Session Traversal Utilities for NAT (STUN)
RFC 8489

Document Type RFC - Proposed Standard (February 2020; Errata)
Obsoletes RFC 5389
Last updated 2020-09-16
Stream IETF
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Reviews
Stream WG state Submitted to IESG for Publication
Document shepherd Tolga Asveren
Shepherd write-up Show (last changed 2018-02-02)
IESG IESG state RFC 8489 (Proposed Standard)
Consensus Boilerplate Yes
Telechat date
Responsible AD Magnus Westerlund
Send notices to Tolga Asveren <tasveren@rbbn.com>, Gonzalo.Camarillo@ericsson.com
IANA IANA review state Version Changed - Review Needed
IANA action state RFC-Ed-Ack
Internet Engineering Task Force (IETF)                 M. Petit-Huguenin
Request for Comments: 8489                            Impedance Mismatch
Obsoletes: 5389                                             G. Salgueiro
Category: Standards Track                                          Cisco
ISSN: 2070-1721                                             J. Rosenberg
                                                                   Five9
                                                                 D. Wing
                                                                  Citrix
                                                                 R. Mahy
                                                            Unaffiliated
                                                             P. Matthews
                                                                   Nokia
                                                           February 2020

               Session Traversal Utilities for NAT (STUN)

Abstract

   Session Traversal Utilities for NAT (STUN) is a protocol that serves
   as a tool for other protocols in dealing with NAT traversal.  It can
   be used by an endpoint to determine the IP address and port allocated
   to it by a NAT.  It can also be used to check connectivity between
   two endpoints and as a keep-alive protocol to maintain NAT bindings.
   STUN works with many existing NATs and does not require any special
   behavior from them.

   STUN is not a NAT traversal solution by itself.  Rather, it is a tool
   to be used in the context of a NAT traversal solution.

   This document obsoletes RFC 5389.

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 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8489.

Petit-Huguenin, et al.       Standards Track                    [Page 1]
RFC 8489                          STUN                     February 2020

Copyright Notice

   Copyright (c) 2020 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
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   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................4
   2. Overview of Operation ...........................................5
   3. Terminology .....................................................7
   4. Definitions .....................................................7
   5. STUN Message Structure ..........................................9
   6. Base Protocol Procedures .......................................11
      6.1. Forming a Request or an Indication ........................11
      6.2. Sending the Request or Indication .........................12
           6.2.1. Sending over UDP or DTLS-over-UDP ..................13
           6.2.2. Sending over TCP or TLS-over-TCP ...................14
           6.2.3. Sending over TLS-over-TCP or DTLS-over-UDP .........15
      6.3. Receiving a STUN Message ..................................16
           6.3.1. Processing a Request ...............................17
                  6.3.1.1. Forming a Success or Error Response .......17
                  6.3.1.2. Sending the Success or Error Response .....18
           6.3.2. Processing an Indication ...........................18
           6.3.3. Processing a Success Response ......................19
           6.3.4. Processing an Error Response .......................19
   7. FINGERPRINT Mechanism ..........................................20
   8. DNS Discovery of a Server ......................................20
      8.1. STUN URI Scheme Semantics .................................21
   9. Authentication and Message-Integrity Mechanisms ................22
      9.1. Short-Term Credential Mechanism ...........................23
           9.1.1. HMAC Key ...........................................23
           9.1.2. Forming a Request or Indication ....................23
           9.1.3. Receiving a Request or Indication ..................23
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