Class of Service
Cisco Unified Communications Manager (CUCM) 5.0 introduced presence support. Presence is similar to the busy station select, busy lamp field functionality used in some traditional PBX system. Standards based presence information can be shared amongst different vendors using SIP trunks in CUCM. It is very common to share presence information with a Microsoft OCS server in environments running the Microsoft Office Communicator (MOC) client. This blog will provide an overview of presence and describe the functionality of the subscribe calling search space (CSS) configuration element. CUCM 5.0 and later support speed dial BLF (busy lamp field) in the configuration of the phone button template. A speed dial BLF operates as a traditional speed dial, but also provides presence (availability) information. If the destination phone number that a speed dial is pointed to is another Cisco IP phone, the LED of the button associated with the speed dial will turn bright red. The red LED is an indicator that the destination is offhook and not available at this time. The icon on the LCD display of the Cisco IP phone will also change to indicate onhook, offhook, or unavaible status. Cisco Type A phones (7940,7960,7910,7912,7905) do not have LED indicators. Presence information can also be enabled in call history lists (missed, received, placed calls) and the corporate directory. Presence information can be shared with other CUCM clusters and third parties through SIP trunks only (H.225 and nont-GK controlled ICT trunks do not support this functionality). All phones are in the same presence group by default and all phones have unrestricted presence viewing capabilities. A phone with a speed dial BLF is known as a watcher in SIP standards language, while the destination DN that’s being watched is known as the presence entity. Managers and executives may not be very happy that the interns can monitor their phone use status. Presence groups and Subscribe CSS represent two techniques for limiting presence viewing. Presence groups should be deployed to restrict presence capabilities before using the subscribe CSS element. An organization may decide to use three different presence groups: Management, Sales, and Staff. Each member of the same presence group can be watched by any other member of the presence group by default. Members of different presence groups cannot watch each other by default, but inter-presence group policies can be configured. The following inter-presence group configurations may be configured: •Management can watch sales and/or staff •Sales can watch staff, but can NOT watch management •Staff can watch other members of staff, but NO other presence group members Although similar presence viewing limitations could be configured with subscribe CSS, the subscribe CSS can be used to further limit who can watch who within the same presence group. There may be a situation where one manager #1 is watching manager #2 and manager #2 does not want manager #1 to have this visibility. A Subscribe CSS can be applied to manager #1’s phone that does not include the partition of the directory number of manager #2. If manager #1 and manager #2 are in the same management partition, additional partitions may need to be configured and the existing dial plan CSS may need to be modified. I will personally try to avoid subscribe CSS at all costs. I would rather create a new, unique presence group for people who do not want to be watched. Unfortunately, they would be able to watch each other, but hopefully that issue would not arise. Links http://unifiedcommunicationsblog.globalknowledge.com/
