Technical Manual
U-SYS MRS6100 Media Resource Server
Chapter 5 MGCP and SIP
Huawei Technologies Proprietary
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To:Value
Cseq:Value
Space
Via:Value
Max-Forwards:Value
Allow:Value
Contact:Value
Supported:Value
Content-Lengh:Value
Content-Type:Value
... ...
Call-ID:Value
User-Agent:Value
SDP
From:Value
Command Peer UPI Version
Start
line
Message
head
Message
body
Figure 5-12 SIP request message format
2) Request message parameters
Here we describe some frequently used parameters.
z Call-ID
The Call-ID field uniquely identifies a particular invitation or all registrations of a
particular client.
A single multimedia conference can give rise to several calls. Each call has its own
Call-ID. For example, a user can invite a single individual several times to the same
(long-running) conference. A user may also receive several INVITEs to the same
conference or call with different Call-IDs. The user can judge the repetition of the
INVITEs by identifications in the session description, for example, session identifier
and version number carried in the o (source) field in the SDP.
Call-IDs have a generic format:
Call-ID: localID@host
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