Internet DRAFT - draft-nandakumar-rtcweb-stun-uri
draft-nandakumar-rtcweb-stun-uri
RTCWEB S. Nandakumar
Internet-Draft G. Salgueiro
Intended status: Standards Track P. Jones
Expires: March 31, 2014 Cisco Systems
M. Petit-Huguenin
Impedance Mismatch
September 27, 2013
URI Scheme for Session Traversal Utilities for NAT (STUN) Protocol
draft-nandakumar-rtcweb-stun-uri-08
Abstract
This document is the specification of the syntax and semantics of the
Uniform Resource Identifier (URI) scheme for the Session Traversal
Utilities for NAT (STUN) protocol.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on March 31, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Definition of the STUN or STUNS URI . . . . . . . . . . . . . 3
3.1. URI Scheme Syntax . . . . . . . . . . . . . . . . . . . . 3
3.2. URI Scheme Semantics . . . . . . . . . . . . . . . . . . 4
4. Implementation Status . . . . . . . . . . . . . . . . . . . . 4
4.1. libjingle . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Firefox . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. STUN URI Registration . . . . . . . . . . . . . . . . . . 6
6.2. STUNS URI Registration . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 9
Appendix B. Design Notes . . . . . . . . . . . . . . . . . . . . 9
Appendix C. Release notes . . . . . . . . . . . . . . . . . . . 9
C.1. Modifications between draft-nandakumar-rtcweb-stun-uri-08
and draft-nandakumar-rtcweb-stun-uri-07 . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
This document specifies the syntax and semantics of the Uniform
Resource Identifier (URI) scheme for the Session Traversal Utilities
for NAT (STUN) protocol.
STUN is a protocol that serves as a tool for other protocols in
dealing with Network Address Translator (NAT) traversal. It can be
used by an endpoint to determine the IP address and port allocated to
it by a NAT, to perform connectivity checks between two endpoints,
and used as a keepalive protocol to maintain NAT bindings. RFC 5389
[RFC5389] defines the specifics of the STUN protocol.
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The "stun" and "stuns" URI schemes are used to designate a standalone
STUN server or any Internet host performing the operations of a STUN
server in the context of STUN usages (Section 14 RFC 5389 [RFC5389]).
With the advent of standards such as WEBRTC [WEBRTC], we anticipate a
plethora of endpoints and web applications to be able to identify and
communicate with such a STUN server to carry out the STUN protocol.
This also implies those endpoints and/or applications to be
provisioned with appropriate configuration required to identify the
STUN 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 'stun/stuns' URI
scheme helps alleviate most of these issues by providing a consistent
way to describe, configure and exchange the information identifying a
STUN server. This would also prevent the shortcomings inherent with
encoding similar information in non-uniform syntaxes such as the ones
proposed in the WEBRTC Standards [WEBRTC], for example.
2. Terminology
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.
3. Definition of the STUN or STUNS URI
3.1. URI Scheme Syntax
A STUN/STUNS URI has the following formal ABNF syntax [RFC5234]:
stunURI = scheme ":" host [ ":" port ]
scheme = "stun" / "stuns"
<host>, and <port> are specified in [RFC3986]. While these two ABNF
productions are defined in [RFC3986] as components of the generic
hierarchical URI, this does not imply that the stun and stuns URI
schemes are hierarchical URIs. Developers MUST NOT use a generic
hierarchical URI parser to parse a stun or stuns URI.
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3.2. URI Scheme Semantics
The "stun" and "stuns" URI schemes are used to designate a standalone
STUN server or any Internet host performing the operations of a STUN
server in the context of STUN usages (Section 14 RFC 5389 [RFC5389]).
The STUN protocol supports sending messages over UDP, TCP or TLS-
over-TCP. The "stuns" URI scheme MUST be used when STUN is run over
TLS-over-TCP (or in the future DTLS-over-UDP) and the "stun" scheme
MUST be used otherwise.
The required <host> part of the "stun" URI denotes the STUN server
host.
For the optional DNS Discovery procedure mentioned in the Section 9
of RFC5389, "stun" URI scheme implies UDP as the transport protocol
for SRV lookup and "stuns" URI scheme indicates TCP as the transport
protocol.
As specified in [RFC5389], the <port> part, if present, denotes the
port on which the STUN server is awaiting connection requests. If it
is absent, the default port is 3478 for both UDP and TCP. The
default port for STUN over TLS is 5349 as per Section 9 of [RFC5389].
4. Implementation Status
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".
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4.1. libjingle
Organization: Google Inc.
Name: libjingle revision 4831 https://code.google.com/p/chromium/
codesearch#chromium/src/third_party/libjingle/source/talk/app/
webrtc/peerconnection.cc
Description: Libjingle is a set of components provided by Google to
implement Jingle protocols XEP-166 (http://xmpp.org/extensions/
xep-0166.html) and XEP-167 (http://xmpp.org/extensions/
xep-0167.html).
Level of maturity: Beta.
Coverage: Implements draft-nandakumar-rtcweb-stun-uri-07 without
IPv6. The stun and stuns schemes are parsed, and TLS is used when
the secure bit is set.
