IPv4 - Address Space Exhaustion

Address Space Exhaustion

Since the 1980s, it was apparent that the pool of available IPv4 addresses was being depleted at a rate that was not initially anticipated in the original design of the network address system. The threat of exhaustion was the motivation for remedial technologies, such as classful networks, Classless Inter-Domain Routing (CIDR) methods, and network address translation (NAT). Eventually, IPv6 was created, which has many more addresses available.

Several market forces accelerated IPv4 address exhaustion:

• Rapidly growing number of Internet users
• Always-on devices — ADSL modems, cable modems
• Mobile devices — laptop computers, PDAs, mobile phones

Some technologies mitigated IPv4 address exhaustion:

• Network address translation (NAT) is a technology that allows a private network to use one public IP address. It permits private addresses in the private network.
• Use of private networks
• Dynamic Host Configuration Protocol (DHCP)
• Name-based virtual hosting of web sites
• Tighter control by regional Internet registries over 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

The primary address pool of the Internet, maintained by IANA, was exhausted on 3 February 2011, when the last 5 blocks were allocated to the 5 RIRs. APNIC was the first RIR to exhaust its regional pool on 15 April 2011, except for a small amount of address space reserved for the transition to IPv6, which will be allocated under a much more restricted policy.

The accepted and standard solution is to use Internet Protocol Version 6. The address size was increased in IPv6 to 128 bits, providing a vastly increased address space that also 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 completion is expected to take considerable time.