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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

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.  This document may not be modified,
   and derivative works of it may not be created, except to format it
   for publication as an RFC or to translate it into languages other
   than English.

   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
   and may be updated, replaced, or obsoleted by other documents at any
   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 July 20, 2013.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


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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