the globally unique address of the machine from which the session was created.
the type of @addr.
the type of network. "IN" is defined to have the meaning "Internet".
is a numeric string such that the tuple of @username, @sess_id, @nettype, @addrtype and @addr form a globally unique identifier for the session.
a version number for this announcement
the user's login on the originating host, or it is "-" if the originating host does not support the concept of user ids.
The contents of the SDP "o=" field which gives the originator of the session (their username and the address of the user's host) plus a session id and session version number.