Summary

After reading this chapter, you should be able to explain the rationale behind IPv6 and should have a basic understanding of the main features and benefits provided by IPv6. In addition, you should remember the following information:

• Studies predict an exhaustion of the current IPv4 address space between 2005 and 2011.

• The IPv4 address space is limited by its 32-bit address scheme. Moreover, large portions of the space are already allocated, and other parts are unavailable as globally unicast addresses.

• As the Internet continues to grow, more IPv4 addresses are requested for new devices and applications.

• The combination of CIDR and NAT mechanisms has helped slow down the exhaustion of the address space. However, NAT breaks the end-to-end model of the IP protocol, so it has many limitations for protocols.

• IPv6 with its 128-bit address scheme provides plenty of IP addresses for the future.

• IPv6's larger address space provides globally unique unicast addresses to support the growth of the Internet.

• IPv6's multiple levels of hierarchy promote efficient and scalable routing to the Internet.

• Multihoming with the preservation of strict route aggregation is possible.

• The autoconfiguration mechanism allows nodes to configure their own IPv6 addresses.

• The transition between IPv6 providers is transparent to end users.

• The IPv6 header is more efficient than IPv4, fewer fields in the header are present, a new field is available, and ARP broadcast is replaced by a multicast use.

• New extension headers replace IPv4's Options field.

• Mobility and security are embedded in the protocol instead of being new functions added, as with IPv4.

• Many transition mechanisms are designed with IPv6 to allow a smooth transition from IPv4 networks to IPv6.

IPv6 is the replacement for IPv4 to ensure the growth of the Internet for future decades. There is no alternative to IPv6.