Address Resolution Protocol (ARP) A key Internet layer protocol used to obtain the physical address associated with an IP address. ARP maintains a cache of recently resolved physical-address-to-IP-address pairs.
Class A, B, C, D, and E A classification system for IP addresses. The network class determines how the address is subdivided into a network ID and host ID.
host ID A portion of the IP address that refers to a node on the network. Each node within a network should have an IP address that contains a unique host ID.
Internet Control Message Protocol (ICMP) A key Internet layer protocol used by routers to send messages that inform the source IP of routing problems. Also used by the ping command to determine the status of other hosts on the network.
Internet Protocol (IP) A key Internet layer protocol used for addressing, delivering, and routing datagrams.
multicast Allows datagrams to be delivered to a group of hosts simultaneously.
network ID A portion of the IP address that identifies the network. All computers on a network should contain an IP address with the same network ID. Note that in this case a network is a physical subdivision of some larger internetwork (refer to Figure 4.2).
Reverse Address Resolution Protocol A TCP/IP protocol that returns an IP address if given a physical address. This protocol is typically used by a diskless workstation that has a remote boot PROM installed in its network adapter.
