| BEHAVE | M. Petit-Huguenin |
| Internet-Draft | Impedance Mismatch |
| Intended status: Standards Track | S. Nandakumar |
| Expires: March 01, 2014 | G. Salgueiro |
| P. Jones | |
| Cisco Systems | |
| August 28, 2013 |
Traversal Using Relays around NAT (TURN) Uniform Resource Identifiers
draft-petithuguenin-behave-turn-uris-06
This document specifies the syntax of Uniform Resource Identifier (URI) schemes for the Traversal Using Relays around NAT (TURN) protocol. It defines two URI schemes to provision the TURN Resolution Mechanism [RFC5928].
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This document specifies the syntax and semantics of the Uniform Resource Identifier (URI) scheme for the Traversal Using Relays around NAT (TURN) protocol.
The TURN protocol is a specification allowing hosts behind NAT to control the operation of a relay server. The relay server allows hosts to exchange packets with its peers. The peers themselves may also be behind NATs. RFC 5766 [RFC5766] defines the specifics of the TURN protocol.
The "turn" and "turns" URI schemes are used to designate a TURN server (also known as a relay) on Internet hosts accessible using the TURN protocol. With the advent of standards such as [WEBRTC], we anticipate a plethora of endpoints and web applications to be able to identify and communicate with such a TURN server to carry out the TURN protocol. This also implies those endpoints and/or applications to be provisioned with appropriate configuration required to identify the TURN server. Having an inconsistent syntax has its drawbacks and can result in non-interoperable solutions. It can result in solutions that are ambiguous and have implementation limitations on the different aspects of the syntax and alike. The "turn/turns" URI scheme helps alleviate most of these issues by providing a consistent way to describe, configure and exchange the information identifying a TURN server. This would also prevent the shortcomings inherent with encoding similar information in non-uniform syntaxes such as the ones proposed in [WEBRTC], for example.
[RFC5928] defines a resolution mechanism to convert a secure flag, a host name or IP address, an eventually empty port, and an eventually empty transport to a list of IP address, port, and TURN transport tuples.
To simplify the provisioning of TURN clients, this document defines a TURN and a TURNS URI scheme that can carry the four components needed for the resolution mechanism.
The key words "MUST", "MUST NOT", "REQUIRED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] when they appear in ALL CAPS. When these words are not in ALL CAPS (such as "should" or "Should"), they have their usual english meanings, and are not to be interpreted as RFC 2119 key words.
A TURN/TURNS URI has the following formal ABNF syntax [RFC5234]:
turnURI = scheme ":" turn-host [ ":" turn-port ]
[ "?transport=" transport ]
scheme = "turn" / "turns"
transport = "udp" / "tcp" / transport-ext
transport-ext = 1*unreserved
turn-host = IP-literal / IPv4address / reg-name
turn-port = *DIGIT
IP-literal = "[" ( IPv6address / IPvFuture ) "]"
IPvFuture = "v" 1*HEXDIG "." 1*( unreserved / sub-delims / ":" )
IPv6address = 6( h16 ":" ) ls32
/ "::" 5( h16 ":" ) ls32
/ [ h16 ] "::" 4( h16 ":" ) ls32
/ [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32
/ [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32
/ [ *3( h16 ":" ) h16 ] "::" h16 ":" ls32
/ [ *4( h16 ":" ) h16 ] "::" ls32
/ [ *5( h16 ":" ) h16 ] "::" h16
/ [ *6( h16 ":" ) h16 ] "::"
h16 = 1*4HEXDIG
ls32 = ( h16 ":" h16 ) / IPv4address
IPv4address = dec-octet "." dec-octet "." dec-octet "." dec-octet
dec-octet = DIGIT ; 0-9
/ %x31-39 DIGIT ; 10-99
/ "1" 2DIGIT ; 100-199
/ "2" %x30-34 DIGIT ; 200-249
/ "25" %x30-35 ; 250-255
reg-name = *( unreserved / pct-encoded / sub-delims )
<unreserved>, <pct-encoded>, and <sub-delims> are specified in [RFC3986]. The core rules <DIGIT> and <HEXDIGIT> are used as described in Appendix B of RFC 5234 [RFC5234].
The <host>, <port> and <transport> components are passed without modification to the [RFC5928] algorithm. <secure> is set to false if <scheme> is equal to "turn" and set to true if <scheme> is equal to "turns" and passed to the [RFC5928] algorithm with the other components.
The TURN protocol supports sending messages over UDP, TCP or TLS-over-TCP. The "turns" URI scheme MUST be used when TURN is run over TLS-over-TCP (or in the future DTLS-over-UDP) and the "turn" scheme MUST be used otherwise.
