Home > Uncategorized > Book review: “Internet multimedia communications using SIP”

Book review: “Internet multimedia communications using SIP”

For a long time my only source of information about SIP was RFC 3261 and others. However, recently we got a new book in a library Book is called “Internet multimedia communications using SIP” by Rogelio Martinez Perea. Now I’ve finished about 90% of the book, so I already have an opinion which I would like to share.

This book is interesting in it’s approach. It tells about lots of things, often oversimplifying them just to show only essential features.

First part is called “Fundamentals”. It explains principles of signaling/media approach, then moves to explanation of TCP/IP protocol family basics. Then on abstract level (without syntax!) it explains functionality of SIP. This part is intended for people who know absolutely nothing about networks.

Second part is called “core protocols”. First it explains basics of SIP syntax and interaction. Then it contains Java practice with free SIP stack. Next it moves to SDP, also with small Java practice. Next it moves to RTP, also with Java practice. And finally, all pieces are assembled together in soft-phone application and proxy application.

For me, such composition of the book is not very good. If somebody needs explanation of TCP/IP principles and never used sockets, then he probably will not be able to troubleshoot an application. On the other hand, advanced people like me will find code too amateurish, and most explanations as oversimplified.

Third part is called “Advanced topics” and tries to cover in small degree many (I’ve found 10) areas of SIP usage. There are no programming here, just concepts. This chapter, in my opinion, is the best in the book.

This book is quite good for students: it contains “main facts” about technology, so person will at least know that is it, and he can get deeper knowledge, if necessary. Other people who can benefit from the book are curious engineers, programmers and managers. I suspect that nobody will actually use practical part of the book.

To prove that I actually read the book and that my opinion has a base, I’m posting here a list of small annoyances, errors and mistakes I’ve found so far. Unfortunately, there are no site or e-mail address where I could send this list, so I’m posting it here in hope that author finds it useful.

  • Figure 6.15 on page 91 has an error. ACK request after 200 OK response always follows the same path as BYE request.
  • In chapter 8.6.7, an Example 4 doesn’t explain at which moment a “Dialog” object was created. There are no code, compared with Example 3, which would create a dialog. I perfectly understand that dialog is created automatically by stack, because default value of property “javax.sip.AUTOMATIC_DIALOG_SUPPORT” is “on”, so dialogs in fact are created in both cases. I believe it is worth mentioning, or replacing with creation of dialog explicitly. I believe that in this case oversimplification is bad.
  • In chapter 12.5.5 author explains that he uses TimerTask to close a dialog in case ACK is not received. Such approach is totally wrong. Actually a timeout for ACK is handled by stack, which will notify SipListener through processTimeout() method. Also, if TimerTask is intended only for ACK timeout, then a task should be cancelled if ACK is received. I believe that TimerTask should be removed at all.
  • In chapter 13.2.1, an exception #4 contains wrong information about CANCEL processing. In fact, proxy doesn’t send “487 terminated” response on INVITE. Such response will be sent by UA. Chapter 13.3.3 contains correct information about processing a CANCEL. I believe that author made this mistake because he wanted to make simpler proxy example.
  • In chapter 13.6.5 author explains proxy example. He uses ArrayList for context storage. A Map should be used instead, because code will be simpler and will work faster.

I hope that author will accept this list as a sign of respect from another professional. I believe that going to the matter is better then empty praise and stupid testimonials.

SIP gets more and more mindshare, and I fill that demand for professionals will grow. That puts me in a good position.

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  1. December 22, 2008 at 2:30 am

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