IP Multicast Requirements for a Network Address Translator (NAT) and a Network Address Port Translator (NAPT)
RFC 5135
| Document | Type |
RFC - Best Current Practice
(February 2008; Errata)
Also known as BCP 135
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Replaces | draft-wing-behave-multicast | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | WG Document | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 5135 (Best Current Practice) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Magnus Westerlund | ||
| Send notices to | (None) | ||
Network Working Group D. Wing
Request for Comments: 5135 T. Eckert
BCP: 135 Cisco Systems, Inc.
Category: Best Current Practice February 2008
IP Multicast Requirements for a Network Address Translator (NAT)
and a Network Address Port Translator (NAPT)
Status of This Memo
This document specifies an Internet Best Current Practices for the
Internet Community, and requests discussion and suggestions for
improvements. Distribution of this memo is unlimited.
Abstract
This document specifies requirements for a for a Network Address
Translator (NAT) and a Network Address Port Translator (NAPT) that
support Any Source IP Multicast or Source-Specific IP Multicast. An
IP multicast-capable NAT device that adheres to the requirements of
this document can optimize the operation of IP multicast applications
that are generally unaware of IP multicast NAT devices.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology Used in This Document . . . . . . . . . . . . . . 2
3. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. NATing IP Multicast Data Packets . . . . . . . . . . . . . 5
4.1.1. Receiving Multicast Data Packets . . . . . . . . . . . 5
4.1.2. Sending Multicast Data Packets . . . . . . . . . . . . 5
4.2. IGMP Version Support . . . . . . . . . . . . . . . . . . . 6
4.2.1. IGMPv1 or IGMPv2 . . . . . . . . . . . . . . . . . . . 7
4.2.2. IGMPv3 . . . . . . . . . . . . . . . . . . . . . . . . 7
4.3. Any Source Multicast Transmitters . . . . . . . . . . . . 8
5. Requirements Summary . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . . 13
Appendix A. Application Considerations . . . . . . . . . . . . . 14
Wing & Eckert Best Current Practice [Page 1]
RFC 5135 NAT IP Multicast Requirements February 2008
1. Introduction
In order for IP multicast applications to function well over NATs,
multicast UDP must work as seamlessly as unicast UDP. However, NATs
have little consistency in IP multicast operation, which results in
inconsistent user experiences and failed IP multicast operation.
This document targets requirements intended to enable correct
operations of Any Source Multicast and Source-Specific Multicast in
devices running Internet Group Management Protocol (IGMP) proxy
routing and NAT and without applying NAT to IP multicast group
addresses. This profile of functionality is the expected best
practice for residential access routers, small branch routers, or
similar deployments.
Most of the principles outlined in this document do also apply when
using protocols other than IGMP, such as Protocol Independent
Multicast - Sparse Mode (PIM-SM), or when performing NAT between
multiple "inside" interfaces, but explicit consideration for these
cases is outside the scope of this document.
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').
This allows a host 'inside' the NAT to both receive multicast traffic
and to source multicast traffic. Hosts on the 'inside' interface(s)
of a NAT indicate their interest in receiving an IP multicast flow by
sending an IGMP message to their local interface. An IP 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 IP multicast traffic to the NAT, which
forwards it to those 'inside' segment(s) with host(s) that had
previously sent IGMP messages for that IP 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
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