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While Session Initiation Protocol (SIP) is still the primary control protocol used by Office Communications Server 2007 R2, Web Conferencing Server, A/V Conferencing Server, and their subcomponents, they also employ other protocols to set up and modify conferences and to set up and break down media streams between different elements in the Office Communications Server2007 R2 network. The following protocols are employed by Office Communications Server 2007 R2:

• Session Initiation Protocol (SIP).The industry standard protocol described in IETF RFC 3261 that defines a standard for session setup, termination, and media negotiation between two parties. It is widely used for Voice over IP (VoIP) call signaling.
  
  
• Asynchronous JavaScript And XML (AJAX).Used in Communicator Web Access to ensure efficient client-server interaction, while keeping the Web user interface (UI) responsive.
  
  
• Centralized Conferencing Control Protocol (C3P).Used to encode Conferencing Control commands in Office Communications Server.
  
  
• HTTPS.The set of rules for exchanging files (that is, text, graphic images, sound, video, and other multimedia files) on the World Wide Web. Relative to the Transmission Control Protocol (TCP)/Internet Protocol (IP) suite of protocols, the basis for information exchange on the Internet, HTTP is an application-layer protocol. HTTPS is the HTTP protocol over Secure Sockets Layer (SSL)/Transport Layer Security (TLS).
  
  
• Interactive Connectivity Establishment (ICE).Used to provide media connectivity across firewalls and Network Address Translation (NAT) devices, thereby enabling audio/video anywhere.
  
  
• Persistent Shared Object Model (PSOM).A proprietary protocol for the transport of real-time data, including audio and video. PSOM uses TCP or TLS as the underlying transport.
  
  
• Remote Desktop Protocol (RDP).The Microsoft protocol that is used in Office Communications Server 2007 R2 for desktop sharing. This is the protocol that is used for Microsoft Remote Desktop Services.
  
  
• Real-time transport protocol/real-time control protocol (RTP/RTCP).The industry standard protocol for the transport of real-time data, including audio and video.
  
  
• Session Description Protocol (SDP).Used to negotiate capabilities between SIP endpoints during call initiation.
  
  
• Secure real-time transport protocol/secure real-time control protocol (SRTP/SRTCP).Encrypted versions of RTP/RTCP.
  
  
• Scale secure real-time transport protocol (SSRTP).Scale secure RTP/RTCP, used for efficient media sessions for multi-point audio/video conferences.
  
  
• Simple Traversal of UDP through NAT (STUN).Used by endpoints to determine the public IP addresses allocated to them by the NAT (if applicable).
  
  
• Transport Layer Security (TLS).Used to encrypt SIP or HTTP trafficin addition to server authentication.
  
  
• Third Party Control Protocol (TPCP).Used for Outside Voice Control.
  
  
• Traversal Using Relay NAT (TURN).A protocol for allocating a public IP address and port on a globally reachable server for the purpose of relaying media from one endpoint to another.
  
  

For detailed specifications for Office Communications Server protocols, including several of those listed in this topic, see “Microsoft Office Protocol Documents” at http://go.microsoft.com/fwlink/?LinkId=158438 .

See Also