Combining presence from multiple SIP devices will inform the
caller that the user is present or not, but the caller will not
need to know on which number to call his buddy. He simply
launches a message to sip:buddy@company.com, and the
SIP server will start the session with the correct device (cell
phone, desk phone, IM) at the correct time using the correct
mode of communication (voice, text, video, and so on).
Further Optimization
As more applications, devices, and networks become SIP
aware, communications will be further optimized.
For instance, presence-aware messaging servers could sense
that the called party is available on his IM client, but not on
the desktop phone that was being called. As a caller leaves a
voice-mail message, instead of simply dropping the message
in an inbox, an IM may be sent telling the called party that a
message has arrived and to the calling party that the called
party has been alerted.
A speech-to-text tool can convert the voice-mail message to a
text-based IM or e-mail message (again, depending upon the
presence of the recipient). Coupling presence servers with
application servers will add much more decision-making
intelligence about where the message should be delivered,
improving the speed at which users respond and communicate.
Communication Systems
That Learn
As users acquire more SIP-enabled means of communication
and as applications become SIP- and presence-aware, users
could be crushed under an avalanche of messages, some of
which are vital, and others of which are not. So SIP will help
devices and applications become smarter about prioritizing.
With more devices and applications using SIP, the rules for
presence will become increasingly complex. Software applica-
tions for managing presence (and, what to do when users or
applications want to communicate at all times of the day and
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