Negotiation Data Channels Using the Session Description Protocol (SDP)
RFC 8864

Document Type RFC - Proposed Standard (January 2021; No errata)
Authors Keith Drage  , Maridi Makaraju  , Richard Ejzak  , Jerome Marcon  , Roni Even 
Last updated 2021-01-19
Replaces draft-ejzak-mmusic-data-channel-sdpneg
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Internet Engineering Task Force (IETF)                          K. Drage
Request for Comments: 8864                                   M. Makaraju
Category: Standards Track                                       R. Ejzak
ISSN: 2070-1721                                                J. Marcon
                                                            Unaffiliated
                                                            R. Even, Ed.
                                                            January 2021

 Negotiation Data Channels Using the Session Description Protocol (SDP)

Abstract

   Data channel setup can be done using either the in-band Data Channel
   Establishment Protocol (DCEP) or some out-of-band non-DCEP protocol.
   This document specifies how the SDP (Session Description Protocol)
   offer/answer exchange can be used to achieve an out-of-band non-DCEP
   negotiation for establishing a data channel.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8864.

Copyright Notice

   Copyright (c) 2021 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
   (https://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
   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.  Conventions
   3.  Terminology
   4.  Applicability Statement
   5.  SDP Data Channel Attributes
     5.1.  SDP DCMAP Attribute
       5.1.1.  DCMAP Attribute Syntax
       5.1.2.  'dcmap-stream-id' Parameter
       5.1.3.  'label' Parameter
       5.1.4.  'subprotocol' Parameter
       5.1.5.  'max-retr' Parameter
       5.1.6.  'max-time' Parameter
       5.1.7.  'ordered' Parameter
       5.1.8.  'priority' Parameter
       5.1.9.  DCMAP Multiplexing Category
     5.2.  SDP DCSA Attribute
       5.2.1.  DCSA Attribute Syntax
       5.2.2.  DCSA Multiplexing Category
   6.  SDP Offer/Answer Procedures
     6.1.  Managing Stream Identifiers
     6.2.  Negotiating Data Channel Parameters
     6.3.  Generating the Initial Offer for a Data Channel
     6.4.  Generating the SDP Answer
     6.5.  Offerer Processing of the SDP Answer
     6.6.  Modifying the Session
       6.6.1.  Closing a Data Channel
     6.7.  Various SDP Offer/Answer Considerations
   7.  Examples
   8.  Security Considerations
   9.  IANA Considerations
     9.1.  Subprotocol Identifiers
     9.2.  New SDP Attributes
       9.2.1.  dcmap
       9.2.2.  dcsa
     9.3.  Registering Attributes for Use with Data Channels
   10. References
     10.1.  Normative References
     10.2.  Informative References
   Appendix A.  Generic Data Channel Negotiation Aspects when Not
           Using DCEP
     A.1.  Stream Identifier Numbering
     A.2.  Generic Data Channel Negotiation Not Using DCEP
       A.2.1.  Overview
       A.2.2.  Opening a Data Channel
       A.2.3.  Closing a Data Channel
   Acknowledgements
   Contributors
   Authors' Addresses

1.  Introduction

   The concept of establishing a bidirectional data channel running on
   top of the Stream Control Transmission Protocol (SCTP) is discussed
   in [RFC8831], allowing applications to use data channels.  An in-band
   Data Channel Establishment Protocol (DCEP) is described in [RFC8832];
   however, other in-band or out-of-band protocols may be used for
   establishing data channels.  Each data channel consists of paired
   SCTP streams sharing the same SCTP Stream Identifier.  Data channels
   are created by endpoint applications using (1) the WebRTC API
   (Application Programming Interface) [WebRtcAPI] or (2)  other
   protocols (e.g., Controlling Multiple Streams for Telepresence (CLUE)
   [RFC8850]).  The protocols can be signaled by the data channel
   'subprotocol' parameter, conceptually similar to a WebSocket
   subprotocol as described in [RFC6455].  However, apart from the
   "subprotocol" value transmitted to the peer, an endpoint application
   can agree on how to instantiate a given subprotocol on a data
   channel, and whether it is signaled in-band using DCEP or out-of-band
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