IP ” The Internet Protocol which has two main functions:
The delivery of datagrams across the network. The delivery mechanism is connectionless because there is no direct connection made between the sender and the receiver.
The splitting up of application data into smaller units, based on the maximum transfer unit (MTU) of the network interface, to fit into an Ethernet II frame. This is known as fragmentation . IP also handles the reassembly of these fragments , after they have been transmitted across the network, in ethernet frames .
IGMP ” The Internet Group Management Protocol, which enables a computer to advertise its multicast group membership to routers on the network.
ICMP ” The Internet Control Message Protocol, an integral part of IP that is used to send error and control messages to other hosts on the network. ICMP communicates using IP and is often used as an invaluable means of diagnosing network problems.
Some of the more common ICMP messages include:
Echo request ” The request sent by the ping command.
Echo reply ” The reply from a ping command.
Destination unreachable ” No route to the specified destination host (or port) can be found.
Network unreachable ” No route to the specified network can be found.
Redirect ” The specified route cannot find the destination, but another route already knows how to get to the destination.
Time Exceeded ” A response has not been received within a specified time.
