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Traversal Using Relays around NAT (TURN): Relay Extensions to Session Traversal Utilities for NAT (STUN)
RFC 5766

Internet Engineering Task Force (IETF)                           R. Mahy
Request for Comments: 5766                                  Unaffiliated
Category: Standards Track                                    P. Matthews
ISSN: 2070-1721                                           Alcatel-Lucent
                                                            J. Rosenberg
                                                             jdrosen.net
                                                              April 2010

               Traversal Using Relays around NAT (TURN):
     Relay Extensions to Session Traversal Utilities for NAT (STUN)

Abstract

   If a host is located behind a NAT, then in certain situations it can
   be impossible for that host to communicate directly with other hosts
   (peers).  In these situations, it is necessary for the host to use
   the services of an intermediate node that acts as a communication
   relay.  This specification defines a protocol, called TURN (Traversal
   Using Relays around NAT), that allows the host to control the
   operation of the relay and to exchange packets with its peers using
   the relay.  TURN differs from some other relay control protocols in
   that it allows a client to communicate with multiple peers using a
   single relay address.

   The TURN protocol was designed to be used as part of the ICE
   (Interactive Connectivity Establishment) approach to NAT traversal,
   though it also can be used without ICE.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5766.

Mahy, et al.                 Standards Track                    [Page 1]
RFC 5766                          TURN                        April 2010

Copyright Notice

   Copyright (c) 2010 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Overview of Operation  . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Transports . . . . . . . . . . . . . . . . . . . . . . . .  8
     2.2.  Allocations  . . . . . . . . . . . . . . . . . . . . . . .  9
     2.3.  Permissions  . . . . . . . . . . . . . . . . . . . . . . . 11
     2.4.  Send Mechanism . . . . . . . . . . . . . . . . . . . . . . 12
     2.5.  Channels . . . . . . . . . . . . . . . . . . . . . . . . . 13
     2.6.  Unprivileged TURN Servers  . . . . . . . . . . . . . . . . 15
     2.7.  Avoiding IP Fragmentation  . . . . . . . . . . . . . . . . 16
     2.8.  RTP Support  . . . . . . . . . . . . . . . . . . . . . . . 17
     2.9.  Anycast Discovery of Servers . . . . . . . . . . . . . . . 17
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . . 18
   4.  General Behavior . . . . . . . . . . . . . . . . . . . . . . . 19
   5.  Allocations  . . . . . . . . . . . . . . . . . . . . . . . . . 22
   6.  Creating an Allocation . . . . . . . . . . . . . . . . . . . . 23
     6.1.  Sending an Allocate Request  . . . . . . . . . . . . . . . 23
     6.2.  Receiving an Allocate Request  . . . . . . . . . . . . . . 24
     6.3.  Receiving an Allocate Success Response . . . . . . . . . . 28
     6.4.  Receiving an Allocate Error Response . . . . . . . . . . . 29
   7.  Refreshing an Allocation . . . . . . . . . . . . . . . . . . . 31
     7.1.  Sending a Refresh Request  . . . . . . . . . . . . . . . . 31
     7.2.  Receiving a Refresh Request  . . . . . . . . . . . . . . . 31
     7.3.  Receiving a Refresh Response . . . . . . . . . . . . . . . 32
   8.  Permissions  . . . . . . . . . . . . . . . . . . . . . . . . . 32
   9.  CreatePermission . . . . . . . . . . . . . . . . . . . . . . . 34
     9.1.  Forming a CreatePermission Request . . . . . . . . . . . . 34
     9.2.  Receiving a CreatePermission Request . . . . . . . . . . . 34

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