Transport Working Group F. Baker Internet-Draft J. Polk Updates: 4542,4594 (if approved) Cisco Systems Intended status: Best Current M. Dolly Practice AT&T Labs Expires: March 31, 2007 September 27, 2006 An EF DSCP for Capacity-Admitted Traffic draft-baker-tsvwg-admitted-voice-dscp-00 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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. This Internet-Draft will expire on March 31, 2007. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document requests a DSCP from the IANA for a class of real-time traffic conforming to the Expedited Forwarding Per Hop Behavior and admitted using a CAC procedure involving authentication, authorization, and capacity admission, as compared to a class of real-time traffic conforming to the Expedited Forwarding Per Hop Behavior but not subject to capacity admission or subject to very Baker, et al. Expires March 31, 2007 [Page 1]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 coarse capacity admission. One of the reasons behind this is the need for classes of traffic that are handled under special policies, such as the non-preemptive Emergency Telecommunication Service, the US DoD's Assured Service (which is similar to MLPP), or e-911. These do not need separate DSCPs or separate PHBs that are separate from each other, but they need a traffic class from which they can deterministically obtain their service requirements from including SLA matters. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Problem . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.3. Proposed Solution . . . . . . . . . . . . . . . . . . . . 6 2. Implementation of the Admitted Telephony Service Class . . . . 6 2.1. Potential implementations of EF in this model . . . . . . 6 2.2. Capacity admission control . . . . . . . . . . . . . . . . 8 2.2.1. Capacity admission control by assumption . . . . . . . 8 2.2.2. Capacity admission control by call counting . . . . . 8 2.2.3. End-point capacity admission performed by probing the network . . . . . . . . . . . . . . . . . . . . . 9 2.2.4. Centralized capacity admission control . . . . . . . . 9 2.2.5. Distributed capacity admission control . . . . . . . . 10 3. Recommendations on implementation of an Admitted Telephony Service Class . . . . . . . . . . . . . . . . . . . . . . . . 10 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7.1. Normative References . . . . . . . . . . . . . . . . . . . 11 7.2. Informative References . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . . . 14 Baker, et al. Expires March 31, 2007 [Page 2]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 1. Introduction This document requests a DSCP from the IANA for a class of real-time traffic conforming to the Expedited Forwarding [RFC3246][RFC3247] Per Hop Behavior and admitted using a CAC procedure involving authentication, authorization, and capacity admission, as compared to a class of real-time traffic conforming to the Expedited Forwarding Per Hop Behavior but not subject to capacity admission or subject to very coarse capacity admission. One of the reasons behind this is the need for classes of traffic that are handled under special policies, such as the non-preemptive Emergency Telecommunication Service, the US DoD's Assured Service (which is similar to MLPP and uses preemption), or e-911, in addition to normal routine calls that use call admission. It is possible to use control plane protocols to restrict session admission such that admitted traffic will receive the desired service, and the policy (e.g., routine, NS/EP, e-911, etc) need not be signaled in a DSCP. However, service providers need to distinguish between special-policy traffic and other classes, particularly the existing VoIP services that perform no capacity admission or only very coarse capacity admission and can exceed their allocated resources. This DSCP applies to the Telephony Service Class described in [RFC4594]. WIthin an ISP and on inter-ISP links (i.e., within networks whose internal paths are uniform at hundreds of megabits or faster), one would expect this traffic to be carried in the Real Time Traffic Class described in [I-D.ietf-tsvwg-diffserv-class-aggr]. 1.1. Definitions The following terms and acronyms are used in this document. PHB: A Per-Hop-Behavior (PHB) is the externally observable forwarding behavior applied at a DS-compliant node to a DS behavior aggregate [RFC2475]. It may be thought of as a program configured on the interface of an internet host or router, specified drop probabilities, queuing priorities or rates, and other handling characteristics for the traffic class. DSCP: The Differentiated Services Codepoint (DSCP), as defined in [RFC2474], is a value which is encoded in the DS field, and which each DS Node MUST use to select the PHB which is to be experienced by each packet it forwards [RFC3260]. It is a number embedded in the TOS field of an IPv4 datagram or the Traffic Class field of an IPv6 datagram. Baker, et al. Expires March 31, 2007 [Page 3]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 CAC: Call Admission Control, which includes concepts of authorization (an