However, IPv6 was chosen for other reasons. Security is still a major concern, and
IPv6 addresses security through encryption (IPsec). This was another driving factor to
standardizing on IPv6 for IMS implementation. IPsec is used to encrypt communications
between devices within a secure domain. This prevents eavesdropping on the
network from internal sources.
An IP address identifies the interface being used for a connection, and not necessarily
the entire node. A node may have multiple IP addresses associated with it, depending
on the function of the node. IPv6 addressing takes the form shown in Figure 4.1.
ABCD:EF01:2345:6789:ABCD:EF01:2345:6789
Addressing in the IMS 93
This example shows that there are eight parts to an IPv6 address, each separated by
a colon. Each part contains a 16-bit number, expressed in binary or hexadecimal. Any
leading zeros can be eliminated, but trailing zeros change the value for that part of the
address if excluded, and therefore, any trailing zeros must be included. An example of
a unicast IPv6 address might be:
2001:AC9:800:0:0:EA2:0:4201
IPv4 addresses may be embedded within an IPv6 address where interoperability is
needed. In this case, the address notation might look like:
2001:AC9:800:0:0:127.14.32.1
Notice that the IPv4 address is at the end of the string, using the period between address
sections rather than colons.
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