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Versions: 00 draft-petithuguenin-tram-stun-dtls

TRAM                                                   M. Petit-Huguenin
Internet-Draft                                       Jive Communications
Updates: 5928, 7065 (if approved)                           G. Salgueiro
Intended status: Standards Track                           Cisco Systems
Expires: August 4, 2014                                 January 31, 2014


  Datagram Transport Layer Security (DTLS) as Transport for Traversal
                     Using Relays around NAT (TURN)
                 draft-petithuguenin-tram-turn-dtls-00

Abstract

   This document specifies the usage of Datagram Transport Layer
   Security (DTLS) [RFC6347] as a transport protocol between a Traversal
   Using Relays around NAT (TURN) [RFC5766] client and a TURN server.
   It also specifies modifications to the TURN URIs [RFC7065] and to the
   TURN resolution mechanism [RFC5928] to facilitate the resolution of
   TURN URIs into the IP address and port of TURN servers supporting
   DTLS as a transport 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
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   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 4, 2014.

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
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   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 . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  DTLS as Transport for TURN  . . . . . . . . . . . . . . . . .   3
   4.  DTLS Support in TURN URIs . . . . . . . . . . . . . . . . . .   3
   5.  Resolution Mechanism for TURN over DTLS . . . . . . . . . . .   3
   6.  Implementation Status . . . . . . . . . . . . . . . . . . . .   4
     6.1.  turnuri . . . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   TURN [RFC5766] defines Transport Layer Security (TLS) over TCP
   (simply referred to as TLS [RFC5246]) as the transport for TURN due
   to additional security advantages it offers over plain UDP or TCP
   transport.  But TLS-over-TCP is not an optimal transport when TURN is
   used for its originally intended purpose, which is to support
   multimedia sessions.  This sub-optimality primarily stems from the
   added latency incurred by the TCP-based head-of-line (HOL) blocking
   problem coupled with additional TLS buffering (for integrity checks).
   This is a well documented and understood transport limitation for
   secure real-time communications.

   TLS-over-UDP (referred to as DTLS [RFC6347]) offers the same security
   advantages as TLS-over-TCP, but without the undesirable latency
   concerns.

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 "must" or "Must"), they have their usual English meanings, and are
   not to be interpreted as RFC 2119 key words.





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3.  DTLS as Transport for TURN

   TURN [RFC5766] defines three combinations of transports/allocations:
   UDP/UDP, TCP/UDP and TLS/UDP.  This document adds DTLS/UDP as a valid
   combination.

   [RFC6062] states that TCP allocations cannot be obtained using a UDP
   association between client and server.  The fact that DTLS uses UDP
   implies that TCP allocations MUST NOT be obtained using a DTLS
   association between client and server.

   By default, TURN over DTLS uses port 5349, the same port as TURN over
   TLS.  However, the SRV procedures can be implemented to use a
   different port (as described in Section 6 of [RFC5766].  When using
   SRV records, the service name MUST be set to "turns" and the
   application name to "udp".

4.  DTLS Support in TURN URIs

   This document does not make any changes to the syntax of a TURN URI
   [RFC7065].  As indicated in Section 3 of [RFC7065], secure transports
   like TURN over TLS, and now TURN over DTLS, MUST use the "turns" URI
   scheme.  When using the "turns" URI scheme to designate TURN over
   DTLS, the transport value of the TURN URI, if set, MUST be "udp".

5.  Resolution Mechanism for TURN over DTLS

   This document defines a new Straightforward Naming Authority Pointer
   (S-NAPTR) application protocol tag: "turn.dtls".

   The <transport> component, as provisioned or resulting from the
   parsing of a TURN URI, is passed without modification to the TURN
   resolution mechanism defined in Section 3 of [RFC5928], but with the
   following alterations to that algorithm:

   o  The acceptable values for transport name are extended with the
      addition of "dtls".

   o  The acceptable values in the ordered list of supported TURN
      transports is extended with the addition of "Datagram Transport
      Layer Security (DTLS)".

   o  The resolution algorithm ckeck rules list is extended with the
      addition of the following step:

         If <secure> is true and <transport> is defined as "udp" but the
         list of TURN transports supported by the application does not
         contain DTLS, then the resolution MUST stop with an error.



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   o  The 5th rule of the resolution algorithm check rules list is
      modified to read like this:

         If <secure> is true and <transport> is not defined but the list
         of TURN transports supported by the application does not
         contain TLS or DTLS, then the resolution MUST stop with an
         error.

   o  Table 1 is modified to add the following line:

                +----------+-------------+----------------+
                | <secure> | <transport> | TURN Transport |
                +----------+-------------+----------------+
                | true     | "udp"       | DTLS           |
                +----------+-------------+----------------+

   o  In step 1 of the resolution algorithm the default port for DTLS is
      5349.

   o  In step 4 of the resolution algorithm the following is added to
      the list of conversions between the filtered list of TURN
      transports supported by the application and application protocol
      tags:

         "turn.dtls" is used if the TURN transport is DTLS.

   Note that using the [RFC5928] resolution mechanism does not imply
   that additional round trips to the DNS server will be needed (e.g.,
   the TURN client will start immediately if the TURN URI contains an IP
   address).

6.  Implementation Status

   [[Note to RFC Editor: Please remove this section and the reference to
   [RFC6982] 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 [RFC6982].
   The description of implementations in this section is intended to
   assist the IETF in its decision processes in progressing drafts to
   RFCs.  Please note that the listing of any individual implementation
   here does not imply endorsement by the IETF.  Furthermore, no effort
   has been spent to verify the information presented here that was
   supplied by IETF contributors.  This is not intended as, and must not
   be construed to be, a catalog of available implementations or their
   features.  Readers are advised to note that other implementations may
   exist.



