BEHAVE D. Wing Internet-Draft Cisco Systems Updates: RFC4605 (if approved) October 23, 2006 Intended status: Best Current Practice Expires: April 26, 2007 Network Address Port Translator (NAPT) Any-Source Multicast Requirement draft-ietf-behave-multicast-04 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 April 26, 2007. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document places a requirement on a Network Address Translator (NAT) and Network Address and Port Translator (NAPT) that supports any-source multicast. Wing Expires April 26, 2007 [Page 1]
Internet-Draft NAPT ASM Requirement October 2006 Requirements Language 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]. Table of Contents 1. Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Extend Mapping Timer for ASM Traffic . . . . . . . . . . . . . 4 4. Considerations for Source-Specific Multicast (SSM) . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8.1. Normative References . . . . . . . . . . . . . . . . . . . 5 8.2. Informational References . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 8 Wing Expires April 26, 2007 [Page 2]
Internet-Draft NAPT ASM Requirement October 2006 1. Problem Statement For users to accept and enjoy any-source multicast, multicast UDP must work as seamlessly as unicast UDP. However, NATs have little consistency in multicast operation which results in inconsistant user experiences and failed multicast operation. 2. Introduction A multicast NAPT device that adheres to the requirements of this document can optimize the operation of any-source multicast applications that are generally unaware of multicast NAPT devices. This document describes the behavior of a device providing any-source multicast proxy functions as described in [RFC4605] using ICMPv1 [RFC1112] or ICMPv2 [RFC2236], and that additionally functions as a Network Address and Port Translator (NAPT), as described in section 4.1.2 of [RFC2663]. Specifically out of scope of this document are PIM-SM [RFC2362], and IPv6. PIM is used only between routers and the IGMP Proxy devices that are scoped in this document do not function as routers. IPv6 is out of scope because NAPT is not considered necessary with IPv6. This document describes how an IGMP Proxy device can NAPT multicast traffic so that existing any-source multicast applications function without awareness the multicast traffic they send has been NAPTted. 2.1. Background When a NAPT 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 Wing Expires April 26, 2007 [Page 3]
Internet-Draft NAPT ASM Requirement October 2006 The primary functions of an IGMP proxy device are to collect IGMP traffic from the 'inside' interface and relay it to the 'outside' interface, and accept multicast traffic from that 'outside' interface and route -- or replicate it -- to the 'inside' interface(s). Packets with a multicast destination IP address do not have their destination IP address changed by a NAPT. However, their source IP address and source UDP port is changed if the packet goes from an 'inside' interface of a NAPT to the 'outside' interface of a NAPT -- similar to the behavior of a a unicast packet. +----+ +-------------+ |host+---+ +---------+ | +-----------+ +----+ | |Multicast| | | DSL modem | +------------+ | | Proxy | +--+ or +-//-+ WAN Router | inside | +---------+ | |cable modem| +------------+ interfaces | | +-----------+ | +------+ | +----+ | | NAPT | | outside |host+---+ +------+ | interfaces +----+ +-------------+ IGMP Proxy NAPT Device Figure 2: Network with NAPTing IGMP Proxy This document is a companion document to "NAT Behavioral Requirements for Unicast UDP" [I-D.ietf-behave-nat-udp]. 3. Extend Mapping Timer for ASM Traffic If a NAPTed host is receiving any multicasts stream, and that NAPTed host sends UDP traffic to the same multicast address the NAPTed host is receiving, the NAPT MUST have a UDP mapping timer of 60 minutes. If a NAPT has exhausted its resources, the NAPT MAY time out a mapping before 60 minutes have elapsed. However, a NAPT is still required to follow the minimum mapping duration (REQ-5 of [I-D.ietf-behave-nat-udp]). Discussion: RTP [RFC3550] uses the source transport address (source IP address and source UDP port), in addition to the 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 NAPT merely followed the requirements of [I-D.ietf-behave-nat-udp] 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. Wing Expires April 26, 2007 [Page 4]
Internet-Draft NAPT ASM Requirement October 2006 This situation can occur, for example, with a multicast group of approximately 300 members with a normal 50kbps audio RTP stream. To prevent this unnecessary RTP collision detection by other session members, the other session members need to see the same source transport address for the RTP and RTCP traffic from the NAPTed host. This requires the NAPT to assign the same UDP source port for that RTCP traffic. This requirement also facilitates other, non-RTP multicast applications which may function similarly. 4. Considerations for Source-Specific Multicast (SSM) There are no special requirements on a NAPT when NAPTing Source- Specific Multicast [RFC4604] traffic. This is because with SSM, the RTCP feedback traffic from a NAPTed host is sent to a unicast address and [I-D.ietf-avt-rtcpssm] encourages SSM applications to not rely exclusively on transport address for collision detection. 5. Security Considerations Compliance with this specification does not increase security risks beyond those already discussed in the Security Considerations section of IGMPv3 [RFC3376] and IGMP/MLD Proxying [RFC4605]. 6. IANA Considerations This document does not require any IANA registrations. 7. Acknowledgments Thanks to Yiqun Cai, Stephen Casner, Marcus Maranhao, Bryan McLaughlin, and Magnus Westerlund for their assistance in writing this document. 8. References 8.1. Normative References [I-D.ietf-behave-nat-udp] Audet, F. and C. Jennings, "NAT Behavioral Requirements for Unicast UDP", draft-ietf-behave-nat-udp-08 (work in progress), October 2006. Wing Expires April 26, 2007 [Page 5]
Internet-Draft NAPT ASM Requirement October 2006 [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. [RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address Translator (NAT) Terminology and Considerations", RFC 2663, August 1999. [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. [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. 8.2. Informational References [I-D.ietf-avt-rtcpssm] Chesterfield, J., "RTCP Extensions for Single-Source Multicast Sessions with Unicast Feedback", draft-ietf-avt-rtcpssm-11 (work in progress), March 2006. [RFC1112] Deering, S., "Host extensions for IP multicasting", STD 5, RFC 1112, August 1989. [RFC2362] Estrin, D., Farinacci, D., Helmy, A., Thaler, D., Deering, S., Handley, M., and V. Jacobson, "Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specification", RFC 2362, June 1998. [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. Wing Expires April 26, 2007 [Page 6]
Internet-Draft NAPT ASM Requirement October 2006 Author's Address Dan Wing Cisco Systems 170 West Tasman Drive San Jose, CA 95134 USA Email: dwing@cisco.com Wing Expires April 26, 2007 [Page 7]
Internet-Draft NAPT ASM Requirement October 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). Wing Expires April 26, 2007 [Page 8]
