BEHAVE Working Group D. Wing Internet-Draft T. Eckert Intended status: Best Current Cisco Systems, Inc. Practice June 20, 2007 Expires: December 22, 2007 Multicast Requirements for a Network Address (and port) Translator (NAT) draft-ietf-behave-multicast-07 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 December 22, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Abstract This document specifies requirements for a Network Address (and port) Translator (NAT) that supports any source multicast or source specific IP multicast. A multicast-capable NAT device that adheres to the requirements of this document can optimize the operation of multicast applications that are generally unaware of multicast NAT devices. Wing & Eckert Expires December 22, 2007 [Page 1]
Internet-Draft NAT Multicast Requirements June 2007 Table of Contents 1. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Conventions Used in this Document . . . . . . . . . . . . . . 5 4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. NATting of IP Multicast Packets . . . . . . . . . . . . . 5 4.2. IGMP Versions . . . . . . . . . . . . . . . . . . . . . . 6 4.2.1. IGMPv1 or IGMPv2 . . . . . . . . . . . . . . . . . . . 7 4.2.2. IGMPv3 . . . . . . . . . . . . . . . . . . . . . . . . 7 4.3. Any Source Multicast Transmitters . . . . . . . . . . . . 8 4.4. Transport Protocol Support . . . . . . . . . . . . . . . . 9 5. Requirements Summary . . . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9.1. Normative References . . . . . . . . . . . . . . . . . . . 12 9.2. Informational References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Intellectual Property and Copyright Statements . . . . . . . . . . 15 Wing & Eckert Expires December 22, 2007 [Page 2]
Internet-Draft NAT Multicast Requirements June 2007 1. Problem Statement In order for multicast applications to function well over NATs, multicast UDP must work as seamlessly as unicast UDP. However, NATs have little consistency in multicast operation which results in inconsistent user experiences and failed multicast operation. 2. Introduction This document describes the requirements of an IP multicast-capable NAT. These requirements allow existing UDP any source IP multicast [RFC1112] applications or source specific IP multicast [RFC4607] applications to function without awareness of the multicast-capable NAT device. Additionally, non-UDP IP multicast applications can be received. This document describes the behavior of a device that functions as a NAT for unicast flows and also forwards IP multicast traffic in either direction ('inside' to 'outside', or 'outside' to 'inside'). Hosts on the 'inside' interface(s) of a NAT indicate their interest in receiving a multicast flow by sending an IGMP message to their local interface. A multicast-capable NAT will see that IGMP message (IGMPv1 [RFC1112], IGMPv2 [RFC2236], IGMPv3 [RFC3376]), possibly perform some functions on that IGMP message, and forward it to its upstream router. This causes the upstream router to send that multicast traffic to the NAT, which forwards it to those inside segment(s) with host(s) that had previously sent IGMP messages for that multicast traffic. Out of scope of this document are PIM-SM [RFC4601] and IPv6 [RFC2460]. The IGMP Proxy devices that are scoped in this document do not forward PIM-SM. IPv6 is out of scope because NAT is not considered necessary with IPv6. This document is a companion document to "NAT Behavioral Requirements for Unicast UDP" [RFC4787]. 2.1. Background Wing & Eckert Expires December 22, 2007 [Page 3]
Internet-Draft NAT Multicast Requirements June 2007 When a NAT isn't used, a host might be connected to the Internet in a configuration such as this: +-------------+ +------+ | DSL modem | +------------+ | host +---+ or +-//-+ WAN Router | +------+ | cable modem | +------------+ +-------------+ Figure 1: Network without NATting IGMP Proxy If instead of a single host as shown in Figure 1, one or more LANs with potentially multiple hosts are to be connected, with the same type of service termination on the DSL or cable modem, a NAT device is added as shown in Figure 2. This device in general perform routing and NAT functions such that it does look like a single host towards the DSL/cable modem. +----+ +-------------+ |host+---+ +---------+ | +-----------+ +----+ | |Multicast| | | DSL modem | +------------+ | | Proxy | +--+ or +-//-+ WAN Router | inside | +---------+ | |cable modem| +------------+ interfaces | | +-----------+ | +------+ | +----+ | | NAT | | outside |host+---+ +------+ | interfaces +----+ +-------------+ IGMP Proxy NAT Device Figure 2: Network with NATing IGMP Proxy In IP multicast, IGMP