[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06 07 draft-ietf-mmusic-sctp-sdp

MMUSIC                                                         S. Loreto
Internet-Draft                                              G. Camarillo
Intended status: Standards Track                                Ericsson
Expires: September 10, 2009                                March 9, 2009


Stream Control Transmission Protocol (SCTP)-Based Media Transport in the
                   Session Description Protocol (SDP)
                    draft-loreto-mmusic-sctp-sdp-03

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on September 10, 2009.

Copyright Notice

   Copyright (c) 2009 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 in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.

Abstract

   SCTP (Stream Control Transmission Protocol) is a transport protocol
   used to establish associations between two endpoints.  This document



Loreto & Camarillo     Expires September 10, 2009               [Page 1]


Internet-Draft    The SCTP protocol identifier for SDP        March 2009


   describes how to express media transport over SCTP in SDP (Session
   Description Protocol).  This document defines the 'SCTP' and 'SCTP/
   TLS' protocol identifiers for SDP.


Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Protocol Identifier . . . . . . . . . . . . . . . . . . . . . . 3
   4.  The Setup and Connection Attributes and Association
       Management  . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Multihoming . . . . . . . . . . . . . . . . . . . . . . . . . . 4
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
     6.1.  Actpass/Passive . . . . . . . . . . . . . . . . . . . . . . 5
     6.2.  Existing Connection Reuse . . . . . . . . . . . . . . . . . 5
     6.3.  SDP description for TLS Connection  . . . . . . . . . . . . 6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   9.  Normative References  . . . . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 7






























Loreto & Camarillo     Expires September 10, 2009               [Page 2]


Internet-Draft    The SCTP protocol identifier for SDP        March 2009


1.  Introduction

   SDP (Session Description Protocol) [RFC4566] provides a general-
   purpose format for describing multimedia sessions in announcements or
   invitations.  RFC4145 [RFC4145] specifies a general mechanism for
   describing and establishing TCP streams.  RFC 4572 [RFC4572] extends
   RFC4145 [RFC4145] for describing TCP-based media streams that are
   protected using TLS [RFC4346].

   This document defines a new protocol identifier, 'SCTP', to describe
   SCTP-based [RFC4960] media streams.  Additionally, this document
   specifies the use of the 'setup' and 'connection' SDP attributes to
   establish SCTP associations.  These attributes were defined in
   RFC4145 [RFC4145] for TCP.  This document discusses their use with
   SCTP.

   Additionaly this document define a new protocol identifier, 'SCTP/
   TLS', to establish secure SCTP-based media streams over Transport
   Layer Security (TLS) [RFC3436] using the Session Description Protocol
   (SDP).  The authentication certificates are interpreted and validated
   as defined in RFC4572 [RFC4572].  Self-signed certificates can be
   used securely, provided that the integrity of the SDP description is
   assured as defined in RFC4572 [RFC4572].
   [I-D.ietf-tsvwg-dtls-for-sctp]


 2.   Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
   RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
   described in BCP 14, RFC 2119 [RFC2119] and indicate requirement
   levels for compliant implementations.


3.  Protocol Identifier

   The following is the format for an 'm' line, as specified in RFC4566
   [RFC4566]:

       m=<media> <port> <proto> <fmt> ...

   This document defines two new values for the 'proto' field: 'SCTP'
   and 'SCTP/TLS'.

   The 'SCTP' protocol identifier is similar to both the 'UDP' and 'TCP'
   protocol identifiers in that it only describes the transport protocol
   and not the upper-layer protocol.  Media described using an 'm' line



Loreto & Camarillo     Expires September 10, 2009               [Page 3]


Internet-Draft    The SCTP protocol identifier for SDP        March 2009


   containing the 'SCTP' protocol identifier are carried using SCTP
   [RFC4960].

   The 'SCTP/TLS' protocol identifier indicates that the media described
   will use the Transport Laryer Secturity protocol [RFC4346] over SCTP
   as specified in RFC3436 [RFC3436].

