Datagram Transport Layer Security (DTLS) as Transport for Session Traversal Utilities for NAT (STUN)
RFC 7350
Internet Engineering Task Force (IETF) M. Petit-Huguenin
Request for Comments: 7350 Jive Communications
Updates: 5389, 5928 G. Salgueiro
Category: Standards Track Cisco Systems
ISSN: 2070-1721 August 2014
Datagram Transport Layer Security (DTLS) as Transport
for Session Traversal Utilities for NAT (STUN)
Abstract
This document specifies the usage of Datagram Transport Layer
Security (DTLS) as a transport protocol for Session Traversal
Utilities for NAT (STUN). It provides guidance on when and how to
use DTLS with the currently standardized STUN usages. It also
specifies modifications to the STUN and Traversal Using Relay NAT
(TURN) URIs and to the TURN resolution mechanism to facilitate the
resolution of STUN and TURN URIs into the IP address and port of STUN
and TURN servers supporting DTLS as a transport protocol. This
document updates RFCs 5389 and 5928.
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/rfc7350.
Petit-Huguenin & Salgueiro Standards Track [Page 1]
RFC 7350 STUN over DTLS August 2014
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. DTLS as Transport for STUN . . . . . . . . . . . . . . . . . 3
4. STUN Usages . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. NAT Discovery Usage . . . . . . . . . . . . . . . . . . . 4
4.1.1. DTLS Support in STUN URIs . . . . . . . . . . . . . . 5
4.2. Connectivity Check Usage . . . . . . . . . . . . . . . . 5
4.3. Media Keep-Alive Usage . . . . . . . . . . . . . . . . . 5
4.4. SIP Keep-Alive Usage . . . . . . . . . . . . . . . . . . 6
4.5. NAT Behavior Discovery Usage . . . . . . . . . . . . . . 6
4.6. TURN Usage . . . . . . . . . . . . . . . . . . . . . . . 6
4.6.1. DTLS Support in TURN URIs . . . . . . . . . . . . . . 7
4.6.2. Resolution Mechanism for TURN over DTLS . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6.1. S-NAPTR Application Protocol Tag . . . . . . . . . . . . 9
6.2. Service Name and Transport Protocol Port Number . . . . . 9
6.2.1. The "stuns" Service Name . . . . . . . . . . . . . . 10
6.2.2. The "turns" Service Name . . . . . . . . . . . . . . 11
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 14
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RFC 7350 STUN over DTLS August 2014
1. Introduction
STUN [RFC5389] defines Transport Layer Security (TLS) over TCP
(simply referred to as TLS [RFC5246]) as the transport for STUN due
to additional security advantages it offers over plain UDP or TCP
transport. But, TCP (and thus TLS-over-TCP) is not an optimal
transport when STUN is used for its originally intended purpose,
which is to support multimedia sessions. This is a well documented
and understood transport limitation for real-time communications.
DTLS-over-UDP (referred to in this document as simply DTLS [RFC6347])
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