/mcp• If there is a session level bandwidth modifier, Unified Communications Manager retrieves the bandwidth value from the modifier. If there is more than one modifier type, it retrieves the modifier in the following order of preference: Transport Independent Application Specific (TIAS), Application Specific (AS), Conference Total (CT). • If there is no session level bandwidth modifier, Unified Communications Manager retrieves the bandwidth value from the sum of the media level bandwidth modifiers. • The allocated bandwidth is the maximum of what the two endpoints support up to the maximum value of the Region setting. The allocated bandwidth cannot exceed the region setting. Unified Communications Manager uses the following logic when communicating with endpoints: • When generating an Answer, Early Offer or Re-Invite Offer to an endpoint that contains more than one session level bandwidth modifier type (TIAS, AS, CT), Unified Communications Manager uses the same bandwidth value for each. • When generating an answer, Unified Communications Manager uses the same session level bandwidth modifier type (TIAS, CT, AS) that was received in the initial offer • For backward compatibility, the older Unified Communications Manager suppresses the Session Level Bandwidth Modifier when a video call is put on hold and music on hold (MOH) is inserted. Video Resolution Support for SIP Phones Cisco Unified Communications Manager supports the imageattr line in the SDP portion of the SIP header for higher resolution video calls. Cisco SIP phones that support w360p (640 x 360), such as the 9951, 9971, and 8961, automatically select the best resolution for video calls depending on the following criteria: • If the session level bandwidth is greater than 800Kb/s and the imageattr[640 x 480] line in the SDP exists, then VGA is used. • If the session level bandwidth is greater than 800Kb/s and the imageattr[640 x 480] line in the SDP does not exist, then w360p is used. • If the session level bandwidth is less than 800Kb/s but greater than 480 bits per second and the imageattr[640 x 480] line exists, then VGA 15 frames per second is used. If you currently have a Cisco IP Phone model 9951, 9971, or 8961 that supports w360p (640 x 360) video resolution and are upgrading to Cisco Unified Communications Manager release 8.5(1) or later, you may notice changes in the resolution of video calls. The w360p resolution was introduced at phone load 9.2(1). Note The following video call flow is between two 9951 phones (Phone A and Phone B) without imageattr line support (for example, using Cisco Unified Communications Manager releases 8.0(1) and earlier): 1. Phone A sends a SIP message with an imageattr line in the SDP. 2. Cisco Unified Communications Manager deletes the imageattr line in the SDP and then sends the modified SIP message to Phone B. 3. Phone B attempts to send video with the w360p resolution because there is no imageattr line in the SDP portion of the SIP header. Feature Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs 877 SIP Interoperability Video Resolution Support for SIP Phones