The ISO/OSI model network layer, sometimes called the Internet layer, defines and handles the routing of datagrams. A datagram is a self-contained, independent packet, carrying sufficient data to be routed from source to destination without relying on exchanges between the source and destination computer and the transporting network. TCP/IP protocols residing in the network layer are: the Internet Protocol (IP), the Internet Control Message Protocol (ICMP), the Internet Group Membership Protocol (IGMP), and the Address Resolution Protocol (ARP).