By now it is clear to see that the business of networking is not as easy as it might first appear. Before the Internet, organizations simply connected their PCs and other devices together and that was that -- but with the advent of the Internet, suddenly careful attention had to be paid to device addresses and how they were used.
Originally, the Internet was envisaged as being for academic institutions, military and government departments. The original addressing plans could cope with those simple requirements but that was before the Internet became the e-business communications backbone that we know today. The problem is compounded by the future where there is a proliferation of mobile devices, all of which will need their own unique IP address, and the time when everything is IPed, from fridges to car and more beyond.
The growing number of Internet hosts has quickly caused a shortage in IP addresses and will eventually consume the entire address space. The theoretical address space size limitation is largely wasted due to the assignment inefficiencies that we have already covered. Furthermore, dividing the address space into Classes A, B and C contributed to the inefficiency of addresses assignment.
IPv4 is based on binary, so certain arithmetical rules must be maintained. So, you can have 8 or 16 addresses but not 10. Fortunately, the procurement departments of many organizations have yet to realize this and merrily go along buying whatever equipment they need rather than paying any attention to the binary limitations of IPv4. And if they need 10 hosts, organizations will have to maintain a 16-host subnet and lose six addresses. Although IPv4 offers around four billion addresses, there are only 240 million in practical usage.
IPv4 was released in 1980. Twenty years later, in 2000, half of the address space had been used and 74% of the addresses are used by North America. Since 2000, IT has moved quickly into new parts of the world such as India and China. The rest of the world has not stood still either as the number of Internet users increases everyday. For the Internet to work, there is a need for each user or device to have a unique identity -- and so there is a problem with IPv4.
Changing the IP addressing scheme is a matter concerning everyone that accesses the Internet and provides an ideal opportunity for providing additional functionality to the IP so that the next version is more responsive to existing and new demands. The new version of IP is often referred to as IPng; in true Star Trek style this stands for "Internet Protocol: The Next Generation" and will use a hierarchical address structure that should be large enough to meet the needs of the Internet for some time to come.
When it was first realized that something needed to be done there were several proposals for IPng. The most likely to become a standard were - Common Architecture for the Internet (CATNIP), Simple Internet Protocol Plus (SIPP) and The TCP/UDP over CLNP-Addressed Networks (TUBA) proposals. When reviewing the proposals the main criteria was - current address assignment policies should not be changed, there is no need to reclaim assigned network numbers and there is no need to renumber most of the Internet. Eventually the Simple Internet Protocol Plus Specification was selected and named IPv6 or IP Version 6.
IPv6 -- the basics?
So, what is in IPv6? The new version of IP provides far larger address spaces for Internet users with the IP address size increased from 32 bits to 128 bits. An address size of 128 bits is large enough to support a huge number of nodes even with the inefficiency of address assignment. This will allow many more nodes than is currently available today, with more levels of addressing hierarchy and simpler auto-configuration of addresses.
The IP header will be changed with some fields being removed in order to keep the overhead low, this is in spite of increasing the number of address bits. Therefore, even though the IPv6 addresses are four times longer than the IPv4 addresses, the IPv6 header is only twice the size of the IPv4 header.
IPv6 will have a new type of address -- a 'Cluster Address', which will identify topological regions. A new function in IPv6 is source routing, which together with Cluster Addressing will allow nodes to control their routing in a more precise way.
With any change to standards, the big question is just how painful the upgrade or transition will be and the good news is that the transition from IPv4 to IPv6 will be simple and flexible. The upgrade will be incremental with current IPv4 hosts and routers being upgraded to IPv6, whilst new hosts and routers can be installed independently. Backward compatibility is catered for, as existing IPv4 hosts or routers that have been upgraded can continue to use their current IPv4 addresses. The startup costs are low and minimal effort is needed to upgrade existing systems to IPv6.
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