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Theory of Computation


Network is the interconnection of a set of devices capable of communication.
There may be 2 kinds of devices in the network
1. Host:- also called end system. (desktop, laptop, cell phone)
2. Connecting Devices:- connects to other devices(modem, router, switch) Network Criteria
1. Performance(evaluated by throughput and delay)
2. Reliability(evaluated by frequency of failure)
3. Scalability(Adding processing capacity)
4. Security(protecting data from unauthorized access)

Application of Computer Networks
1. Business Application
a) Resource Sharing
b) High Reliability
c) Saving Money
2. Home Application
a) Access to Remote Information(WWW)
b) Person to Person communication
c) Interactive Entertainment(Live TV, Games)

• Allows File Sharing/ Resource Sharing
• Inexpensive System
• Flexible to be Used
• Increase in Storage Capacity of the Software

• Security Difficulties(Hacking)
• Presence of Computer Viruses and Other Malwares

Network Models
• There are several classification for networks
• Classification based on Scale(size)
• Classification based on Topology
• Classification based on Architecture

Network Models : Based on Scale

• According to the scale(size) of the networks is classified into following
1. PAN (Personal Area Network)
2. LAN (Local Area Network)
3. CAN (Campus Area Network)
4. MAN (Metropolitan Area Network)
5. DAN (Desert Area Network)
6. CAN* (Country Area Network)
7. WAN (Wide Area Network)
8. GAN (Global Area Network)

Personal Area Network(PAN)
• Used for data transmission among devices such as computers, mobile phones, PDA etc.
• Within few meters like 10 meters only
• Medium : Bluetooth, Infrared
• Only very few connections will be available

Local Area Network(LAN)
• It is a computer network that spans a relatively small area
• Most LANs are confined to a single building or group of buildings
• One LAN can be connected to other LANs over any distance via telephone lines and radio waves (WAN)
• Medium: optical fibers, coaxial cables, twisted pair, wireless.
• Low latency (except in high traffic periods).
• High speed networks (0.2 Mb/sec to 1Gb/sec).
• Speeds adequate for most distributed systems

Campus Area Network(CAN)
• Computer network that links the buildings and consists of two or more local area networks (LANs) within the limited geographical area
• It can be the college campus, enterprise campus, office buildings, military base, industrial complex
• CAN is one of the type of MAN (Metropolitan Area Network) on the area smaller than MAN
• The Campus networks usually use the LAN technologies, such as Ethernet, Token Ring, Fibber Distributed Data Interface (FDDI), Fast Ethernet, Gigabit Ethernet, Asynchronous Transfer Mode (ATM)

Metropolitan Area Network(MAN)
• Metropolitan Area Network, are data networks designed for a town In terms of geographic breadth
• MANs are larger than local area networks (LANs), but smaller than wide-area networks s)
• MANs are usually characterized by very high-speed connections using fiber optical cable or other digital media

• Generally covers towns and cities (50 kms)
• Medium: optical fibers, cables.
• Data rates adequate for distributed computing applications.

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