A special type of federation called public IM connectivity (PIC) enables MCS users to communicate with contacts using the various public IM networks. Although many organizations have deployed previous versions of a Communications Server and support federation, there are still needs to communicate with public IM contacts at times.
Lync Server supports the following public IM providers:
Additionally, federation to Google Talk users can be provisioned through the XMPP Gateway Server role. PIC connectivity provides presence and peer-to-peer IM for all providers, but in Lync Server, peer-to-peer A/V conversations can also be used with Windows Live and Skype contacts.