on IP: IPv4 and IPv6

IP is the main protocol at the network layer of the Internet. Essentially, every data sent by any top level layer i.e. transport and application layer, gets sent as IP datagrams over the Internet. IP datagrams is the building block for internetwork communications provided by IP. IP is meant to be a best effort protocol for sending data over a network, hence it is inherently unreliable. An advantage of this particular design decision is that implementation of IP in network interfaces and routers is relatively simple. Moreover, IP is also connectionless, meaning that IP does not maintain any state information of the datagrams coming its way. Each datagram is handled independently from one another. Datagrams of the same message gets delivered to its destination on possibly many different paths and may arrive at its destination out of order [1]. Hence, a protocol like TCP is needed on top of IP to provide a reliable service needed by most Internet applications.

An IP address identifies uniquely each device i.e. hosts, routers, connected to or in the Internet. IP uses a rather simple and intuitive mechanism in routing datagrams from a source to its destination. Routing is done on a hop-by-hop basis. A routing table is maintained by hosts and routers which they use in forwarding a datagram to the next-hop router or network interface indicated in the routing table entry associated with the datagram’s destination IP address. Using ICMP, a router can build its routing table through advertisement and solicitation messages from other routers [1].

The current widely deployed version of IP, IPv4, uses 32-bit IP addresses amounting to approximately 4.3 billion addresses. With the rapid growth in the deployment of applications, services, hosts, etc. on the Internet, exhaustion of available addresses in IPv4 seems inevitable. As an answer to this likely possibility, the Internet Engineering Task Force developed IPv6, which offers a much larger address space, to succeed IPv4 [3]. IPv6 uses a 128-bit addressing scheme allowing about 2¹²⁸ unique IP addresses. Aside from having a much larger address space and changes in the IP datagram format, other changes were incorporated to IPv6 which include among others: IMCPv6 for automatic host configuration upon connection to a IPv6 network and network level security through mandatory IPSec implementation [2]. Initial deployment of the service has been performed in countries like the USA, CANADA, JAPAN, and CHINA with JAPAN enjoying full government support while CHINA showcased it in the 2008 Beijing Summer Olympics.

References:

[1] Stevens ,W. R. (1993). Internet Protocol. In B. Kernighan (Ed.). TCP/IP Illustrated Volume 1 (). Addison Wesley.

[2] Das, K. IPv6 – The Next Generation Internet. IPv6.com [@http://ipv6.com/articles/general/ipv6-the-next-generation-internet.htm]

[3] IPv6. Wikipedia. [@http://en.wikipedia.org/wiki/IPv6]