rfc3261 sip协议

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

modifying, and terminating sessions with one or more participants.

These sessions include Internet telephone calls, multimedia

distribution, and multimedia conferences.

SIP invitations used to create sessions carry session descriptions

that allow participants to agree on a set of compatible media types.

SIP makes use of elements called proxy servers to help route requests

to the user’s current location, authenticate and authorize users for

services, implement provider call-routing policies, and provide

features to users. SIP also provides a registration function that

allows users to upload their current locations for use by proxy

2 Overview of SIP Functionality ....................... 9

3 Terminology.............................................10

4 Overview of Operation...................................10

5 Structure of the Protocol...............................18

6 Definitions.............................................20

7 SIP Messages............................................26

7.1 Requests................................................27

7.2 Responses...............................................28

7.3 Header Fields...........................................29

7.3.1 Header Field Format.....................................30

8 General User Agent Behavior.............................34

8.1 UAC Behavior............................................35

8.1.1 Generating the Request..................................35

8.1.1.1 Request-URI.............................................35

8.1.1.2 To......................................................36

8.1.1.3 From....................................................37

8.1.1.4 Call-ID.................................................37

8.1.1.5 CSeq....................................................38

8.1.1.6 Max-Forwards............................................38

8.1.1.7 Via.....................................................39

8.1.3.2 Unrecognized Responses..................................42

8.1.3.3 Vias....................................................43

8.1.3.4 Processing 3xx Responses................................43

8.1.3.5 Processing 4xx Responses................................45

8.2 UAS Behavior............................................46

8.2.1 Method Inspection.......................................46

8.2.2 Header Inspection.......................................46

8.2.2.1 To and Request-URI......................................46

8.2.2.2 Merged Requests.........................................47

8.2.2.3 Require.................................................47

8.2.7 Stateless UAS Behavior..................................50

8.3 Redirect Servers........................................51

9 Canceling a Request.....................................53

9.1 Client Behavior.........................................53

9.2 Server Behavior.........................................55

10 Registrations...........................................56

10.1 Overview................................................56

10.2 Constructing the REGISTER Request.......................57

10.2.1 Adding Bindings.........................................59

10.2.1.1 Setting the Expiration Interval of Contact Addresses 60

10.2.7 Transmitting a Request..................................62

10.2.8 Error Responses.........................................63

10.3 Processing REGISTER Requests............................63

11 Querying for Capabilities...............................66

11.1 Construction of OPTIONS Request.........................67

11.2 Processing of OPTIONS Request...........................68

12 Dialogs.................................................69

12.1 Creation of a Dialog....................................70

12.1.1 UAS behavior............................................70

12.1.2 UAC Behavior............................................71

13 Initiating a Session....................................77

13.1 Overview................................................77

13.2 UAC Processing..........................................78

13.2.1 Creating the Initial INVITE.............................78

13.2.2 Processing INVITE Responses.............................81

13.2.2.1 1xx Responses...........................................81

13.2.2.2 3xx Responses...........................................81

13.2.2.3 4xx, 5xx and 6xx Responses..............................81

13.2.2.4 2xx Responses...........................................82

13.3 UAS Processing..........................................83

14.1 UAC Behavior............................................86

14.2 UAS Behavior............................................88

15 Terminating a Session...................................89

15.1 Terminating a Session with a BYE Request................90

15.1.1 UAC Behavior............................................90

15.1.2 UAS Behavior............................................91

16 Proxy Behavior..........................................91

16.1 Overview................................................91

16.2 Stateful Proxy..........................................92

16.3 Request Validation......................................94

16.10 CANCEL Processing......................................115

16.11 Stateless Proxy........................................116

16.12 Summary of Proxy Route Processing......................118

16.12.1 Examples...............................................118

16.12.1.1 Basic SIP Trapezoid....................................118

16.12.1.2 Traversing a Strict-Routing Proxy......................120

16.12.1.3 Rewriting Record-Route Header Field Values.............121

17 Transactions...........................................122

17.1 Client Transaction.....................................124

17.1.1 INVITE Client Transaction..............................125

17.1.3 Matching Responses to Client Transactions..............132

17.1.4 Handling Transport Errors..............................133

17.2 Server Transaction.....................................134

17.2.1 INVITE Server Transaction..............................134

17.2.2 Non-INVITE Server Transaction..........................137

17.2.3 Matching Requests to Server Transactions...............138

17.2.4 Handling Transport Errors..............................141

18 Transport..............................................141

18.1 Clients................................................142

18.1.1 Sending Requests.......................................142

19 Common Message Components..............................147

19.1 SIP and SIPS Uniform Resource Indicators...............148

19.1.1 SIP and SIPS URI Components............................148

19.1.2 Character Escaping Requirements........................152

19.1.3 Example SIP and SIPS URIs..............................153

19.1.4 URI Comparison.........................................153

19.1.5 Forming Requests from a URI............................156

19.1.6 Relating SIP URIs and tel URLs.........................157

19.2 Option Tags............................................158

19.3 Tags...................................................159

20.6 Authentication-Info....................................165

20.7 Authorization..........................................165

20.8 Call-ID................................................166

20.9 Call-Info..............................................166

20.10 Contact................................................167

20.11 Content-Disposition....................................168

20.12 Content-Encoding.......................................169

20.13 Content-Language.......................................169

20.14 Content-Length.........................................169

20.15 Content-Type...........................................170

20.22 Max-Forwards...........................................173

20.23 Min-Expires............................................173

20.24 MIME-Version...........................................173

20.25 Organization...........................................174

20.26 Priority...............................................174

20.27 Proxy-Authenticate.....................................174

20.28 Proxy-Authorization....................................175

20.29 Proxy-Require..........................................175

20.30 Record-Route...........................................175

20.31 Reply-To...............................................176