Session Traversal Utilities for NAT (STUN) Message Handling for Session Initiation Protocol (SIP) Back-to-Back User Agents (B2BUAs)
draft-ietf-straw-b2bua-stun-03

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STRAW                                                    R. Ravindranath
Internet-Draft                                                  T. Reddy
Intended status: Standards Track                            G. Salgueiro
Expires: September 5, 2015                                         Cisco
                                                           March 4, 2015

Session Traversal Utilities for NAT (STUN) Message Handling for Session
      Initiation Protocol (SIP) Back-to-Back User Agents (B2BUAs)
                     draft-ietf-straw-b2bua-stun-03

Abstract

   Session Initiation Protocol (SIP) Back-to-Back User Agents (B2BUAs)
   are often designed to be on the media path, rather than just
   intercepting signaling.  This means that B2BUAs often act on the
   media path leading to separate media legs that the B2BUA correlates
   and bridges together.  When acting on the media path, B2BUAs are
   likely to receive Session Traversal Utilities for NAT (STUN) packets
   as part of Interactive Connectivity Establishment (ICE) processing.
   It is critical that B2BUAs handle these STUN messages properly.

   This document defines behavior for a B2BUA performing ICE processing.
   The goal of this draft is to ensure that ICE used for NAT and
   Firewall traversal of multimedia sessions works when there are B2BUAs
   in place and the B2BUAs handle STUN messages properly.

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
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 5, 2015.

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Copyright Notice

   Copyright (c) 2015 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  SDP-Modifying Signaling-only B2BUA  . . . . . . . . . . . . .   5
   4.  Media Plane B2BUAs  . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  ICE Termination with B2BUA  . . . . . . . . . . . . . . .   6
     4.3.  ICE Passthrough with B2BUAs . . . . . . . . . . . . . . .   8
     4.4.  STUN Handling in B2BUA with Forked Signaling  . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  12
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   In many SIP deployments, SIP entities exist in the SIP signaling and
   media path between the originating and final terminating endpoints,
   which go beyond the definition of a traditional SIP proxy.  These SIP
   entities, commonly known as Back-to-Back User Agents (B2BUAs), are
   described in [RFC7092] and often perform functions not defined in
   Standards Track RFCs.

   The Session Initiation Protocol (SIP) [RFC3261], and other session
   control protocols that try to use direct path for media, are
   typically difficult to use across Network Address Translators (NATs).
   These protocols use IP addresses and transport port numbers encoded
   in the signaling, such as the Session Description Protocol (SDP)
   [RFC4566] and, in the case of SIP, various header fields.  Such

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