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Versions: (draft-petithuguenin-tram-stun-dtls) 00 01 02 03 04 05 RFC 7350

TRAM                                                   M. Petit-Huguenin
Internet-Draft                                       Jive Communications
Updates: 5389, 5928 (if approved)                           G. Salgueiro
Intended status: Standards Track                           Cisco Systems
Expires: December 29, 2014                                 June 27, 2014


   Datagram Transport Layer Security (DTLS) as Transport for Session
                   Traversal Utilities for NAT (STUN)
                      draft-ietf-tram-stun-dtls-05

Abstract

   This document specifies the usage of Datagram Transport Layer
   Security (DTLS) as a transport protocol for Session Traversal
   Utilities for NAT (STUN).  It provides guidances on when and how to
   use DTLS with the currently standardized STUN Usages.  It also
   specifies modifications to the STUN URIs and TURN URIs and to the
   TURN resolution mechanism to facilitate the resolution of STUN URIs
   and TURN URIs into the IP address and port of STUN and TURN servers
   supporting DTLS as a transport protocol.  This document updates RFC
   5389 and 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 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 December 29, 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



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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.  DTLS as Transport for STUN  . . . . . . . . . . . . . . . . .   3
   4.  STUN Usages . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  NAT Discovery Usage . . . . . . . . . . . . . . . . . . .   4
       4.1.1.  DTLS Support in STUN URIs . . . . . . . . . . . . . .   5
     4.2.  Connectivity Check Usage  . . . . . . . . . . . . . . . .   5
     4.3.  Media Keep-Alive Usage  . . . . . . . . . . . . . . . . .   5
     4.4.  SIP Keep-Alive Usage  . . . . . . . . . . . . . . . . . .   6
     4.5.  NAT Behavior Discovery Usage  . . . . . . . . . . . . . .   6
     4.6.  TURN Usage  . . . . . . . . . . . . . . . . . . . . . . .   6
       4.6.1.  DTLS Support in TURN URIs . . . . . . . . . . . . . .   6
       4.6.2.  Resolution Mechanism for TURN over DTLS . . . . . . .   7
   5.  Implementation Status . . . . . . . . . . . . . . . . . . . .   8
     5.1.  turnuri . . . . . . . . . . . . . . . . . . . . . . . . .   8
     5.2.  rfc5766-turn-server . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  S-NAPTR application protocol tag  . . . . . . . . . . . .  10
     7.2.  Service Name and Transport Protocol Port Number . . . . .  10
       7.2.1.  The stuns Service Name  . . . . . . . . . . . . . . .  10
       7.2.2.  The turns Service Name  . . . . . . . . . . . . . . .  11
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  14
   Appendix B.  Release notes  . . . . . . . . . . . . . . . . . . .  15
     B.1.  Modifications between ietf-tram-stun-dtls-04 and ietf-
           tram-stun-dtls-05 . . . . . . . . . . . . . . . . . . . .  15
     B.2.  Modifications between ietf-tram-stun-dtls-03 and ietf-
           tram-stun-dtls-04 . . . . . . . . . . . . . . . . . . . .  16
     B.3.  Modifications between ietf-tram-stun-dtls-02 and ietf-
           tram-stun-dtls-03 . . . . . . . . . . . . . . . . . . . .  16
     B.4.  Modifications between ietf-tram-stun-dtls-01 and ietf-
           tram-stun-dtls-02 . . . . . . . . . . . . . . . . . . . .  17
     B.5.  Modifications between ietf-tram-stun-dtls-00 and ietf-
           tram-stun-dtls-01 . . . . . . . . . . . . . . . . . . . .  17
     B.6.  Modifications between petithuguenin-tram-stun-dtls-00 and



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           ietf-tram-stun-dtls-00  . . . . . . . . . . . . . . . . .  17
     B.7.  Modifications between petithuguenin-tram-turn-dtls-00 and
           petithuguenin-tram-stun-dtls-00 . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   STUN [RFC5389] defines Transport Layer Security (TLS) over TCP
   (simply referred to as TLS [RFC5246]) as the transport for STUN due
   to additional security advantages it offers over plain UDP or TCP
   transport.  But TCP (and thus TLS-over-TCP) is not an optimal
   transport when STUN is used for its originally intended purpose,
   which is to support multimedia sessions.  This is a well documented
   and understood transport limitation for real-time communications.

