A CAC (Call Admission Control) Group represents the group of endpoints being served by each bandwidth-limited link which needs to be monitored. A CAC group is required regardless of the type of network topology present. It represents the group of endpoints being served by the bandwidth-limited link which needs to be monitored. A group is the entity to which the CAC policies are applied.
CAC Group Definition
When a call is set up, the CAC service enforces the restrictions imposed on the calling and called party, according to their CAC Group.
A CAC Group, in turn, is intended to represent a particular segment of the corporate network. It should be provisioned to contain all subscribers, that are currently
located at this segment. A CAC Group can be defined based on the following attributes:
Can for example be used for endpoints representing a network segment behind an SBC (from TCS's perspective)
Up to 128 constituent IP adresses can be provisioned per group.
Typically used for corporate network segments that are not hidden by an intermediate SBC
Up to 128 constituent IP subnets can be provisioned per group.
DNs or DN prefixes (such as 1561555*)
From the resource perspective this only makes sense if the subscribers are immobile and the DN assignment "mirrors" the network segmentation.
Up to 64 constituent DNs or DN prefixes can be provisioned per group.
This is used to impose common restrictions on a group of "child" CAC groups.
Since Lotus Sametime Unified Telephony 220.127.116.11 the preferred solution for network segments behind SBCs (from Lotus Sametime Unified Telephony's perspective).
Location Domains created via endpoint provisioning shall take precedence over any Location Domain information received via SIP signalling
Up to 64 constituent Location Domains can be provisioned per group.
Defining a CAC Group based on different attribute types is not possible.
If there are mobile users that are allowed to connect via different network segments, the DN-based definition doesn't serve well. See the topics on Location Identification for the proposed solution.
As a prerequisite, mobile user agents have to be provisioned for DHCP!
Figure 1. Valid CAC group definitions.
In addition, CAC groups can be provisioned with the following information needed to support a backup access link for subscriber rerouting:
Access router type
Access route IP address and interface name
Overlapping Group Definitions
If two or more CAC groups have overlapping definitions, the CAC service prioritizes the CAC groups as follows:
CAC groups based on IP address have the highest priority, followed by CAC groups based on subnet.
Subnets with a bigger mask have higher priority—for example, 18.104.22.168/24 has a higher priority than 22.214.171.124/16.
CAC groups based on location domains have lower priority than IPs and subnets but higher priority than DNs
CAC groups based on DN have the lowest priority.
To support up to 6000 CAC groups in Lotus Sametime Unified Telephony 126.96.36.199, the default values of the following RTP parameters have been modified:
Srx/Rdal/RdalGroupPolicyTblSize from 1000000 to 12000000 bytes
Srx/Rdal/RdalPolicyBWTblSize from 5000000 to 12000000 bytes
Srx/Rdal/RdalIpMapDataTblSize from 1400000 to 12000000 bytes
Srx/Rdal/RdalDnMapDataTblSize from 1000000 to 12000000 bytes
Srx/Rdal/RdalGrpToGrpTblSize from 1000000 to 12000000 bytes
Srx/Rdal/RdalParentGrpTblSize from 100000 to 12000000 bytes
Srx/Rdal/RdalResvDataTblSize from 15000000 to 12000000 bytes
Srx/Rdal/RdalSdpOlineTblSize from 2000000 to 12000000 bytes
and the following new RTP parameters were introduced:
Parent topic: CAC (Call Admission Control)
Subscriber Location Identification
RTP Management via Telephony Control Server Assistant