identified and authenticated user is determined to also be authorized to use the service) and capacity admission (at the present time, under some stated policy, capacity exists to support the call). In the Internet, these are separate functions, while in the PSTN they and call routing are carried out together. UNI: A User/Network Interface (UNI) is the interface (often a physical link or its virtual equivalent) that connects two entities that do not trust each other, and in which one (the user) purchases connectivity services from the other (the network). Figure 1 shows two user networks connected by what appears to each of them to be a single network ("The Internet", access to which is provided by their service provider) which provides connectivity services to other users. NNI: A Network/Network Interface (NNI) is the interface (often a physical link or its virtual equivalent) that connects two entities that trust each other within limits, and in which the two are seen as trading services for value. Figure 1 shows three service networks that together provide the connectivity services that we call "the Internet". They are different administrations and are very probably in competition, but exchange contracts for connectivity and capacity that enable them to offer specific services to their customers. Queue: There are multiple ways to build a multi-queue scheduler. Weighted Round Robin (WRR) literally builds multiple lists and visits them in a specified order, while a calendar queue (often used to implement Weighted Fair Queuing,or WFQ) builds a list for each time interval and enqueues at most a stated amount of data in each such list for transmission during that time interval. While these differ dramatically in implementation, the external difference in behavior is generally negligible when they are properly configured. Consistent with the definitions used in the Differentiated Services Architecture [RFC2475], these are treated as equivalent in this document, and the lists of WRR and the classes of a calendar queue will be referred to uniformly as "queues". Baker, et al. Expires March 31, 2007 [Page 4]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 _.--------. ,-'' `--. ,-' `-. ,-------. ,',-------. `. ,' `. ,',' `. `. / User \ UNI / / Service \ \ ( Network +-----+ Network ) `. \ / ; \ / : `. ,' ; `. .+ : '-------' / '-------' \ NNI \ ; \ : ; "The Internet" \ ,-------. : ; +' `. : UNI: User/Network Interface / Service \ | | ( Network ) | NNI: Network/Network Interface \ / | : +. ,' ; : / '-------' ; : / ; ,-------. \ ,-------. / NNI / ,' `. : ,' `+ ; / User \ UNI / Service \ ; ( Network +-----+ Network ) ,' \ / \ \ / / `. ,' `.`. ,' ,' '-------' `.'-------' ,' `-. ,-' `--. _.-' `--------'' Figure 1: UNI and NNI interfaces 1.2. Problem In short, the Telephony Service Class described in X permits the use of capacity admission in implementing the service, but present implementations either provide no capacity admission services or do so in a manner that depends on specific traffic engineering. In the context of the Internet backbone, the two are essentially equivalent; the edge network is depending on specific engineering by the service provider that may not be present. However, services are being requested of the network that would specifically make use of capacity admission, and would distinguish among users or the uses of available Voice-on-IP capacity in various ways. Various agencies would like to provide services as described in section 2.6 of [RFC4504] or in [RFC4190]. This requires the use of capacity admission to differentiate among users (which might be Baker, et al. Expires March 31, 2007 [Page 5]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 911 call centers, other offices with preferential service contracts, or individual users gaining access with special credentials) to provide services to them that are not afforded to routine customer- to-customer IP telephony sessions. 1.3. Proposed Solution The IETF is asked to differentiate, in the Telephony Service, between sessions that are originated without capacity admission or using traffic engineering and sessions that are originated using more robust capacity admission procedures. Sessions of the first type use a traffic class in which they compete without network-originated control as described in Section 2.2.1 or Section 2.2.2, and in the worst case lose traffic due to policing. Sessions of the second type cooperate with network control, and may be given different levels of preference depending on the policies that the network applies. In order to provide this differentiation, the IETF requests that the IANA assign a separate DSCP value to admitted sessions using the Telephony service (see Section 4). 