Although the book was written back in 2010, it is sadly still VERY relevant to the Voice-over-IP (VoIP) systems deployed today. I would have loved it if vendors would have made systems so much more secure that this book could be forgotten about... but the security concerns have only increased in the time since the publication. Even six years later it still offers relevant advice and suggestions about how to make sure your IP communication systems are as secure as possible.
I am a big fan of buying ebooks directly from O’Reilly because doing so gets you:
- DRM-free – no stupidity with license restrictions.
- Free lifetime access
- Multiple formats (ex. ePUB, PDF, Kindle, etc.)
- Free updates
- Sync with Dropbox, Google Drive and other similar services