July 2002
Intermediate to advanced
528 pages
15h 13m
English
Content preview from Practical VoIP Using VOCALBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Message Headers
In the previous section, the message flows began with an INVITE message. Earlier in this chapter, we looked at how the INVITE message contains SIP headers and an SDP attachment. In this section, we will look at these components more closely.
The INVITE
The following is an INVITE that has been generated by a User Agent and sent to a Proxy:
-----------------------------------------------------------------
INVITE sip:6713@192.168.26.180:6060;user=phone SIP/2.0
Via: SIP/2.0/UDP 192.168.22.36:6060
From: UserAgent<sip:6710@192.168.22.36:6060;user=phone>
To: 6713<sip:6713@192.168.26.180:6060;user=phone>
Call-ID: 96561418925909@192.168.22.36
CSeq: 1 INVITE
Subject: VovidaINVITE
Contact: <sip:6710@192.168.22.36:6060;user=phone>
Content-Type: application/sdp
Content-Length: 168
v=0
o=- 238540244 238540244 IN IP4 192.168.22.36
s=VOVIDA Session
c=IN IP4 192.168.22.36
t=3174844751 0
m=audio 23456 RTP/AVP 0
a=rtpmap:0 PCMU/8000
a=ptime:20
-----------------------------------------------------------------Breakdown of the Headers
The INVITE is divided into two sections. The top section contains the SIP headers, and the bottom section contains the body of the SIP message, in this case, an SDP session. The headers are separated from the body by a blank line. SDP session description information is discussed later in this chapter.
INVITE
The first line identifies the message type, the address of the called party, and the version of SIP that the caller supports. In the example, it is: ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.