CUCM Presence Characteristics
With the Communications Manager solution there's kind of a built-in Presence capabilities if not the full blown Presence functionality you get with a separate server and software package, but you do get, I kind of call it busy lamp field support. Busy lamp Fields let a attendant know, for example, if somebody was on the phone or off the phone. That's kind of what we see here. We have Skinny Client Control Protocol (SCCP) lines, Session Initiation Protocol or SIP lines and trunks that can be monitored or watched, and at this point what we can do is see three possible states. Either the entity is not registered and you get one icon. Maybe they're there but they are on hook so they are available or they are registered and they're off hook. So that's kind of the busy lamp field capabilities of yesteryear other than the fact that we may not see the unregistered capability, but this gives us a nice kind of a default Presence capabilities built into the Communications Manager that we could leverage.
Presence Status on IP Phones
To view Presence status on our IP phones we can see it on our speed dial buttons, call lists or directories. However, we choose to view the various indicators that let us know if someone's available or if maybe they're not registered at this time. So we can browse through a directory or call list and see by that symbol what the current status is of that individual.
BLF Call Pickup
With our Busy Lamp Fields we can set it so that we can do call pickup functionality. So here's an example.
User A watches directory number 2000, at that point user C dials 2000 in this case and the Busy Lamp Field indicates that there's a ringing call or an alerting message. At that point user A can press the Busy Lamp Field button and pick up the call. So this is also another way to use call coverage along with your Busy Lamp Field or Presence capability.
Limited Presence Visibility
With Presence we may not want it to be a free for all. So we can limit Presence visibility. We can setup Presence-enabled speed dials. They can be statically configured. We can subscribe calling search spaces and partitions and none of this can be configured by the end users. So as an administrator of the situation you have control over how this can be set up and the Presence-enabled call and directory lists. They're also subscribed calling search space and partitions and Presence groups that we could use to control this. And again the end user cannot ultimately decide to watch the CEO of the company unless you've given them permission to do so.
Looking closer at calling search spaces when it comes to the Presence capabilities, like I mentioned we need to give permission for an entity to be watched and be able to see the Presence capabilities and so we set up a Subscribe Calling Search Space or we can also work with Presence groups. The Subscribe Calling Search Space is then associated with a watcher and the list of partitions that the watcher is allowed to see. So with this we can have great granularity and we can assign this to a device or a user for Cisco Extension Mobility.
With a Presence group this controls what we can monitor and a group could be assigned to devices, directory numbers and users. And by default all users are assigned to the Standard Presence Group but we can go in and we can set the Inter-Presence Group subscribe policy. We can do this through a service parameter. We can also have one group that may have a relationship with another group. This can be again setup using some system default settings and a service parameter. And then finally if we have Inter-Presence Group subscribe policies set as a service parameter we can set this to disallow and the Communications Manager will block the requests even if the Subscribed Calling Search Space allows it. So the Presence group kind of like takes control over any of the Calling Search Spaces that you may have setup.