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Versions: (draft-patil-tram-alpn) 00 01 02 03 04 05 06 07 08 RFC 7443

TRAM                                                            P. Patil
Internet-Draft                                                  T. Reddy
Intended status: Standards Track                            G. Salgueiro
Expires: March 14, 2015                                            Cisco
                                                       M. Petit-Huguenin
                                                      Impedance Mismatch
                                                      September 10, 2014

  Application Layer Protocol Negotiation (ALPN) for Session Traversal
 Utilities for NAT (STUN) and Traversal Using Relays around NAT (TURN)


   Application Layer Protocol Negotiation (ALPN) labels for the Session
   Traversal Utilities for NAT (STUN) and Traversal Using Relays around
   NAT (TURN) are defined in this document to allow the application
   layer to negotiate STUN, TURN within the Transport Layer Security
   (TLS) connection.  The STUN ALPN protocol identifier and TURN ALPN
   identifier applies to both TLS and Datagram Transport Layer Security

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
   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 March 14, 2015.

Copyright Notice

   Copyright (c) 2014 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   STUN can be securely transported using TLS-over-TCP (referred to as
   TLS [RFC5246]), as specified in [RFC5389], or TLS-over-UDP (referred
   to as DTLS [RFC6347]), as specified in [I-D.ietf-tram-stun-dtls].

   ALPN [RFC7301] enables an endpoint to positively identify STUN
   protocol and TURN in TLS/DTLS and distinguish them from other TLS/
   DTLS protocols.  With ALPN, the client sends the list of supported
   application protocols as part of the TLS/DTLS ClientHello message.
   The server chooses a protocol and sends the selected protocol as part
   of the TLS/DTLS ServerHello message.  The application protocol
   negotiation can thus be accomplished within the TLS/DTLS handshake,
   without adding network round-trips, and allows the server to
   associate a different certificate with each application protocol, if

   TURN ALPN is useful in the following scenarios:

   1.  Consider an Enterprise network that deploys a TURN server in a
       DeMilitarized Zone (DMZ) to audit all media sessions from inside
       the Enterprise premises to any external peer.  In this
       deployment, an Enterprise firewall could use the TURN ALPN
       identifer to detect, and act accordingly, the use of a TURN
       server outisde the Enterprise domain (i.e., a TURN server
       provided by an application server, access network etc).

   2.  If a firewall is configured to block all outgoing traffic except
       for TCP traffic to specific ports (e.g., 443 for HTTPS), a TURN

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       server listening on its default ports (3478 for TCP/UDP, 5349 for
       TLS) would not be reachable.  However, despite the restrictions
       imposed by the firewall, the TURN server can still be reached on
       the allowed HTTPS port if the TURN ALPN identifier is used to
       establish usage of TURN as part of the TLS handshake.  In this
       case, the TURN ALPN identifier sent by the client will be used by
       the server to identify that the client intends to make a TURN
       request and it must act as a TURN server to relay the traffic to
       and from the remote peer.

   3.  If a TURN server is in a resource exhausted state then it could
       use the TURN ALPN identifier sent by the client to identify that
       the connection will be used to allocate resouces, which the
       server cannot accommodate, and hence reject the (D)TLS handshake
       with a fatal error.

   This document defines entries ("stun") and ("turn") in the
   "Application Layer Protocol Negotiation (ALPN) Protocol IDs" registry
   established by [RFC7301] to identify the STUN protocol and usage of

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

3.  IANA Considerations

   The following entry is to be added to the "Application Layer Protocol
   Negotiation (ALPN) Protocol IDs" registry established by [RFC7301].

   The "stun" label identifies STUN over TLS/DTLS:

      Protocol: Session Traversal Utilities for NAT (STUN)

      Identification Sequence: 0x73 0x74 0x75 0x6E ("stun")

      Specification: This document (RFCXXXX)

   The "turn" label identifies TURN over TLS/DTLS:

      Protocol: Traversal Using Relays around NAT (TURN)

      Identification Sequence: 0x74 0x75 0x72 0x6E ("turn")

      Specification: This document (RFCXXXX)

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4.  Security Considerations

   The ALPN STUN protocol identifier does not introduce any specific
   security considerations beyond those detailed in the TLS ALPN
   Extension specification [RFC7301].  It also does not impact security
   of TLS/DTLS session establishment nor application data exchange.

5.  Acknowledgements

   This work benefited from the discussions and invaluable input by the
   various members of the TRAM working group.  These include Simon
   Perrault, Paul Kyzivat, Brandon Williams and Andrew Hutton.  Special
   thanks to Martin Thomson and Oleg Moskalenko for their constructive
   comments, suggestions, and early reviews that were critical to the
   formulation and refinement of this document.

6.  References

6.1.  Normative References

              Petit-Huguenin, M. and G. Salgueiro, "Datagram Transport
              Layer Security (DTLS) as Transport for Session Traversal
              Utilities for NAT (STUN)", draft-ietf-tram-stun-dtls-05
              (work in progress), June 2014.

              Belshe, M. and R. Peon, "SPDY Protocol", draft-mbelshe-
              httpbis-spdy-00 (work in progress), February 2012.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246, August 2008.

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

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, January 2012.

   [RFC7301]  Friedl, S., Popov, A., Langley, A., and E. Stephan,
              "Transport Layer Security (TLS) Application-Layer Protocol
              Negotiation Extension", RFC 7301, July 2014.

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6.2.  Informative References

   [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.

Authors' Addresses

   Prashanth Patil
   Cisco Systems, Inc.

   Email: praspati@cisco.com

   Tirumaleswar Reddy
   Cisco Systems, Inc.
   Cessna Business Park, Varthur Hobli
   Sarjapur Marathalli Outer Ring Road
   Bangalore, Karnataka  560103

   Email: tireddy@cisco.com

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

   Email: gsalguei@cisco.com

   Marc Petit-Huguenin
   Impedance Mismatch

   Email: marc@petit-huguenin.org

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