Since the 1980s it has been apparent that the number of available IPv4 addresses is being exhausted at a rate that was not initially anticipated in the design of the network. This was the motivation for the introduction of classful networks, for the creation of CIDR addressing, and finally for the redesign of the Internet Protocol, based on a larger address format IPv6.
Today, there are several driving forces for the acceleration of IPv4 address exhaustion
- Rapidly growing number of Internet users
- Always-on devices — ADSL modems, cable modems
- Mobile devices — laptop computers, PDAs, mobile phones
The accepted and standardized solution is the migration to IPv6. The address size in IPv6 was increased from 32 bits in IPv4 to 128 bits, providing a vastly increased address space that allows improved route aggregation across the Internet and offers large subnetwork allocations of a minimum of 264 host addresses to end-users. Migration to IPv6 is in progress but is expected to take considerable time.
Methods to mitigate the IPv4 address exhaustion are:
- Network address translation (NAT)
- Use of private networks
- Dynamic Host Configuration Protocol (DHCP)
- Name-based virtual hosting
- Tighter control by Regional Internet Registries on the allocation of addresses to Local Internet Registries
- Network renumbering to reclaim large blocks of address space allocated in the early days of the Internet
As of October 2010 predictions of exhaustion date of the unallocated IANA pool converge to between January 2011 and January 2012
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