Comments
INVITE Message Indicates that the user or service is being invited to participate in a session.
And Invite message is used to established dialog creating transactions, such as INVITE or SUBSCRIBE, and managed by the SIP stack. A single dialog can contain many transactions.
And there are som Idempotent INVITEs in which SIP requests are said to be idempotent , i.e., receiving more than one copy of a request does not change the server state
Posted by sagitraz
The INVITE method indicates that the user or service is being invited to participate in a session. The message body contains a description of the session to which the callee is being invited. For two-party calls, the caller indicates the type of media it is able to receive and possibly the media it is willing to send as well as their parameters such as network destination. A success response MUST indicate in its message body which media the callee wishes to receive and MAY indicate the media the callee is going to send.
Not all session description formats have the ability to indicate sending media. A server MAY automatically respond to an invitation for a conference the user is already participating in, identified either by the SIP Call-ID or a globally unique identifier within the session description, with a 200 (OK) response. If a user agent receives an INVITE request for an existing call leg with a higher CSeq
sequence number than any previous INVITE for the same Call-ID, it MUST check any version identifiers in the session description or, if there are no version identifiers, the content of the session description to see if it has changed. It MUST also inspect any other header fields for changes. If there is a change, the user agent MUST update any internal state or information generated as a result of that header. If the session description has changed, the user agent server MUST adjust the session parameters accordingly, possibly after asking the user for confirmation. (Versioning of the session description can be used to accommodate the capabilities of new arrivals to a conference, add or delete media or change from a unicast to a multicast conference.)
This method MUST be supported by SIP proxy, redirect and user agent servers as well as clients.
Posted by snjysanjay05
-