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An H.323 Gatekeeper serves the purpose of Call Admission Control and translation services from E.164 IDs (commonly a phone number) to IP addresses in an H.323 telephony network. Gatekeepers can be combined with a gateway function to proxy H.323 calls and are sometimes referred to as Session Border Controllers. A gatekeeper can also deny access or limit the number of simultaneous connections to prevent network congestion. H.323 endpoints are not required to register with a gatekeeper to be able to place point to point calls, but they are essential for any serious H.323 network to control call prefix routing and link capacities among other functions. A typical H.323 Gatekeeper call flow for a successful call may look like:- | | | | Endpoint A Endpoint B 1234 1123 # Endpoint A dials 1123 from the system. # Endpoint A sends ARQ (Admission Request) to the Gatekeeper. # Gatekeeper returns ACF (Admission Confirmation) with IP address of endpoint B. # Endpoint A sends Q.931 call setup messages to endpoint B. # Endpoint B sends the Gatekeeper an ARQ, asking if it can answer call. # Gatekeeper returns an ACF with IP address of endpoint A. # Endpoint B answers and sends Q.931 call setup messages to endpoint A. # IRR sent to Gatekeeper from both endpoints. # Either endpoint disconnects the call by sending a DRQ (Disconnect Request) to the Gatekeeper. # Gatekeeper sends a DCF (Disconnect Confirmation) to both endpoints. The gatekeeper allows calls to be placed either: Directly between endpoints (Direct Endpoint Model), or Route the call signaling through itself (Gatekeeper Routed Model). ==See also== * GNU Gatekeeper (GnuGK) * Cisco IOS release version 11.3(2)NA and 12.0(3)T * Cisco Multimedia Conference Manager (MCM) * Emblaze-VCON Media Exchange Manager (MXM) * Pexip Infinity * TANDBERG Video Communication Server (VCS) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「H.323 Gatekeeper」の詳細全文を読む スポンサード リンク
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