June 2005
Intermediate to advanced
502 pages
21h 48m
English
Content preview from Switching to VoIP
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Chapter 7
CHAPTER 7
Replacing Call Signaling with VoIP
In Chapter 6, the process of transmitting voice sounds in virtual media channels, via
codecs, was presented. In order for those media channels to be set up, monitored,
and destroyed when needed, a PBX calls on signaling. Different methods are used for
different kinds of endpoints and trunks. On the PSTN, the SS7 network handles sig-
naling. On a POTS voice channel, the signaling is accomplished using analog FXS
signaling.
SS7, FXS, and the dozens of other signaling technologies in use on the PSTN, though
all signaling protocols, are outside the realm of VoIP. They could all be considered
legacy technology, since just about all of their signaling functions have been repli-
cated using several new, modern, open TCP/IP-centric standards. Even though SS7 is
a packet-based protocol and there are attempts underway to make it compatible with
VoIP softPBX systems (Asterisk included), its roots are in the PSTN, not the Internet.
This chapter describes the standards for call signaling in a softPBX-based VoIP net-
work; it also describes the ways these standards compete with and complement one
another.
VoIP Signaling Protocols
A signaling protocol is a common language spoken by telephones and call-manage-
ment servers, the PSTN, and legacy
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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.
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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.