| It defines how data is formatted for transmission and how access to the physical media is controlled. | |
| It segments data from the system of the sending host and reassembles the data into a data stream on the system of the receiving host. | |
| It provides the connectivity and path selection between two host systems that may be located on geographically separated networks. | |
| It establishes, manages, and terminates sessions between two communicating hosts. |
| OSPF | |
| ARP | |
| IS-IS | |
| EIGRP | |
| RIP |
| discard frame | |
| send ICMP unreachable message to source | |
| flood packet on all ports | |
| send gratuitous ARP on all ports and wait for reply before forwarding | |
| compare destination IP address against an ACL to determine if it is permitted |