Path MTU Discovery (PMTUD) for RTP/RTCP
draft-petithuguenin-dispatch-rtp-pmtud-00

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DISPATCH                                               M. Petit-Huguenin
Internet-Draft                                        Impedance Mismatch
Intended status: Standards Track                            G. Salgueiro
Expires: September 14, 2017                                        Cisco
                                                          March 13, 2017

                Path MTU Discovery (PMTUD) for RTP/RTCP
               draft-petithuguenin-dispatch-rtp-pmtud-00

Abstract

   This document describes an implementation of the Path MTU Discovery
   (PMTUD) protocol for RTP sessions.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on September 14, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Overview of Operations  . . . . . . . . . . . . . . . . . . .   2
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   4.  Probe Support Signaling . . . . . . . . . . . . . . . . . . .   3
   5.  Path MTU Discovery Using the Simple Probing Mechanism . . . .   3
   6.  Path MTU Discovery Using the Complete Probing Mechanism . . .   3
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The Guidelines for Writers of RTP Payload Formats (RFC 2736,BCP 36
   [RFC2736]) states in Section 4 that "[i]f a codec's frame size is
   larger than the MTU, the payload format must not rely on IP
   fragmentation."  Similarly, RFC 3550 [RFC3550] states that "...only
   the subset [of RR packets into one compound RTCP packet] that will
   fit into one MTU SHOULD be included in each interval."

   These statements can be extended to the Path MTU, as fragmentation
   along the media path is no better than fragmentation on the first
   link-layer.

   RTP and RTCP [RFC3550] were not designed with a mechanism to discover
   the Path MTU, so this document describes a way to add this capability
   by using the PMTUD protocol defined in [I-D.ietf-tram-stun-pmtud].

2.  Overview of Operations

   Multiplexing between RTP/RTCP packets and STUN packets is a well-
   known technique used for example to discover the IP address of a NAT
   [RFC5389] or to check connectivity [RFC5245].

   The PMTUD mechanism for RTP/RTCP uses either the Simple Probing
   Mechanism described in Section 4.1 of [I-D.ietf-tram-stun-pmtud] or
   the Complete Probing Mechanism described in Section 4.2.

3.  Terminology

   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 [RFC2119].

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