russell@tekelec.com SIP/2.0
VIA: SIP/2.0/UDP pchome101@aol.com:5060; branch=z9hG4bK74gh5
Session Initiation Protocol (SIP) 59
FROM: Deby Russell
;tag=9hz34567sl
TO: Travis Russell
MAX-FORWARDS: 70
CALL-ID: 82167534@126.18.27.0
CSEQ: 1 INVITE
CONTACT: Deby Russell
CONTENT-TYPE: application/SDP
CONTENT-LENGTH: 154
Note that the first line contains the type of request (INVITE) with the address where
the request is to be sent. This address may be simply the next hop in the network, or
it may be the final destination, depending on how routing is configured within the network.
The SIP/2.0 indicates the version of SIP that was used to create the request. This
allows receiving nodes to determine how the message is to be processed.
The rest of the lines consist of headers. Each of the headers contains expected parameters
providing additional details about the request. The last line of the message is
the CONTENT-LENGTH, which defines the length of the message body itself. The message
body then follows.
The contents of the message body are described in the header CONTENT-TYPE. In the
preceding example, the content is the application ???Session Description Protocol (SDP).???
This means that the message body will contain yet another protocol known as the Session
Description Protocol (SDP) that describes the details about the session being requested.
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