RFC 2543:SIP: Session Initiation Protocol
RFC-Ref

SIP: Session Initiation Protocol


1. Introduction
1.1. Overview of SIP Functionality
1.2. Terminology
1.3. Definitions
1.4. Overview of SIP Operation
1.4.1. SIP Addressing
1.4.2. Locating a SIP Server
1.4.3. SIP Transaction
1.4.4. SIP Invitation
1.4.5. Locating a User
1.4.6. Changing an Existing Session
1.4.7. Registration Services
1.5. Protocol Properties
1.5.1. Minimal State
1.5.2. Lower-Layer-Protocol Neutral
1.5.3. Text-Based
2. SIP Uniform Resource Locators
3. SIP Message Overview
4. Request
4.1. Request-Line
4.2. Methods
4.2.1. INVITE
4.2.2. ACK
4.2.3. OPTIONS
4.2.4. BYE
4.2.5. CANCEL
4.2.6. REGISTER
4.3. Request-URI
4.3.1. SIP Version
4.4. Option Tags
4.4.1. Registering New Option Tags with IANA
5. Response
5.1. Status-Line
5.1.1. Status Codes and Reason Phrases
6. Header Field Definitions
6.1. General Header Fields
6.2. Entity Header Fields
6.3. Request Header Fields
6.4. Response Header Fields
6.5. End-to-end and Hop-by-hop Headers
6.6. Header Field Format
6.7. Accept
6.8. Accept-Encoding
6.9. Accept-Language
6.10. Allow
6.11. Authorization
6.12. Call-ID
6.13. Contact
6.14. Content-Encoding
6.15. Content-Length
6.16. Content-Type
6.17. CSeq
6.18. Date
6.19. Encryption
6.20. Expires
6.21. From
6.22. Hide
6.23. Max-Forwards
6.24. Organization
6.25. Priority
6.26. Proxy-Authenticate
6.27. Proxy-Authorization
6.28. Proxy-Require
6.29. Record-Route
6.30. Require
6.31. Response-Key
6.32. Retry-After
6.33. Route
6.34. Server
6.35. Subject
6.36. Timestamp
6.37. To
6.38. Unsupported
6.39. User-Agent
6.40. Via
6.40.1. Requests
6.40.2. Receiver-tagged Via Header Fields
6.40.3. Responses
6.40.4. User Agent and Redirect Servers
6.40.5. Syntax
6.41. Warning
6.42. WWW-Authenticate
7. Status Code Definitions
7.1. Informational 1xx
7.1.1. 100 Trying
7.1.2. 180 Ringing
7.1.3. 181 Call Is Being Forwarded
7.1.4. 182 Queued
7.2. Successful 2xx
7.2.1. 200 OK
7.3. Redirection 3xx
7.3.1. 300 Multiple Choices
7.3.2. 301 Moved Permanently
7.3.3. 302 Moved Temporarily
7.3.4. 305 Use Proxy
7.3.5. 380 Alternative Service
7.4. Request Failure 4xx
7.4.1. 400 Bad Request
7.4.2. 401 Unauthorized
7.4.3. 402 Payment Required
7.4.4. 403 Forbidden
7.4.5. 404 Not Found
7.4.6. 405 Method Not Allowed
7.4.7. 406 Not Acceptable
7.4.8. 407 Proxy Authentication Required
7.4.9. 408 Request Timeout
7.4.10. 409 Conflict
7.4.11. 410 Gone
7.4.12. 411 Length Required
7.4.13. 413 Request Entity Too Large
7.4.14. 414 Request-URI Too Long
7.4.15. 415 Unsupported Media Type
7.4.16. 420 Bad Extension
7.4.17. 480 Temporarily Unavailable
7.4.18. 481 Call Leg/Transaction Does Not Exist
7.4.19. 482 Loop Detected
7.4.20. 483 Too Many Hops
7.4.21. 484 Address Incomplete
7.4.22. 485 Ambiguous
7.4.23. 486 Busy Here
7.5. Server Failure 5xx
7.5.1. 500 Server Internal Error
7.5.2. 501 Not Implemented
7.5.3. 502 Bad Gateway
7.5.4. 503 Service Unavailable
7.5.5. 504 Gateway Time-out
