BEHAVE D. Wing Internet-Draft Cisco Systems Expires: December 18, 2006 June 16, 2006 Multicast Requirements for a Network Address Port Translator (NAPT) draft-ietf-behave-multicast-02 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 18, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document places requirements on a Network Address Translator (NAT) and Network Address and Port Translator (NAPT) that supports IP multicast by implementing an IGMP proxy. 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]. Wing Expires December 18, 2006 [Page 1]
Internet-Draft NAPT Multicast Requirements June 2006 Table of Contents 1. Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 3 3. NAPT Multicast Requirements . . . . . . . . . . . . . . . . . . 4 3.1. Keep NAT Binding Open . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5 7. Normative References . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . . . 7 Wing Expires December 18, 2006 [Page 2]
Internet-Draft NAPT Multicast Requirements June 2006 1. Problem Statement For users to accept and enjoy multicast, multicast UDP must work as seamlessly as unicast UDP. However, today's equipment has little consistency in multicast operation which results in inconsistant user experiences and failed multicast operation. 2. Introduction This document describes the behavior of a device providing multicast functions similar to [I-D.ietf-magma-igmp-proxy] 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: * sending multicast traffic, * PIM-SM [RFC2362], * IPv6, and, * IGMPv1. Sending multicast traffic is out of scope because it requires NATting the source IP address of such transmitted multicast traffic. Similarly, 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 NAT is not considered necessary with IPv6. IGMPv1 is not significantly deployed on the Internet. This document does not describe how to implement multicast, IGMPv2, or IGMPv3 in an IGMP Proxy device. Rather, it provides requirements for an IGMP Proxy device so that hosts behind the NAT can receive multicast traffic without any knowledge of the IGMP Proxy. 2.1. Background As detailed in the Document Scope section, the primary functions of an IGMP proxy device are to collect IGMP traffic from one interface and relay it to another interface, and accept multicast traffic from thatinterface and route -- or replicate it -- to other interface(s). 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 | +------------+ Wing Expires December 18, 2006 [Page 3]
Internet-Draft NAPT Multicast Requirements June 2006 +-------------+ When an IGMP Proxy device is added to such a network, its behavior is identical towards the upstream (WAN) router. Specifically, when dealing with multicast, the IGMP Proxy has the same behavior towards the WAN as if it was a host. +------+ +------------+ +-------------+ | host +--+ | | DSL modem | +------------+ +------+ | IGMP Proxy +---+ or +---//---+ WAN Router | +------+ | (NAPT) | | cable modem | +------------+ | host +--+ | +-------------+ +------+ +------------+ This document is a companion document to "NAT/Firewall Behavioral Requirements" [I-D.ietf-behave-nat-udp]. 3. NAPT Multicast Requirements All requirements of [I-D.ietf-magma-igmp-proxy] apply equally to NAPTs and are incorporated herein by reference. Additionally, there are some requirements particular to NATs that implement IGMP proxies: 3.1. Keep NAT Binding Open The NAT UDP requirements [I-D.ietf-behave-nat-udp] document only requires that a NAT binding be kept open for inside-to-outside UDP flows. However, with multicast traffic, UDP traffic will only arrive outside-to-inside. Hosts will periodically send IGMP Report messages to indicate continued interest in receiving the multicast traffic. As long as the IGMP Proxy sees a host is interested in receiving the flow, the NAT MUST continue to receive multicast traffic from the WAN and send it to the interfaces with interested hosts. Per IGMPv3, the default transmission interval for the periodic Membership Report is one second. Per IGMPv2, the default transmission interval for the periodic Unsolicited Report Interval is 10 seconds. If a host no longer sends its periodic messages within those timeframes, the NAT MAY consider the host no longer wants to receive the multicast traffic and can inform the upstream WAN router and close the NAT binding. However, it is suggested that the NAT wait until 3 missing unsolicited reports (to account for packet loss on the LAN, especially wireless LANs), or that the NAT first query Wing Expires December 18, 2006 [Page 4]
Internet-Draft NAPT Multicast Requirements June 2006 the host using IGMPv2 or IGMPv3. 4. Security Considerations Compliance with this specification does not increase security risks beyond those already discussed in the Security Considerations section of IGMPv3 [RFC3376]. 5. IANA Considerations This document does not require any IANA registrations. 6. Acknowledgments Thanks to Bryan McLaughlin and Yiqun Cai for their assistance in writing this document. 7. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. Thyagarajan, "Internet Group Management Protocol, Version 3", RFC 3376, October 2002. [RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address Translator (NAT) Terminology and Considerations", RFC 2663, August 1999. [I-D.ietf-magma-igmp-proxy] Fenner, B., He, H., Haberman, B., and H. Sandick, "IGMP/ MLD-based Multicast Forwarding ('IGMP/MLD Proxying')", draft-ietf-magma-igmp-proxy-06 (work in progress), April 2004. [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. [I-D.ietf-behave-nat-udp] Audet, F. and C. Jennings, "NAT Behavioral Requirements for Unicast UDP", draft-ietf-behave-nat-udp-07 (work in progress), June 2006. Wing Expires December 18, 2006 [Page 5]
Internet-Draft NAPT Multicast Requirements June 2006 Author's Address Dan Wing Cisco Systems 170 West Tasman Drive San Jose, CA 95134 USA Email: dwing@cisco.com Wing Expires December 18, 2006 [Page 6]
Internet-Draft NAPT Multicast Requirements June 2006 Intellectual Property Statement 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. Disclaimer of Validity 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. 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Wing Expires December 18, 2006 [Page 7]
