BEHAVE
Internet Engineering Task Force (IETF)                 M. Petit-Huguenin
Internet-Draft
Request for Comments: 7065                            Impedance Mismatch
Intended status:
Category: Standards Track                                  S. Nandakumar
Expires: March 31, 2014
ISSN: 2070-1721                                             G. Salgueiro
                                                                P. Jones
                                                           Cisco Systems
                                                      September 27,
                                                           November 2013

 Traversal Using Relays around NAT (TURN) Uniform Resource Identifiers
                draft-petithuguenin-behave-turn-uris-08

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 to provision the TURN
   Resolution Mechanism [RFC5928]. (RFC 5928).

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 an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list  It represents the consensus of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid the IETF community.  It has
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   Information about the current status of this document, any errata,
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   This Internet-Draft will expire on March 31, 2014.
   http://www.rfc-editor.org/info/rfc7065.

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.  Definitions of the TURN "turn" and TURNS "turns" URI . . . . . . . . . . . .   3
     3.1.  URI Scheme Syntax . . . . . . . . . . . . . . . . . . . .   3
     3.2.  URI Scheme Semantics  . . . . . . . . . . . . . . . . . .   4
   4.  Implementation Status . . . . . . . . . . . . . . . . . . . .   4
     4.1.  turnuri . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  libjingle . . . . . . . . . . . . . . . . . . . . . . . .   5
     4.3.  Firefox . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  TURN   4
     5.1.  "turn" URI Registration . . . . . . . . . . . . . . . . . .   6
     6.2.  TURNS   5
     5.2.  "turns" URI Registration  . . . . . . . . . . . . . . . . .   7
   7.   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   8.   6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     8.1.   6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.   6
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   9   7
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .   9   7
   Appendix B.  Design Notes . . . . . . . . . . . . . . . . . . . .   9
   Appendix C.  Release notes  . . . . . . . . . . . . . . . . . . .  10
     C.1.  Modifications between petithuguenin-behave-turn-uris-08
           and petithuguenin-behave-turn-uris-07 . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10   7

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 [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" "turn" and
   "turns" URI
   scheme helps schemes help alleviate most of these issues by providing
   a consistent way to describe, configure 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, a potentially empty port, and a potentially
   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
   the "turn" and a TURNS "turns" URI scheme schemes that can carry the four components
   needed for the resolution mechanism.

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.  Definitions of the TURN "turn" and TURNS "turns" URI

3.1.  URI Scheme Syntax

   A TURN/TURNS URI has

   The "turn" and "turns" URIs have the following formal ABNF syntax
   [RFC5234]:

   turnURI       = scheme ":" host [ ":" port ]
                   [ "?transport=" transport ]
   scheme        = "turn" / "turns"
   transport     = "udp" / "tcp" / transport-ext
   transport-ext = 1*unreserved

   <host>,

   <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 that the turn "turn" and turns "turns"
   schemes are hierarchical URIs.  Developers MUST NOT use a generic
   hierarchical URI parser to parse a turn "turn" or turns "turns" URI.

   The <host>, <port> <port>, and <transport> components are passed without
   modification to the [RFC5928] algorithm.  <secure> is set to false if
   <scheme> is equal to "turn" "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" and "turns" URI schemes are used to designate a TURN
   server (also known as a relay) on Internet hosts accessible using the
   TURN protocol.  The TURN protocol supports sending messages over UDP,
   TCP
   TCP, or TLS-over-TCP.  The "turns" URI scheme MUST be used when TURN
   is run over TLS-over-TCP (or (or, in the future DTLS-over-UDP) 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.

[4.  Implementation Considerations]

5.

4.  Security Considerations

   Security considerations for the resolution mechanism are discussed in
   Section 5 of [RFC5928].  Note that this section contains normative
   text defining authentication procedures to be followed by turn
   clients when TLS is used.

