I am working within a global enterprise with around 40.000 employees. We are currently testing the Microsoft products for IM (OCS) which seems to work well. However, I´d like to investigate whether there are any open source based alternatives (XMPP based maybe?) that could work for us. I have been googling for references for enterprise size installations of open source based IM, but without any luck.
Anyone out there who knows more about this? For instance about other companies going in this direction? Is XMPP and the solutions available scalable and reliable enough for large installations? How do they integrate into i.e. LDAP servers (in our case MS Active Directory) and Office/email products (in our case MS Office and Exchange)?