A wired transmission family of technologies frequently adapted for data transfer across the internet. Exists in the physical layer of the OSI model. Has two main implementations: Fast Ethernet (obsolete) and Gigabit Ethernet (current).
Standards
Ethernet has different classifications for the cabling used, in line with that of the cable types associated with twisted pair cables. The table below summarises the main differences:
| Fast Ethernet layer | Transmission rate | Cable type | Maximum distance |
|---|---|---|---|
| 100BASE-TX | 100 Mbps | UTP (Cat 5) | 100 metres |
| 100BASE-FX | 100 Mbps | Optical fibre (multi-mode) | 400 metres (half-duplex); 2 kilometres (full duplex) |
| 1000BASE-T | 1 Gbps | UTP (Cat 5e/6) | 100 metres |
| 1000BASE-TX | 1 Gbps | UTP (Cat 6) | 100 metres |
| 1000BASE-SX | 1 Gbps | Optical fibre (multi-mode) | 550 metres |
| 1000BASE-LX | 1 Gbps | Optical fibre (both modes) | 550 metres (multi-mode); 5 kilometres (single-mode) |
Nomenclature
For each layer’s name, there is a nomenclature that the layer’s name abides to. In general, the designation has the following structure:
XXXXYYYY-ZN
where:
- XXXX refers to the transmission rate (e.g., 100, 1000, 10G)
- YYYY refers to either BASE, BROAD, or PASS where:
- BASE refers to baseband signaling;
- BROAD refers to broadband signalling; and
- PASS refers to passband signalling; and
- Z refers to either one of the following where:
- T refers to twisted pair;
- F refers to optical fibre (various wavelengths);
- S refers to optical fibre (multi-mode, 850 nm short wavelength);
- L refers to optical fibre (usually single-mode, 1300 nm long wavelength);
- T1 refers to single-pair twisted pair;
- E or Z refers to optical fibre (single-mode, 1500 nm extra long wavelength);
- B refers to optical fibre (usually single-mode, bidirectional) using WDM;
- P refers to optical fibre (passive); and
- H refers to plastic optical fibre.
- N refers to the PCS encoding method where:
- X refers to an 8b/10b or 4B5B block encoding; and
- R refers to large block encoding.
Type II Ethernet Frame
A data link protocol data unit that includes information about a particular packet. Spans between 64 and 1518 bytes. Has three primary components to it, namely the:
- MAC header spanning 14 bytes (6 + 6 + 2), including the:
- destination MAC address;
- source MAC address; and
- EtherType (used to indicate which protocol is encapsulated in the payload);
- payload spanning 46 to 1500 bytes; and
- CRC checksum spanning 4 bytes.