Quality of Service and performance characterization of IPv6 relative to IPv4

II.9 IPv6 FEATURES

IPv6 was designed to build on the existing features of IPv4 and provide new services and capabilities. Listed below is an overview of several features and benefits IPv6 is intended to provide.

· Extend the IP address space enough to offer a unique IP address to any device.

Larger address space: IPv6 increases the IP address size from 32 bits to 128 bits. Increasing the size of the address field increases number of unique IP addresses from approximately 4.3×10⁹ to 3.4 × 10³⁸.

· Coexistence with IPv4 network

IPv6 will be an important and major upgrade to all our networks and to the Internet. With all the transition mechanisms defined though, it will gradually grow into our networks. There will not be a flag day like there was with IPv4 in 1983, where the Internet was switched directly to TCP.

IPv6 can and will coexist with IPv4 for a long time and the transition mechanisms are so flexible, that there is no specific upgrade order required. This means, as a home user you can use IPv6 even if your ISP does not offer it yet. And within a corporate network you can for instance roll out IPv6 at the edge of the network, while your backbone is till IPv4 only.

· Auto-configuration

Clients using IPv4 addresses use the Dynamic Host Configuration Protocol (DHCP) server to establish an address each time they log into a network. This address assignment process is called stateful auto-configuration. IPv6 supports a revised DHCPv6 protocol that supports stateful auto-configuration, and supports stateless auto-configuration of nodes. Stateless auto-configuration does not require a DHCP server to obtain addresses. Stateless auto-configuration uses router advertisements to create a unique address. This creates a «plug-and-play» environment, simplifying address management and administration. IPv6 also allows automatic address configuration and reconfiguration. This capability allows administrators to re-number network addresses without accessing all clients.

· More header compression

Some fields from the IPv4 Header have been removed, renamed or modified and a new field has been added.^32(*)

II.10 DIFFERENCE BETWEEN IPv4 AND IPv6

IPv6 is based on IPv4; it is an evolution of IPv4. So many things that we find with IPv6 are familiar to us. The main differences are illustrated in the table below:

IPv4	IPv6
The size of an address in IPv4 is 32 bits	The size of an address in IPv6 is 128 bits
Address Shortages: IPv4 supports 4.3×10^9 (4.3 billion) addresses, which is inadequate to give one (or more if they possess more than one device) to every living person.	Larger address space: IPv6 supports 3.4×10^38 addresses, or 5×10^28(50 octillion) for each of the roughly 6.5 billion people alive today.^33(*)
IPv4 header has 20 bytes IPv4 header has many fields (13 fields)	IPv6 header is the double, it has 40 bytes IPv6 header has fewer fields, it has 8 fields.
IPv4 is subdivided into classes <A-E>.	IPv6 is classless. IPv6 uses a prefix and an Identifier ID known as IPv4 network
IPv4 address uses a subnet mask.	IPv6 uses a prefix length.
IPv4 has lack of security. IPv4 was never designed to be secure - Originally designed for an isolated military network - Then adapted for a public educational & research network	IPv6 has a built-in strong security - Encryption - Authentication
ISP have IPv4 connectivity or have both IPv4 and IPv6	Many ISP don't have IPv6 connectivity
Non equal geographical distribution (>50% USA)	No geographic limitation

Table 3: IPv4 versus IPv6

Source: http://www.go6.net, Internetworking with TCP/IP principle, protocols and Architectures, Fourth Edition, Douglas E. Comer, ISBN 81-7808-444-9, page 612.

* ³² http://www.soi.wide.ad.jp/class/20020032/slides/09/7.html (October 21, 2006)

* ³³ http://www.ipv6.org/ (May 12, 2006)