is the protocol used by hosts, such as the one shown in Figure 1. For the NAT device in Figure 2 to look like the single host for IP multicast services towards the DSL/cable modem and to forward IP multicast traffic from and to the multiple hosts in the picture, it needs to perform so called "IGMP Proxying" [RFC4605] -- but within the context of also performing NAT. NAT is not covered by [RFC4605]. Adding NAT to IGMP proxying does not need to change the processing of the IGMP messages as defined in RFC4605: IGMP messages are never logically forwarded by the IGMP proxying device, but rather sourced or received by it. In general, receipt of IGMP messages by the device updated IGMP state maintained by the device and either those changes or timers trigger the sending of IGMP messages. "Forwarding" of IGMP protocol messages may thus only happen implicitly by implementation optimizations that create Wing & Eckert Expires December 22, 2007 [Page 4]
Internet-Draft NAT Multicast Requirements June 2007 shortcuts in this machinery. This specifically means that IGMP protocol packets sent by the NAT device will always use IP address of th interface (inside or outside) to which they are sent, but because those packets are logically "sourced" and not "forwarded" , NAT does not have any impact into this. Adding NAT to IGMP proxying does change the processing of IP multicast data packets forwarded across the IGMP proxying device as described in the following sections. These changes do actually simplify the ability to deploy IGMP proxying over a device that does NOT perform NAT. With an IGMP Proxy NAT Device, IP multicast data traffic sourced from hosts on the inside is NATed such that it will look like being sourced from a directly connected host to the WAN router, thus eliminating all non-standard PIM-SM concerns/configurations described in section 3.2 of [RFC4605]. 3. Conventions Used in this Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. In this document, the term "NAT" applies to both Network Address and Port Translator (NAPT) as well as a NAT that does not translate ports. The term 'inside' refers to the interface(s) on a NAT which contain hosts that wish to send or receive multicast traffic. The term 'outside' refers to the interface(s) the NAT forwards IGMP membership messages to, and where the NAT routes multicast traffic that originates from hosts on its 'inside' interface. 4. Requirements 4.1. NATting of IP Multicast Packets Unlike unicast flows, packets with a multicast destination IP address do not have their destination IP address or destination port changed by a NAT. However, their source IP address (and source UDP port, in some cases with a NAPT) is changed if the packet goes from an 'inside' interface of a NAT to the 'outside' interface of a NAT -- similar to the behavior of a unicast packet across those same Wing & Eckert Expires December 22, 2007 [Page 5]
Internet-Draft NAT Multicast Requirements June 2007 interfaces. REQ-1: For IP multicast packets that are forward to a host(s) on its inside interface(s), a NAT MUST NOT modify the destination IP address or destination port of the packets. Note: If a NAT were to violate this requirement and modify the destination IP or port addresses, the NAT would also need to modify session announcements (e.g., electronic program guides, SAP) and session establishment and control (e.g., SIP, RTSP) messages. Such modification is not considered a best practice. Note: This behavior is required for UDP, but has a useful side- effect that it permits other, non-UDP multicast protocols across a NAT (e.g., PGM [RFC3208], RSVP [RFC2750]). The following requirement is normal NAT behavior for unicast packets, as described in [RFC4787], and provides support for multicast senders behind the NAT: REQ-2: A NAT MUST modify the source IP address of packets that arrive from an 'inside' interface towards the 'outside' interface so that those packets use the NAT's public IP address(es). a: If the NAT also performs port translation (that is, it is a NAPT), the NAT MUST also create a mapping to allow responses to that multicast packet to be received by the appropriate host. For any source multicast, also see Section 4.3. For source specific multicast, also see Section 4.2.2. b: To support learning their public transport address, the NAT MUST have "Endpoint-Independent Mapping" behavior (REQ-1 of [RFC4787]) no matter if the destination IP address is a unicast address or a multicast address. 4.2. IGMP Versions REQ-3: A NAT MAY support IGMPv1 (although IGMPv1 is considered obsolete). REQ-4: A NAT MUST support IGMPv2. REQ-5: A NAT SHOULD support IGMPv3. Wing & Eckert Expires December 22, 2007 [Page 6]