   An 'm' line that specifies 'SCTP' or 'SCTP/TLS' MUST further qualify
   the application-layer protocol using an fmt identifier.


4.  The Setup and Connection Attributes and Association Management

   The use of the 'setup' and 'connection' attributes in the context of
   an SCTP association is identical to the use of these attributes in
   the context of a TCP connection.  That is, SCTP endpoints MUST follow
   the rules in Sections 4 and 5 of RFC 4145 [RFC4145] when it comes to
   the use of the 'setup' and 'connection' attributes in offer/answer
   [RFC3264] exchanges.

   The management of an SCTP association is identical to the management
   of a TCP connection.  That is, SCTP endpoints MUST follow the rules
   in Section 6 of RFC 4145 [RFC4145] to manage SCTP associations.
   Whether to use the SCTP ordered or unordered delivery service is up
   to the applications using the SCTP association.


5.  Multihoming

   An SCTP endpoint, unlike a TCP endpoint, can be multihomed.  An SCTP
   endpoint is considered to be multihomed if it has more than one IP
   address.  A multihomed SCTP endpoint informs a remote SCTP endpoint
   about all its IP addresses using the address parameters of the INIT
   or the INIT-ACK chunk (depending on whether or not the multihomed
   endpoint is the one initiating the establishment of the association).
   Therefore, once the address provided in the 'c' line has been used to
   establish the SCTP association (i.e., to send the INIT chunk),
   address management is performed using SCTP.  This means that two SCTP
   endpoints can use addresses that were not listed in the 'c' line but
   that were negotiated using SCTP mechanisms.

   OPEN ISSUE: that intermediaries such as SBCs will not be aware of
   some of the IP addresses used for media because they will not appear
   in the SDP.  We can RECOMMEND that SCTP endpoints use a main address
   all the time (e.g., not to retransmit to a backup address) and that
   they send a re-INVITE every time they change that address.
   Alternatively (or additionally), we could add SDP attributes with all
   the IP addresses that can be used by the association.



Loreto & Camarillo     Expires September 10, 2009               [Page 4]


Internet-Draft    The SCTP protocol identifier for SDP        March 2009


6.  Examples

   The following examples show the use of the 'setup' and 'connection'
   SDP attributes.  As discussed in Section 4, the use of this
   attributes with an SCTP association is identical to their use with a
   TCP connection.  For the purpose of brevity, the main portion of the
   session description is omitted in the examples, which only show 'm'
   lines and their attributes (including 'c' lines).

6.1.  Actpass/Passive

   An offerer at 192.0.2.2 signals its availability for an SCTP
   association at SCTP port 54111.  Additionally, this offerer is also
   willing to initiate the SCTP association:

              m=image 54111 SCTP *
              c=IN IP4 192.0.2.2
              a=setup:actpass
              a=connection:new

   The endpoint at 192.0.2.1 responds with the following description:

              m=image 54321 SCTP *
              c=IN IP4 192.0.2.1
              a=setup:passive
              a=connection:new

   This will cause the offerer (at 192.0.2.2) to initiate an SCTP
   association to port 54321 at 192.0.2.1.

6.2.  Existing Connection Reuse

   Subsequent to the exchange in Section 6.1, another offer/answer
   exchange is initiated in the opposite direction.  The endpoint at
   192.0.2.1, which now acts as the offerer, wishes to continue using
   the existing association:

              m=application 54321 SCTP *
              c=IN IP4 192.0.2.1
              a=setup:passive
              a=connection:new

                                 Figure 1

   The endpoint at 192.0.2.2 also wishes to use the existing SCTP
   association and responds with the following description:





Loreto & Camarillo     Expires September 10, 2009               [Page 5]


Internet-Draft    The SCTP protocol identifier for SDP        March 2009


              m=application 9 SCTP *
              c=IN IP4 192.0.2.2
              a=setup:active
              a=connection:new

                                 Figure 2

   The existing SCTP association between 192.0.2.2 and 192.0.2.1 will be
   reused.

