Introduction to Computer Networks Lecture slides ppt

Week-10
 Introduction to Computer Networks
Application of Computer Network
 Host, Terminal, Client Server Network, Peer to Peer Network
 Networking Devices (NIC (Physical Address), Modem, Hub,
Switch & Router)
 Categories of Network
 Network Topology (Bus, Star, Ring and Mesh Topology)
 Bandwidth, Broadband & Baseband Communication
 Transmission Modes (Simplex, Half Duplex, & Full Duplex)

Network
 A network is a set of devices (often referred to as nodes) connected
by communication links.
 A node can be a computer, printer, or any other device capable of
sending and/or receiving data generated by other nodes on the network.
 A group of computers and other devices joint together through some
transmission medium is called Computer Network.

The concept of connected computers sharing resources is called
Networking.
Computer network that is part of network can share the following, Data,
Messages, Graphics, Printers, Modem, Fax machine & other Hardware
resources.
Why Computer Network?
To share information or receive a service via a network, or group of
members able to communicate with each other.

Applications of Networks
Resource Sharing
Hardware (computing resources, disks, printers)
Software (application software)
Information Sharing
Easy accessibility from anywhere (files, databases)
Search Capability (WWW)
Communication
Email
Message broadcast

What do you find on a network?
The following types of nodes may be found on a data communications
system.
 Host: - A central computer which stores data and executes programs
for terminals.
 It is usually associated with minicomputers or mainframes.
 It requires a multi-tasking, multi-user operating system such as Unix.
 Terminal: - A computing device which is composed of a video screen
and a keyboard. It allows a user to communicate with a host by typing
in information or commands.
 The host communicates with the terminal by updating the CRT (video).
 Terminals cannot execute programs.

 Client
 A computer which takes advantage of the services provided by servers on
the network.
 Client also called Front End computer.
 Server
 The computer which used and provide services & resources is called
Server.
 Server is also called Back End computer.
A Network with two Clients and one Server.
What do you find on a Network? (Cont’d)

 Client Server Network
 Server based network also called client-server network, containing Client &
the server that support them.
 The Web is known as a client-server system. Your computer is the client;
the remote computers that store electronic files are the servers.
Examples include file, print or communication servers.
     

 Peer-to-Peer Network: - Peer-to-Peer or simply peer means the computer
which has both qualities as server as well as client.
 It means which both use & provide network resources.
 Peer network which have no servers & use the network to share resources
among independent peers.
 Users simply share disk space & resources, such as printers & faxes.
In a peer-to-peer system there are no fixed clients and servers.

Network Interface Card
 A computer is connected to the network cabling with a network
interface card, (also called a "NIC", "nick", or network adapter.
 Faster computers, like high-speed Pentiums, Dual Core, and Core 2
Duo or Core 2 Quad, often have 32-bit, 64-bit or PCI slots.
 These PCs require 32-bit NICs to achieve the fastest networking
speeds possible for speed-critical applications like desktop video,
multimedia, publishing, and databases.

 Physical address: - It is also known as link address.
 The physical addresses have authority over the network (LAN & WAN).
 Ethernet uses a 48-bit (6-byte) physical address written as 12 hexadecimal
digits; every byte (2 hexadecimal digits) is separated by a colon.
 The first 6 Hexa-decimal digits of a Mac address contain a manufacturer,
identification (vender code) also known as the organizationally unique
identifier (OUT). The last 6 digit are given by each vender and often the
represents the interface serial no.
 On most LAN interface card the MAC address is burned into ROM. It is
only used for LAN communication.
07:01:02:01:2C:4B
A 6-byte (12 hexadecimal digits) physical address.
Network Interface Card (Cont’d)

 Example:
 In Figure, a node with physical address 10 sends a frame to a node with
physical address 87. The two nodes are connected by a link (bus
topology LAN). As the figure shows, the computer with physical address
10 is the sender, and the computer with physical address 87 is the
receiver.
Network Interface Card (Cont’d)

 MODEM short for modulator/demodulator.
 The modem is necessary because the phone network transmits audio, not
data bits.
 The modem is for compatibility with existing equipment.
 Modulation is a prescribed method of encoding digital (or analog) signals
onto a waveform (the carrier signal).
 Once encoded, the original signal may be recovered by an inverse process
called demodulation.
MODEM

HUB
 HUB is a common connection point for devices in a network.
 The benefits of HUB used in a network is that if a cable break on a
network, the break cable node will only affected and not affect on
the rest of network.
 HUB internally uses BUS topology.
 Network can be easily expanded using Hubs.
 Active Hub: - A HUB that regenerate and retransmit signals are
called Active Hub.
 Active HUB is also called multi-port repeater.
 Active HUB requires electrical Power to run.
 Passive HUB: - A HUB that do not regenerate and do not
retransmit signals are called Passive HUB.
 Passive HUB do not require electrical power to run.

