What is the difference between update and re-invite?
An UPDATE is similar to a RE-INVITE request, but unlike a RE-INVITE, it can be sent before the initial INVITE is answered. A RE-INVITE affects the session (the media stream) and the dialog.
What is a re-invite?
A Re-INVITE, it comes after a session has been established. This means that it will apply to an existing INVITE after a final response has been received and an ACK has been sent.
Is it mandatory to send SDP in invite?
2. INVITE request without SDP. When a UAC does not include an SDP body in the INVITE request, it expects the offer to be received with the first reliable response. The UAC will send the answer in the request to acknowledge the response, i.e. PRACK or ACK request of the reliable response.
What is a SIP dialog?
A dialog represents a peer-to-peer SIP relationship between two user agents. A dialog persists for some time and it is very important concept for user agents. Dialogs facilitate proper sequencing and routing of messages between SIP endpoints. Dialogs are identified using Call-ID, From tag, and To tag.
What is invite in SIP?
The INVITE is a SIP method that specifies the action that the requester (Calling Party) wants the server (Called Party) to take. The INVITE request contains a number of header fields. Header fields are named attributes that provide additional information about a message.
What is SDP offer?
Basic Offer/Answer Model for Media Session Setup Within SIP, SDP (as defined in RFC 3264) provides a mechanism by which two or more entities intending to set up a call or conference can make use of Offer/Answer Session Description Protocol (SDP) model to arrive at a common view of a multimedia session.
What is invite SDP?
Calls are started by means of the methods INVITE together with SDP (Session Description Protocol) which carry the information necessary to allow the endpoints of the calls to exchange audio in form of RTP (Real Time Protocol) packets.
What is the difference between dialog and session?
A dialog is just a series of transactions between two SIP peers. The purpose of a dialog is to setup, possibly modify, and then teardown a session. Hence the name Session Initiation Protocol.
What is dialogue session?
1 conversation between two or more people. 2 an exchange of opinions on a particular subject; discussion. 3 the lines spoken by characters in drama or fiction.
What is a SIP invite?
The SIP INVITE request is the message sent by the calling party, inviting the recipient for a session. The SIP headers included in this SIP INVITE request provide information about the message.