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In this article we are going to provide the description of each SIP Requests. Which are the codes used by SIP (Session Initiation Protocol) for communication. SIP Responses complement these SIP Requests, which generally indicate whether the request is a successful or a failed one, and in a latter case, why it failed.
Request name Description Defined in INVITE Indicates a client is being invited to participate in a call session. RFC 3261 ACK Confirms that the client has received a final response to an INVITE request. RFC 3261 BYE Terminates a call and can be sent by either the caller or the callee. RFC 3261 CANCEL Cancels any pending request. RFC 3261 OPTIONS Queries the capabilities of servers. RFC 3261 REGISTER Registers the address listed in the To header field with a SIP server. RFC 3261 PRACK Provisional acknowledgement. RFC 3262 SUBSCRIBE Subscribes for an Event of Notification from the Notifier. RFC 3265 NOTIFY Notify the subscriber of a new Event. RFC 3265 PUBLISH Publishes an event to the Server. RFC 3903 INFO Sends mid-session information that does not modify the session state. RFC 6086 REFER Asks recipient to issue SIP request (call transfer.) RFC 3515 MESSAGE Transports instant messages using SIP. RFC 3428 UPDATE Modifies the state of a session without changing the state of the dialog. RFC 3311