SIP has a number of advantages over previous VoIP protocols:
The SIP "language" is similar to HTTP. It is highly flexible and extensible.
SIP is "agnostic" as to the service being provided - plain telephone call, video conference, SMS, etc.
SIP only needs a simple network architecture to be useful. In fact, two endpoints on an IP
network are all that is needed to place an IP telephone call.
SIP call setup times are inherently fast, with relatively few messages needed.
