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A Session Description Protocol (SDP) Offer/Answer Mechanism to Enable File Transfer
RFC 5547

Network Working Group                                   M. Garcia-Martin
Request for Comments: 5547                                      Ericsson
Category: Standards Track                                     M. Isomaki
                                                                   Nokia
                                                            G. Camarillo
                                                               S. Loreto
                                                                Ericsson
                                                              P. Kyzivat
                                                           Cisco Systems
                                                                May 2009

      A Session Description Protocol (SDP) Offer/Answer Mechanism
                        to Enable File Transfer

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

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

   This document provides a mechanism to negotiate the transfer of one
   or more files between two endpoints by using the Session Description
   Protocol (SDP) offer/answer model specified in RFC 3264.  SDP is
   extended to describe the attributes of the files to be transferred.
   The offerer can describe either the files it wants to send or the
   files it would like to receive.  The answerer can either accept or
   reject the offer separately for each individual file.  The transfer
   of one or more files is initiated after a successful negotiation.
   The Message Session Relay Protocol (MSRP) is defined as the default
   mechanism to actually carry the files between the endpoints.  The
   conventions on how to use MSRP for file transfer are also provided in
   this document.

Garcia-Martin, et al.       Standards Track                     [Page 1]
RFC 5547           SDP Offer/Answer for File Transfer           May 2009

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................4
   3. Definitions .....................................................4
   4. Overview of Operation ...........................................5
   5. File Selector ...................................................6
   6. Extensions to SDP ...............................................7
   7. File Disposition Types .........................................13
   8. Protocol Operation .............................................13
      8.1. The 'file-transfer-id' Attribute ..........................14
      8.2. Offerer's Behavior ........................................17
           8.2.1. The Offerer Is a File Sender .......................17
           8.2.2. The Offerer Is a File Receiver .....................18
           8.2.3. SDP Offer for Several Files ........................18
      8.3. Answerer's Behavior .......................................19
           8.3.1. The Answerer Is a File Receiver ....................19
           8.3.2. The Answerer Is a File Sender ......................20
      8.4. Aborting an Ongoing File Transfer Operation ...............22
      8.5. Indicating File Transfer Offer/Answer Capability ..........25
      8.6. Reusage of Existing "m=" Lines in SDP .....................26
      8.7. MSRP Usage ................................................26
      8.8. Considerations about the 'file-icon' Attribute ............28
   9. Examples .......................................................28
      9.1. Offerer Sends a File to the Answerer ......................28
      9.2. Offerer Requests a File from the Answerer and
           Second File Transfer ......................................33
      9.3. Example of a Capability Indication ........................40
   10. Security Considerations .......................................41
   11. IANA Considerations ...........................................42
      11.1. Registration of New SDP Attributes .......................42
           11.1.1. Registration of the file-selector Attribute .......43

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