Tech Primer
Ethernet is the protocol that controls data transmission over a Local Area Network.
Ethernet is a physical and data link layer technology for local area networks ( LANs).
The term Ethernet refers to the family of local-area network (LAN) products covered by the IEEE 802.3 standard that defines what is commonly known as the CSMA/CD protocol. Three data rates are currently defined for operation over optical fiber and twisted-pair cables:
- 10 Mbps—10Base-T Ethernet
- 100 Mbps—Fast Ethernet
- 1000 Mbps—Gigabit Ethernet
10-Gigabit Ethernet is under development.
Each device in an Ethernet network is uniquely identified by a 48-bit (6 bytes) address called Ethernet address. Ethernet address is also known as Media Access Control (MAC) address. Ethernet addresses are represented as six pairs of hexadecimal digits separated by a colon. The manufacturer buries Ethernet addresses in the network adapter. An Ethernet address of a device cannot be changed. Example: 00:60:08:11:B1: AB, 00:00:c0:5e:83:0e
Ethernet uses a protocol called CSMA/CD, this stands for Carrier Sense, Multiple Access with Collision Detection.
The CSMA/CD protocol was originally developed as a means by which two or more stations could share a common media in a switch-less environment when the protocol does not require central arbitration, access tokens, or assigned time slots to indicate when a station will be allowed to transmit. Each Ethernet MAC determines for itself when it will be allowed to send a frame.
Each must stop transmitting as soon as it has detected the collision and then must wait a quasi-random length of time (determined by a back-off algorithm) before attempting to retransmit the frame.
The Ethernet protocol allows for linear bus, star, or tree topologies. Data can be transmitted over wireless access points, twisted pair, coaxial, or fiber optic cable at a speed of 10 Mbps up to 1000 Mbps.
Other Resources
- Ethernet Article 1
- Ethernet Article 2
- Handbook
- Ethernet 802.3 standard
- Ethernet Designations/types of media segments supported by Ethernet
- Coming soon
- Ethernet - Q&A
- Basic Ethernet operation
Glossary:
| 10BASE-T | 10 Mbps Ethernet system based on Manchester signal encoding transmitted over Category 3 or better twisted-pair cable. |
| 10BASE2 | 10 Mbps Ethernet system based on Manchester signal encoding transmitted over thin coaxial cable. Also called Cheapernet or ThinNet. |
| 100BASE-T | 100 Mbps Fast Ethernet system, including both twisted-pair and fiber optic media types. |
| 100BASE-TX | Refers to any Fast Ethernet media system based on 4B/5B block encoding. Includes 100BASE-TX and 100BASE-FX media systems. |
| 802.3 | IEEE Working Group for CSMA/CD LANs (local area networks). |
| Ethernet | Originally developed by DIX, then standardized by IEEE 802.3 for local area network communication. Now it is expanded to MAN and WAN services. |
| MAC | Medium Access Control is a protocol operating at the data link layer used to manage a station’s access to the communication channel. |
| MAC Address | A unique address assigned to a station interface, identifying that station on the network. With Ethernet, this is the unique 48-bit station address. |
| PHY | Physical Layer Device. The name used for a transceiver in Fast Ethernet and Gigabit Ethernet systems. |
| RJ-45 | An 8-pin modular connector used on twisted-pair links |