RIPv1 (Routing Information Protocol version 1)
A distance-vector routing protocol, dating from the 1980s, that has a maximum hop count of 15. These routers sent out updates every 30 seconds, causing huge network overloads. It was also limited to only working with Classful address, not recognizing CIDR subnets. Plus, it had no authorization mechanism, leaving these routers open to hackers sending false routing table information.
RIPv2 (Routing Information Protocol version 2)
The current version of this distance vector routing protocol that was adopted in 1994. It fixes many of the problems with earlier versions. It has support for CIDR addressing, updates at random intervals, and has a built-in authentication protocol. It still has the 15-hop limit and time-to-convergence problems on large WANs, so it is considered obsolete for all but small, private WANs.
BGP (Border Gateway Protocol)
A dynamic distance vector exterior routing protocol used on the internet to exchange routing info between autonomous systems, large sections of the internet.
OSPF (Open Shortest Path First)
A link-state, hierarchical routing algorithm derived from an earlier version of the IS-IS protocol, whose features include multipath routing, load balancing, and least-cost routing.
IS-IS (Intermediate System to Intermediate System)
Similar to OSPF but has been working with IPv6 from the start. Is a link-state routing protocol, and also uses the concept of areas.