The required <host> part of the "turn" URI denotes the TURN server host.
As specified in [RFC5766] and [RFC5928], the <port> part, if present, denotes the port on which the TURN server is awaiting connection requests. If it is absent, the default port is 3478 for both UDP and TCP. The default port for TURN over TLS is 5349.
Note to RFC Editor: Please remove this section and the reference to [RFC6982] before publication.
This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in [RFC6982]. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist.
According to [RFC6982], "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit".
Security considerations for the resolution mechanism are discussed in [RFC5928].
The "turn" and "turns" URI schemes do not introduce any specific security issues beyond the security considerations discussed in [RFC3986].
Security considerations for the resolution mechanism are discussed in Section 5 of [RFC5928]. Note that that section contains normative text defining authentication procedures to be followed by turn clients when TLS is used.
This section contains the registration information for the "turn" and "turns" URI Schemes (in accordance with [RFC4395]).
URI scheme name: turn
Status: permanent
URI scheme syntax: See Section 3.1.
URI scheme semantics: See Section 3.2.
Encoding considerations: There are no encoding considerations beyond those in [RFC3986].
Applications/protocols that use this URI scheme name:
Interoperability considerations: N/A
Security considerations: See Section 5.
Contact: Marc Petit-Huguenin <petithug@acm.org>
Author/Change controller: The IESG
References: RFCXXXX
[[NOTE TO RFC EDITOR: Please change XXXX to the number assigned to this specification, and remove this paragraph on publication.]]
URI scheme name: turns
Status: permanent
URI scheme syntax: See Section 3.1.
URI scheme semantics: See Section 3.2.
Encoding considerations: There are no encoding considerations beyond those in [RFC3986].
Applications/protocols that use this URI scheme name:
Interoperability considerations: N/A
Security considerations: See Section 5.
Contact: Marc Petit-Huguenin <petithug@acm.org>
Author/Change controller: The IESG
References: RFCXXXX
[[NOTE TO RFC EDITOR: Please change XXXX to the number assigned to this specification, and remove this paragraph on publication.]]
Thanks to Margaret Wasserman, Magnus Westerlund, Juergen Schoenwaelder, Sean Turner, Ted Hardie, Dave Thaler, Alfred E. Heggestad, Eilon Yardeni, Dan Wing, Alfred Hoenes, and Jim Kleck for the comments, suggestions and questions that helped improve the draft-petithuguenin-behave-turn-uri-bis document.
Many thanks to Cullen Jennings for his detailed review and thoughtful comments on the draft-nandakumar-rtcweb-turn-uri document.
Thanks to Bjoern Hoehrmann, Dan Wing, Russ Housley, S. Moonesamy, Graham Klyne, Harald Alvestrand, Hadriel Kaplan and Tina Tsou for the comments, suggestions and questions that helped improve this document.
The authors would also like to express their gratitude to Dan Wing for his assistance in shepherding this document. We also want to thank Gonzalo Camarillo, the Real-time Applications and Infrastructure Director, for sponsoring this document as well his careful reviews.
The <turn-port> and <turn-host> ABNF productions have been copied from the <port> and <host> ABNF productions from [RFC3986].
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC3986] | Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. |
| [RFC5234] | Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. |
| [RFC5766] | Mahy, R., Matthews, P. and J. Rosenberg, "Traversal Using Relays around NAT (TURN): Relay Extensions to Session Traversal Utilities for NAT (STUN)", RFC 5766, April 2010. |
| [RFC5928] | Petit-Huguenin, M., "Traversal Using Relays around NAT (TURN) Resolution Mechanism", RFC 5928, August 2010. |
| [RFC4395] | Hansen, T., Hardie, T. and L. Masinter, "Guidelines and Registration Procedures for New URI Schemes", BCP 35, RFC 4395, February 2006. |
| [WEBRTC] | Bergkvist, A., Burnett, D., Jennings, C. and A. Narayanan, "WebRTC 1.0: Real-time Communication Between Browsers", World Wide Web Consortium WD WD-webrtc-20120821, August 2012. |
| [RFC6982] | Sheffer, Y. and A. Farrel, "Improving Awareness of Running Code: The Implementation Status Section", RFC 6982, July 2013. |
Table 1 shows how the <secure>, <port> and <transport> components are populated from various URIs. For all these examples, the <host> component is populated with "example.org".
| URI | <secure> | <port> | <transport> |
|---|---|---|---|
| turn:example.org | false | ||
| turns:example.org | true | ||
| turn:example.org:8000 | false | 8000 | |
| turn:example.org?transport=udp | false | UDP | |
| turn:example.org?transport=tcp | false | TCP | |
| turns:example.org?transport=tcp | true | TLS |
This section must be removed before publication as an RFC.