Computer Networks: Lec 9
Terms
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- What are computer Networks used for?
- Used to link computers locally or to the internet
- What are four types of network media?
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Twisted-Pair Wire
Coaxial Cable
Fiber-Optic Cable
Wireless Links - What are Twisted-Pair Wires?
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-was orginally standard telephone wire
-consited of two copper strands, individually wrapped in plastic, and then twisteed together, and bound together in another layer of plastic insulation
-able to carry signals up to 100Mbps
-does not protect data from electromagnetic interference - What are Coaxial Cables?
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-used for cable TV
-contains two conductors: one is a single wire int he centre of the cable, and the other wire is a wiremesh shield that surrounds the central wire, with an insulator in between.
-able to carry more data than older twisted-pair wiring
-wire mesh shields against interference
-can carry data up to 10 mbps (slow compared to newer twistedpair and fiber-optic wiring) - What are Fiber-optic Cables?
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-think strand of glass that transmit pulsating beams of light
-light is carried from one end to the other
- a disadvantage is that it cannot turn sharp corners
- transfer rate is up to 500 Mbps
- not affected by electromagnetic interference - What are three wireless links?
- Infrared, radio waves, communications satelites
- What are infrared light waves used for?
- Used to transmit data a few metres -> wireless keyboards, mice, printers
- What are Radio Waves used for?
- companies can transmit inventory data from each store to a central computer
- what are communications satellites used for?
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-used when data must be transported thousands of miles
-large businesses, universities, and governments use for data communication - what is a computer network?
- defined as a way to connect computers together so that they are aware of each other and pool resources together
- what is a network interface card?
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cards used to connect various computers in a network
-fits into expansion slot - what is a router (hub)?
- a common point of connection for computers and devices in a network
- what are bridges and gateways?
- hardware devices that can pass messages between networks
- what are three networking advantages?
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1. sharing peripheral devices (hardware)
2. Simultaneous access and easier backup (software)
3. Communication (people) - Explain why sharing peripheral devices is an advantage
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-can share infrequently used devices (scanners, cd writers, back up devices)
-allows for jusitication of the cost of expensive devices (color laser printer)
- sharing is easy within a network - Explain why why Simultaneous access and easier back up is an advantage
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-saves money by using networked version of software (saves time and storage)
-ensures data integrity
-backing up data is easier - Explain why Communication is an advantage.
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-email
-effient and inexpensive
-real time - What are some types of networks?
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-Local Area network (LAN)
-Metropolitan Area Network (MAN)
-Wide Area Network (WAN)
-Client-Server Relationship
-Peer-to-Peercomputing - What are LANs?
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Local Area Networks are:
-a network of computers that are relatively close to each ther and connected by a contiguous wire
-usually within a single room, building, or group of adjacent buildings
-can share hardware and software - What are WANS?
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wide area networks are:
-compromised of two ore more lans connected over a wider area
-may connect a number of lans in several different cities
-LANS can be connected using fiber-optic backbones, or satellite uplinks and downlinks - Client-Server Relationships?
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generally, there is a server node that is used to satisfy the requests of each of the other notes in the network. the server is designated as a file server, compute server, or databse server
-in a database network, the databse server program runs one note in the network, the other noteds send requests to the server which sends data back as requested - What are four types of Network topologies?
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1. Linear Bus
2. Star
3. Ring
4. Hybrid topologies - What is a linear bus topology?
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-network nods send data along a common corridor
-if a collision happens, the node waits a small, random amount of time before retransmission - What is a Star topology?
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-nodes are arranged around a central hub (precents collision by acting as a traffic cop) data packets are routed through the central hub to destination
-if hub goes down, network goes down too - what is a ring topology?
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-nodes are connected in a circular chain
- each node examines data that is sent through the rin, but only accepts data that is addressed to it
- no danger of collision
- if one node goes down, the whole network goes down - what is a hybrid topology?
- - the linear bus, star, and ring can be combined to make a hybrid network
- What are network protocols?
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-set of rules or language that is used to communicate data
-ethernet is most common network protocol
-there is also Token ring and ARCNET