That is a SMALL part of OCS, or rather
Here's a link from someone asking the same basic question of "what is OCS", which has some links in it..
http://social.technet.microsoft.com/Forums/en-US/ucccommunityocsdeployment/thread/013ea8c5-1177-43ea-a66c-eadab88a6aefHere's the official OCS site:
http://www.microsoft.com/communicationsserver/en/us/default.aspxI have to say that installing an OCS environment for this alone is kind of like installing Microsoft office just to be able to edit your boot.ini.. Sure, there's a component that will do it, but it's way overkill for the job in general...
OCS is made to be a corporate instant message, chat, voice, video conferencing system, and ONE function of it is desktop sharing, so yes - if you had OCS, you could create an ad-hoc desktop sharing session, and invite an external user to join the meeting, then have them become the presenter and share their desktop.. It's not as straight forward as the logmein experience..
-Steve