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Introduction to Computer Networks
Dr. Sanjay P. Ahuja, Ph.D.2010-14 FIS Distinguished Professor of
Computer ScienceSchool of Computing, UNF
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Introduction
Computer networks are used to interconnect separate, autonomous computers to be able to exchange information. E.g., the Internet.
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Computer Network vs. Distributed System
In a distributed system, the existence of multiple autonomous computers is transparent to the user.
The distributed system is a special case of a network, one whose software gives it a high degree of transparency.
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Why Networks?Resource Sharing
Reliability
Economics
Communication Medium
Interactive Entertainment / Online Gaming
Social Networks (Facebook, Twitter, Linkedin)
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Client – Server Model
The client-server model involves requests and replies.
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Classification of Interconnected Processors By Scale
Classification of interconnected processors by scale.
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Network Structure
WAN that connects three branch offices in Australia.
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Network StructureIn any network there is a collection of machines, called hosts, which run user programs (applications).
The hosts are connected by the communication subnet or subnet.
The subnet (in WANs) consists of channels and switching elements.
Channels or links are the transmission lines carrying the actual bits between machines.
Switching elements are called Packet Switching Nodes (PSNs) or routers and connect two or more channels.
Incoming data is sent on an appropriate outgoing channel by the router or PSN.
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Types of Subnets
Packet Switched or Store and Forward Subnet
A link connects a pair of nodes/routers.
WANs have S/F subnets.
Generally have irregular topologies.
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Types of Subnets
Broadcast Subnet
Most LANs are of this type.
Subnets has only one channel shared by all machines on the network.
E,g. of Broadcast Subnets:
Bus Topology (IEEE 802.3, i.e. the Ethernet)Ring Topology (IEEE 802.5, i.e. the Token Ring)Satellite or Radio Networks
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Wireless Networks
There are 3 main categories of wireless networks:
System Interconnection Networks (PANs)
Wireless LANs
Wireless WANs
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System Interconnection Network: Personal Area Network
Bluetooth PAN configuration.
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Wireless LANs
Wireless and wired LANs. (a) 802.11. (b) Switched Ethernet.