2. Implementation of the Admitted Telephony Service Class 2.1. Potential implementations of EF in this model There are at least two possible ways to implement the Expedited Forwarding PHB in this model. They are to implement separate classes as a set of o Multiple data plane priority queues having separate policers, or o A single data plane priority queue with multiple policers feeding it relevant to separate traffic classes We will explain the difference, and describe in what way they differ in operation. The reason this is necessary is that there is current confusion in the industry, including a widely reported test for NS/EP services that implemented the policing model and described it as an implementation of the multi-priority model, and discussion in other environments of the intermixing of voice and video traffic at relatively low bandwidths in the policing model. The multi-priority model is shown in Figure 2. In this model, traffic from each service class is placed into a separate priority queue. If data is present in both queues, traffic from one of them will always be selected for transmission. This has the effect of transferring jitter from the higher priority queue to the lower priority queue, and reordering traffic in a way that gives the higher Baker, et al. Expires March 31, 2007 [Page 6]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 priority traffic a smaller average queuing delay. Each queue must have its own policer, however, to protect the network from errors and attacks; if a traffic class thinks it is carrying a certain data rate but an abuse sends significantly more, the effect of simple prioritization would not preserve the lower priorities of traffic, which could cause routing to fail or otherwise impact an SLA. . policers priorities |`. EF ---------> <=> ----------||----+ `. high| `. EF2---------> <=> ----------||----+ .'----------- . medium .' rate queues |`. +-----+ .' Priority AF1------>||----+ `. / low |' Scheduler | `. / AF2------>||----+ .'-+ | .' CS0------>||----+ .' Rate Scheduler |' (WFQ, WRR, etc) Figure 2: Implementation as a data plane priority The multi-policer model is shown in Figure 3. In this model, traffic from each service class is policed according to its SLA requirements, and then placed into a common priority queue. Unlike the multi- priority model, the jitter experienced by the traffic classes in this case is the same, as there is only one queue, but the sum of the traffic in this higher priority queue experiences less average jitter than the elastic traffic in the lower priority. policers priorities . EF ---------> <=> -------\ |`. --||----+ `. EF2---------> <=> -------/ high| `. . | .'-------- rate queues |`. +-----+ .' AF1------>||----+ `. / low | .' Priority | `. / |' Scheduler AF2------>||----+ .'-+ | .' CS0------>||----+ .' Rate Scheduler |' (WFQ, WRR, etc) Figure 3: Implementation as a data plane policer The difference between the two operationally is, as stated, the issues of loss due to policing and distribution of jitter. Baker, et al. Expires March 31, 2007 [Page 7]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 If the two traffic classes are, for example, voice and video, datagrams containing video data are relatively large (generally the size of the path MTU) while datagrams containing voice are relatively small. On lower speed links (less than 10 MBPS), the jitter introduced by video to voice can be disruptive, while at higher speeds the jitter is nominal compared to the jitter requirements of voice. At access network speeds, therefore, [RFC4594] recommends separation of video and voice into separate queues, while at optical speeds [I-D.ietf-tsvwg-diffserv-class-aggr] recommends that they use a common queue. If, on the other hand, the two traffic classes are carrying the same type of application with the same jitter requirements, then giving one preference in this sense does not benefit the higher priority traffic and may harm the lower priority traffic. In such a case, using separate policers and a common queue is a superior approach. 2.2. Capacity admission control The question that remains is how to manage loss due to policing, and how generally to satisfy the needs of the various types of services that are under discussion. We will discuss this in three parts - capacity admission strategies, the requirements of various policies, and recommendations. 2.2.1. Capacity admission control by assumption The first approach is to ignore the matter entirely. If one assumes that the capacity available to the application is uniformly far in excess of its requirements, it is perhaps overhead that can be ignored. This assumption is currently made in Internet VoIP offerings such as Skype and Vonage; the end user is responsible to place his service on a LAN connected to the Internet backbone by a high speed broadband connection and use capable ISPs to deliver the service. There is an authorization step in the sense that the service ensures that the user pays his bills, but no capacity admission is considered. 