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7/29/2019 Networking Essentials II Rev
1/21
COMPUTER NETWORKING
( Part-II )
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Network Types
Broadly, three types of Networks-
-LAN ( Local Area Network)
-MAN ( Metropolitan Area Network )
-WAN ( Wide Area Network )
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LOCAL AREA NETWORK(LAN)
LANs are usually confined to a Building or a set
of Buildings in a Campus.
LANs are localised & small Networks connected
with a number of Computers .
A number of LANs may be interconnected by
suitable means through Bridges, Routers etc.
LANs are usually connected through Media Cables.Wireless Links are also being used instead of
Media Cables..
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METROPOLITAN AREA
NETWORK(MAN) A MAN is normally designed to extend over a
City.
MANs are connected using Cables, Routers andGateways etc.
Cable Laying for a MAN may be costly and
problematic affairs. In such cases, the concerned
authority may take help of Telecom Service
Providers for hiring of Cables on rental basis.
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WIDE AREA
NETWORKS(WAN) Terminals of a WAN are located at different cities/towns.
A WAN may be implemented by interconnecting a
number of LANs of an organisation located at variousplaces through dedicated or dialup links.
A WAN may be a simple one if number of remote users
are few. But when a large number LANs are
interconnected and more number of users are there, the
set up may become very much complex and it may need
lot of maintenance efforts.
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A TYPICAL COMPUTER NETWORK
11.0.0.0 12.0.0.0 14.0.0.0
Server
Server
Gateway
ExecutiveEngineering Marketing
Internet
Intran
et
DMZ
Internet171.69.236.1
171.69.236.3 171.69.236.4
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TOPOLOGY OF COMPUTER
NETWORKS Topology refers to the arrangements of Computers
and associated elements in a Network.
There are two Topologies--Physical Topology
-Logical Topology
Physical Topology is concerned with the inter-connection of the H/W components of the N/W.
Logical Topology gives information about how the
Communication occurs among the N/W elements.
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PHYSICAL TOPOLOGY
There three primary categories-
-Bus Topology: Here all the Computers are
connected to a common path called Bus.-Star Topology: In this case the N/W componentsare extended from the Server through somedistribution points like Hubs/Switches.
-Ring Topology: It is the case where the N/Welements are connected one after another in theform of a Ring.
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BUS TOPOLOGY NETWORK
A B C D
4321
A sends to 4
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PHYSICAL TOPOLOGY
(Contd.)Apart from above three Topology categories,
there are some other Topology options like-
-Tree Topology which is basically acombination of Bus and Star Topologies.
-Star-Wired Ring Topology which is externallya Star Topology but from working point of viewa Ring Topology.
-Mesh Topology where each Computer hasredundant data paths to some other Computers.
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GENERAL FEATURES OF PHYSICAL
TOPOLOGIES
Bus Topology- Easy to connect terminals &needs less Cable lengths. Maintenance is
not smooth. Star Topology- Easy installation and
maintenance. It requires more cable lengthsand costlier than Bus Topology.
Ring Topology- Point to Point wiring withcomplex procedures to configure.
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LOGICAL TOPOLOGY
Logical Topologies are actually Networking Protocols
which define the rules related to the Communication
between the N/W elements of Networks.
The rules include guidelines that regulate the
following characteristics of a Network-
-Access Method
-Allowed Physical Topologies
-Types of Cablings
-Speed of Data Transfer
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COMMONLY USED
PROTOCOLS The most common protocols are-
-Ethernet
-Local talk
-Token Ring
-FDDI(Fibre Distributed Data Interface )
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ETHERNET
Developed as per IEEE standard 802.3
Works on the principle of CSMA/CD
(Carrier Sense Multiple Access / Collision Detect).
The principle is that if two Computers transmit at
the same time , Collision occurs. So a Computer
listens for sometime before transmission of data and
if the N/W is free then it transmits. Thus Collision is
avoided.
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ETHERNET (Contd.)
Ethernet uses NIC to identify the StationAddress. The NIC has 6-byte physical
address. In order to increase the speed of Ethernet
working, new standards were developed .These are termed as Fast Ethernet.
Now Ethernet working speed goes upto 100mbps.
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LOCAL TALK
A N/W protocol developed by Apple Computers, Inc.
This was meant for Macintosh Computers.
It works on CSMA/CA ( Carrier Sense MultipleAccess / Collision Avoidance )
Here a Computer signals it intents before it transmits.
It can work in Bus, Star etc. Topologies. Speed of transmission is low-230 kbps.
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TOKEN RING
In Ethernet Collision cannot be avoided totally.
So IEEE developed Token Ring according to its standard
known as 802.5
It works on round-robin fashion. Each device is given a Token for certain time and during this
period, it is to perform its job. When time out occurs, it has to
release the Token to the next device and same thing is
repeated. Once a cycle is over, then second cycle will start. It uses NIC with 6-byte station address.
Speed is possible upto 100 mbps with Copper Cables.
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FDDI
Standardised by ANSI and ITU-T.
Initial developments were aiming to overcome the
shortcomings of Ethernet and Token Ring over
Copper Cables.
It uses Fibre Optic Cables instead of Copper Cables.
The arrangements are complex and cost is more.
FDDI uses Token Ring principle for Communicatingand it uses NIC with 6-byte address.
Speed is 100 mbps and even more..
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THANKS