I typically don’t repost links to existing documentation, but occasionally I run across items that are not too well known and I feel this is a prime example. Just when I though I had all of the OCS-related documentation stashed away in a folder I ran into an entire section on TechNet that contains some very detailed technical specifications for various Microsoft protocols used by Office Communications Server 2007 and 2007 R2.
Microsoft Office Protocol Documents
For example, there are detailed PDF files on topics like the Address Book Service, A/V Edge Authentication, RTP Payload, ICE extensions, SIP, and SRTP to name just a few. If there is any communication protocol of OCS that you want to have a deeper understanding of then I highly recommend thumbing through these documents.
Thanks to Rick Kingslan for bringing these to my attention.