Without the ability
for switches to communicate and query these databases, we would not be able to
provide many services we enjoy today.
However, the IN has run out of gas. The IN and SS7 were designed specifically for
voice and data communications; they are not equipped for other media types. The entire
protocol would require modification to be able to support IP networks and multimedia
services. Even then, the IN and SS7 are not suitable for IP-based multimedia, and
therefore the entire infrastructure for the network core has been redefined. The very
communications and the procedures defined for call treatment had to be recreated to
support multimedia over an IP network.
And thus the Session Initiation Protocol (SIP) was born. SIP is like SS7 in some
aspects, but provides much more than SS7 ever could. It was used first for Voice over
IP (VoIP) networks as a control protocol and has quickly gained in popularity. It was
adapted by the 3GPP for use within the IMS core as the control protocol of choice, and
it forms the basis of all things IMS.
The principle difference between SS7 and SIP lies in the ability to support various
media types. The structure of the protocol is fundamentally different; that is why it
can support all media types. Consideration was also given to how services are charged
within an IP network, with SIP playing a major role.
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