Download Computer Network

Computer Network
Objectives
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Students will get the basic concept of Networking
They will capable to identify the type of network
They can select the transmission media depending upon the layout of site
They will capable to select the topology depending upon the layout.
They will able to understand about the different network protocols
They will get the knowledge of different switching techniques.
Students will know the pros and cons of peer to peer and server dedicated
network
 They will familiar with different networking devices.
 Students will get the knowledge of wireless networking,
Definition ****Network is a connection between two or more then two computers
which are together to share resources like CD-ROM, Printer etc., to exchange files and to
communicate with each others. Computer can be connected using cables, microwave,
satellite and infrared rays etc.
Type of Network
LAN (Local Area Network)
MAN (Metropolitan Area Network)
WAN (Wide Area Network)
LAN: This network is within a very limited area like an office building, a school, or a home. It
is simpler and cheaper than other network. In a typical LAN there is a server which
consist additional software and hardware. A LAN is useful for sharing resources like
files, printers, games or other applications.
Most local area networks are built with relatively inexpensive hardware such as Ethernet
cables, network adapters, and hubs. Wireless LAN and other more advanced LAN
hardware options also exist.
Specialized operating system software may be used to configure a local area network. For
example, Microsoft Windows provide a software package called Internet Connection
Sharing (ICS) that supports controlled access to LAN resources.
File Server
Node 1
Node 2
Printer
Node 3
Node 4
 MAN: - Metropolitan Area Network extended up to a city or a larger geographical area.
Through the MAN network different network can be connected. In this network mostly
Brides, repeaters, routers are used to connect the computers.
City
Network
 WAN: - It is the network that is extended to a large geographical area like one country
to another country. WANs often connect multiple smaller networks, such as local area
networks (LANs) or metropolitan area networks (MANs). Communication is done
through the satellite. It also uses routers/gateways.
Source:
http://www.tele-strategy.com/clientlogo/479a3979d66a4wide_area_network.gif
WANs generally utilize different and much more expensive networking equipment than
do LANs. Key technologies often found in WANs include SONET, Frame Relay, and
ATM.
The Difference between LAN and WAN
LAN
1.0-2 KM
2.0-200 computer can be connected.
3.1-1000 mbps
4.Simple routing
5.Bridge/ repeaters/ hub
6.1-100 ms delays
1.
2.
3.
4.
5.
6.
WAN
100 Km or more
500 or more computer can be connected.
1-1000 mbps
Complex
Gateway/ router
100-ms-100s delays
Advantage of Network
a) Speed
b) Cost
c) Security
d) Centralized software Management
e) Resources sharing
f) Communication
g) Flexible Access
h) Work group computing
Disadvantage of Network
a) Expensive to install
b) Requires administrative time
c) File server may fail
d) Cables may brake
Transmission Media
The transmission of different data signals between two or more than two
computer from one location to another location to share different resources is termed as
transmission media.
Transmission Media
Wireless Media
Micro Wave
Satellite
Mire Media
Twisted pair
Coaxial Cable
Fiber Optic
Transponder
…………………….
The types of Cabling
UTP
1. Twisted Pair
STP
2. Coaxial Cable
3. Fiber Optic
1) Twisted Pair
Twisted pair cable has fore pair of twisted cables.
The Features of twisted Cables
 Each pair is twisted with each other to eliminate interference.
 Tighter the twisting, grater the transmission rate.
 There are five categories of twisted pair specifies by EIA/TIA
Category 1: Voice only
Category 1: Data up to 4 mbps
Category 1: Data up to 10 mbps
Category 1: Data up to 20 mbps
Category 1: Data up to 100 mbps
In that category 3 & 4 are widely used.
 The twisted pair cable is connected with the help of RJ-45 connector.
The Difference between UTP & STP
UTP
- Outer layer is thin.
- Can interference by outer data signals.
- Can not carry the data signal for long
distance.
- It is not widely used as STP
2) Coaxial cable (coax)
STP
- Outer layer is thick.
- Can not interference by outer data signals.
- Can carry the data signal for long distance.
- It is more reliable than UTP so widely used.
- It is highly resist interference.
- It supports greater cable length.
Thin coax: 10 base2
(10 mbps up to 200m)
Types
Thick coax: 10 bases5
(10 mbps up to 500m)
(Extras protective layer to keep moisture away from the centre conductor)
Disadvantages of Coaxial Cable
 Difficult to install
 It doesn’t bend
Connector: BNC connector.