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

3.  DTLS as Transport for STUN

   STUN [RFC5389] defines three transports: UDP, TCP, and TLS.  This
   document adds DTLS as a valid transport for STUN.

   STUN over DTLS MUST use the same retransmission rules as STUN over
   UDP (as described in Section 7.2.1 of [RFC5389]).  It MUST also use
   the same rules that are described in Section 7.2.2 of [RFC5389] to
   verify the server identity.  Instead of TLS_RSA_WITH_AES_128_CBC_SHA,
   which is the default cipher suite for STUN over TLS, implementations
   of STUN over DTLS, and deployed clients and servers, MUST support
   TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 and
   TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, and MAY support other
   ciphersuites.  Perfect Forward Secrecy (PFS) cipher suites MUST be
   preferred over non-PFS cipher suites.  Cipher suites with known
   weaknesses, such as those based on (single) DES and RC4, MUST NOT be
   used.  Implementations MUST disable TLS-level compression.  The same
   rules established in Section 7.2.2 of [RFC5389] for keeping open and
   closing TCP/TLS connections MUST be used as well for DTLS
   associations.




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   In addition to the path MTU rules described in Section 7.1 of
   [RFC5389], if the path MTU is unknown, the actual STUN message needs
   to be adjusted to take into account the size of the (13-byte) DTLS
   Record header, the MAC size, and the padding size.

   By default, STUN over DTLS MUST use port 5349, the same port number
   as STUN over TLS.  However, the SRV procedures can be implemented to
   use a different port (as described in Section 9 of [RFC5389]).  When
   using SRV records, the service name MUST be set to "stuns" and the
   protocol name to "udp".

   Classic STUN [RFC3489] defines only UDP as a transport and DTLS MUST
   NOT be used.  Any STUN request or indication without the magic cookie
   (see Section 6 of [RFC5389]) over DTLS MUST always result in an
   error.

4.  STUN Usages

   [RFC5389] Section 7.2 states that STUN usages must specify which
   transport protocol is used.  The following sections discuss if and
   how the existing STUN usages are used with DTLS as the transport.
   Future STUN usages MUST take into account DTLS as a transport and
   discuss its applicability.  In all cases, new STUN usages MUST
   explicitly state if implementing the denial-of-service counter-
   measure described in Section 4.2.1 of [RFC6347] is mandatory.

4.1.  NAT Discovery Usage

   As stated by Section 13 of [RFC5389], "...TLS provides minimal
   security benefits..." for this particular STUN usage.  DTLS will also
   similarly offer only limited benefit.  This is because the only
   mandatory attribute that is TLS/DTLS protected is the XOR-MAPPED-
   ADDRESS, which is already known by an on-path attacker, since it is
   the same as the source address and port of the STUN request.  On the
   other hand, using TLS/DTLS will prevent an active attacker to inject
   XOR-MAPPED-ADDRESS in responses.  The TLS/DTLS transport will also
   protect the SOFTWARE attribute, which can be used to find
   vulnerabilities in STUN implementations.

   Regardless, this usage is rarely used by itself, since using TURN
   [RFC5766] with ICE [RFC5245] is generally indispensable, and TURN
   provides the same NAT Discovery feature as part of an Allocation
   creation.  In fact, with ICE, the NAT Discovery usage is only used
   when there is no longer any resource available for new Allocations in
   the TURN server.






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   A STUN server implementing the NAT Discovery Usage and using DTLS
   MUST implement the denial-of-service counter-measure described in
   Section 4.2.1 of [RFC6347].

4.1.1.  DTLS Support in STUN URIs

   This document does not make any changes to the syntax of a STUN URI
   [RFC7064].  As indicated in Section 3.2 of [RFC7064], secure
   transports like STUN over TLS, and now STUN over DTLS, MUST use the
   "stuns" URI scheme.

   The <host> value MUST be used when using the rules in Section 7.2.2
   of [RFC5389] to verify the server identity.  A STUN URI containing an
   IP address MUST be rejected, unless the domain name is provided by
   the same mechanism that provided the STUN URI, and that this domain
   name can be passed to the verification code.

