The internal CAC solution in Lotus Sametime Unified Telephony restricts the voice codecs for calls between SIP/SIP-Q endpoints. Since legacy system this feature is also applicable for MGCP connections to the Media Server for announcements, tones or conference.
This feature is not applicable to T.38 Fax over UDPTL in either version.
The internal CAC solution in Lotus Sametime Unified Telephony allows the system administrator to limit the voice codecs which can be used over a specific link. If required, the administrator can also assign attributes to endpoints and subscribers that override restrictions that are otherwise in effect.
Enhanced CAC codec restrictions also include calls to the Media Server via MGCP. The subscriber has the (switch-wide) capability to either restrict or not the MGCP sessions, when the flag Ignore MS Calls
is applied to a CAC policy.
Voice codec restriction permits the customer to have excellent voice quality in local connections by setting the preferred codecs for all phones and endpoints to high-quality codecs e.g. G.711 or G.722.
For WAN connections, however, the customer may prefer to restrict the allowed codecs to compressed codecs only—for example, G.723 or G.729. In this manner, the customer can optimize the usage of the bandwidth and allow more simultaneous connections while still guaranteeing an acceptable quality of service.
Figure 1. Sample Network Topology Requiring Voice Codec Restriction
Now assume that the administrator only wants to allow G.729 for calls over the L1 link because it only supports 300 Kbps. On the other hand, there need be no restrictions for calls over the L2 link that supports 1 Mbps—that is, all codecs are allowed.
In this case, the CAC groups and policies shown in figure below should be created to control the traffic over the bandwidth-limited links L1 and L2. In legacy system, the CAC groups and policies can be created in a comparable manner to limit the video codecs.
Figure 2. Sample CAC Policies to Restrict Voice Codecs
Parent topic: CAC (Call Admission Control)