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VoIP Hacks

Theodore Wallingford
Published by O'Reilly Media
326 pages
£ 20.99
Published: January 6, 2006
reviewed by Mike Smith
   in the June 2006 issue (pdf), (html)

I thought it a good idea to review this pair of books to compare their content, as the subject matter of the two is related. Skype is obviously one form of VoIP, and we should expect the VoIP book to look at SIP phones, H.323 and hopefully a range of wider issues. This review also continues a theme from previous newsletters, as I have looked at a number of the members of the hacks series now.

Both books are a little thicker than the previous hacks books I have studied -- they still have 100 hacks, and this is an indication of richer content, and bodes well.

Skype Hacks This book is split into 12 chapters, ranging from the basics of setting up and configuring Skype through to advanced uses for business, mobile devices, chat, voicemail and tools. The last chapter on automation looks interesting, with email, calendar and SMS integration.

I've had Skype for a long time, but not a regular user, and at one stage did buy some SkypeOut credit just to try it out. I should have heeded hack #21, which warns you not to forget that you need to actively use SkypeOut at least once every 180 days, or you lose your outstanding credit! With renewed interest because of this review, I tried to use some of my apparent 9.77 Euro credit reported by the Skype client -- only to find out when I attempted a connection that credit is no longer there. Rats.

Most people look at Skype, and VoIP in general, because they want to reduce their telephony costs. Of course this is true with Skype when calls are placed only over the Internet. However you have to think twice if you're considering SkypeIn or SkypeOut. One factor in the cost of calls is the unit of time that call durations are rounded up to for billing -- whether per second, per 6 seconds or per minute, say. SkypeOut uses per minute billing (rounding up to the next whole minute) so if you have something less it may not be a straight-forward reduction in costs for you (though in general I'm sure it probably is). There's a whole chapter dedicated to the financial side in this book.

[I hadn't heard the term Dry DSL previously -- meaning a DSL service without an associated telephone number and voice service. We're getting to the stage where this would be a real benefit in the UK as we could run all of our home and office voice over it and do away with the analogue services. Let's hope.]

There's a nice Skype toolbar, outlined in Hack #43 that will let you call telephone numbers using Skype from a browser, and you can create shortcuts to common numbers/contacts by using command-line parameters, which is great (Hack #49).

Hack #54 outlines how Skype can be used to provide call centre facilities. I find this amazing, but not sure if anyone is using it in this manner.

There are all sorts of other tips, such as setting up freecall numbers, and alternative international numbers for your mobile. Jyve needs to be checked out, and there are add-ons like Gizmoz which looks fun (animated faces that presumably move in unison with your voice).

Overall I like the variety of hacks in this book and recommend it if you're set on using Skype. It contains lots of food for thought in possible configurations that will reduce your dependency on, and perhaps even eliminate, your fixed line voice services.

VoIP Hacks This book has its 100 hacks split into just 7 chapters, one of which covers Skype. The 13 hacks in that chapter can be considered a distillation and the most important messages from the Skype Hacks book -- though they are not the same. Examples are integration with address books, Jyve and a few other topics.

The Skype protocol is proprietary, and the dominant VoIP protocol is now SIP (Session Initiation Protocol). A new contender is IAX (pronounced eeks) has the advantage that it works in NAT environments, so we'll have to watch how its usage grows. The rest of the book covers infrastructure and clients using these protocols.

I found much of this text, and especially the first chapter on broadband VoIP providers to be US centric. So the advice is sound, but the examples not always appropriate. You can get a list of UK providers here:

There's a chapter on Asterisk, which I am sure you'll know is now an important way to run a telephony server on Linux (and Mac and BSD) systems. I've had a look at Asterisk previously without much success due to lack of time (and a hardware SIP phone), but again this review gave me the impetus to have another go (there are a bunch of softphones listed at

SJPhone and Firefly look reasonably good. Some of the hacks cover the basics of configuring Asterisk and a little on reporting and some tricks (like obtaining automated weather reports).

There's actually a pre-built VMWare VM with Asterisk (using astLinux) that might save you some time if you want to experiment -- have a look on the VMWare website.

There's a chapter with a dozen hardware hacks. Many of these were specific to one particular model of IP Phone or other hardware. I think its unlikely typical readers will use the array of hardware addressed in each of the hacks, so I think the content has somewhat limited use.

The penultimate chapter looks at monitoring and some internals of the VoIP protocols, looking at latency and jitter, graphing the stats and traffic shaping. This has a lot of good (but brief) information on diagnostics.

The last chapter, ``Hard-Core Voice'', covers some advanced topics, such as interfacing Skype with Asterisk, and indeed the whole lot with your home (IP) phones so that incoming Skype calls with ring everything. Good stuff.

The book provides hacks for Windows, Linux and Mac based applications, and there are number of Mac-only hacks, so the relevance of the whole to the UKUUG community may be slightly reduced, but I still think this is a worthwhile wide-ranging set of hacks for general knowledge.

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