HP-UX C SIP Stack Programmer's Guide (Novembery 2007)

Working with SIP Messages 149
Message Objects
MESSAGE OBJECTS A message holds all message parts, which include the message start line, one or
more header fields and an optional message-body. The message holds most of its
headers in a sequential list. The Call-ID, To, From, CSeq, Content-Type and
Content-Length headers are held separately. These headers can only appear once
in a SIP message. Figure 9-1 illustrates a SIP message.
Figure 9-1 Message Object
Start Line
Message
Object
Body
Content-Type
Content-Length
Call-ID
From
To
CSeq
Via Contact Date