IPv6 versus IPv4

IPv6 versus IPv4
IPv6 is a major revamp to the IPv4 architecture. The upgrade is largely seen as driven by a shortage
of IP addresses, but it is more correct to say that it was motivated by fragmentation of the address
space. However, the designers of IPv6 used the opportunity presented by this upgrade to address a
number of lingering problems in IPv4. As a result, it is a major upgrade [497].
IPv6 increases the IP address size from 32 bits to 128 bits to support more levels of addressing
hierarchy. IPv6 provides a much greater number of addressable nodes and employs a simpler automatic
configuration of addresses. In addition, IPv6 defines a new type of address that is called an anycast
address. An anycast address identifies sets of nodes. A packet that is sent to an anycast address is
delivered to one of the nodes. The use of anycast addresses in the IPv6 source route allows nodes
to control the path over which their traffic flows. Furthermore, some IPv4 header fields have been
dropped or have been made optional. This change reduces the common-case processing cost of packet
handling, and keeps the bandwidth cost of the IPv6 header as low as possible, despite the increased
size of the addresses. Even though the IPv6 addresses are four times longer than the IPv4 addresses,
the IPv6 header is only twice the size of the IPv4 header [498].
It would be difficult to predict what kind of new requirements the future will impose on Internet
architecture. An extensible protocol like IPv6 has more prospects to meet the unforeseen needs than
its rigid IPv4 counterpart. IPv6’s flexibility is made possible by extension headers and options built
into its design. While IPv6 enjoys clean extensibility in its architectural design, IPv4 is limited to a
slow, costly, and limited patching process that further upsets its original design principles [504].