June 2005
Intermediate to advanced
502 pages
21h 48m
English
Content preview from Switching to VoIP
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This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.
SIP Packet Inspection
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253
To spot the incorrect username, highlight packet 4 and scroll down the bottom pane
until you see the SIP User header in the ASCII-encoded column of the packet con-
tents on the right side.
Similar capture and analysis techniques can be used to troubleshoot access control
and dial-plan configuration problems on the SIP server, or misconfigurations on SIP
phones. If you’re daring enough to decode ASN.1, you can even use this technique to
troubleshoot H.323 signaling.
Project 11.2. Inspect SDP Capabilities Negotiation
What you need for this project:
• A SIP-compatible softPBX such as Asterisk
• A SIP phone such as X-Lite
• Ethereal software
• LAN
The Session Description Protocol is an essential part of SIP call signaling. Its ele-
ments are text tokens sent in SIP packets with the SDP content-type header. These
tokens advertise the capabilities and requirements of each endpoint according to the
parameters of the application, be it a telephone call, instant message, or something
else.
During call setup, specifically during the SIP INVITE method, the SDP payload is
sent from one endpoint to the other. A SIP 200 OK response indicates agreement
with the SDP parameters, while a 4xx response indicates disagreement or incapabil-
ity. If you need a refresher on SIP signaling, ...
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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.