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Overview
The Call Agent feature enables the Excel platform to connect calls with or without bearer paths through the Excel platform. The Excel platform can accept requests from SIP clients for a specific host-based voice service and then establish a SIP signaling connection for the requested service.
Call control is resident on the Excel platform so the RTP stream does not have to pass through the Excel platform via the VDAC card which avoids "hairpinning" the call. The Excel platform is now Call Agent mode. You can switch modes and have the RTP stream pass through the VDAC card. The Excel platform is in VDAC mode.
Figure 1-1 VDAC or Call Agent Mode
Call agent switching technology is driven by the convergence of telecommunication and data networks. Data networks such as IP are typically self-routing and connectionless. Therefore, are more like circuit-switched transport networks.
Refer to the Call Agent chapter for a full explanation of Call Agent in the Excel platform.