SIP Requests
From Wikipedia, the free encyclopedia
SIP requests are the codes used by Session Initiation Protocol for communication. To complement them there are SIP Responses, which generally indicate whether this request succeeded or failed, and in the latter case, why it failed.
[edit] Requests
RFC 3261 (SIP) uses six types (methods) of requests:
- INVITE—Indicates a client is being invited to participate in a call session.
- ACK—Confirms that the client has received a final response to an INVITE request.
- BYE—Terminates a call and can be sent by either the caller or the callee.
- CANCEL—Cancels any pending searches but does not terminate a call that has already been accepted.
- OPTIONS—Queries the capabilities of servers.
- REGISTER—Registers the address listed in the To header field with a SIP server.
RFC 3262 Reliability of Provisional Responses in SIP
- PRACK-Provisional acknowledgement.
RFC 3265 extends the basic requests, to support notification:
- SUBSCRIBE—Subscribes for an Event of Notification from the Notifier.
- NOTIFY—Notify the subscriber of a new Event.
RFC 3903 extends the basic requests, to publish event changes to the server:
- PUBLISH - publishes an event to the Server.
Other requests introduced in SIP are:
- INFO - Sends mid-session information that does not modify the session state. (RFC 2976)
- REFER - Ask recipient to issue SIP request (call transfer.) (RFC 3515)
- MESSAGE - The MESSAGE is used to transport instant messages using SIP. (RFC 3428)
- UPDATE - The UPDATE method is used to modify the state of a session without changing the state of the dialog. (RFC 3311).