Connector RJ-45
 The standard connector for twisted pair cabling is an RJ-45
connector. This is a plastic connector that looks like a large
telephone-style connector.
 Cable used as a medium to carry the signal.
 Coaxial Cable
 Twisted-Pair Cable
 Fiber-optic Cable

Today when we speak, we are generally referring the primary
categories LAN, MAN and WAN.
The category into which a network falls is determined by
Technology,
its Size,
Standard Port & Media.
Categories of Networks

 A Local Area Network can connect many types of computing devices
together such as microcomputers, minicomputers and switches.
 A LAN is usually privately owned links the devices in a single office,
building, or campus.
 Depending on the need of organization and the type of technology used.
 A LAN can be as simple as two PCs and a printer in someone’s home
office, or it extend throughout a company and include voice, sound, and
video peripherals. Currently LAN size is limited to a few kilometers.
Ethernet, token ring
Local Area Network

 It has two main components Hardware & Software.
 Network hardware includes NIC, Hub, Switch, Medium, Connectors
(RJ-45).
 Network software includes, Protocols (TCP/IP), Network services.
 It usually uses cable (coaxial, twisted pair or fiber) but may use
radio waves, infrared or micro waves.
 It is used by a single organization.
Local Area Network (Cont’d)

 A high speed (100Mbps) network which spans city distances. or
 It may be a single network such as a cable television network, or
 It may be a means of connecting a number of LANs into a larger
network, so that resources may be shared LAN-to-LAN as well as
device-to-device. FDDI, ATM
 Many telephone companies provided a popular MAN service called
Switched Multi-megabit Data Service (SMDS). It is a service for
handling high-speed communication for metropolitan area network.
A metropolitan area network based on cable TV.
Metropolitan Area Network

 WAN: - The network between different cities, countries or in the world
using WAN standard port & routing technology is called WAN.
 A WAN is a network that covers a large geographical area using
communication channel that combines many types of media such as
telephone lines, cables & radio waves.
 The Internet is the worlds largest WAN.
 They use data lines which belong to a third party service provider such as
the telephone company.
 They require special interfaces to the data lines such as synchronous
modems & routers.
 Routing technology is a crucial component of a WAN. Routers decide how a
packet should be sent in order that it arrives at its intended destination.
Wide Area Network

Line Configuration
Line Configuration defines the attachment of communication Devices to a
link. OR
It concerned with the connection of devices to the media.

Network Topology
The network topology is the shape or the physical connectivity
Of the network.

 A bus topology is a multipoint. One long cable acts as a backbone to
link to the entire device in a network.
 In this topology all the computers are connected in a series to one
cable.
 Nodes are connected to the bus cable by drop-line and tap.
 A drop-line is a connection running b/w the device and main cable.
 A tap is a connector that either splices into the main cable to
create a contact with the metallic core.
Bus Topology

 In star topology, each device has a dedicated point-to-point link
only to the central controller, usually called HUB.
 In star topology communication with a central HUB that resend
the message either to all the computers
(in a broadcast star network) or only to the destination computer
(in a switch star network).
 The devices are not directly linked to one another. The controller
acts as an exchange, if one device want to send data to another,
it send the data to the controller, which than relays the data to
the other connected device.
Star Topology

 In ring topology, each device has a dedicated point-to-point
connection with only to the two devices on either side of it.
A signal is passed along the ring in one direction, from device to
device, until it reaches its destination.
 Each device in the ring incorporates the repeater, when a device
receives a signal intended for another device; its repeater generates
the bit and passes them along.
Ring Topology

 In mesh topology, every device has a dedicated point-to-point
link to every other device.
 The term dedicated means that link carries traffic only b/w two
devices it connects.
 So we need n (n-1) physical link, however, if physical link allow
communication in both direction (duplex mode), we can divide the no;
of links by 2.
In other words we can say that in mesh topology we need n (n-1)/2
duplex mode links.
Mesh Topology

Bandwidth, Baseband & Broadband Transmission
 Bandwidth refers to the way of allocating the capacity of
transmission media.
 The total media capacity or bandwidth can be divided into
channels.
 A channel is simply a portion of the bandwidth that can be used for
transmitting data.
 The two ways of allocating the capacity of bounded transmission
media are the following.
 Base band transmission
 These transmissions use the entire media bandwidth for a single
channel. Base band is commonly used for digital signaling. It can
also be used for analog signals. Most LANs use base band signaling.

 Broadband transmission: - These transmissions provide the ability
to divide the entire media bandwidth into multiple channels.
 Since each channel can carry a different analog signals, broad band
network support multiple simultaneous conversion over a single
transmission medium.
Baseband & Broadband Transmission (Cont’d)

Data Transmission Modes
 There are three modes of communication.
 Simplex
 In simplex transmission mode, communication can take place in only
one direction.
 It means the sender will always send & the receiver will always
receive.
 An example is TV waves, we can watch different channels on TV but
there is no need to send any type of signals from TV. Another
example is line printer.
 Half-Duplex
 A half-duplex system can transmit data in both direction, but only in
one direction at a time.
 It means that at a time one computer can only send or receive, when
one device completes a transmission, this device must “turn over” the
medium to the other device so that this second device has turn to
transmit. e.g. wireless

 Full-Duplex
 This mode allows a device to send & receive data simultaneously
is called duplex or full-duplex mode.
 This mode provides two ways to simultaneously data transfer by
providing each device with a separate communication channel.
Voice telephone is full-duplex devices and either party to a
conversation can talk at any time.
Data Transmission Modes (Cont’d)

Data Transmission Modes (Cont’d)

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Introduction to Computer Networks Lecture slides ppt