Internet-Draft NAT Multicast Requirements June 2007 4.2.1. IGMPv1 or IGMPv2 For IGMPv1 and IGMPv2, a NAT can successfully operate by merely forwarding IGMP membership reports and queries between the interested hosts (on its internal interface) towards its external interface. REQ-6: If a NAT supports IGMPv1 and/or IGMPv2 (but not IGMPv3), the NAT MAY simply receive IGMP membership reports on the inside interface, NAT them, and relay the IGMP membership report, and do the same function in the opposite direction to the IGMP listeners. That is, the NAT does not need to do any aggregation of IGMP messages. a: However, it is RECOMMENDED that such a NAT implement IGMP/MLD Proxying [RFC4605], because IGMP aggregation provides a useful optimization. 4.2.2. IGMPv3 When a IGMPv3 proxying device receives an IGMP membership on an inside interface, it creates its own IGMP proxying membership state and its own IGMP forwarding table. It then creates an independent IGMP membership report on its outside interface reporting the multicast groups/channels -- but there is no direct relationship or "forwarding" of IGMP membership reports or queries across the interfaces. The NAT device will subsequently receive a multicast data packet on the outside ('public') interface and forward the multicast packet to inside ('internal') interfaces based on its IGMP forwarding table. By performing NAT on IGMPv3 membership reports, the membership reports appear to originate from a single IGMPv3 reporter instead of different reporters. Because IGMPv3 has different types of membership reports differentiating between status (IS_INCLUDE, IS_EXCLUDE) and change indication (e.g., TO_INCLUDE, TO_EXCLUDE), if a NAT were to interleave reports from two or more reporters (joining and leaving the same groups) the NAT would create a sequence of packets that are not compliant with an IGMPv3 reporter [RFC3376]. For this reason, the following requirements are specified: REQ-7: If a NAT supports IGMPv3, the NAT MUST: a: implement IGMP/MLD Proxying [RFC4605]. Such compliance causes the NAT to aggregate the IGMPv3 membership reports and report only the aggregated information upstream, and; Wing & Eckert Expires December 22, 2007 [Page 7]
Internet-Draft NAT Multicast Requirements June 2007 b: support any source multicast listeners and transmitters (Section 4.3), and; c: support source specific multicast listeners and transmitters ([RFC4604], section 4.2 of [RFC4607]). Failure to implement IGMP aggregation ([RFC4605]) will cause undesired temporary blackholing of multicast traffic. For example, consider two hosts behind the same NAT. If one host is joining a session at the same time another is leaving the session, and the NAT were to merely relay the join and leave upstream, the session will be terminated, and the join and leave announcements would not comply with section 5 of [RFC3376]. Primarily due to NATs functioning as IGMP proxies with multiple receivers behind the NAT, multicast applications are encouraged to use identifiers, rather than IP addresses and UDP ports, to identify specific multicast receivers (e.g., [I-D.ietf-avt-rtcpssm] encourages SSM applications to not rely exclusively on transport addresses for collision detection). As compared to any source multicast, the use of such receiver identifiers removes the need for the NAT to have long mapping timers; instead, the timers in [RFC4787] are used when a host transmits to a source specific IP multicast address. Note: SSM requires listeners to know the SSM channel (S,G), which is comprised of the IP source address (S) and the multicast group (G). An SSM sender needs to communicate its IP address in its SSM session establishment message (e.g., SDP). When the SSM sender is behind a NAT and the SSM receiver(s) are on the other side of that NAT, the SSM sender will need to determine its IP source address relevant to the SSM receivers; generally, this will be the public IP address of the NAT. This public address needs to be included in the SSM session establishment message (e.g., SDP) so that listeners on the public side of the NAT can receive the SSM channel. If there are SSM listeners on both the public and private side of the NAT, it may be valuable to consider using ICE [I-D.ietf-mmusic-ice] in the session advertisement; the full scope of the interaction between SSM and ICE is beyond the scope of this document 4.3. Any Source Multicast Transmitters Any source multicast (ASM) uses the IP addresses in the 224/8 through 231/8, and 233/8 through 239/8 range [IANA-ALLOC]. When a host both receives an ASM stream and sends traffic into it, Wing & Eckert Expires December 22, 2007 [Page 8]
