A Dialog is a peer-to-peer relationship between two user agents. It represents a context that facilitates the sequencing of messages between the user agents and proper routing of requests between both of them. The following sequence of figures illustrates the creation of a dialog, the processing of requests during this dialog, and the termination of the dialog. This example shows two proxies that request to be maintained in the signalling path by inserting Record-Route header fields. Only the header fields relevant to the dialog and the routing of requests are shown in the SIP messages.
Note that 100 Trying provisional responses are not shown.