/mcpThe following video call flow is between two 9951 phones (Phone A and Phone B) with imageattr line support (for example, using Cisco Unified Communications Manager releases 8.5(1) and later): 1. Phone A sends a SIP message with the imageattr line in the SDP. 2. Cisco Unified Communications Manager does not delete the imageattr line and sends the SIP message to Phone B unchanged. 3. Phone B attempts to send video with the VGA resolution. Alternate Routing If an endpoint cannot obtain the bandwidth that it needs for a video call, a video call retries as an audio call for the default behavior. To use route/hunt lists or Automated Alternate Routing (AAR) groups to try different paths for such video calls, uncheck the Retry Video Call as Audio setting in the configuration settings for applicable gateways, trunks, and phones. For more information, see Configure AAR Group section under Configure Call Routing chapter in the System Configuration Guide for Cisco Unified Communications Manager. Flexible DSCP Markings Differentiated Services Code Point (DSCP) packet marking, is used to specify the class of service for each packet. DSCP marking lets you prioritize certain types of calls or media over other types. For example, you can prioritize audio over video so that, even if you experience network bandwidth issues, audio calls should not experience bandwidth issues. You can customize DSCP markings in either of these ways: • Configure cluster wide service parameters to set the default DSCP settings for the cluster • (Optional) For a subset of the DSCP categories, you can assign customized DSCP settings to devices via the SIP Profile. For the devices that use the profile, the customized settings override the service parameter defaults. For more information on how to configure DSCP markings, see 'Configure Flexible DSCP Marking and Video Promotion' chapter in the Feature Configuration Guide for Cisco Unified Communications Manager. Phone Configuration for Video Calls The following setting for video-enabled devices affects video calls: • Retry Video Call as Audio-By default, this check box remains checked. Thus, if an endpoint (phone, gateway, trunk) cannot obtain the bandwidth that it needs for a video call, call control retries the call as an audio call. This setting applies to the destination devices of video calls. • Video Capabilities Enabled/disabled-This drop-down list box turns video capabilities on and off. Conference Control for Video Conferencing Unified Communications Manager supports the following conference controls capabilities: Feature Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs 878 SIP Interoperability Alternate Routing