3) Optical Fiber
Optical fibers cabling consists a center a glass core which is surrounded by
several layers of protective materials optical fiber cable transmits light signals rather than
electronic signals such that electronic interference is highly eliminated.
Fig: - Optical Fiber
Fiber optical cable has the ability to transmit signals over much longer distance
than coaxial and twisted pair cable this cable has the capability to carry information at
greater speeds the cables used for services like video conference and interactive services
the cost of the fiber optical is higher than others cable is difficult to install and modify.
This cable is connected with the help of S-T connector.
Networking Topologies
The pattern of inter connection of computers in a network is called topology.
According with dictionary “configuration formed by connections” is called topology.
The types of Networking Topologies
Bus topology or linear topology
Star topology
Ring topology
Tree topology
Mesh topology
1) Bus Topology
A bus topology connects each computer to a segment called trunk.
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Coaxial cables are mostly used.
Terminator absorbs the signals, so it doesn’t reflect back across the bus.
Signals are broadcast to all stations.
CSMA/CD (carries sense multiple across / collision detection) access method is
used.
Advantage of bus topology
 Easy to implement & extend.
 Well suited for temporary n/w.
 Typically the cheapest toplogy to implement.
 Failure of one station (node) doesn’t affect other.
Disadvantages of Bus Topology
 Difficult to diagnosis the error.
 Limited cable length & number of nods.
 A cable break can disable the entire n/w.
 Maintenance costs may be higher.
2) Star topology
- All stations or nods are connected to the central hub
- Adding & removing computers is easy task
- Twisted pair cable is commonly used
Advantage of star topology
 Easy to add new stations
 Easy to monitor & troubleshoot
 Can accommodate different wiring
Disadvantage of star topology
 Failure of hub disturbs all stations
 More cable required
3) Ring Topology
1
4
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3
2
- Stations are connected serially.
- No terminated ends of cables.
- MAU (Multi station Access Unit) is used as control device.
- Token is used to transmit data.
- Twisted pair or optical fiber is used as a cable.
Advantage of Ring Topology
 Growth of system has minimal impact on performance.
 All stations have equal access.
Disadvantage of Ring Topology
 Expensive
 Failure of a computer affects others.
 Complex.
4) Tree Topology
- Combination of star & bus topology.
- Allow expansion of the network.
Advantages of Tree Topology
 Point to point wiring for individual segment.
 Supported by several network & s/w.
Disadvantages of Tree Topology
 It the backbone is break, the entine segement goes down
 More difficult to configures.
5) Mesh Topology
Each computer is connected to all other computers such that more cable is required.
Advantages of Mesh Topology
 Direct Connection between any two computers.
 Data transmission is fast
 This network more reliable.
Disadvantages Mesh Topology
 More Cables are required.
 Wiring is complex.
 Expensive
Protocol
The protocol is the set of rules that govern the communication between devices
in a network . The set of rules include. Access method, Topology, Cables and speed.
These are different types of protocol which includes. They are highlighted below: Ethernet
 Local Palk
 Token Ring
 FDDI
 ATM
 Ethernet
Access method=CSMALCD
Topologies: Bus, star, ring
Cables: Twisted Pair, Coaxial, Fiber optic
Speed: 10 Mbps (Megabit per second)
 Local Palk
Access method: CSMA/CD
Topologies: Bus, star, ring
Cables: Twisted Pair
Speed: 230 kbps
 Token Ring
Access method: Token passing
Topologies: Ring
Speed: 4 Mbps to 16 Mbps
 FODI (Fiber Distributed Data Interference)
Access method: Token Passing
Topologies: Ring
Cables: optical Fiber
Speed: 100 Mbps
 ATM (asynchronous Transfer Mode)
Access method: CSMA/ CD
Topologies: Ring
Cables: Optical Fiber / twisted Pair
Speed: 155 Mbps $ higher
OSI / ISO Model
[
Open system inter connection (OSI) protocol is developed by international standard
organization (ISO) .this protocol describe flow of data on a computer network.
 In OSI model defines a “layered” architecture in the term of a protocol stack.
 These are specific discrete functions that take place at each layers of the protocol
stake with lower layer communicate on the network; information is sent down
through the protocol stack of one system; over the cable layer on the other system.
