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RTCWEB                                                     S. Nandakumar
Internet-Draft                                              G. Salgueiro
Intended status: Standards Track                                P. Jones
Expires: March 17, 2013                                    Cisco Systems
                                                       M. Petit-Huguenin
                                                      Impedance Mismatch
                                                             May 7, 2013


   URI Scheme for Session Traversal Utilities for NAT (STUN) Protocol
                  draft-nandakumar-rtcweb-stun-uri-04

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 17, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.












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   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   described in the Simplified BSD License.

   This document may not be modified, and derivative works of it may not
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   translate it into languages other than English.

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 . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  STUN URI Registration . . . . . . . . . . . . . . . . . .   6
     6.2.  STUNS URI Registration  . . . . . . . . . . . . . . . . .   6
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .   8
   Appendix B.  Design Notes . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

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].

3.  Definition of the STUN or STUNS URI

3.1.  URI Scheme Syntax

   The "stun" URI takes the following form (the example below is non-
   normative):

      stun:<stun-host>:<stun-port>

      stuns:<stun-host>:<stun-port>

   Note that the <port> part and the preceding ":" (colon) character, is
   OPTIONAL.

   A STUN/STUNS URI has the following formal ABNF syntax [RFC5234]:

   stunURI       = scheme ":" stun-host [ ":" stun-port ]
   scheme        = "stun" / "stuns"
   stun-host     = IP-literal / IPv4address / reg-name
   stun-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



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                   / [ *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].

3.2.  URI Scheme Semantics

   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 <stun-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.

   The <stun-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 RFC 5389 [RFC5389].

4.  Implementation Status

   Note to RFC Editor: Please remove this section 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



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   [RUNNING-CODE].  According to [RUNNING-CODE], "this will allow
   reviewers and working groups to assign due consideration to documents
   that have the benefit of running code, by considering the running
   code as evidence of valuable experimentation and feedback that has
   made the implemented protocols more mature.  It is up to the
   individual working groups to use this information as they see fit".

4.1.  libjingle

   Name:   libjingle 0.7.1

   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-01 without
      IPv6.

   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

   Name:   Firefox Aurora 21

   Description:   Mozilla Firefox is a free and open source web browser.

   Level of maturity:   Beta.

   Coverage:   Implements draft-nandakumar-rtcweb-stun-uri-03.

   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

5.  Security Considerations





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   The "stun" and "stuns" URI schemes do not introduce any specific
   security issues beyond the security considerations discussed in
   [RFC3986].

6.  IANA Considerations

   This section contains the registration information for the "stun" and
   "stuns" URI Schemes (in accordance with [RFC4395]).

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 that
      might need access to a STUN server.

   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.




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   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 "stuns" URI scheme is intended to be used by applications that
      might need access to a STUN server 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

   Many thanks to Cullen Jennings for his detailed review and thoughtful
   comments on this document.

   Thanks to Ted Hardie, Bjoern Hoehrmann for their comments,
   suggestions and questions that helped to improve the this document.

   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.




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8.2.  Informative References

   [RFC2629]  Rose, M.T., "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.

   [RFC5389]  Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
              "Session Traversal Utilities for NAT (STUN)", RFC 5389,
              October 2008.

   [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>.

   [RUNNING-CODE]
              Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: the Implementation Status Section", draft-sheffer-
              running-code-04 (work in progress), April 2013.

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 of
      ";proto=" for the STUN URI cannot be sufficiently explained and
      supporting it would render into an incomplete specification.  This
      would also result in loosing symmetry between the TURN and STUN
      URIs.  A more detailed account of the reasoning behind this is



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      available at <http://blog.marc.petit-huguenin.org/2012/09/on-
      design-of-stun-and-turn-uri-formats.html>

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


   Marc Petit-Huguenin
   Impedance Mismatch

   Email: petithug@acm.org














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