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Versions: (draft-wing-behave-multicast) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 5135

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
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   Internet-Drafts are working documents of the Internet Engineering
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   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.






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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





























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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










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   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.



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   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.




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   [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.









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Author's Address

   Dan Wing
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA  95134
   USA

   Email: dwing@cisco.com










































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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
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Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





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