Internet Engineering Task Force MMUSIC WGINTERNET-DRAFT Handley/Schulzrinne/Schooler/Rosenbergdraft-ietf-mmusic-sip-new-00.ps ACIRI/Columbia U./Caltech/Bell Labs.August 1999Expires: February 2000SIP: Session Initiation ProtocolStatus of this MemoThis document is an Internet-Draft. Internet-Drafts are working documents of the Internet EngineeringTask Force (IETF), its areas, and its working groups. Note that other groups may also distribute workingdocuments 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 materialor to cite them other than as “work in progress.”To view the entire list of current Internet-Drafts, please check the “1id-abstracts.txt” listing contained inthe Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe), ftp.nis.garr.it(Southern Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast).Distribution of this document is unlimited.Copyright NoticeCopyright (c) The Internet Society (1999). All Rights Reserved.AbstractThe Session Initiation Protocol (SIP) is an application-layer control (signaling) protocol for creat-ing, modifying and terminating sessions with one or more participants. These sessions include Internetmultimedia conferences, Internet telephone calls and multimedia distribution. Members in a session cancommunicate via multicast or via a mesh of unicast relations, or a combination of these.SIP invitations used to create sessions carry session descriptions which allow participants to agreeon a set of compatible media types. SIP supports user mobility by proxying and redirecting requeststo the user’s current location. Users can register their current location. SIP is not tied to any particularconference control protocol. SIP is designed to be independent of the lower-layer transport protocol andcan be extended with additional capabilities.Contents1 Introduction 71.1 Overview of SIP Functionality ................................. 71.2 Terminology........................................... 81.3 Definitions............................................ 81.4 OverviewofSIPOperation................................... 101.4.1 SIPAddressing..................................... 111.4.2 LocatingaSIPServer ................................. 111.4.3 SIPTransaction..................................... 121.4.4 SIPInvitation...................................... 131.4.5 LocatingaUser..................................... 141.4.6 ChanginganExistingSession ............................. 151.4.7 RegistrationServices.................................. 15INTERNET-DRAFT draft-ietf-mmusic-sip-new-00.ps August 19991.5 Protocol Properties ....................................... 151.5.1 MinimalState...................................... 151.5.2 Lower-Layer-ProtocolNeutral............................. 151.5.3 Text-Based ....................................... 162 SIP Uniform Resource Locators 163 SIP Message Overview 204 Request 214.1 Request-Line .......................................... 224.2 Methods ............................................. 224.2.1 INVITE ......................................... 224.2.2 ACK .......................................... 234.2.3 OPTIONS ....................................... 244.2.4 BYE .......................................... 244.2.5 CANCEL ........................................ 244.2.6 REGISTER ...................................... 254.3 Request-URI .......................................... 274.3.1 SIPVersion....................................... 274.4 OptionTags........................................... 274.4.1 RegisteringNewOptionTagswithIANA....................... 285 Response 285.1 Status-Line ........................................... 285.1.1 StatusCodesandReasonPhrases ........................... 296 Header Field Definitions 316.1 GeneralHeaderFields ..................................... 326.2 Entity Header Fields ...................................... 336.3 RequestHeaderFields ..................................... 336.4 Response Header Fields . . . .................................. 346.5 End-to-endandHop-by-hopHeaders.............................. 346.6 HeaderFieldFormat ...................................... 346.7 Accept ............................................. 346.8 Accept-Encoding ....................................... 356.9 Accept-Language ....................................... 356.10 Allow .............................................. 356.11 Authorization .......................................... 356.12 Call-ID ............................................. 356.13 Contact ............................................. 366.14 Content-Encoding ....................................... 396.15 Content-Length ........................................ 396.16 Content-Type .......................................... 406.17 CSeq .............................................. 406.18 Date ............................................... 41Handley/Schulzrinne/Schooler/Rosenberg Expires February 2000 [Page 2]INTERNET-DRAFT draft-ietf-mmusic-sip-new-00.ps August 19996.19 Encryption ........................................... 416.20 Expires ............................................. 426.21 From .............................................. 436.22 Hide ............................................... 446.23 In-Reply-To ........................................... 446.24 Max-Forwards ......................................... 456.25 Organization .......................................... 456.26 Priority ............................................. 456.27 Proxy-Authenticate ...................................... 466.28 Proxy-Authorization ...................................... 466.29 Proxy-Require ......................................... 466.30 Record-Route ......................................... 466.31 Require ............................................. 476.32 Response-Key ......................................... 486.33 Retry-After ........................................... 486.34 Route .............................................. 496.35 Server ............................................. 496.36 Subject ............................................. 496.37 Timestamp ........................................... 496.38 To ................................................