You're on the right track! Microsoft Internet Locator Server is an LDAP-based directory service for Microsoft NetMeeting. An ILS maintains a directory of NetMeeting users, enabling them to select participants for real-time conferencing and collaboration.
If you've ever installed NetMeeting on a machine running Outlook, you may have noticed that NetMeeting integrates itself into Outlook, enabling you to invite someone from an Outlook address list to a NetMeeting. If you populate an Outlook user's Exchange mailbox properties with the ILS Server and ILS Account info, Outlook will be able to pass the information to NetMeeting, which will then be able to do an LDAP lookup against the ILS server's in-memory database of NetMeeting users, locate the invitee, and start the conference.
If you're running NetMeeting and wanting to further deploy or leverage conferencing in your organization, then look into Exchange 2000 Conferencing Server. For more information on the ILS, see http://www.microsoft.com/windows/netmeeting/ and http://www.netmeet.net/.
This was first published in April 2001