By linking multiple modes of communication with user prefer-
ence, SIP provides a unifying solution that helps to reduce
user and operating costs by making even advanced com-
munications more intuitive and more consistent to the user.
Instead of requiring the user to interpret and interact with
multiple applications, interfaces, and addresses, the commu-
nication system adapts to the need of the user.
Catering to the Mobile
User with SIP
Because SIP enables a user to associate a single address with
multiple communication devices, communication types, or
User Agents (UAs), as discussed in Part 2, SIP natively enables
mobility-based communications.
Because an AOR can be associated with any number of
devices and/or phone numbers, SIP can help your company
leverage all kinds of mobile communication devices as part of
a SIP-enabled enterprise. Applying the concepts of intelligent
forking described earlier in the section “Using Presence to
Route Communications,” SIP can direct communications to
any number of mobile UACs (user aagent client devices)
including cell phones, mobile IM devices (such as BlackBerry
devices and Treos), and SIP softphones on laptops.
As with e-mail addresses, users probably won’t memorize
other users’ SIP AORs. Instead, they’ll have address books
and buddy lists, just like they do on their e-mail systems, cell
phones, and IM clients today. A SIP AOR will be just another
data field associated with each person or group. When used
by a SIP device, the URI will be retrieved and used to start
communicating with another party.
Initial efforts to develop SIP-enabled converged seamless
mobility solutions might appear to be aimed mainly at wire-
less voice calls within wireless networks, to lower usage
charges and require fewer phones. For example, Avaya and
its partners have pioneered the development of multimode
SIP phones, with both cellular and Wi-Fi antennae. Although
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