4.2.  Connectivity Check Usage

   Using DTLS would hide the USERNAME, PRIORITY, USE-CANDIDATE, ICE-
   CONTROLLED and ICE-CONTROLLING attributes.  But because MESSAGE-
   INTEGRITY protects the entire STUN response using a password that is
   known only by looking at the SDP exchanged, it is not possible for an
   attacker that does not have access to this SDP to inject an incorrect
   XOR-MAPPED-ADDRESS, XOR-MAPPED-ADDRESS which would subsequently be
   used as a peer reflexive candidate.

   Adding DTLS on top of the connectivity check would delay, and
   consequently impair, the ICE process.  Adding additional round-trips
   to ICE is undesirable, so much that there is a proposal
   ([I-D.thomson-rtcweb-ice-dtls]) to use the DTLS handshake used by the
   WebRTC SRTP streams as a replacement for the connectivity checks.

   STUN URIs are not used with this usage.

4.3.  Media Keep-Alive Usage

   When STUN Binding Indications are being used for media keep-alive
   (described in Section 10 of [RFC5245]), it runs alongside an RTP or
   RTCP session.  It is possible to send these media keep-alive packets
   inside a separately negotiated non-SRTP DTLS session if DTLS-SRTP
   [RFC5764] is used, but that would add overhead, with minimal security
   benefit.

   STUN URIs are not used with this usage.






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4.4.  SIP Keep-Alive Usage

   The SIP keep-alive (described in [RFC5626]) runs inside a SIP flow.
   This flow would be protected if a SIP over DTLS transport mechanism
   is implemented (such as described in [I-D.jennings-sip-dtls]).

   STUN URIs are not used with this usage.

4.5.  NAT Behavior Discovery Usage

   The NAT Behavior Discovery usage is Experimental and to date has
   never being effectively deployed.  Despite this, using DTLS would add
   the same security properties as for the NAT Discovery Usage
   (Section 4.1).

   The STUN URI can be used to access the NAT Discovery feature of a NAT
   Behavior Discovery server, but accessing the full features would
   require definition of a "stun-behaviors:" URI, which is out of scope
   for this document.

   A STUN server implementing the NAT Behavior Discovery Usage and using
   DTLS MUST implement the denial-of-service counter-measure described
   in Section 4.2.1 of [RFC6347].

4.6.  TURN Usage

   TURN [RFC5766] defines three combinations of transports/allocations:
   UDP/UDP, TCP/UDP and TLS/UDP.  This document adds DTLS/UDP as a valid
   combination.  A TURN server using DTLS MUST implement the denial-of-
   service counter-measure described in Section 4.2.1 of [RFC6347].

   [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 number 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 protocol
   name to "udp".

4.6.1.  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




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   scheme.  When using the "turns" URI scheme to designate TURN over
   DTLS, the transport value of the TURN URI, if set, MUST be "udp".

   The <host> value MUST be used when using the rules in Section 7.2.2
   of [RFC5389] to verify the server identity.  A TURN URI containing an
   IP address MUST be rejected, unless the domain is provided by the
   same mechanism that provided the TURN URI, and that this domain name
   can be passed to the verification code.

4.6.2.  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 check 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.

   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           |
                +----------+-------------+----------------+



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   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).

5.  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.

   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".

5.1.  turnuri

   Organization:   Impedance Mismatch

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





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   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>.

5.2.  rfc5766-turn-server

   Organization:   This is a public project, the full list of authors
      and contributors here: http://turnserver.open-sys.org/downloads/
      AUTHORS.

   Name:   http://code.google.com/p/rfc5766-turn-server/

   Description:   A mature open-source TURN server specs implementation
      (RFC 5766, RFC 6062, RFC 6156, etc) designed for high-performance
      applications, especially geared for WebRTC.

   Level of maturity:   Production level.

   Coverage:   Fully implements DTLS with TURN protocol.

   Licensing:   BSD: http://turnserver.open-sys.org/downloads/LICENSE

   Implementation experience:   DTLS is recommended for secure media
      applications.  It has benefits of both UDP and TLS.

   Contact:   Oleg Moskalenko <mom040267@gmail.com>

6.  Security Considerations

   STUN over DTLS as a STUN transport does not introduce any specific
   security considerations beyond those for STUN over TLS detailed in
   [RFC5389].

