LAN protocols - Ethernet

The Ethernet protocol (created in Xerox's Palo alto labs) allows creating a LAN (Local Area Network) spanning several hundred meters, that connects tens or hundreds of computers over shared media.

A shared media (named 'segment') is made of a set of cables (in a 10baseT, or coax \ network), or a set of cables connected to a passive HUB (in a 10Base2, or a UTP network). The HUB simply forwards each packet it receives via one entry, to all its exit entries.

Each Ethernet packet is 1500 bytes long. The packet is made of a header, containing source and target MAC addresses, and a data (or payload) field, containing a higher-level protocol's data.