Ethernet Message Formats

The Ethernet data format is defined by RFC 894 and 1042. The addresses specified in the Ethernet protocol are 48 bit addresses.

The types of data passed in the type field are as follows:

1. 0800 IP Datagram

2. 0806 ARP request/reply

3. 8035 RARP request/reply

There is a maximum size of each data packet for the Ethernet protocol. This size is called the maximum transmission unit (MTU). What this means is that sometimes packets may be broken up as they are passed through networks with MTUs of various sizes. SLIP and PPP protocols will normally have a smaller MTU value than Ethernet. This document does not describe serial line interface protocol (SLIP) or point to point protocol (PPP) encapsulation.