4.1.  Informative References   [NewArch] Clark, D. et al.,  "New Arch: Future Generation Internet             Architecture",http://www.isi.edu/newarch/iDOCS/final.finalreport.pdf   [RFC1958] Carpenter, B., Ed., "Architectural Principles of the             Internet",RFC 1958, June 1996.   [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,             "Definition of the Differentiated Services Field (DS Field)             in the IPv4 and IPv6 Headers",RFC 2474, December 1998.   [RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski,             "Assured Forwarding PHB Group",RFC 2597, June 1999.Aboba & Davies               Informational                     [Page 11]

RFC 4924          Reflections on Internet Transparency         July 2007   [RFC2747] Baker, F., Lindell, B., and M. Talwar, "RSVP Cryptographic             Authentication",RFC 2747, January 2000.   [RFC2775] Carpenter, B., "Internet Transparency",RFC 2775, February             2000.   [RFC2826] Internet Architecture Board, "IAB Technical Comment on the             Unique DNS Root",RFC 2826, May 2000.   [RFC3182] Yadav, S., Yavatkar, R., Pabbati, R., Ford, P., Moore, T.,             Herzog, S., and R. Hess, "Identity Representation for             RSVP",RFC 3182, October 2001.   [RFC3246] Davie, B., Charny, A., Bennet, J., Benson, K., Le Boudec,             J., Courtney, W., Davari, S., Firoiu, V., and D. Stiliadis,             "An Expedited Forwarding PHB (Per-Hop Behavior)",RFC 3246,             March 2002.   [RFC3489] Rosenberg, J., Weinberger, J., Huitema, C., and R. Mahy,             "STUN - Simple Traversal of User Datagram Protocol (UDP)             Through Network Address Translators (NATs)",RFC 3489,             March 2003.   [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic             Host Configuration Protocol (DHCP) version 6",RFC 3633,             December 2003.   [RFC3662] Bless, R., Nichols, K., and K. Wehrle, "A Lower Effort             Per-Domain Behavior (PDB) for Differentiated Services",RFC3662, December 2003.   [RFC3724] Kempf, J., Ed., Austein, R., Ed., and IAB, "The Rise of the             Middle and the Future of End-to-End: Reflections on the             Evolution of the Internet Architecture",RFC 3724, March             2004.   [RFC3947] Kivinen, T., Swander, B., Huttunen, A., and V. Volpe,             "Negotiation of NAT-Traversal in the IKE",RFC 3947,             January 2005.   [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.             Rose, "Protocol Modifications for the DNS Security             Extensions",RFC 4035, March 2005.   [RFC4084] Klensin, J., "Terminology for Describing Internet             Connectivity",BCP 104,RFC 4084, May 2005.Aboba & Davies               Informational                     [Page 12]

RFC 4924          Reflections on Internet Transparency         July 2007   [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing             Architecture",RFC 4291, February 2006.   [RFC4306] Kaufman, C., Ed., "Internet Key Exchange (IKEv2) Protocol",RFC 4306, December 2005.   [RFC4380] Huitema, C., "Teredo: Tunneling IPv6 over UDP through             Network Address Translations (NATs)",RFC 4380, February             2006.   [RFC4592] Lewis, E., "The Role of Wildcards in the Domain Name             System",RFC 4592, July 2006.   [RFC4718] Eronen, P. and P. Hoffman, "IKEv2 Clarifications and             Implementation Guidelines",RFC 4718, October 2006.   [RFC4966] Aoun, C. and E. Davies, "Reasons to Move the Network             Address Translator - Protocol Translator (NAT-PT) to             Historic Status",RFC 4966, July 2007.Acknowledgments   The authors would like to acknowledge Jari Arkko, Stephane   Bortzmeyer, Brian Carpenter, Spencer Dawkins, Stephen Kent, Carl   Malamud, Danny McPherson, Phil Roberts and Pekka Savola for   contributions to this document.Aboba & Davies               Informational                     [Page 13]

RFC 4924          Reflections on Internet Transparency         July 2007Appendix A - IAB Members at the Time of Approval   Bernard Aboba   Loa Andersson   Brian Carpenter   Leslie Daigle   Elwyn Davies   Kevin Fall   Olaf Kolkman   Kurtis Lindqvist   David Meyer   David Oran   Eric Rescorla   Dave Thaler   Lixia ZhangAuthors' Addresses   Bernard Aboba   Microsoft Corporation   One Microsoft Way   Redmond, WA 98052   EMail: bernarda@microsoft.com   Phone: +1 425 706 6605   Fax:   +1 425 936 7329   Elwyn B. Davies   Consultant   Soham, Cambs   UK   Phone: +44 7889 488 335   EMail: elwynd@dial.pipex.comAboba & Davies               Informational                     [Page 14]

RFC 4924          Reflections on Internet Transparency         July 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.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Aboba & Davies               Informational                     [Page 15]