unicast-extensions/OVERVIEW.md

Timeline

• 1972 ARPANET rolled out
• 1981 TCP/IP rolled out
• 1992 CIDR developed The original IPv4 address space was a 32 bit "address extension" to the ARPANET address space, which only supported 256 nodes. We carved up the world into into class A, class B, class C, class D (multicast), and class E (reserved).

It seemed an eminently good division at the time. By 1989, however, it was obvious that these divisions were straining at the seams, and CIDR was developed to fix it.

• 1994 IPv6 started
• 2012 IPv6 rollout started