Practical VoIP Using VOCAL
MGCP, H.323, SIP, RTP, COPS, RADIUS, and More...
Publisher: O'Reilly Media
Final Release Date: July 2002
Pages: 528

While many books describe the theory behind Voice over IP, only Practical VoIP Using VOCAL describes how such a phone system was actually built, and how you too can acquire the source code, install it onto a system, connect phones, and make calls.

VOCAL (the Vovida Open Communication Application Library) is an open source software project that provides call control, routing, media, policy, billing information and provisioning on a system that can range from a single box in a lab with a few test phones to a large, multi-host carrier grade network supporting hundreds of thousands of users. VOCAL is freely available from the Cisco Systems-sponsored community web site (

A Silicon Valley start-up called Vovida Networks, Inc (think of VOice, VIdeo, DAta) created VOCAL and invested over one hundred man years into its development. Since Cisco acquired Vovida in 2000, individuals representing every significant telecom company and service provider in the world have downloaded the source code. Today, more and more people are successfully building VOCAL into professional solutions, while contributing fixes and new functionality back to

Because VOCAL is open source, you can look "under the hood" to the base code and protocol stack levels and discover not only how the system works, but also how common problems are being worked out in the development environment. We're hoping that you will be inspired to take this system to another level by implementing a feature or functionality that no one has thought of before.

Written by a team from Vovida Networks, Practical VoIP Using VOCAL includes the following topics


  • Installing and configuring VOCAL 1.4.0 onto a single host and onto a multi-host network with phones and gateways
  • C++, C and Java architecture found within VOCAL
  • Provisioning a VoIP system
  • SIP (Session Initiation Protocol), SDP (Session Description Protocol) and RTP (Real-time Transport Protocol) for call control and media
  • TRIP (Telephony Routing over IP), DNS SRV and ENUM for routing
  • MGCP (Media Gateway Control Protocol) and H.323 for call control and translation into SIP
  • COPS (Common Open Policy Service), OSP (Open Settlement Protocol) and RSVP (Reservation Protocol) for policy and Quality of Service
  • RADIUS (Remote Authentication Dial In User Service) for interfacing with billing servers
  • SNMP (Simple Network Management Protocol)

If you're interested in VoIP, this is the only book available that focuses on the real issues facing programmers and administrators who need to work with these technologies.

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This is a great book for software developers.

By zazz

from Atlanta, Georgia

About Me Designer, Developer

Verified Reviewer


  • Accurate
  • Concise
  • Easy to understand
  • Helpful examples
  • Well-written


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    Comments about oreilly Practical VoIP Using VOCAL:

    Having read five books on SIP, for me this was the best, while it is 15 years old, this is still the best book out there for developers writing their own SIP stack or adding functionality onto an existing one. Other books apply if you are a network administrator.

    (4 of 6 customers found this review helpful)


    Practical VoIP Using VOCAL Review

    By Dave Kitabjian

    from Undisclosed

    Comments about oreilly Practical VoIP Using VOCAL:

    I was disappointed with this book.

    It's very heavy on the internals, classes, programming APIs, and state machines of their software, presumably, based on what they say, because they are trying to recruit more developers into the community.

    That's fine, except for one thing: if we can't figure out how to be expert USERS of VOCAL, we don't have any hope of becoming developers. And this book is miserably void of any serious info on how to USE VOCAL.

    For example, other than a few "./ua" lines, there is almost NO discussion of how to do anything from the Unix command line. Knowing how to use Dial Patterns, fundamental to any real learning, is buried in Appendix A. Coming up with a simple list of what-service-is-running-on-what-port in the all-in-one config should have been listed in a convenient table in the book; instead, I had to do lots of clicking through the GUI to figure out all that.

    Figuring out how to place a variety of call between ./ua, Cisco ATA 186s, and the PSTN works to some extent, but leaves a lot of questions unanswered.

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