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Old 27th August 2012
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jggimi jggimi is offline
More noise than signal
 
Join Date: May 2008
Location: USA
Posts: 7,977
Default Chapter 2: Layer 1: Physical layer: hubs/switches/cables/connections

There are a wide variety of physical infrastructure, for two types of network:
  1. Local Area Network (LAN) - equipment designed for high speed communication over relatively short distances, often within a building, or part of a building. The communication media may be shielded coaxial cable, unshielded twisted pair wiring, fiber optic cabling, or radio.
  2. Wide Area Network (WAN) - equipment designed for long distance communication, from across a city to across the planet. The communication media are entirely under control of telecommunications carriers and are commonly carried by fiber and satellite connections. Local service connections may be of a wide variety of methods, from low speed voice telephone lines to high speed fiber connections, or radio.
Simply put, your ISP provides you with WAN services. Your LAN interconnects your local computers and network attached peripheral devices such as printers. The device that connects your WAN to your LAN is a gateway device. It may be provided by your ISP, or you may have acquired it separately. It may be called a gateway, or a router, or a modem, or have some other name ... but the one thing they all have in common is they interconnect between a WAN and a LAN.

LANs may use radio or different types of cabling. But they have common types of equipment:

  • Bridge - a device which interconnects two different types of physical media on the same LAN.
  • Router - a device which interconnects separate LANs, or LANs and WANs, permitting the movement of information between them.
  • Switch - a device which interconnects individual point to point wiring to allow any-to-any communication.
  • Hub - interconnects wiring to broadcast data from one connection to all. Significantly less efficient than a switch, as all incoming data is broadcast to all connected end points.
  • Repeater - a device which rebroadcasts signals, lengthening the distance a LAN can reach. Most commonly deployed with WiFi infrastructures.
You'll commonly find combination devices. The typical Small Office / Home Office router is 3-in-1: combining a WiFi bridge with a twisted pair switch and a router to a WAN connection. And the WiFi bridge is also a hub, as radio traffic is shared among all wireless devices.

If the router connects directly with the WAN (such as DSL), the router is the gateway device. Instead, the router may have a small point-to-point LAN with an external gateway device.

A computer running BSD may be a router or a bridge. All it needs is two or more Network Interface Controllers (NICs).

Last edited by jggimi; 28th August 2012 at 04:06 PM.
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