Microsoft Office Communications Server

Microsoft Office Communications Server 2007, OCS 2007, is an enterprise real-time communications server, providing the infrastructure to allow instant messaging, presence, audio-video conferencing and web conferencing functionality.
Client Software
Microsoft Office Communicator 2007 (MOC07) and Live Meeting console are the client side applications paired for use with OCS 2007. Microsoft Office Communicator leverages the OCS server to find, monitor, and communicate (instant messages, presence, and telephony) with other users within an organization.
Features
One basic use of Office Communications Server is instant messaging and presence within a single organization. This includes support for rich presence information, file transfer, instant messaging as well as voice and video communication. (These latter features are often not possible even within a single organisation using public IM clients, due to the effects of negotiating the corporate firewall and Network Address Translation).
OCS 2007 also supports remote users, both corporate users on the internet (e.g. home workers) as well as users in partner companies. OCS 2007 supports "federation" - enabling interoperability with other corporate IM networks. Federation can be configured either manually (where each partner manually configures the relevant edge servers in the other org) or based on use of the appropriate SRV records in the DNS.
Microsoft Office Communications Server uses the Session Initiation Protocol (SIP) for signaling along with the SIMPLE extensions to SIP for IM and presence. Media is transferred using RTP/SRTP. The Live Meeting client uses PSOM to download meeting content. The Communicator client also uses HTTPS to connect with the web components server to download address books, expand distribution lists, etc. By default, Office Communications Server encrypts all signaling and media traffic using SIP over TLS and SRTP. There is one exception to this - traffic between the Mediation Server and a basic media gateway is carried as SIP over TCP and RTP.
Compliance
OCS 2007 also has the capability to log and archive all instant message traffic passing through the server and to create Call Detail Records for conferences and voice. These features provide a measure of compliance, increasingly a legal requirement for many organizations, however the Archiving server is not an overall end-to-end compliance solution. Archiving requires you to install the Archiving Server and to configure front end servers accordingly.
Public IM Connectivity (PIC)
OCS 2007 also enables organizations to interoperate with the three of public IM providers: AOL, MSN, and Yahoo. PIC was first introduced with Service Pack 1 for Live Communications Server 2005, PIC is licensed separately.
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