CUCM Subscribe CSS
Figure 14-4 describes how the subscribe CSS controls presence watchers.
Figure 14-4 CUCM Subscribe CSS
CUCM provides the capability to set policy for users who request presence status:
- Configure a CSS to route SIP SUBSCRIBE messages for presence status.
- Configure presence groups with which watchers can be associated, that specify rules for viewing the presence status of presence entities that are associated with another group.
The first aspect of presence policies for CUCM is the subscribe CSS. CUCM uses the subscribe CSS to determine how to route presence requests. Presence requests are SUBSCRIBE messages with the Event field set to Presence. These messages are sent from the watcher, which can be a phone or a trunk. The subscribe CSS is associated with the watcher and lists the partitions that the watcher is allowed to see. This mechanism provides an additional level of granularity for the presence SUBSCRIBE requests to be routed independently from the normal call-processing CSS.
With the subscribe CSS set to <None>, BLF speed dial and call list presence status does not work (if no directory number or route pattern is associated with the <None> partition) and the subscription message is rejected as “user unknown.” When a valid subscribe CSS is specified, the indicators work and the SUBSCRIBE messages are accepted and routed properly.