You also have to think beyond voice to also including instant messaging/IM, video, presence, mobile devices and more. And... you have to think about them in the context of a globally-distributed IP infrastructure.
Information about the book and links to resources mentioned in the book are available from the books website:
I have also posted links there to two podcast interviews I've done related to the book:
I am working on getting permission to run those both as Blue Box Special Editions (I have approval on the VUC session).
In many ways, much of the book came out of the three years of great conversations that Jonathan and I had with so many of you - and I have to thank all of you who have participated in the Blue Box community over the years for your questions, your comments and all the feedback. I hope you will find that this book continues that dialogue and discussion about how to secure our communications networks.