RARP (Reverse Address Resolution Protocol) is a protocol that can be used to translate a physical address, such as an Ethernet address, into an IP address. RARP is commonly used by diskless workstations, which often only know their hardware interface addresses when booted. They must discover their IP addresses from an external source, such as a RARP server. In this case, the host broadcasts its physical address and a RARP server replies with the host's IP address.

On the other hand, ARP (Address Resolution Protocol) is a network layer protocol used to convert an IP address into a physical address, such as an Ethernet address. A host wishing to obtain a physical address broadcasts an ARP request onto the network. The host on the network that has the IP address in the request then replies with its physical hardware address.

On the other hand, ICMP (Internet Control Message Protocol) is a message control and error-reporting protocol that uses IP datagrams. In contrast, SLIP and PPP are two communication protocols which allow a computer connected to a server via a serial line (such as a modem) to become a actual node on the internet.

References: http://en.wikipedia.org/wiki/RARP
References: http://en.wikipedia.org/wiki/Address_Resolution_Protocol
References: http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ppp.htm