BEHAVE                                                 M. Petit-Huguenin
Internet-Draft                                              Unaffiliated
Intended status: Standards Track                           S. Nandakumar
Expires: August 5, 2012                                     G. Salgueiro
                                                                P. Jones
                                                           Cisco Systems
                                                        February 2, 2012


 Traversal Using Relays around NAT (TURN) Uniform Resource Identifiers
                draft-petithuguenin-behave-turn-uris-00

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 August 5, 2012.

Copyright Notice

   Copyright (c) 2012 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.  Syntax of a TURN or TURNS URI  . . . . . . . . . . . . . . . .  4
     3.1.  URI Scheme Syntax  . . . . . . . . . . . . . . . . . . . .  4
     3.2.  URI Scheme Semantics . . . . . . . . . . . . . . . . . . .  6
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  6
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
     5.1.  TURN URI Registration  . . . . . . . . . . . . . . . . . .  7
     5.2.  TURNS URI Registration . . . . . . . . . . . . . . . . . .  8
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     7.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     7.2.  Informative References . . . . . . . . . . . . . . . . . .  9
   Appendix A.  Examples  . . . . . . . . . . . . . . . . . . . . . . 10
   Appendix B.  Release notes . . . . . . . . . . . . . . . . . . . . 11
     B.1.  Merge of draft-nandakumar-rtcweb-turn-uri-00 and
           draft-petithuguenin-behave-turn-uri-bis-05 . . . . . . . . 11
     B.2.  Modifications between petithuguenin-05 and
           petithuguenin-04 . . . . . . . . . . . . . . . . . . . . . 11
     B.3.  Modifications between petithuguenin-04 and
           petithuguenin-03 . . . . . . . . . . . . . . . . . . . . . 12
     B.4.  Modifications between petithuguenin-03 and
           petithuguenin-02 . . . . . . . . . . . . . . . . . . . . . 12
     B.5.  Modifications between petithuguenin-02 and
           petithuguenin-01 . . . . . . . . . . . . . . . . . . . . . 12
     B.6.  Modifications between petithuguenin-01 and
           petithuguenin-00 . . . . . . . . . . . . . . . . . . . . . 12
     B.7.  Design Notes . . . . . . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12












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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/turns" URI scheme is 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", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   "SHOULD", "SHOULD NOT", "RECOMMENDED", and "NOT RECOMMENDED" are



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   appropriate when valid exceptions to a general requirement are known
   to exist or appear to exist, and it is infeasible or impractical to
   enumerate all of them.  However, they should not be interpreted as
   permitting implementors to fail to implement the general requirement
   when such failure would result in interoperability failure.


3.  Syntax of a TURN or TURNS URI

3.1.  URI Scheme Syntax

   The "turn" URI takes the following form (the syntax below is non-
   normative):

      turn:<userinfo>@<host>:<port>
      turns:<userinfo>@<host>:<port>

   Note that <userinfo> with the "@" (at) sign character, as well as the
   <port> part and the preceding ":" (colon) character, is OPTIONAL.

   A TURN/TURNS URI has the following formal ABNF syntax [RFC5234]:






























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   turnURI       = scheme ":" [ userinfo "@" ] turn-host
                   [ ":" turn-port ] [ "?transport=" transport ]
   scheme        = "turn" / "turns"
   userinfo      = user [ ":" password ]
   user          = 1*(%x21-24 / %x26-39 / %x3B-3F / %x41-7F
                   / escaped)
                       ; The symbols "%", ":", "@", and symbols
                       ; with a character value below 0x21 may
                       ; be represented as escaped sequences.
   password      = 1*(%x21-24 / %x26-3F / %x41-7F / escaped)
                       ; The symbols "%", "@", and symbols with
                       ; a character value below 0x21 may be
                       ; represented as escaped sequences.
   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 )
   escaped       = "%" HEXDIG HEXDIG

   <unreserved>, <sub-delims>, and <pct-encoded> are specified in
   [RFC3986].

   The <host>, <port> and <transport> components are passed without
   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.  The core rules <ALPHA>, <DIGIT> and <HEXDIGIT> are used
   as described in Appendix B of RFC 5234 [RFC5234].



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   The eventual <user> and <password> components are used as input for
   the TURN [RFC5766] protocol itself.

3.2.  URI Scheme Semantics

   The TURN protocol supports sending messages over UDP, TCP or TLS-
   over-TCP.  The "turns" URI scheme SHALL be used when TURN is run over
   TLS-over-TCP (or in the future DTLS-over-UDP) and the "turn" scheme
   SHALL be used otherwise.

   The required <host> part of the "turn" URI denotes the TURN server
   host.

   The <userinfo> part identifies the credentials required for the long-
   term credential mechanism as described in the section 10.2 of RFC
   5389 [RFC5389].

   The <port> part, if present, denotes the port on which the TURN
   server is awaiting connection requests.  If it is absent, the default
   port SHALL be 3478 for both UDP and TCP.  The default port for TURN
   over TLS SHALL be 5349.

   The <userinfo> part specifies the username and password.  Both the
   <user> and <password> values are UTF-8 encoded and escaped as per
   section 2.5 of RFC 3986 [RFC3986].


4.  Security Considerations

   Security considerations for the resolution mechanism are discussed in
   [RFC5928].

