The Session Description Protocol (SDP) is the companion protocol to SAP and is used to encode the actual session information. It is a format for describing streaming media initialization parameters. SDP is not really a transport protocol in the same sense as SAP. SDP is actually an ASCII-text-based format specification that uses a number of lines of text to describe a session. SDP is intended for describing multimedia communication sessions for the purposes of session announcement, session invitation, and parameter negotiation. SDP does not deliver any media by itself but is used between endpoints for negotiation of media type, format, and all associated properties. The set of properties and parameters are often called a session profile. SDP is designed to be extensible to support new media types and formats.