7.5.6. 505 Version Not Supported
7.6. Global Failures 6xx
7.6.1. 600 Busy Everywhere
7.6.2. 603 Decline
7.6.3. 604 Does Not Exist Anywhere
7.6.4. 606 Not Acceptable
8. SIP Message Body
8.1. Body Inclusion
8.2. Message Body Type
8.3. Message Body Length
9. Compact Form
10. Behavior of SIP Clients and Servers
10.1. General Remarks
10.1.1. Requests
10.1.2. Responses
10.2. Source Addresses, Destination Addresses and Connections
10.2.1. Unicast UDP
10.2.2. Multicast UDP
10.3. TCP
10.4. Reliability for BYE, CANCEL, OPTIONS, REGISTER Requests
10.4.1. UDP
10.4.2. TCP
10.5. Reliability for INVITE Requests
10.5.1. UDP
10.5.2. TCP
10.6. Reliability for ACK Requests
10.7. ICMP Handling
11. Behavior of SIP User Agents
11.1. Caller Issues Initial INVITE Request
11.2. Callee Issues Response
11.3. Caller Receives Response to Initial Request
11.4. Caller or Callee Generate Subsequent Requests
11.5. Receiving Subsequent Requests
12. Behavior of SIP Proxy and Redirect Servers
12.1. Redirect Server
12.2. User Agent Server
12.3. Proxy Server
12.3.1. Proxying Requests
12.3.2. Proxying Responses
12.3.3. Stateless Proxy: Proxying Responses
12.3.4. Stateful Proxy: Receiving Requests
12.3.5. Stateful Proxy: Receiving ACKs
12.3.6. Stateful Proxy: Receiving Responses
12.3.7. Stateless, Non-Forking Proxy
12.4. Forking Proxy
13. Security Considerations
13.1. Confidentiality and Privacy: Encryption
13.1.1. End-to-End Encryption
13.1.2. Privacy of SIP Responses
13.1.3. Encryption by Proxies
13.1.4. Hop-by-Hop Encryption
13.1.5. Via field encryption
13.2. Message Integrity and Access Control: Authentication
13.2.1. Trusting responses
13.3. Callee Privacy
13.4. Known Security Problems
14. SIP Authentication using HTTP Basic and Digest Schemes
14.1. Framework
14.2. Basic Authentication
14.3. Digest Authentication
14.4. Proxy-Authentication
15. SIP Security Using PGP
15.1. PGP Authentication Scheme
15.1.1. The WWW-Authenticate Response Header
15.1.2. The Authorization Request Header
15.2. PGP Encryption Scheme
15.3. Response-Key Header Field for PGP
16. Examples
16.1. Registration
16.2. Invitation to a Multicast Conference
16.2.1. Request
16.2.2. Response
16.3. Two-party Call
16.4. Terminating a Call
16.5. Forking Proxy
16.6. Redirects
16.7. Negotiation
16.8. OPTIONS Request
17. A Minimal Implementation
17.1. A.1 Client
17.2. A.2 Server
17.3. A.3 Header Processing
18. B Usage of the Session Description Protocol (SDP)
18.1. B.1 Configuring Media Streams
18.2. B.2 Setting SDP Values for Unicast
18.3. Multicast Operation
18.4. B.4 Delayed Media Streams
18.5. B.5 Putting Media Streams on Hold
18.6. B.6 Subject and SDP "s=" Line
18.7. B.7 The SDP "o=" Line
19. C Summary of Augmented BNF
19.1. Basic Rules
20. D Using SRV DNS Records
21. E IANA Considerations
22. F Acknowledgments
23. G Authors' Addresses
24. H Bibliography
25. Full Copyright Statement

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