   The usage of "udp" as a transport parameter with the "stuns" URI
   scheme does not introduce any specific security issues beyond those
   discussed in [RFC7064].




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   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].

7.  IANA Considerations

7.1.  S-NAPTR application protocol tag

   This specification contains the registration information for one
   S-NAPTR application protocol tag in the "Straightforward-NAPTR
   (S-NAPTR) Parameters/S-NAPTR Application Protocol Tags" registry (in
   accordance with [RFC3958]).

   Application Protocol Tag:   turn.dtls

   Intended Usage:   See Section 4.6.2

   Interoperability considerations:   N/A

   Security considerations:   See Section 6

   Relevant publications:   This document

   Contact information:   Marc Petit-Huguenin <petithug@acm.org>

   Author/Change controller:   The IESG

7.2.  Service Name and Transport Protocol Port Number

   This specification contains the registration information for two
   Service Name and Transport Protocol Port Numbers in the "Service
   Names and Transport Protocol Port Numbers/Service Name and Transport
   Protocol Port Number" registry (in accordance with [RFC6335]).

7.2.1.  The stuns Service Name

   IANA is requested to modify the following entry in the registry
   "Service Names and Transport Protocol Port Numbers/Service Name and
   Transport Protocol Port Number":



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   Service Name:   stuns

   Transport Protocol(s):   UDP

   Assignee:

   Contact:

   Description:   Reserved for a future enhancement of STUN

   Reference:   RFC5389

   Port Number:   5349


   Such as it contains the following:

   Service Name:   stuns

   Transport Protocol(s):   UDP

   Assignee:   IESG

   Contact:   IETF Chair <chair@ietf.org>

   Description:   STUN over DTLS

   Reference:   RFC-to-be

   Port Number:   5349

   Assignment Notes:   This service name was initially created by RFC
      5389

7.2.2.  The turns Service Name

   IANA is requested to modify the following entry in the registry
   "Service Names and Transport Protocol Port Numbers/Service Name and
   Transport Protocol Port Number":

   Service Name:   turns

   Transport Protocol(s):   UDP

   Assignee:

   Contact:




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   Description:   Reserved for a future enhancement of TURN

   Reference:   RFC5766

   Port Number:   5349


   Such as it contains the following:

   Service Name:   turns

   Transport Protocol(s):   UDP

   Assignee:   IESG

   Contact:   IETF Chair <chair@ietf.org>

   Description:   TURN over DTLS

   Reference:   RFC-to-be

   Port Number:   5349

   Assignment Notes:   This service name was initially created by RFC
      5766

8.  Acknowledgements

   Thanks to Alan Johnston, Oleg Moskalenko, Simon Perreault, Thomas
   Stach, Simon Josefsson, Roni Even, Kathleen Moriarty, Benoit Claise,
   Martin Stiemerling, Jari Arkko, and Stephen Farrell for the comments,
   suggestions, and questions that helped improve this document.

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.

   [RFC3489]  Rosenberg, J., Weinberger, J., Huitema, C., and R. Mahy,
              "STUN - Simple Traversal of User Datagram Protocol (UDP)
              Through Network Address Translators (NATs)", RFC 3489,
              March 2003.

   [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.



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   [RFC5245]  Rosenberg, J., "Interactive Connectivity Establishment
              (ICE): A Protocol for Network Address Translator (NAT)
              Traversal for Offer/Answer Protocols", RFC 5245, April
              2010.

   [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.

   [RFC5626]  Jennings, C., Mahy, R., and F. Audet, "Managing Client-
              Initiated Connections in the Session Initiation Protocol
              (SIP)", RFC 5626, October 2009.

   [RFC5764]  McGrew, D. and E. Rescorla, "Datagram Transport Layer
              Security (DTLS) Extension to Establish Keys for the Secure
              Real-time Transport Protocol (SRTP)", RFC 5764, May 2010.

   [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.

   [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.

   [RFC7064]  Nandakumar, S., Salgueiro, G., Jones, P., and M. Petit-
              Huguenin, "URI Scheme for the Session Traversal Utilities
              for NAT (STUN) Protocol", RFC 7064, November 2013.

