Audio and multimedia calls require high bandwidth and low latency for best user experience. Call Admission Control (CAC), also known as Bandwidth Management, provides an efficient means to prevent degradation of quality by limiting the number of concurrent calls over limited bandwidth links. Based on location level settings, Avaya Aura® Session Manager provides the following set of CAC functionality using Session Description Protocol (SDP):

1. Recognizes different types of calls categorized either as audio or multimedia. Multimedia includes video and other forms of non-audio media sent by endpoints as part of a session.
2. Provisions a second, lesser limit on the bandwidth usage permitted for a location. This second limit applies only to multimedia calls (Multimedia Bandwidth) and prevents such calls from consuming too large a percentage of the available bandwidth of a location (Total Bandwidth).
3. If the Total Bandwidth is left BLANK then Session Manager does not perform CAC for calls in the Location.
4. Allows audio and multimedia bandwidth sharing at a location by selecting the option Audio Calls Can Take Video Bandwidth.
   • If selected, then Session Manager considers only the Total Bandwidth when deciding whether a new audio call can proceed.
   • If not selected, then Session Manager considers the Total Bandwidth minus the Multimedia Bandwidth when deciding whether a new audio call can proceed.
5. Specifies per-call bandwidth limits (as specified in Per-Call Bandwidth Parameters section), restricting the size of individual multimedia calls. Session Manager alters the SDP provided by call parties by enforcing the bandwidth limits as follows:

   • Determines how much bandwidth to be reserved for each call and counts the determined value against the provisioned limit.
   • If the multimedia bandwidth is beyond what is provisioned (Maximum Multimedia Bandwidth (Intra-Location) or Maximum Multimedia Bandwidth (Inter-Location)), Session Manager can reduce the multimedia bandwidth as low as the administered multimedia minimum (Minimum Multimedia Bandwidth) limit. In such cases, users experience a reduction in media (usually video) quality. Otherwise, calls are either alternate-routed or denied when limit enforcement cannot be achieved by quality reduction. Audio call quality is not modified by Session Manager.
   • If Session Manager cannot allow the multimedia minimum (Minimum Multimedia Bandwidth), then multimedia streams are removed from the call by setting their ports to zero, which results in denying the multimedia portion of the call

For information about administering CAC, see Administering Avaya Aura® Session Manager.