2.2.2. Capacity admission control by call counting The H.323 gatekeeper, originally specified in 1996, operates on the model that the considerations of Section 2.2.1 generally apply, and that it is therefore sufficient to count calls in order to ensure that any bottlenecks in the network are never overloaded. This approach is consistent with the original design of H.323, which in 1996 was a mechanism for connecting H.320 media gateways across a LAN. VoIP has come a long way since then, however, and the engineering trade-offs this approach requires in complex networks are Baker, et al. Expires March 31, 2007 [Page 8]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 unsatisfactory. In short, if there is a bottleneck anywhere in the network that might be used to connect two gatekeepers, SIP proxies, or other call management systems, the amount of traffic between the two must be contained below that bottleneck even if the normal path is of much higher bandwidth. In addition, the multiplexing of traffic streams between different pairs of gatekeepers over a common LAN infrastructure is not handled by the application, and so must be managed in the engineering of the network. 2.2.3. End-point capacity admission performed by probing the network [I-D.briscoe-tsvwg-cl-architecture] is one of many proposals that have looked at probing of the network by the end system to determine its capacity to accept a new session. Such proposals have been made a number of times by the likes of NTT Labs, UIUC researchers, Cisco Systems (which used its Service Assurance Architecture to probe capacity using pings and report when network delay variability increased), and others. Many of the proposals tested in research have fared reasonably well in high bandwidth environments where actual network congestion is unusual, but have not scaled down to slower access links. The problem has been, in essence, that variable rate codecs can be on the quiet side of the average for lengthy periods of time and then become noisier. New sessions can be disrupted or disrupt existing sessions if they perform their capacity admission procedures at a quiet time and find themselves overrunning the allocated capacity during a noisy time. In addition, for a service in which the network must exercise control and differentiate among users, the users cannot be depended on to differentiate among themselves in the network's favor. The network must manage that service. For this reason, [I-D.briscoe-tsvwg-cl-architecture] is only proposed as a solution within backbone networks, leaving access networks to provide other forms of capacity admission, and more generally such techniques are only recommended in high bandwidth contexts. 2.2.4. Centralized capacity admission control The concept of a Bandwidth Broker was first discussed in the research world surrounding ESNET and Internet II in the late 1990's, and has been discussed in the literature pertaining to the Differentiated Services Architecture [RFC2475]. It is, in short, a central system that performs a variety of services on behalf of clients of a network including applying AAA services (as in [RFC2904])and authorizing them to use specified capacity at specified times. Its strength is that it is relatively simple, at least in concept, and can keep track of simple book-keeping functions apart from network elements such as Baker, et al. Expires March 31, 2007 [Page 9]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 routers. Its weakness is that it has no idea what the specific routing of any stated data flow is, or its capacity apart from services such as MPLS Traffic Engineering or engineering assumptions specified by the designers of a network, and obtaining that information from the network via SNMP GET or other network management action can impose a severe network overhead. For scaling reasons, operational Bandwidth Brokers generally take on a semi-distributed or fully distributed nature. They are implemented on a per-point-of-presence basis, and in satellite networks might be implemented in each terminal. At this point, they become difficult to operationally distinguish from distributed capacity admission services such as described in Section 2.2.5. 2.2.5. Distributed capacity admission control The IETF developed the Integrated Services Model and the RSVP capacity admission protocol in the early 1990's, and then integrated it with the Differentiated Services Architecture in [RFC2998]. Since then, the IETF has worked to describe a next generation capacity admission protocol, which is calls NSIS, and which is limited in scope to considering unicast sessions. [RFC4542] looked at the issue of providing preferential services in the Internet, and determined that RSVP with its defined extensions could provide those services to unicast and multicast sessions. As with the Bandwidth Broker model, there are concerns regarding scaling, mentioned in [RFC2208]. Present implementations that have been measured have been found to not display the scaling concerns, however, and in any event the use of RSVP Aggregation enables the backbone to handle such sessions in a manner similar to an ATM Virtual Path, bundling sessions together for capacity management purposes. 