/mcpobjects for registration with Cisco Unified Communications Manager. This step informs Cisco Unified Communications Manager that the application will act as the endpoint for all calls to or from a particular directory number, as determined by the device configuration in the Cisco Unified Communications Manager configuration. Payload Selection When a bidirectional media stream is about to be created between two endpoints, for instance, when a call is answered at an endpoint, Cisco Unified Communications Manager selects an appropriate payload type (codec) for the media stream. Cisco Unified Communications Manager compares the media capabilities of both endpoints that are involved in the call and selects the appropriate common payload type and payload parameters to use. The basis for payload selection includes endpoint capabilities and location, although other criteria may get added to this selection logic in the future. Endpoints do not get dynamically involved in selecting payload types on a call-by-call basis. Receive Channel Allocation If Cisco Unified Communications Manager can find a common payload type for the RTP stream between the two endpoints, it requests that each endpoint create a logical “receive channel”; that is, a unique IP address and port at which the endpoint will receive RTP data for the call. Each endpoint returns an IP address and port to Cisco Unified Communications Manager in response to this request. Currently, only IP phones and gateways perform this step. Cisco Unified Communications Manager requires JTAPI applications to specify a fixed IP address and port during initialization. Therefore, JTAPI applications cannot terminate more than one media stream simultaneously for the same endpoint. Applications that want to terminate multiple media streams must register multiple endpoints simultaneously. If the endpoint does not respond to the open receive channel request quickly enough, Cisco Unified Communications Manager disconnects the call. Because JTAPI applications always supply an IP address when CiscoMediaTerminals are registered, calls to application-controlled endpoints do not get disconnected for this reason. However, if Cisco Unified Communications Manager cannot find a common payload type between the two endpoints that are involved in the call, Cisco Unified Communications Manager disconnects the call. Starting Transmission and Reception After Cisco Unified Communications Manager receives channel information for both parties, it informs each endpoint of the codec parameters that it selected for the RTP stream and the destination address for the other endpoint. This information gets conveyed in two messages to each endpoint: a start transmission message and a start reception message. JTAPI applications receive the CiscoRTPOutputStartedEv and CiscoRTPInputStartedEv events that contain all the codec parameters that are necessary for sending and receiving RTP data. As a part of the QoS baselining effort in JTAPI, CiscoRTPOutputStartedEv provides the getPrecedenceValue() API to applications. CTI presents this value, The DSCP for Audio Calls to JTAPI. Using this value, applications can set the DSCP value for the media streams that they open. Cisco Unified JTAPI Developers Guide for Cisco Unified Communications Manager, Release 15 and SUs 52 Features Supported by Cisco Unified JTAPI Payload Selection