The Presence Server publishes the SIP presence information for users of the BCS Unified Communications system.
Even if presence information can be exchanged in peer-to-peer mode from client to client, the existence of a presence server provides many other additional services. The main advantages are that it can:issue presence information even to users who are not currently on line;
- permanently record presence information;
- apply centrally defined policies for access to the information;
- compile information from various sources in a single presence document. For example, in the BCS platform the presence status is composed of information from the registrar server which states whether or not the user can be reached, and from the information derived from the same client which, by means of accessibility parameters, can provide alternative phone numbers to use when the client is not registered. So if the user is not registered but has provided an alternative number, the single presence document compiled by the server states that the user can be reached.
Detailed Presence Status
The binary ‘open/closed’ status value, the only one officially recognized in the RFC 3863 Presence Information Data Format, is somewhat meager for a BCS platform, so the information is integrated with extended status values as described below.
Extended values of the ‘open’ status
- The user has declared him/herself to be available to accept new sessions and is reachable, i.e. the BCS Server knows how to route the requests intended for him/her.
- The user is available but is currently dealing with other sessions. This does not mean that he/she cannot accept new sessions even if, obviously, it is not advisable to contact him/her at the moment.
- The user has an incoming call which he/she has yet to answer. As well as the call, the user may still be dealing with other sessions.
Extended values of the ‘closed’ status
- The user does not wish to be disturbed or, in other words, has declared him/herself to be unavailable. In this state the BCS Server does not route requests to him/her. To be precise: the requests for the user (new sessions or instant messages) are rejected with the ‘480 Temporarily Unavailable’ response or redirected to voicemail (if the user has activated it). The user can add a text comment to provide details of why he/she is unavailable (for example, “On holiday until the end of the month” or “On my lunch break. Back soon”).
- L’utente non è attualmente raggiungibile (ciò non è registrato né ha definito recapiti alternativi).
The user cannot be reached (he/she is not registered and has not provided alternative numbers).
The donotdisturb value prevails over the unreachable value (if the status value is donotdisturb, the fact that the user is reachable or not becomes irrelevant).
NB These extensions are ignored by other VoIP devices if they are not based on the BCS client.