Foreword
T
hese days, in communications circles, Session Initiation
Protocol, or SIP for short, is seemingly everywhere.
SIP is supported by practically every manufacturer of IP Phone,
Gateway, Call Manager, and IP PBX. It is part of the IP Multimedia
Subsystem (IMS). It is powering the fastest growing VoIP resi-
dential and enterprise providers. It is a part of PC operating
systems and has been enthusiastically adopted by the open
source movement.
Years ago, someone proposed a usage of SIP that was dubbed
“SIP for Light Bulbs”! Don’t laugh, it may happen yet.
So what is SIP and why is the industry buzzing about it?
This book will tell you. What can you use SIP for? This book
will tell you that too. Why is SIP so important? You’ll find that
here, too.
Before I leave you in the competent hands of the authors, I
will add a few of my own answers here. SIP can be called a
“rendezvous” protocol. That is, it allows endpoints on the
Internet to discover, locate, negotiate, and establish sessions.
What kind of sessions? Any kind of sessions. SIP is used to
establish VoIP (of course), video, gaming, text, call control,
and others I’m sure I’ve left out. Recent extensions to SIP add
in instant messaging and presence capability. What is pres-
ence? This book will tell you, but presence stands ready to
revolutionize enterprise communications the same way
public Instant Messenger networks have revolutionized con-
sumer communications.
Besides all these applications and uses, SIP is also generating
its own ecosystem. In the same way that the Internet opened
up networking by displacing closed, proprietary networking
protocols, SIP has opened up communications and displaced
closed and proprietary signaling protocols. It has created an
entire ecosystem of interoperable and configurable devices
and services that is revolutionizing the way communications
is done.
03_041498 flast.qxp 3/16/06 5:51 PM Page v