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




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9.2.  Informative References

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

   [I-D.thomson-rtcweb-ice-dtls]
              Thomson, M., "Using Datagram Transport Layer Security
              (DTLS) For Interactivity Connectivity Establishment (ICE)
              Connectivity Checking: ICE-DTLS", draft-thomson-rtcweb-
              ice-dtls-00 (work in progress), March 2012.

   [I-D.jennings-sip-dtls]
              Jennings, C. and N. Modadugu, "Using Interactive
              Connectivity Establishment (ICE) in Web Real-Time
              Communications (WebRTC)", draft-jennings-sip-dtls-05 (work
              in progress), October 2007.

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 200 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

Appendix B.  Release notes

   This section must be removed before publication as an RFC.

B.1.  Modifications between ietf-tram-stun-dtls-04 and ietf-tram-stun-
      dtls-05

   o  Resolve nits: Updates RFC in abstract.

   o  Update short title to reflect long title

   o  Simplify the introduction to simply states that TCP is not optimal
      for realtime communications.



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   o  Add refereence to RFC 5389 section 6 for the magic cookie.

   o  s/domain/domain name/

   o  Make clear that knowledge of the SDP is needed to be able to
      inject a false XOR-MAPPED-ADDRESS.

   o  Invert the sentence about ICE round-trips to make clear that the
      cited draft is just an evidence, not an advice.

   o  Rewrite of the IANA templates for Port numbers.

   o  Remove compression from the list of element to take in accoutn to
      adjust the PMTU size, as it is now forbidden.

B.2.  Modifications between ietf-tram-stun-dtls-03 and ietf-tram-stun-
      dtls-04

   o  Add text to disable TLS compression.

   o  Add text to require usage of the DTLS cookie for NAT discovery and
      NAT behavior discovery.

   o  Add text to so new usages talk about cookie usage.

   o  Change TLS-over-UDP to DTLS-over-UDP and use DTLS as alias for
      DTLS over UDP..

   o  Use new text proposed by Simon Josefsson for the cipher suites.

   o  s/the same port/the same port number/

   o  s/application name/protocol name/

   o  Make clear that section 4.3 is only about the STUN Indication
      method of media keep-alive.

   o  Changed contact information to IETF Chair in Port number template.

   o  Added email addresses in IANA templates.

B.3.  Modifications between ietf-tram-stun-dtls-02 and ietf-tram-stun-
      dtls-03

   o  Make it clear that both cipher suites are mandatory.

   o  Clarify that the ciphers suites listed are replacing the TLS
      cipher suites.



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   o  Change text so "mandatory" is not understood as compliance.

   o  Clarify that STUN URI are not to be used with some usages.

   o  Fix incorrect interpretation of ICE media keep-alive (and fixed
      section #).

   o  Explain that sending media keep-alive inside DTLS is possible if
      RFC 5764 is used.

   o  Added title/subtitle of IANA registries.

   o  Change to normatively update RFC 5389 and RFC 5928.

B.4.  Modifications between ietf-tram-stun-dtls-01 and ietf-tram-stun-
      dtls-02

   o  Add text saying that PFS is preferred over non-PFS, to be in sync
      with the decision in the rtcweb session in London.

   o  Add text about IP address in STUN/TURN URIs.

   o  Nits

B.5.  Modifications between ietf-tram-stun-dtls-00 and ietf-tram-stun-
      dtls-01

   o  Update the mandatory cipher suites.

   o  Add a new open item to determine if we want to specify favoring
      cipher suites which support PFS over non-PFS cipher suites.

   o  Close remaining opening items from previous draft.

B.6.  Modifications between petithuguenin-tram-stun-dtls-00 and ietf-
      tram-stun-dtls-00

   o  Draft renamed after WG adoption.

B.7.  Modifications between petithuguenin-tram-turn-dtls-00 and
      petithuguenin-tram-stun-dtls-00

   o  Add RFC 6982 information for rfc5766-turn-server project.

   o  Rename the draft as TURN is now just one of the usages.

   o  Remove the references in the abstract to make idnits happy.




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   o  No longer updates other standard drafts.

   o  Rewrite from a STUN over DTLS point of view.  The previous text
      becomes section 4.6.

   o  Add IANA request for stuns port.

   o  Add acknowledgement section.

Authors' Addresses

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

   Email: marcph@getjive.com


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

   Email: gsalguei@cisco.com
























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