Datasheet

Introducing Session Initiation Protocol
Session Initiation Protocol (SIP) is the protocol that Live Communications Server uses to transfer mes-
sages between Live Communications Server clients. While this book introduces SIP for its use within
Live Communications Server, I recommend that you read the Request for Comment (RFC) 3261, avail-
able via the Internet by browsing to
www.ietf.org/rfc/rfc3261.txt. To describe SIP in laypersons’
terms, SIP messages are initiated by a client application that requests information from a SIP server. SIP
manages not only instant messages, but also multimedia communications as a whole. In relation to Live
Communications Server, Microsoft Office Communicator 2005 and Windows Messenger both initiate SIP
requests to a Live Communications Server, and the Live Communications Server responds to each client
by sending and receiving instant messages, invoking collaboration requests that include whiteboard
sharing, and invoking video and voice communications. This is why when enterprises are interested in
integrating Live Communications Server with their VoIP service, the VoIP routers and phones must be
SIP compliant in order to provide a seamless connection.
Session Initiation Protocol is the primary multimedia messaging protocol and it is heavily used not
only by Live Communications Server, but also by VoIP, PSTN, and PBX providers, as these solutions
are becoming increasingly popular in the commercial and residential markets. You’ve likely heard
the Vonage “Woo Hooo” commercial more than one million times. The point is that telephony
services, instant communications, and collaboration are now both here and in demand, and Live
Communications Server is the best interface for this technology with the release of Microsoft Office
Communicator 2005.
Real-time communications have become a necessity among business and consumer markets. The
demand for instant communications between individuals has reached an unprecedented level, com-
munications that include not only Instant Messaging, but integrated video, voice, and collaboration
communication. Although many people think of teenagers as the prime users of Instant Messaging
and webcams, using popular technologies that include Yahoo Messenger, AOL Instant Messenger, and
MSN Messenger, these applications have emerged in the business landscape and are rapidly becoming
a preferred tool of communication over e-mail. Why not? You can now reach someone immediately
and in return receive an immediate response. As suggested earlier, the main issue involved with
enabling these popular applications within a business enterprise today is that public network messaging
applications do not provide the level of security that businesses require to protect corporate data and
communications.
SIP Architecture
SIP is divided into three different components. A SIP proxy receives client requests and then determines
where to forward these requests (to other SIP servers). With regard to Live Communications Server, a
client using Microsoft Office Communicator 2005 sends a SIP request to an LCS SIP proxy server, which
sends the request to a Live Communications Server pool server or Standard Edition server. The Live
Communications Server pool server or Standard Edition server then acts as the next component of an
SIP server: a SIP redirect server. A redirect server receives requests from a SIP proxy or a SIP client direc-
tory and then responds to a client as to where the message is to be sent. The final SIP component is an
SIP registrar server, which receives a SIP client request and then maps that client to a specific SIP uniform
resource identifier (URI). The SIP URI is the sign-in name that LCS users will use to sign into the LCS
service. It is important that you first outline what the SIP URI for your company or customer will be
before deploying LCS, as the SIP URI will be a user’s identity for all Microsoft Unified Communications
products. Currently, the best practice is to use a client’s e-mail address as the SIP URI, such as
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