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TCP/IP SUITE AND INTERNET STACK PROTOCOLS 33
networks. By September 1993, it was clear that the growth in Internet users would require
an interim solution while the details of IPv6 were being finalised. The resulting proposal
was submitted as RFC 1519 titled ‘Classless Inter-Domain Routing (CIDR): an Address
Assignment and Aggregation Strategy.’ CIDR is classless, representing a move away from
the original IPv4 network class model. CIDR is concerned with interdomain routing rather
than host identification. CIDR has a strategy for the allocation and use of IPv4 addresses,
rather than a new proposal.
2.1.5 IP Version 6 (IPv6, or IPng)
The evolution of TCP/IP technology has led on to attempts to solve problems that improve
service and extend functionalities. Most researchers seek new ways to develop and extend
the improved technology, and millions of users want to solve new networking problems
and improve the underlying mechanisms. The motivation behind revising the protocols
arises from changes in underlying technology: first, computer and network hardware
continues to evolve; second, as programmers invent new ways to use TCP/IP, additional
protocol support is needed; third, the global Internet has experienced huge growth in size
and use. This section examines a proposed revision of the Internet protocol which is one
of the most significant engineering efforts so far.
The network layer protocol is currently IPv4. IPv4 provides the basic communication
mechanism of the TCP/IP suite. Although IPv4 is well designed, data communication has
evolved since the inception of IPv4 in the 1970s. Despite its sound design, IPv4 has some
deficiencies that make it unsuitable for the fast-growing Internet. The IETF decided to
assign the new version of IP and to name it IPv6 to distinguish it from the current IPv4.
The proposed IPv6 protocol retains many of the features that contributed to the success of
IPv4. In fact, the designers have characterised IPv6 as being basically the same as IPv4
with a few modifications: IPv6 still supports connectionless delivery, allows the sender to
choose the size of a datagram, and requires the sender to specify the maximum number
of hops a datagram can make before being terminated. In addition, IPv6 also retains most
of IPv4’s options, including facilities for fragmentation and source routing.
IP version 6 (IPv6), also known as the Internet Protocol next generation (IPng), is the
new version of the Internet Protocol, designed to be a full replacement for IPv4. IPv6
has an 128-bit address space, a revised header format, new options, an allowance for
extension, support for resource allocation and increased security measures. However, due
to the huge number of systems on the Internet, the transition from IPv4 to IPv6 cannot
occur at once. It will take a considerable amount of time before every system in the
Internet can move from IPv4 to IPv6. RFC 2460 defines the new IPv6 protocol. IPv6
differs from IPv4 in a number of significant ways:
• The IP address length in IPv6 is increased from 32 to 128 bits.
• IPv6 can automatically configure local addresses and locate IP routers to reduce configuration
and setup problems.
• The IPv6 header format is simplified and some header fields dropped. This new header
format improves router performance and make it easier to add new header types.
• Support for authentication, data integrity and data confidentiality are part of the IPv6
architecture.