Bruce Hartpence - Packet Guide to Voice Over IP: A system administrators guide to VoIP technologies

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A short while ago, as network engineers made plans for the future, one of the considerations was the eventuality of Voice over the Internet Protocol, or VoIP. For several years, VoIP was always on the horizon or around the corner, as many believed that it was coming but were unsure about the timing. The question was whether network designers and educational programs should become early adopters, building in capacity and knowledge now or whether they should make it part of the next deployment cycle. Pulling the trigger early might put you at risk of making the wrong decision in terms of vendor or protocol. Adopting late might put you behind the competition or make you rush to deploy a system that is not well understood by the local staff.

Voice over the Internet Protocol, a.k.a. Voice over IP, or VoIP, is a huge topic. Those trying to really understand how VoIP systems operate and the issues associated with their deployment must delve into protocols and architecture requirements such as power over Ethernet, or PoE. New security issues arise because voice is now packetized on the data network and accessible via ubiquitous wireless links. Quality-of-service issues associated with mixing data and voice on the same network cause headaches as network administrators are inundated with real-time data. Interconnecting IP voice connections with the public switched telephone network (PSTN) and unified communications (UC) brings additional concerns and increasing workloads to the beleaguered staff.

This book provides an explanation of VoIP from the perspective of operating networks and the packets caught on those networks. Since the topologies were built for the purpose of developing content for the book, the issues and supporting structures necessary for VoIP are also explored. Thus, readers will get a firsthand under-the-hood view of the protocols and architectures used by VoIP-based systems as we track connections from the time VoIP phones boot, through calls and during subsequent connection teardown. Like the previous Packet Guide books (OReillys Packet Guide to Core Network Protocols and the Packet Guide to Routing and Switching ), the tool of choice for viewing the packets will be Wireshark, which is still available for free out at wireshark.org . The author built and configured everything seen in this book.

Most basic packetized voice networks start of with some very similar components; will begin with these. Components include not only VoIP-specific items such as gateways and phones but also requirements such as Dynamic Host Configuration Protocol (DHCP) and Trivial File Transfer Protocol (TFTP).

The files and website support the lab activities in this book. Simple networking experiences can be accomplished on almost any topology. However, it is not always possible to obtain the resources necessary to build and study voice networks. So, for the lab activities in this book, I have posted capture files posted on the companion website. For additional background, a YouTube channel provides another resource.

With the exception of those for Skinny, all of the references used for this book are standards from the ITU-T (International Telecommunications Union-Telecom), the IEEE (Institute of Electrical and Electronics Engineers), Request for Comments (RFC) from the Internet Engineering Task Force, or material obtained from operating networks.