What does VoIP really mean anyway?
The term VoIP is officially an acronym for Voice over Internet Protocol, but is also used to loosely
refer to any application where packet based data networks are used to packet switch telephone calls
in real time. This type of telephony contrasts to traditional hard wired analog telephony which is
circuit switched. Going to VoIP based telephony technology has several advantages, both technical
and economic, but also introduces some new complexities that must be a managed part of the data
network.
Traditionally, data networks and the Internet in general were developed only as a best effort
service. The network was designed to get the data there as fast as possible and when there are
problems to get as much data there as possible, eventually. This is a good design characteristic for
data, but it has problems where there are true real-time constraints to support toll quality telephone
calls. For telephone audio, not only is bandwidth and throughput important, but packet loss, latency,
and jitter performance are also critical factors to good sounding audio. Therefore real-time
applications like VoIP gave rise to engineering and managing the Quality of Service (QoS) of data
networks.
Designing networks for QoS factors and diagnosing QoS problems is an entirely new dimension in
data networks for many people. In VoIP applications, not only is a valid data connection required to
insure application success, but also a high quality and maintainable QoS. It is not uncommon for data
networks to have throughput or packet loss problems that go completely unnoticed until VoIP systems
are deployed. Therefore, when deploying VoIP systems it is important to inspect or validate the
existing network to make sure it is going to be VoIP ready from a QoS perspective. This is especially
important consideration when VoIP calls are going to be placed over data connections between
physical locations. QoS topics are further explored in a later section of this document, but the main
items of interest are network packet latency, jitter, and packet loss rates.