This allows
operators to re-use IP addresses, rather than use dedicated IP addresses for each subscriber.
Dynamic addressing is widely used by Internet service providers (ISPs) today.
IP addresses are a series of numbers. Some could argue that we are very accustomed
to using numbers within the switched network; however, we have to look up the numbers
of people we want to call (except for those numbers we call frequently, which we
can memorize). Could you imagine having to enter an IP address anytime you wanted
to visit a company??™s Web site? You would first have to look up the company??™s address,
and you would have to know the machine address you wanted to connect with.
Sound familiar? This is the model created for the world??™s telephone networks. If you
want to reach someone, you have to know the number or look it up in the directory. The
Internet model was designed to be much more user friendly, and this concept is now
being extended to voice services.
The IP address format is dependent on whether or not IPv4 or IPv6 is being used.
Since IPv6 is what IMS calls for, we will only discuss IPv6 addressing. IPv6 extends
the number of possible IP addresses supported by IPv4 significantly, which is why it
is well suited for IMS. Imagine every device connecting to the network requiring its
own unique IP address. We would quickly run out of addresses using the current IPv4
model.
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