The Open Source Zone

Good book on SIP. Bought it to expand our knowledge of SIP in an Asterisk enviroment.

The initial introduction is a bit too-long. I think that when you buy a book on SIP, you already know IP telephony and alikes works.

Before buying, keep in mind that the book is on SIP, generally speaking, and SIP is used on lots of places, not only on Internet/IP telephony.

This is a great book for absolute beginners. If you have already read the SIP RFC(s) then this book is clearly not for you, on the other hand if you are an engineer beginning to learn SIP then this could provide a great introduction.
The first few chapters are not about SIP but about telecom, VoIP in general and IETF process. I found that quite useful too.
After having read this book you will be able to understand RFC 3261 much better. This is a fast read, I finished this book in a day when I read it several years ago. This could also be a whirlwind refresher for someone who had once worked on SIP but now wants to brush up for a sales meeting tommorow.

This is one of the worst books yet. There are spelling errors and grammer errors throughout the book. Nowhere in this book does the author talk about ENUM, DDDS or NAPTR. Nor does he talk about DHCP (option 120) nor DNS. The examples are poor, not enough detail and it falls along the line of "Once Upon A Time." No offence to the Brothers Grimm.

I thought this book was very helpful to understand the basic concepts of SIP.

Author is really good but the way SIP described in the book is a kind of child-story , details on important parts of SIP and on unified services are skipped instead make-up parts are highlighted.