Internet-Draft NAT Multicast Requirements June 2007 using RTP [RFC3550], there is a potential problem if a NAT merely followed the requirements of [RFC4787]. The problem is that RTP uses the source transport address (source IP address and source UDP port) and the RTP/RTCP SSRC value to identify session members. If a session member sees the same SSRC arrive from a different transport address, that session member will perform RTP collision detection (section 8.2 of [RFC3550]). If a NAT merely followed the requirements of [RFC4787] and timed out a UDP session after 2 minutes of inactivity and RTCP receiver reports are sent less often than every 2 minutes, RTP collision detection would be performed by other session members sharing the same SSRC, complicating diagnostic tools and potentially interfering with jitter buffer algorithms. This situation can occur, for example, with a multicast group of approximately 300 members with a normal 50kbps audio RTP stream. REQ-8: If a host on the inside interface of a NAT belongs to an any source multicast host group and the host sends a UDP packet to the same group, the NAT SHOULD have a UDP mapping timer of 60 minutes for that mapping. a: This UDP mapping SHOULD be destroyed when the host leaves that host group. The NAT is aware of this through receipt of an IGMP message from the host. b: If a NAT has exhausted its resources, the NAT MAY time out that mapping before 60 minutes have elapsed, but this is discouraged. Note that even in a situation with resource exhaustion, a NAT is still required to follow the minimum mapping duration of 2 minutes (REQ-5 of [RFC4787]). 4.4. Transport Protocol Support REQ-9: A NAT MUST support transport of multicast UDP with both multicast receivers and with multicast transmitters on the 'inside' interface(s) of the NAT. REQ-10: A NAT SHOULD support transport of multicast non-UDP protocols (e.g., PGM [RFC3208], RSVP [RFC2750]) with multicast receivers on the 'inside' interface(s) of the NAT. 5. Requirements Summary This section summarizes the requirements; if there is a difference in this summary and the text in the main body of the document, the main body takes precedence. Wing & Eckert Expires December 22, 2007 [Page 9]
Internet-Draft NAT Multicast Requirements June 2007 REQ-1: For IP multicast packets that are forward to a host(s) on its inside interface(s), a NAT MUST NOT modify the destination IP address or destination port of the packets. REQ-2: a NAT MUST modify the source IP address of packets that arrive from an 'inside' interface towards the 'outside' interface so that those packets use the NAT's public IP address(es). a: If the NAT also performs port translation (that is, it is a NAPT), the NAT MUST also create a mapping to allow responses to that multicast packet to be received by the appropriate host. For any source multicast, also see Section 4.3. For source specific multicast, also see Section 4.2.2. b: To support learning their public transport address, the NAT MUST have "Endpoint-Independent Mapping" behavior (REQ-1 of [RFC4787]) no matter if the destination IP address is a unicast address or a multicast address. REQ-3: A NAT MAY support IGMPv1 (although IGMPv1 is considered obsolete). REQ-4: A NAT MUST support IGMPv2. REQ-5: A NAT SHOULD support IGMPv3. REQ-6: If a NAT supports IGMPv1 and/or IGMPv2 (but not IGMPv3), the NAT MAY simply receive IGMP membership reports on the inside interface, NAT them, and relay the IGMP membership report, and do the same function in the opposite direction to the IGMP listeners. That is, the NAT does not need to do any aggregation of IGMP messages. a: However, it is RECOMMENDED that such a NAT implement IGMP/MLD Proxying [RFC4605], because IGMP aggregation provides a useful optimization. REQ-7: If a NAT supports IGMPv3, the NAT MUST: a: implement [RFC4605]. Such compliance causes the NAT to aggregate the IGMPv3 membership reports and report only the aggregated information upstream, and; Wing & Eckert Expires December 22, 2007 [Page 10]
