Introduced in 1973 by Robert Metcalfe in his PhD thesis. Named after ether the imaginary substance. Became the IEEE 802.3 Standard. Used in all 3 types of networks.
Dominant in the industry because:
- cheap
- simple (compared to token LANs, ATMs)
- good performance (10Mbps - 10Gbps)
Frame structure
Maximum 1518 bytes, excluding preamble.
| Preamble (64 bits) | Dest Addr (48 bits) | Source Addr (48 bits) | Type/Length (16 bits) | Data (46–1500 bytes) | FCS/CRC (32 bits) |
Preamble
56 bits alternating 1s and 0s, followed by SFD (Start Frame Delimiter): 8 bits 10101011. Used to synchronize receiver and sender clock rates.
Address
6 byte source and destination MAC addresses.
Type/Length
Value ≤1518 indicates frame length. Value >1518 indicates higher-layer protocol number assigned by IEEE.
Examples: IP, Novell IPX, AppleTalk.
CRC
To check if there are any errors with the frame. If so, the frame is discarded.