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   According to [RFC6982], "this will allow reviewers and working groups
   to assign due consideration to documents that have the benefit of
   running code, which may serve as evidence of valuable experimentation
   and feedback that have made the implemented protocols more mature.
   It is up to the individual working groups to use this information as
   they see fit".

6.1.  turnuri

   Organization:   Impedance Mismatch

   Name:   turnuri 0.5.0 http://debian.implementers.org/stable/source/
      turnuri.tar.gz

   Description:   A reference implementation of the URI and resolution
      mechanism defined in this document, RFC 7065 [RFC7065] and RFC
      5928 [RFC5928].

   Level of maturity:   Beta.

   Coverage:   Fully implements the URIs and resolution mechanism
      defined in this specification, in RFC 7065 and in RFC 5928.

   Licensing:   AGPL3

   Implementation experience:   TBD

   Contact:   Marc Petit-Huguenin <marc@petit-huguenin.org>.

7.  Security Considerations

   TURN over DTLS as a TURN transport does not introduce any specific
   security considerations beyond those for TURN over TLS detailed in
   [RFC5766].

   The usage of "udp" as a transport parameter with the "turns" URI
   scheme does not introduce any specific security issues beyond those
   discussed in [RFC7065].

   The new S-NAPTR application protocol tag defined in this document as
   well as the modifications this document makes to the TURN resolution
   mechanism described in [RFC5928] do not introduce any additional
   security considerations beyond those outlined in [RFC5928].

8.  IANA Considerations

   This specification contains the registration information for one
   S-NAPTR application protocol tags (in accordance with [RFC3958]).



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   Application Protocol Tag:   turn.dtls

   Intended Usage:   See Section 5

   Interoperability considerations:   N/A

   Security considerations:   See Section 7

   Relevant publications:   This document

   Contact information:   Marc Petit-Huguenin

   Author/Change controller:   The IESG

   This specification also contains the registration information for one
   Service Name and Transport Protocol Port Number (in accordance with
   [RFC6335]).

   Service Name:   turns

   Transport Protocol(s):   UDP

   Assignee:   IESG

   Contact:   Marc Petit-Huguenin

   Description:   TURN over DTLS

   Reference:   This document

   Port Number:   5349

9.  References

9.1.  Normative References

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

   [RFC3958]  Daigle, L. and A. Newton, "Domain-Based Application
              Service Location Using SRV RRs and the Dynamic Delegation
              Discovery Service (DDDS)", RFC 3958, January 2005.

   [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.





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   [RFC5928]  Petit-Huguenin, M., "Traversal Using Relays around NAT
              (TURN) Resolution Mechanism", RFC 5928, August 2010.

   [RFC6062]  Perreault, S. and J. Rosenberg, "Traversal Using Relays
              around NAT (TURN) Extensions for TCP Allocations", RFC
              6062, November 2010.

   [RFC6335]  Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
              Cheshire, "Internet Assigned Numbers Authority (IANA)
              Procedures for the Management of the Service Name and
              Transport Protocol Port Number Registry", BCP 165, RFC
              6335, August 2011.

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

   [RFC7065]  Petit-Huguenin, M., Nandakumar, S., Salgueiro, G., and P.
              Jones, "Traversal Using Relays around NAT (TURN) Uniform
              Resource Identifiers", RFC 7065, November 2013.

9.2.  Informative References

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

   [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> and <transport> components are
   populated for a TURN URI that uses DTLS as its transport.  For all
   these examples, the <host> component is populated with "example.net".

   +---------------------------------+----------+--------+-------------+
   | URI                             | <secure> | <port> | <transport> |
   +---------------------------------+----------+--------+-------------+
   | turns:example.net?transport=udp | true     |        | DTLS        |
   +---------------------------------+----------+--------+-------------+

                                  Table 1

   With the DNS RRs in Figure 1 and an ordered TURN transport list of
   {DTLS, TLS, TCP, UDP}, the resolution algorithm will convert the TURN
   URI "turns:example.net" to the ordered list of IP address, port, and
   protocol tuples in Table 2.




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   example.net.
   IN NAPTR 100 10 "" RELAY:turn.udp:turn.dtls "" datagram.example.net.
   IN NAPTR 200 10 "" RELAY:turn.tcp:turn.tls "" stream.example.net.

   datagram.example.net.
   IN NAPTR 100 10 S RELAY:turn.udp "" _turn._udp.example.net.
   IN NAPTR 100 10 S RELAY:turn.dtls "" _turns._udp.example.net.

   stream.example.net.
   IN NAPTR 100 10 S RELAY:turn.tcp "" _turn._tcp.example.net.
   IN NAPTR 200 10 A RELAY:turn.tls "" a.example.net.

   _turn._udp.example.net.
   IN SRV   0 0 3478 a.example.net.

   _turn._tcp.example.net.
   IN SRV   0 0 5000 a.example.net.

   _turns._udp.example.net.
   IN SRV   0 0 5349 a.example.net.

   a.example.net.
   IN A     192.0.2.1

                                 Figure 1

                 +-------+----------+------------+------+
                 | Order | Protocol | IP address | Port |
                 +-------+----------+------------+------+
                 | 1     | DTLS     | 192.0.2.1  | 5349 |
                 | 2     | TLS      | 192.0.2.1  | 5349 |
                 +-------+----------+------------+------+

                                  Table 2

Authors' Addresses

   Marc Petit-Huguenin
   Jive Communications
   1275 West 1600 North, Suite 100
   Orem, UT  84057
   USA

   Email: marcph@getjive.com







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

   Email: gsalguei@cisco.com












































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