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

   While the turn and turns URIs do

   Although a "turn" or "turns" URI does not themselves itself include the username
   or password that will be used to authenticate the TURN 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 turns "turns" URI is sent to that client.  Thus, in such
   situations, if the username and password were received in clear the clear,
   there would be little or no benefit to using a turns "turns" URI.  For this reason
   reason, a TURN client MUST ensure that the username, password, and turns URI
   "turns" URI, and any other security-relevant parameters are received
   with equivalent security before using the turns "turns" URI.  Receiving
   those parameters over another TLS session can provide the appropriate
   level of security, if both TLS sessions are similarly parameterised, e.g.
   e.g., with commensurate strength ciphersuites.

6.

5.  IANA Considerations

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

6.1.  TURN

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].

   Applications/protocols that use this URI scheme name:

      The "turn" URI scheme is intended to be used by applications with
      a need to identify a TURN server to be used for NAT traversal.

   Interoperability considerations: N/A

   Security considerations: See Section 5. 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.]]

6.2.  TURNS 7065

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 with
      a need to identify a TURN server to be used for NAT traversal over
      a secure connection.

   Interoperability considerations: N/A
   Security considerations: See Section 5. 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.]]

7. 7065

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
   the comments, suggestions suggestions, and questions that helped improve the
   draft-petithuguenin-behave-turn-uri-bis document.
   "Traversal Using Relays around NAT (TURN) Uniform Resource
   Identifiers" by M. Petit-Huguenin (October 2011).

   Many thanks to Cullen Jennings for his detailed review and thoughtful
   comments on the draft-nandakumar-rtcweb-turn-uri document. "URI Scheme for Traversal Using Relays around NAT (TURN)
   Protocol" by S. Nandakumar, et al.  (October 2011).

   Thanks to Bjoern Hoehrmann, Dan Wing, Russ Housley, S. Moonesamy,
   Graham Klyne, Harald Alvestrand, Hadriel Kaplan, Tina Tsou, Spencer
   Dawkins, Ted Lemon, Barry Leiba, Pete Resnick, and Stephen Farrell
   for the comments, suggestions 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 Area Director, for sponsoring this document as well as
   his careful reviews.

8.

7.  References

8.1.

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.

8.2.

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-20120821, August 2012,
              <http://www.w3.org/TR/2012/WD-webrtc-20120821>.

   [RFC6982]  Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: The Implementation Status Section", RFC 6982, July
              2013.

Appendix A.  Examples

   Table 1 shows how the <secure>, <port> <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.  Design Notes

   o  One recurring comment was to stop using the suffix "s" on the 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>
      formats.html>.

   o  Following the advice of Section 2.2 of RFC 4395 section 2.2., 4395, and because the
      TURN URI does not describe a hierarchical structure, the TURN URIs
      are opaque URIs.

   o  <password> is not used in the URIs because it is deprecated
      [RFC3986].  <username> and <auth> are not used in the URIs because
      they do not guide the resolution mechanism.

   o  As discussed at IETF 72 in Dublin, there is are no generic parameters
      in the URI to prevent compatibility issues.

Appendix C.  Release notes

   This section must be removed before publication as an RFC.

C.1.  Modifications between petithuguenin-behave-turn-uris-08 and
      petithuguenin-behave-turn-uris-07

   o  s/eventually/potentially/

   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

   Marc Petit-Huguenin
   Impedance Mismatch

   Email:

   EMail: petithug@acm.org

   Suhas Nandakumar
   Cisco Systems
   170 West Tasman Drive
   San Jose, CA  95134
   US

   Email:

   EMail: snandaku@cisco.com

   Gonzalo Salgueiro
   Cisco Systems
   7200-12 Kit Creek Road
   Research Triangle Park, NC  27709
   US

   Email:

   EMail: gsalguei@cisco.com

   Paul E. Jones
   Cisco Systems
   7025 Kit Creek Road
   Research Triangle Park, NC  27709
   US

   Email:

   EMail: paulej@packetizer.com