SIP Transactions and Dialogs

The structural integrity of SIP communications is fundamentally dependent on the robust transaction and dialog mechanisms as defined in the SIP specification. Transactions act as the singular exchanges—a request and its responses—that maintain the protocol, ensuring messages are reliably passed back and forth. Dialogs are the sustained conversations, the sessions that stretch beyond a single exchange, where the state and sequence of the communication are meticulously preserved. This chapter delves into the mechanics of SIP transactions and dialogs, dissecting their roles, behaviors, and how they collectively sustain the continuity of our digital interactions.