BEHAVE M. Petit-Huguenin
Internet-Draft Impedance Mismatch
Intended status: Standards Track S. Nandakumar
Expires: July 20, 2013 G. Salgueiro
P. Jones
Cisco Systems
January 16, 2013
Traversal Using Relays around NAT (TURN) Uniform Resource Identifiers
draft-petithuguenin-behave-turn-uris-03
Abstract
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 that can be used to provision
the configuration values needed by the resolution mechanism defined
in [RFC5928].
Status of this Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Definitions of the TURN and TURNS URI . . . . . . . . . . . . . 4
3.1. URI Scheme Syntax . . . . . . . . . . . . . . . . . . . . . 4
3.2. URI Scheme Semantics . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
5.1. TURN URI Registration . . . . . . . . . . . . . . . . . . . 5
5.2. TURNS URI Registration . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . . 7
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . . 8
Appendix B. Release notes . . . . . . . . . . . . . . . . . . . . 8
B.1. Design Notes . . . . . . . . . . . . . . . . . . . . . . . 8
B.2. Modifications between
petithuguenin-behave-turn-uris-03 and
petithuguenin-behave-turn-uris-02 . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
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.
A reference implementation [REF-IMPL] is available.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described in [RFC2119].
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3. Definitions of the TURN and TURNS URI
3.1. URI Scheme Syntax
The "turn" URI takes the following form (the syntax below is non-
normative):
turn:<host>:<port>
turns:<host>:<port>
Note that the <port> part and the preceding ":" (colon) character, is
OPTIONAL.
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>, <sub-delims>, and <pct-encoded> 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
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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.
3.2. URI Scheme Semantics
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.
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.
4. Security Considerations
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].
5. IANA Considerations
This section contains the registration information for the "turn" and
"turns" URI Schemes (in accordance with [RFC4395]).
5.1. TURN URI Registration
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].
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Applications/protocols that use this URI scheme name:
The "turn" URI scheme is intended to be used by applications that
might need access to a TURN server.
Interoperability considerations: N/A
Security considerations: See Section 4.
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.]]
5.2. TURNS URI Registration
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:
The "turns" URI scheme is intended to be used by applications that
might need access to a TURN server over a secure connection.
Interoperability considerations: N/A
Security considerations: See Section 4.
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.]]
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6. Acknowledgements
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
their comments, suggestions and questions that helped to 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 for his comments, suggestions and
questions that helped to improve the this document.
The <turn-port> and <turn-host> ABNF productions have been copied
from the <port> and <host> ABNF productions from [RFC3986].
7. References
7.1. Normative References
[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.
7.2. Informative References
[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-
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20120821, August 2012,
<http://www.w3.org/TR/2012/WD-webrtc-20120821>.
[REF-IMPL]
Petit-Huguenin, MPH., "Reference Implementation of TURN
resolver and TURN URI parser".
<http://debian.implementers.org/stable/source/
turnuri.tar.gz>.
Appendix A. Examples
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 |
+---------------------------------+----------+--------+-------------+
Table 1
Appendix B. Release notes
This section must be removed before publication as an RFC.
B.1. Design Notes
o One recurring comment was to stop using the suffix "s" on URI
scheme, and to move the secure option to a parameter (e.g.
";proto=tls"). We decided against this idea because the STUN URI
does not have a ";proto=" parameter and we would have lost the
symmetry between the TURN and STUN URIs. A more detailed account
of the reasoning behind this is available at <http://
blog.marc.petit-huguenin.org/2012/09/
on-design-of-stun-and-turn-uri-formats.html>
o Following the advice of RFC 4395 section 2.2., and because the
TURN URI does not describe a hierarchical structure, the TURN URIs
are opaque URIs.
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o <password> is not used in the URIs because it is deprecated.
<username> is not used in the URIs because it is not used to guide
the resolution mechanism.
o As discussed in Dublin, there is no generic parameters in the URI
to prevent compatibity issues.
B.2. Modifications between petithuguenin-behave-turn-uris-03 and
petithuguenin-behave-turn-uris-02
o Changed affiliation.
o Cleaned RFC 2119 section.
o Changed title section 3.
o Fixed reference URI scheme semantics in registrations.
o s/SHALL/MUST/.
o s/SHALL be/is/.
o "turn/turns" URI scheme -> "turn" and "turns" URI schemes.
Authors' Addresses
Marc Petit-Huguenin
Impedance Mismatch
Email: petithug@acm.org
Suhas Nandakumar
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
US
Email: snandaku@cisco.com
Gonzalo Salgueiro
Cisco Systems
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: gsalguei@cisco.com
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Paul E. Jones
Cisco Systems
7025 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: paulej@packetizer.com
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