Licensing: BSD 3-clauses license.
Contact: https://code.google.com/p/chromium/
URL: https://code.google.com/p/chromium/codesearch#chromium/src/
third_party/libjingle/source/talk/app/webrtc/peerconnection.cc
4.2. Firefox
Organization: Mozilla
Name: Firefox Aurora 21 http://hg.mozilla.org/mozilla-central/rev/
6b5016ab9ebb
Description: Mozilla Firefox is a free and open source web browser.
Level of maturity: Beta.
Coverage: Implements draft-nandakumar-rtcweb-stun-uri-03. The
mozilla code parses the turn and turns schemes but does not seems
to use TLS.
Licensing: Mozilla Public License, v. 2.0.
Contact: http://www.mozilla.org/en-US/firefox/channel/
URL: http://hg.mozilla.org/mozilla-central/file/4ff1e574e509/media/
webrtc/signaling/src/peerconnection/PeerConnectionImpl.cpp
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5. Security Considerations
The "stun" and "stuns" URI schemes do not introduce any specific
security issues beyond the security considerations discussed in
[RFC3986]. These URI schemes are intended for use in specific
environments that involve NAT traversal. Users of the scheme need to
carefully consider the security properties of the context in which
they are using them.
While the stun and stuns URIs do not themselves include the username
or password that will be used to authenticate the STUN client, in
certain environments, such as WebRTC, the username and password will
almost certainly be provisioned remotely by an external agent at the
same time as a stuns URI is sent to that client. Thus, in such
situations, if the username and password were received in clear there
would be little or no benefit to using a stuns URI. For this reason
a STUN client MUST ensure that the username, password, and stuns URI
and any other security-relevant parameters are received with
equivalent security before using the stuns URI. Receiving those
parameters over another TLS session can provide the appropriate level
of security, if both TLS sessions are similarly parameterised, e.g.
with commensurate strength ciphersuites.
6. IANA Considerations
This section contains the registration information for the "stun" and
"stuns" URI Schemes (in accordance with [RFC4395]). Note that these
URI schemes are intended for use in very specific NAT traversal
environments, and should not be used otherwise on the open Web or
Internet.
6.1. STUN URI Registration
URI scheme name: stun
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 "stun" URI scheme is intended to be used by applications with
a need to identify a STUN server to be used for NAT traversal.
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Interoperability considerations: N/A
Security considerations: See Section 5.
Contact: Suhas Nandakumar <snandaku@cisco.com>
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.]]
6.2. STUNS URI Registration
URI scheme name: stuns
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 "stun" URI scheme is intended to be used by applications with
a need to identify a STUN server to be used for NAT traversal over
a secure connection.
Interoperability considerations: N/A
Security considerations: See Section 5.
Contact: Suhas Nandakumar <snandaku@cisco.com>
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.]]
7. Acknowledgements
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The authors would like to extend a very special thanks to Cullen
Jennings for bringing to our attention the WebRTC need for this
document, as well as his detailed review and thoughtful comments on
this document.
This document has benefited from extensive discussion and review of
many of the members of the RTCWEB and BEHAVE working groups. The
authors would also like to acknowledge Ted Hardie, Bjoern Hoehrmann,
Russ Housley, Subramanian Moonesamy, Hadriel Kaplan, Graham Klyne,
Peter Saint-Andre, Ted Lemon, Barry Leiba, Pete Resnick, Spencer
Dawkins, Stephen Farrell and Harald Alvestrand for their invaluable
input, reviews, feedback comments, and suggestions that helped to
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.
This document was written with the xml2rfc tool described in
[RFC2629].
8. References
8.1. 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.
8.2. Informative References
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 35, RFC
4395, February 2006.
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[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
October 2008.
[RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", RFC 6982, July
2013.
[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,
<http://www.w3.org/TR/2012/WD-webrtc-20120821>.
Appendix A. Examples
Table 1 shows examples for 'stun/stuns'uri scheme. For all these
examples, the <host> component is populated with "example.org".
+-----------------------+
| URI |
+-----------------------+
| stun:example.org |
| stuns:example.org |
| stun:example.org:8000 |
+-----------------------+
Table 1
Appendix B. 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 need for
";proto=" for the STUN URI cannot be sufficiently explained and
supporting it would render an incomplete specification. This
would also result in lost 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 Section 2.2 of [RFC4395], and because the
STUN URI does not describe a hierarchical structure, the STUN URIs
are opaque.
Appendix C. Release notes
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NOTE TO RFC EDITOR: This section must be removed before publication
as an RFC.
C.1. Modifications between draft-nandakumar-rtcweb-stun-uri-08 and
draft-nandakumar-rtcweb-stun-uri-07
o Changed the ABNF to use references from RFC 3986 instead of
copying them.
o Converted the design note about hierarchical parsers into a MUST
NOT statement.
o Updated the RFC 6982 forms for Chrome and Firefox.
o Added text in security section about verifying that username,
password and uris are received over a secure connection.
Authors' Addresses
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
Paul E. Jones
Cisco Systems
7025 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: paulej@packetizer.com
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Marc Petit-Huguenin
Impedance Mismatch
Email: petithug@acm.org
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