Which of the following is not a component of a SIP message?

A Session Initiation Protocol (SIP) message consists of various components that facilitate the initiation, management, and termination of communication sessions in VoIP (Voice over Internet Protocol) applications. The components included in a SIP message are essential for its functionality.

The Request URI is the target address of the SIP message, indicating where the request is being sent. The Contact header provides information about how to reach the sender of the message, and the Message body can contain additional information related to the session, such as session descriptions in SDP (Session Description Protocol) format.

Codec replacement, however, is not a component of a SIP message. While codecs are indeed vital for encoding and decoding audio/video streams during a session, they are not specified within the SIP message itself. Instead, codecs are negotiated during the session establishment phase using the information carried in SIP messages, but they don't constitute a standalone component of the SIP header or body.

This distinction helps clarify the role of SIP messages in establishing communication parameters while recognizing that codec management is part of the broader session negotiation process, often represented in the information exchanged but not as an individual message component.