The method of allocating address space according to need is known as CIDR. Further information about this strategy may be found in RFC 1519, Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy.

All information sent across the Internet is encapsulated into IP datagrams. At present IPv4 is used: see RIPE-405, the RIPE document for IPv4 Address Allocation and Assignment Policies.

Since RIPE NCC documents are frequently updated, the status of this document can be checked at: 
http://www.ripe.net/ripe/docs/titletoc.html.