The network layer protocol in the TCP/IP protocol suite is currently IPv4. IPv4 provides the host-to-host communication between systems in the Internet. Although IPv4 is well designed, data communication has evolved since the inception of IPv4 in the 70s. IPv4 has some deficiencies that make it unsuitable for the fast growing Internet, including the following:
- Despite all short term solutions,such as subnetting, classless addressing, and NAT, address depletion is still a long term problem in Internet
- The Internet must accommodate real time audio and video transmission. This type of transmission requires minimum delay strategies & reservation of resources not provided by IPv4 design.
- The Internet must accommodate encryption & authentication of data for some applications. No encryption or authentication is provided by IPv4.
To overcome these, IPv6 also known as IPng (Internet Protocol next generation) was proposed and is now a standard.In IPv6, the Internet protocol was extensively modified to accommodate the unforeseen growth of the Internet. The format and the length of the IP addresses were changed along with the packet format. Related protocols such as ICMP were also modified. Other protocols in the network layer, such as ARP, RARP, IGMP were either deleted or included in ICMPv6 protocol. Routing protocols such as RIP and OSPF were slightly modified to accommodate these changes.
The adoption of IPv6 has been slow. The reason is that the original reason for its development, depletion of IPv4 addresses, has been slowed down because of 3 short term remedies
- Classless addressing
- Use of DCHP for dynamic address allocation
However, the fast spreading use of Internet and new services such as mobile IP, IP telephony, and IP-capable mobile telephony, may require the total replacement of IPv4 by IPv6.
Advantages os IPv6
Larger address space-An IPv6 address is 128 bit long. Compared with the 32 bit long IPv4 address, this is huge increase in address space.
Better Header format-IPv6 uses a new header format in which options are separated from the base header and inserted when needed, between the base header and the upper layer data. This simplifies and speeds up the routing process because most of the options do not need to be checked by routers.
New Options-IPv6 has new options to allow for additional functionalities.
Allowance for extension-IPv6 is designed to allow the extension of protocol if required by new technologies or applications.
Support for resource allocation-In IPv6, the type-of-service field has been removed, but mechanism called Flow label has been added to enable the source to request special handling of packet. This mechanism can be used to support traffic such as real-time audio and video.
Support for more security-The encryption and authentication options in IPv6 provide confidentiality and integrity of the packet.
Above figure shows the IPv6 header