Last modified on 27 May 2009, at 12:34

Objective 2.6: Local Area Networks


Objective 2.6: Categorize LAN technology types and properties

A LAN, or Local Area Network, is a small network of computers, usually in the same building. They consist of several nodes (the PCs, or to be technical, the Network Interface Cards), all connected together using a topology and the cables that connect the nodes.

EthernetEdit

Ethernet is a family of frame-based computer networking technologies for local area networks (LANs). The name comes from the physical concept of the ether. It defines a number of wiring and signaling standards for the Physical Layer of the OSI networking model, through means of network access at the Media Access Control (MAC) /Data Link Layer, and a common addressing format.

Ethernet is standardized as IEEE 802.3. The combination of the twisted pair versions of Ethernet for connecting end systems to the network, along with the fiber optic versions for site backbones, is the most widespread wired LAN technology. It has been in use from around 1980[1] to the present, largely replacing competing LAN standards such as token ring, FDDI, and ARCNET.

Ethernet was originally based on the idea of computers communicating over a shared coaxial cable acting as a broadcast transmission medium. The methods used show some similarities to radio systems, although there are fundamental differences, such as the fact that it is much easier to detect collisions in a cable broadcast system than a radio broadcast. The common cable providing the communication channel was likened to the ether and it was from this reference that the name "Ethernet" was derived.

From this early and comparatively simple concept, Ethernet evolved into the complex networking technology that today underlies most LANs. The coaxial cable was replaced with point-to-point links connected by Ethernet hubs and/or switches to reduce installation costs, increase reliability, and enable point-to-point management and troubleshooting. StarLAN was the first step in the evolution of Ethernet from a coaxial cable bus to a hub-managed, twisted-pair network. The advent of twisted-pair wiring dramatically lowered installation costs relative to competing technologies, including the older Ethernet technologies.

Above the physical layer, Ethernet stations communicate by sending each other data packets, blocks of data that are individually sent and delivered. As with other IEEE 802 LANs, each Ethernet station is given a single 48-bit MAC address, which is used to specify both the destination and the source of each data packet. Network interface cards (NICs) or chips normally do not accept packets addressed to other Ethernet stations. Adapters generally come programmed with a globally unique address, but this can be overridden, either to avoid an address change when an adapter is replaced, or to use locally administered addresses.

Despite the significant changes in Ethernet from a thick coaxial cable bus running at 10 Mbit/s to point-to-point links running at 1 Gbit/s and beyond, all generations of Ethernet (excluding early experimental versions) share the same frame formats (and hence the same interface for higher layers), and can be readily interconnected.

Due to the ubiquity of Ethernet, the ever-decreasing cost of the hardware needed to support it, and the reduced panel space needed by twisted pair Ethernet, most manufacturers now build the functionality of an Ethernet card directly into PC motherboards, eliminating the need for installation of a separate network card.

10BaseTEdit

100BaseTXEdit

100BaseFXEdit

1000BaseTEdit

1000BaseXEdit

10GBaseTEdit

10GBaseSR/10GBaseSWEdit

"Short range"

10GBaseSW is designed to interoperate with OC-192 (Optical Carrier) SONET (Synchronous Optical Networking) equipment using a light-weight SONET frame running at 9.953 Gbit/s. It uses the same type of fiber and supports the same distances as 10GBaseSR.

  • Speed: 10 Gbit/s
  • Medium: Multimode optical fiber
  • Distance: 26 meters, 82 meters, 300 meters; depending on cable type

10GBaseLR/10GBaseLWEdit

"Long range"

10GBaseLW is designed to interoperate with OC-192 (Optical Carrier) SONET (Synchronous Optical Networking) equipment using a light-weight SONET frame running at 9.953 Gbit/s. It uses the same types of fiber and supports the same distance as 10GBaseLR.

10GBaseER/10GBaseEWEdit

"Extended range"

10GBaseEW is designed to interoperate with OC-192 (Optical Carrier) SONET (Synchronous Optical Networking) equipment using a light-weight SONET frame running at 9.953 Gbit/s. It uses the same type of fiber and supports the same distance as 10GBaseER.

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Objective 2.6: Local Area Networks
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