This presents many cost savings and
allows operators to implement just about any type of service they want to offer, as long
as their MGCFs can communicate and support it.
A voice application server, for example, may provide mobility services, conferencing
services, or even messaging. Operators such as Skype and Vonage are heavily dependent
on these application servers because this is where mobility is supported. Mobility,
by the way, is the concept of receiving calls no matter where you are located. The network
always knows your IP address and always knows how to route calls to your device
(as well as what device to route calls to).
In essence, the VoIP model is almost IMS ready, except that many different protocols
are used to support all of the communications between all of the network entities, and
very few security and authentication controls are provided by the network. Almost
all of the security and authentication controls are functions of the MGCF and require
implementation by the operator.
However, the concept of inserting a module within the subscriber device for the exchange
of authentication credentials is largely a wireless concept. VoIP implementations
may have some security, but there is no means of authenticating the subscriber
device today.
Certainly an operator can provide packetized services today, with all of the features
and capabilities that can be provided within the IMS, and indeed many are doing
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this now.
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