Computer Networks An Introduction Networks • Network is defined as: A group of two or more computer systems linked together Topologies • local-area networks (LANs) : The computers are geographically close together (that is, in the same building). • wide-area networks (WANs) : The computers are farther apart and are connected by telephone lines or radio waves. • metropolitan-area networks MANs): A data network designed for a town or city. • In addition to these types, the following characteristics are also used to categorize different types of networks: • topology : The geometric arrangement of a computer system. Common topologies include a bus, star, and ring. See the Network topology diagrams in the Quick Reference section of Webopedia. • protocol : The protocol defines a common set of rules and signals that computers on the network use to communicate. One of the most popular protocols for LANs is called Ethernet. Another popular LAN protocol for PCs is the IBM token-ring network . • architecture : Networks can be broadly classified as using either a peer-to-peer or client/server architecture. Peer to Peer Network Ethernet Packets • Think of a packet as a suitcase, tagged to travel to a different city, moving along a conveyor belt in an airport: In addition to the data itself, each packet carries a destination address and your computer's "home" address. Network Equipment • Inside the LAN, packets flow along wires; the arrangement of the wires and connected computers is called the topology of the network. Though the Ethernet specification accounts for many topologies, the most popular configuration is called the star topology. In this kind of network, each computer (or node) connects directly to a centralized device (or hub). Hubs receive packets from one node and distribute them to other nodes. Passive hubs simply pass every incoming packet out to every connected node; switched hubs send packets to only the node to which the packet is addressed. Hubs Switches Cable that carries the signal • • • • • CAT3- 10 MBPS CAT5- 100 MBPS CAT5E- 1000 MBPS CAT6- 10 gig Fiber- No Maximum found yet, they have pushed over a Terabyte in one second over single strand fiber.