Internet-Draft NAT Multicast Requirements June 2007 b: support any source multicast listeners and transmitters (Section 4.3), and; c: support source specific multicast listeners and transmitters ([RFC4604], section 4.2 of [RFC4607]). REQ-8: If a host on the inside interface of a NAT belongs to an any source multicast host group and the host sends a UDP packet to the same group, the NAT SHOULD have a UDP mapping timer of 60 minutes for that mapping. a: This UDP mapping SHOULD be destroyed when the host leaves that host group. The NAT is aware of this through receipt of an IGMP message from the host. b: If a NAT has exhausted its resources, the NAT MAY time out that mapping before 60 minutes have elapsed, but this is discouraged. Note that even in a situation with resource exhaustion, a NAT is still required to follow the minimum mapping duration of 2 minutes (REQ-5 of [RFC4787]). REQ-9: A NAT MUST support transport of multicast UDP with both multicast receivers and multicast transmitters on the 'inside' interface(s) of the NAT. REQ-10: A NAT SHOULD support transport of multicast non-UDP protocols (e.g., PGM [RFC3208], RSVP [RFC2750]) with multicast receivers on the 'inside' interface(s) of the NAT. 6. Security Considerations The Security Considerations sections of IGMPv3 [RFC3376] and IGMP Proxying [RFC4605] apply to a device complying with this document. When a host is using RTP and participating in an any source multicast session, the host's periodic RTCP receiver reports cause the NAT to create a mapping. When the group size is less than approximately 300, the RTCP reports are sent frequently enough that a NAT's mapping will always be kept open. When the group size is larger than approximately 300, the RTCP reports are sent less frequently. The recommendation in Section 4.3 causes the NAT mapping to be kept open for the duration of the host's participation in that multicast session no matter the size of the multicast host or periodicity of the host's RTCP transmissions. Wing & Eckert Expires December 22, 2007 [Page 11]
Internet-Draft NAT Multicast Requirements June 2007 7. IANA Considerations This document does not require any IANA registrations. 8. Acknowledgments Thanks to Yiqun Cai, Stephen Casner, Remi Denis-Courmont, Alfred Hines, Prashant Jhingran, Albert Manfredi, Marcus Maranhao, Bryan McLaughlin, Pekka Savola, and Magnus Westerlund for their assistance in writing this document. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2236] Fenner, W., "Internet Group Management Protocol, Version 2", RFC 2236, November 1997. [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. Thyagarajan, "Internet Group Management Protocol, Version 3", RFC 3376, October 2002. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003. [RFC4604] Holbrook, H., Cain, B., and B. Haberman, "Using Internet Group Management Protocol Version 3 (IGMPv3) and Multicast Listener Discovery Protocol Version 2 (MLDv2) for Source- Specific Multicast", RFC 4604, August 2006. [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, "Internet Group Management Protocol (IGMP) / Multicast Listener Discovery (MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying")", RFC 4605, August 2006. [RFC4787] Audet, F. and C. Jennings, "Network Address Translation (NAT) Behavioral Requirements for Unicast UDP", BCP 127, RFC 4787, January 2007. Wing & Eckert Expires December 22, 2007 [Page 12]
Internet-Draft NAT Multicast Requirements June 2007 9.2. Informational References [I-D.ietf-avt-rtcpssm] Chesterfield, J., "RTCP Extensions for Single-Source Multicast Sessions with Unicast Feedback", draft-ietf-avt-rtcpssm-13 (work in progress), March 2007. [I-D.ietf-mmusic-ice] Rosenberg, J., "Interactive Connectivity Establishment (ICE): A Protocol for Network Address Translator (NAT) Traversal for Offer/Answer Protocols", draft-ietf-mmusic-ice-16 (work in progress), June 2007. [IANA-ALLOC] Internet Assigned Numbers Authority, "Internet Multicast Addresses", <http://www.iana.org/assignments/multicast-addresses>. [RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5, RFC 1112, August 1989. [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. [RFC2750] Herzog, S., "RSVP Extensions for Policy Control", RFC 2750, January 2000. [RFC3208] Speakman, T., Crowcroft, J., Gemmell, J., Farinacci, D., Lin, S., Leshchiner, D., Luby, M., Montgomery, T., Rizzo, L., Tweedly, A., Bhaskar, N., Edmonstone, R., Sumanasekera, R., and L. Vicisano, "PGM Reliable Transport Protocol Specification", RFC 3208, December 2001. [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, August 2006. [RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for IP", RFC 4607, August 2006. Wing & Eckert Expires December 22, 2007 [Page 13]
Internet-Draft NAT Multicast Requirements June 2007 Authors' Addresses Dan Wing Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134 USA Email: dwing@cisco.com Toerless Eckert Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134 USA Email: eckert@cisco.com Wing & Eckert Expires December 22, 2007 [Page 14]
Internet-Draft NAT Multicast Requirements June 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). 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, 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 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). Wing & Eckert Expires December 22, 2007 [Page 15]