OSI model consists seven layers, which are follows :
(a)
(b)
(c)
(d)
(e)
(f)
(g)
Physical layers
Data link layers
Network layers
Transport layers
Session layers
Present anion layers
Application layers
(a) Physical layers
 Establishes the physical characteristic of the network c types of cable, connectors
length)
 Also defines electricity characteristic of signals to transmit data. The physical
layers transmit binary data as electricity or optical signal.
(b) Data link layers
 Converts frames in to bits in send side and bits in to frame in to receive side .
 Performs error checking.
 Resends acknowledgement (NIC card)
(c) Network layers
 Concerned with addressing & routing.
 Logical address are converted to physical add
 Traffic control.
 IP / IPX
(d) transport layer
 Responsible for flow control & ensuring messages are delivered or not.
 Error handling.
 TCP, UDP protocols are used.
(e) session layer
 Establish / maintain / terminate a connection.
 Managing session means involves synchronization of user tasks & dialog control.
 Synchronization involves the use of check points in the data stream.
 Security function takes place at this layer.
 Win sock & net BIOS are used in this layer.
(f) presentation layer
 Responsible for data translation, compression, de compression and encryption.
 Common protocols used in this layer are SMB, NCP and NFS.
(g) Application layer
 User interface to network services such as file transfer / data base access.
 RPC is used.
Switching techniques
In large network, these are multiple paths to connect sinter & receive.
Switching techniques are used to switch data to the receives selecting path (s). The most
common switching techniques are:
(1) circuit switching
(2) packet switching
1. Circuit switching
Circuit switching is a techniques that directly connect the sender & the receives in
the broken path. In these switching techniques, once connection is established. A
dedicated path exists between both ends until the connection is terminated.
Advantages of circuit switching
 The communication channel (once established) is detailed.
Disadvantages of circuit switching
 Possible long wait to establish a connection.
 More expensive then other switching techniques.
 Inefficient use of communication channel.
2. Packet switching
In packet switching a manage is broken in to small parts called
packets. Each packet is tagged with appropriate source and destination address. In these
techniques, packet can be stored in main memory instead of disk; therefore access delay
& cost are minimized. Transmission nodes are also optimized.
Advantage of packet switching
 Packet switching is cost effective because switching devices don’t need massive
amount of secondary storage.
 Packet switching offers improved delay characteristics.
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Packets can be retransmitted if these are any problem.
Packet switching maximizes the link efficiency.
Disadvantage of pocket switching
 Protocol for packet switching is complex.
 Initial high cost for implementation.
 Packet is lost; sender needs to retransmit the data.
 No dedicated path.
Net work architecture
1. Clinet Servers Model
2. Peer to peer Model
1) Client serves model of networking
Client
Request
Server
Response
Request
Client Process
Operating
System
Server Process
Response
Communicatio
n Facilities
Advantage of client server
a. Flexibility
b.Extensibility
c. Modularity
d.Simplicity
Disadvantage
a. Server may fail
b.Server is a potential bullet neck
c. Expensive
Operating
System
Communicatio
n Facilities
2) Peer to peer model of networking
File Client
Program
File Server
Program
Server or
Client
A
File Client
Program
File Server
Program
File Client
Program
B
File Client
Program
File Server
Program
File Client
Program
Z
In peer to peer model, each computer is treated as client as well as server. This
model is in expensive and simple to set up and manage but main slip side (draw back) of
this network is that it has limited extensibility.
Network Devices
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Switch
Repeater
Bridge
Router
NIC (Network Interface Card)
Switch
 It is the central connecting device, in which work station server and other device
are connected
 Switch amplify the obtained signals
 Switch memorize, the all computers connected to it
 Often used witch star & ring topology
 Also called hubs.
Bridge
 Bridge connected smaller network to form large network to form large network
 The bridge manages the traffic to the maintain performance
Repeater
 It amplifies the obtained signals
 Repeater spark network device
 This device is used when total length of network exceeds standard
 This device is used when total length of network exceeds standard
Router
 It delivers massage from one device to another
 It selects the best path to the router the message
 It prevents data collisions
NIC (network interface card)
 It is like a modem but it only understand the digital signals
(0 1 2 3 4 5) digital signals
(0 1 2 3 4 5 6 7 8 9 10) analog signals
 It has high band width for data transmission.
 NIC has a drives to operate it.
Exercises
Objective type questions