   As described in Section 3.2.1 of STD 66 [RFC3986], having
   authentication information (specifically passwords) in a URI means
   that the URI must be handled carefully:

      The passing of authentication information in clear text has proven
      to be a security risk in almost every case where it has been used.

   Section 3.2.1 contains advice on handling URI that contain passwords
   in the userinfo portion.  Implementations of this specification MUST
   implement that advice.

   Specifically if a URI that contains credentials leaks, then it would
   allow an attacker to use the TURN server which is referenced by the
   URI.  Such an attack has two major impacts.  First, it uses up the
   operator's bandwidth.  Second, if the operator bills the user for
   TURN server usage, then it may expose the user to costs incurred by



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   the attacker.  However, the attacker never obtains the user's private
   information, nor does this attack allow for traffic amplification.

   The expected use environment mitigates to some degree concerns about
   TURN URIs compared to other URIs, such as HTTPS.  First, users do not
   dereference TURN URIs directly.  Instead, they are passed to the TURN
   stack.  Thus, concerns about confusion or leakage due to the URI
   being displayed to the user are significantly reduced; indeed the URI
   need never be available to the user at all.

   One of the primary use cases for a TURN URI with credentials is
   WebRTC.  In this case, a web server will be offering a calling
   service and may have an associated TURN server it can use.  In this
   case, the browser will need to use the TURN server and the browser
   has no long term or preexisting relationship with the TURN server.
   The web server needs to provide some credential to the client which
   it can use to access the TURN server.  Since TURN authentication is
   via username and password, this implies that the credential is a
   username/password pair.  While this must be transmitted securely
   (i.e., over HTTPS), the security properties are the same whether the
   password is carried separately or is part of the URL.  Moreover,
   because the web server and TURN servers can cooperate, a new password
   can be issued for every call, making short-term credentials feasible
   and thus significantly mitigating the risk.

   If a TURN URI is transferred between hosts, it MUST be done over a
   protocol that provides confidentiality such as HTTPS [RFC2818].  It
   is RECOMMENDED that the credential only be valid for a single call
   and preferably for no more than one day.  That "preferably" is bad.


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.

   URI scheme semantics: See [RFC5928].

   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.

   URI scheme semantics: See [RFC5928].

   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.

   The <turn-port> and <turn-host> ABNF productions have been copied
   from the <port> and <host> ABNF productions from [RFC3986].

   This document was written with the xml2rfc tool described in
   [RFC2629].


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

   [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.

   [RFC5769]  Denis-Courmont, R., "Test Vectors for Session Traversal
              Utilities for NAT (STUN)", RFC 5769, April 2010.

   [WEBRTC]   W3C, "WebRTC 1.0: Real-time Communication Between
              Browsers".

              <http://dev.w3.org/2011/webrtc/editor/webrtc.html>.

   [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    |        |             |
   | turn:user:pwd@example.org       | false    |        |             |
   | turns:example.org               | true     |        |             |
   | turns:user:pwd@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

   Table 2 shows how the <username>, <password> and <host> components
   are populated from various URIs.  For all the examples, the secure
   component is populated with false and the port and transport
   components are empty.






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   +---------------------------+------------+------------+-------------+
   | URI                       | <username> | <password> | <host>      |
   +---------------------------+------------+------------+-------------+
   | turn:example.org          |            |            | example.org |
   | turn:192.0.2.1            |            |            | 192.0.2.1   |
   | turn:[2001:DB8::1]        |            |            | 2001:DB8::1 |
   | turn:user@example.org     | user       |            | example.org |
   | turn:user:pwd@example.org | user       | pwd        | example.org |
   +---------------------------+------------+------------+-------------+

                                  Table 2

   The following example produces the username and password used as
   example in section 2.4 of [RFC5769]:

   turn:%E3%83%9E%E3%83%88%E3%83%AA%E3%83%83%E3%82%AF%E3%82%B9:The%C2%
   ADM%C2%AAtr%E2%85%A8@example.org


Appendix B.  Release notes

   This section must be removed before publication as an RFC.

B.1.  Merge of draft-nandakumar-rtcweb-turn-uri-00 and
      draft-petithuguenin-behave-turn-uri-bis-05

   o  Changed author list.
   o  Draft is now standard track.
   o  Merged abstract, introduction, acknowledgement and security
      sections.
   o  Added two introductory paragraphs to the beginning iof the
      introduction.
   o  Took Section 3 and divided it into Section 3.1 URI Scheme Syntax
      and Section 3.2 URI Scheme Semantics.
   o  Explained that most components are passed as is to RFC 5928.
   o  Added username and password in ABNF.
   o  Added RFC 5389 as reference.
   o  Added examples.
   o  Updated design notes.
   o  Various minor nits and grammatical issues fixed.

B.2.  Modifications between petithuguenin-05 and petithuguenin-04

   o  Nits.
   o  Fixed schemes registration.






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B.3.  Modifications between petithuguenin-04 and petithuguenin-03

   o  Fixed references code link.

B.4.  Modifications between petithuguenin-03 and petithuguenin-02

   o  Updated RFC references.

B.5.  Modifications between petithuguenin-02 and petithuguenin-01

   o  Nits.

B.6.  Modifications between petithuguenin-01 and petithuguenin-00

   o  Shorten I-D references.

B.7.  Design Notes

   o  As discussed in Dublin, there is no generic parameters in the URI
      to prevent compatibity issues.


Authors' Addresses

   Marc Petit-Huguenin
   Unaffiliated

   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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