6.3.  SDP description for TLS Connection

   An offerer at 192.0.2.2 signals the availability of a T.38 fax
   session over SCTP/TLS.

           m=image 54111 SCTP/TLS t38
           c=IN IP4 192.0.2.2
           a=setup:actpass
           a=connection:new
           a=fingerprint:SHA-1 \
                  4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB


7.  Security Considerations

   See RFC 4566 [RFC4566] for security considerations on the use of SDP
   in general.  See RFC 3264 [RFC3264], RFC 4145 [RFC4145] and RFC 4572
   [RFC4572] for security considerations on establishing media streams
   using offer/answer exchanges.  See RFC 4960 [RFC4960] for security
   considerations on SCTP in general and RFC 3436 [RFC3436] for security
   consideration using TLS on top of SCTP.  This specification does not
   introduce any new security consideration in addition to the ones
   discussed in those specifications.


8.  IANA Considerations

   This document defines a new proto value: SCTP.  Its format is defined
   in Section 3.  This proto value should be registered by the IANA
   under "Session Description Protocol (SDP) Parameters" under "proto".

   The SDP specification, [RFC4566], states that specifications defining
   new proto values, like the SCTP and SCTP/TLS proto values defined in
   this RFC, must define the rules by which their media format (fmt)
   namespace is managed.  For the SCTP protocol, new formats SHOULD have
   an associated MIME registration.  Use of an existing MIME subtype for
   the format is encouraged.  If no MIME subtype exists, it is
   RECOMMENDED that a suitable one is registered through the IETF



Loreto & Camarillo     Expires September 10, 2009               [Page 6]


Internet-Draft    The SCTP protocol identifier for SDP        March 2009


   process [RFC2048] by production of, or reference to, a standards-
   track RFC that defines the transport protocol for the format.


9.  Normative References

   [RFC2048]  Freed, N., Klensin, J., and J. Postel, "Multipurpose
              Internet Mail Extensions (MIME) Part Four: Registration
              Procedures", BCP 13, RFC 2048, November 1996.

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

   [RFC3264]  Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
              with Session Description Protocol (SDP)", RFC 3264,
              June 2002.

   [RFC4145]  Yon, D. and G. Camarillo, "TCP-Based Media Transport in
              the Session Description Protocol (SDP)", RFC 4145,
              September 2005.

   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.1", RFC 4346, April 2006.

   [RFC3436]  Jungmaier, A., Rescorla, E., and M. Tuexen, "Transport
              Layer Security over Stream Control Transmission Protocol",
              RFC 3436, December 2002.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, July 2006.

   [RFC4572]  Lennox, J., "Connection-Oriented Media Transport over the
              Transport Layer Security (TLS) Protocol in the Session
              Description Protocol (SDP)", RFC 4572, July 2006.

   [RFC4960]  Stewart, R., "Stream Control Transmission Protocol",
              RFC 4960, September 2007.

   [I-D.ietf-tsvwg-dtls-for-sctp]
              Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram
              Transport Layer Security for Stream Control Transmission
              Protocol", draft-ietf-tsvwg-dtls-for-sctp-00 (work in
              progress), October 2008.








Loreto & Camarillo     Expires September 10, 2009               [Page 7]


Internet-Draft    The SCTP protocol identifier for SDP        March 2009


Authors' Addresses

   Salvatore Loreto
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: Salvatore.Loreto@ericsson.com


   Gonzalo Camarillo
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   Email: Gonzalo.Camarillo@ericsson.com

































Loreto & Camarillo     Expires September 10, 2009               [Page 8]


Html markup produced by rfcmarkup 1.129d, available from https://tools.ietf.org/tools/rfcmarkup/