3. Recommendations on implementation of an Admitted Telephony Service Class It is the belief of the authors that either data plane PHB described in Section 2.1, if coupled with adequate AAA and capacity admission procedures as described in Section 2.2.5, are sufficient to provide the services required for an Admitted Telephony service class. On the point of what protocols and procedures are required for authentication, authorization, and capacity admission, we note that clear standards do not at this time exist for bandwidth brokers, NSIS has not at this time been finalized and in any event is limited to unicast sessions, and that RSVP has been standardized and has the Baker, et al. Expires March 31, 2007 [Page 10]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 relevant services. We therefore recommend the use of RSVP at the UNI. Procedures at the NNI are business matters to be discussed between the relevant networks, and are recommended but not required. 4. IANA Considerations This note, fundamentally, requests IANA the assign a DSCP value to a second EF traffic class consistent with [RFC3246] and [RFC3247] and implementing the Telephony Service Class described in [RFC4594] at lower speeds and [I-D.ietf-tsvwg-diffserv-class-aggr] at higher speeds. This new traffic class requires the use of capacity admission such as RSVP services together with AAA services at the User/Network Interface (UNI); the use of such services at the NNI is at the option of the interconnected networks. The recommended value for the code point 101100, paralleling the EF code point, which is 101110, and both of which are allocated from Pool 1 as described in [RFC2474]. The code point should be referred to as EF-ADMIT. 5. Security Considerations A major requirement of this service is effective use of a signaling protocol such as RSVP, with the capabilities to identify its user either as an individual or as a member of some corporate entity, and assert a policy such as "routine" or "priority". This capability, one has to believe, will be abused by script kiddies and others if the proof of identity is not adequately strong or if policies are written or implemented improperly by the carriers. This goes without saying, but this section is here for it to be said... 6. Acknowledgements 7. References 7.1. Normative References [I-D.ietf-tsvwg-diffserv-class-aggr] Chan, K., "Aggregation of DiffServ Service Classes", draft-ietf-tsvwg-diffserv-class-aggr-00 (work in progress), June 2006. [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, Baker, et al. Expires March 31, 2007 [Page 11]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, December 1998. [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998. [RFC2998] Bernet, Y., Ford, P., Yavatkar, R., Baker, F., Zhang, L., Speer, M., Braden, R., Davie, B., Wroclawski, J., and E. Felstaine, "A Framework for Integrated Services Operation over Diffserv Networks", RFC 2998, November 2000. [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. [RFC3247] Charny, A., Bennet, J., Benson, K., Boudec, J., Chiu, A., Courtney, W., Davari, S., Firoiu, V., Kalmanek, C., and K. Ramakrishnan, "Supplemental Information for the New Definition of the EF PHB (Expedited Forwarding Per-Hop Behavior)", RFC 3247, March 2002. [RFC3260] Grossman, D., "New Terminology and Clarifications for Diffserv", RFC 3260, April 2002. [RFC4542] Baker, F. and J. Polk, "Implementing an Emergency Telecommunications Service (ETS) for Real-Time Services in the Internet Protocol Suite", RFC 4542, May 2006. 7.2. Informative References [I-D.briscoe-tsvwg-cl-architecture] Briscoe, B., "An edge-to-edge Deployment Model for Pre- Congestion Notification: Admission Control over a DiffServ Region", draft-briscoe-tsvwg-cl-architecture-03 (work in progress), June 2006. [RFC2208] Mankin, A., Baker, F., Braden, B., Bradner, S., O'Dell, M., Romanow, A., Weinrib, A., and L. Zhang, "Resource ReSerVation Protocol (RSVP) Version 1 Applicability Statement Some Guidelines on Deployment", RFC 2208, September 1997. [RFC2904] Vollbrecht, J., Calhoun, P., Farrell, S., Gommans, L., Gross, G., de Bruijn, B., de Laat, C., Holdrege, M., and D. Spence, "AAA Authorization Framework", RFC 2904, Baker, et al. Expires March 31, 2007 [Page 12]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 August 2000. [RFC4190] Carlberg, K., Brown, I., and C. Beard, "Framework for Supporting Emergency Telecommunications Service (ETS) in IP Telephony", RFC 4190, November 2005. [RFC4504] Sinnreich, H., Lass, S., and C. Stredicke, "SIP Telephony Device Requirements and Configuration", RFC 4504, May 2006. [RFC4594] Babiarz, J., Chan, K., and F. Baker, "Configuration Guidelines for DiffServ Service Classes", RFC 4594, August 2006. Authors' Addresses Fred Baker Cisco Systems Santa Barbara, California 93117 USA Phone: +1-408-526-4257 Email: fred@cisco.com James Polk Cisco Systems Richardson, Texas 75082 USA Phone: +1-817-271-3552 Email: jmpolk@cisco.com Martin Dolly AT&T Labs Middletown Township, New Jersey 07748 USA Phone: +1-732-420-4574 Email: mdolly@att.com Baker, et al. Expires March 31, 2007 [Page 13]
Internet-Draft An EF DSCP for Capacity-Admitted Traffic September 2006 Full Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 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 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 in BCP 78 and BCP 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 at http://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. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Baker, et al. Expires March 31, 2007 [Page 14]