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The A/V Conferencing Server also incorporates elements of the IETF drafts for Interactive Connectivity Establishment (ICE) as a means to enable the exchange of media between two or more clients that are using Network Address Translators (NATs). ICE is an extension to Session Description Protocol (SDP) that enables media streams to traverse NATs by including in the SDP multiple IP address and port combinations for a particular transport protocol, known as candidate transport addresses that the client can use to communicate with other clients. In an Office Communications Server environment, a client uses Session Traversal Utilities for NAT (STUN) and Traversal Using Relay NAT (TURN) protocols to obtain its candidate transport addresses from the Office Communications Server A/V Conferencing Edge Server. During negotiation, clients on either end exchange SDPs and then test candidate addresses for peer-to-peer connectivity. After the connectivity checks, clients renegotiate by including only the candidate transport address that succeeded in the SDP for a SIP re-INVITE request and response.
Although the A/V Conferencing Server incorporates elements of ICE, the server is not compliant with the drafts. As a result, interoperability is not supported with third-party implementations of ICE, STUN, or TURN. For more information about IETF drafts for ICE, see http://ietfreport.isoc.org/all-ids/draft-ietf-mmusic-ice-18.txt.
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Microsoft Office Communications Server 2007
Conferencing Servers
http://technet.microsoft.com/en-us/library/bb894511.aspx