As more and more organisations start using Microsoft Live Communications Server, the real advantages of presence integration are extended beyond the borders of your own organisation. Through federation the LCS environments of external organisations can be linked to your internal network énabling presence integration and Real Time Communication with external organisations. Around the current internal LCS environment Microsoft IT has produced a lot of information:

… Internet Access and Federation Between Organizations

Many enterprise users also use public instant messaging services to communicate with fellow employees, customers, friends, family members, and other associates. Live Communications Server 2005 helps IT departments manage these diverse needs by supporting:

• More secure, inter-enterprise federation of real-time presence and communications
• Managed access to public instant messaging services

Federation enables a trust to be established between two organizations that allow presence and instant messages to be freely but more securely exchanged between the Live Communications Server 2005 infrastructures running in each organization. Access proxy servers run in the perimeter network to verify each incoming request. Depending on whether a server pool or individual home server approach is used to deploy Live Communications Server 2005, the incoming request will be directed to a director server or front-end server. …

What does it do for me ? Well, I can have Presence based Real Time Communication with for example our business partners. Microsoft has set up federation with a number of our partners already, allowing for 1 communications interface for all your contacts :

Next to the name you see a little icon with the company logo; in this case e-Office
(Gerco, I hope you don’t mind me using you as an example 😉 )