What is the distinction between "call establishment" and "call termination" in SIP?

The distinction between call establishment and call termination is pivotal in understanding how SIP (Session Initiation Protocol) operates. Call establishment refers to the process of initiating a session, which involves setting up the parameters for a communication session between two or more parties. During this phase, SIP messages are exchanged to negotiate details such as the codecs to be used, the media types, and the participants involved in the session. This process ensures that both parties are prepared for the call before any media transmission takes place.

Conversely, call termination encompasses the process of concluding a session. This involves the exchange of SIP messages that signal the end of the communication, ensuring that resources are released and that both parties are made aware that the call has officially ended.

Recognizing this distinction helps clarify the different phases of a communication session in SIP and the role each part plays in setting up and closing connections appropriately. While call establishment involves initiating the session, including media negotiations, call termination simply refers to the completion of that session, ensuring proper handling of resources and notifications.