Ethernet Standards
Unit: 2 Lesson: 1 aliases:
- IEEE 802.3
the IEEE defines 802.3 standards for ethernet cables
Official documentation for the 802.3 standards as defined by the IEEE can be found here.
The 802.3 standards are in common use in both LANs and WANs. They ensure that hardware devices meet the minimum bandwidth requirements for user applications. 802.3 standards are organized using a three-part naming convention:
- Example:
xBASE-y - where $x$ is the bitrate in Mbps
- where $BASE$ represents either baseband or broadband (most use baseband)
- where $y$ is the media type designator (e.g.
-Tfor twisted pair copper cabling).
Using this three-part naming convention, 10BASE-T denotes an early implementation of Ethernet that works at 10 Mbps using twisted pair cabling.
Media Access Control
This refers to the methods a network technology uses to detect when nodes are allowed to send and receive messages on a shared link, and how to resolve issues that arise when using shared links, like two nodes sending data simultaneously.
Ethernet uses a contention-based MAC system. All nodes on the network that are connected to the same media (e.g. a bus topology or Ethernet hub) are said to be on the same collision domain. Should two nodes attempt to send data at the same time, they collide, and neither packets reach their destination.
Ethernet uses a governing protocol called Carrier Sense Multiple Access w/ Collision Detection (CSMA/CD), which forces nodes to wait a random amount of time (called backoff) before resending their data. This means that with CSMA/CD, only half-duplex transmission is possible (a node can only receive or transmit data at once, but not at the same time).
Raw Lesson Content: In the 10BASE-T star wiring physical topology, each node is cabled to an Ethernet hub. The hub repeats incoming signals to each connected node. Consequently, every host connected to the same hub is within the same collision domain. However, this 10BASE-T physical topology dates from 1990. You are very unlikely to find it deployed in a modern network.
100BASE-TX (Fast Ethernet)
100BASE-TX is the 802.3 standard called Fast Ethernet. It's a legacy implementation that was developed as the common switch from hubs to switches were being made, using hubs. It also uses the CSMA/CD protocol but with higher frequency signaling and better data encoding.
At that time, switches were preferred for modern networks since the contention-based access method wasn't very scalable. Each LAN port on the switch was considered a separate collision domain, allowing for full-duplex transmission using the full 100Mbps bandwidth supported by the Cat-5 (minimum) twisted pair cable link.
Autonegotiation of bandwidth speed and transmission types are supported using 16-bit data packets called Fast Link Pulses. Nodes that don't support autonegotiation can do the same thing using Normal Link Pulses.
Fast Ethernet is not in common deployment in modern computer networks, but may need maintenance in legally installations.
Gigabit Ethernet
These versions of Ethernet measure bandwidth in units of 1 Gbps, or 1,000 Mbps. They also require at least Cat 5 cabling, but it doesn't support network hubs; it only supports switches.
Gigabit Ethernet is the standard for modern access networks (networks used to connect client nodes to a local network), and the network admin gets to choose between fiber optic cabling and normal twisted-pair copper cabling. Fiber optic provides better speeds and future-proofing, but copper cabling is more common in NICs.
10 Gigabit Ethernet is exactly what it sounds like, a 10x improvement in bandwidth over normal Ethernet. However, a Gigabit Ethernet implementation is more expensive to setup and can only run over shorter distances using higher-spec unshielded twisted-pair cabling.
| Specification | Cable Type | Max Distance |
|---|---|---|
| 10GBASE-T | Cat-6 (Unshielded) Cat 6A (Unshielded) Cat-7 (Shielded) |
180ft 328ft 328ft |
| 40GBASE-T | Cat-8 (Shielded) | 100ft |
Fiber Ethernet
Fiber optic cabling uses infrared light signals to transmit data, and isn't susceptible to interference and attenuation. It also better supports higher bandwidth over longer distances. It's divided into two modes:
- single mode (SMF)
- multimode (MMF) -> split into optical mode designations
- OM1 through OM4
The 802.3 standards denote Ethernet over Fiber using cable for 100 Mbps, 1 Gbps, 10 Gbps, and 40 Gbps. There are variants for long wavelength optics (used for long-distance transmission) and short wavelength optics. They're often implemented in server interconnections, network backbones, storage area networks, and more.
| Specification | Optics | Cable | Max Distance | Connectors |
|---|---|---|---|---|
| 100BASE-FX | 1300 nm | MMF (OM1) | 4 km | ST, SC, MT-RJ |
| 100BASE-SX | 850 nm | MMF (OM1, OM2) | 300 m | ST, SC, LC |
| 1GBASE-SX | 850 nm | MMF (OM1) MMF (OM2, OM3) |
275 m 550 m |
ST, SC, LC, MT-RJ |
| 10GBASE-LX | 1300 nm 1310 nm |
MMF (OM1, OM2, OM3) SMF (OS1, OS2) |
550 m 5 km |
SC, LC |
| 10GBASE- SR | 850 nm | MMF (OM1) MMF (OM2) MMF (OM3) MMF (OM4) |
33 m 82 m 300 m 400 m |
SC, LC |
| 10GBASE-LR | 1310 nm | SMF (OS1, OS2) | 10 km | SC, LC |
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