computer network basic
TRANSCRIPT
Mr Satyendra Mohan Srivastava JIT Barabanki
COMPUTER NETWORKS
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COMPUTER NETWORKS
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A network is a collection of device referred to as nodes connected via media links
A node may be a computer, joysticks, printer and other devices generated by other nodes on the network
The various links connecting the devices are known as communication channels
The main purpose of a communication system is the exchange of data or information between two parties or points
TransmitterTransmission
systemSource Receiver Destination
Source System Destination System
BASIC COMMUNICATION MODEL
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PSTNServerModemModem
Public Telephone NetworkWorkstation
ESTABLISMENT OF COMMUNICATION
BASIC COMMUNICATION MODEL
The terminology communication refers to information or data transfer mechanism via telegraphy, telephony, television and other modes
The generated information or data transfer mechanism must follow the agreement between the two parties
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COMPUTER NETWORK CRITERIA
A network must meet certain criteria. Few of them are:
Performance
a) Transit time (Time elapsed between two devices)b) Response time (Time elapsed between enquiry and response)
Reliability
Security
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OSI MODEL
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International Organization of standardization (ISO) ensure the nationwide and world wide data communication
The various standards can be accumulated into a framework. The framework designed and developed by the ISO is known as Model for Open System Interconnection (OSI)
It is usually known as OSI reference model
It is also known as ISO-OSI model due to its ability to deal with other system
The term open refers to the systems which are open for interconnection with the other systems
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OSI MODEL
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Layer 7 Application layer
Layer 6 Presentation Layer
Layer 5 Session Layer
Layer 4 Transport Layer
Layer 3 Network Layer
Layer 2 Data Link Layer
Layer 1 Physical Layer
Layer 0 Transmission media
User
A seven layer ISO-OSI reference model
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OSI MODEL
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Router Router Host A Host B
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
Presentation
Session
Transport
Network
Data Link
PhysicalPhysical Physical
Physical Physical
Physical Physical
Application protocol
Presentation protocol
Session protocol
Transport protocol
Respective layer host router protocol
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OSI MODEL
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All the application may or may not use all the seven layers
The lowest three layers are mostly used by all applications
Each layer must handle the message or data above or below it
Each layer must process the data to the next layer
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AN EXCHANGE USING OSI MODEL
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7
6
5
4
3
2
1
7
6
5
4
3
2
1
Transmission Medium
T2 T2
1110010101010101010101
H6
L7 data
L7 data
L6 data H5
L5 data H4
L4 data H3
L3 data H2
H6
L7 data
L7 data
L6 data H5
L5 data H4
L4 data H3
L3 data H2
1110010101010101010101
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PHYSICAL LAYER
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101010100101
L2 data
Physical layer
Physical layer
101010100101
L2 data
From data link layer To data link layer
Transmission Medium
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PHYSICAL LAYER
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The physical layer allows the transfer of data from one computer to another
The bits on the physical layer is only concerned with reception and transmission of signals
The electrical and physical signals are usually represented by either 1 or 0
It defines the type of encoding, transmission rate (the no. of bits transmitted per second) and synchronization of transmitter and receiver
It determine the type of topologies, network connection type (point to point connection or multipoint connection), bandwidth and multiplexing among devices
It also determines the characteristics and transmission mode between two devices
The various connecting device associated at the physical layer are hubs, couplers, cables, connectors, repeater, receivers, transmitters and multiplexers
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DATA LINK LAYER
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From network layer
Data link layer
L3 data
L3 data T2 H2
10101100011101
Frame Frame
L3 data
L3 data T2 H2
10101100011101
Data link layer
To network layer
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DATA LINK LAYER
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Data link layer is responsible for node to node delivery of the data
The reliability of data packet is major focus point
The various data from network layer in the form of packets are transform into frames
The various frames at the Data link layer is provided to the physical layer
Frames are usually manageable data units received from network layer
It add header with the frame to define the address of the receiver or the physical address of the sender
It provide the mechanism for flow, error and access control
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NETWORK LAYER
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From Transport layer
Network layer
L4 data
L4 data H3 Packet
L3 data
To data link layer
From Transport layer
Network layer
L4 data
L4 data H3 Packet
L3 data
To data link layer
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NETWORK LAYER
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The function of network layer is ensure the delivery of packets from source node to the destination node across networks
Network layer doesn’t play an important role when the system are connected via the same links
The network layer transform the logical network address into the physical machine address
It also provide the priorities and routes to the messages
It is mainly focused on the circuits or packet switching (messages)
It mainly provide the various communication services like network layer error control, flow control and packet sequence control
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TRANSPORT LAYER
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From session layer
To network layer
L4 data
Transport layer
L5 data
H4 H4 H4
Packets
L4 data
L4 data From network layer
L4 data
Transport layer
L5 data
H4 H4 H4
Packets
L4 data
L4 data
To session layer
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TRANSPORT LAYER
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Transport layer ensures the arrival of intact and in order messages
It also ensure the error and flow control from source to the destination level
It provide the mechanism for division of messages into the packets
The header of transport layer include the services of addressing of different processes to the destination
End to end flow control is provided rather than a single link
It ensure the error free intact and in order arrival of message
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SESSION LAYER
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From presentation layer
To transport layer
L6 data
H5
Sessionlayer
synsynsyn
L5 data
To presentation layer
From transport layer
L6 data
H5
Sessionlayer
synsynsyn
L5 data
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SESSION LAYER
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The Session layer ensure the synchronization, establishment and maintenance of communication system
It allows an interaction session(dialogue) between the two systems
It provide the mechanism for check points(synchronization of points)
In the transmission during the crash, it ensures the transmission of data from that point irrespective of the retransmission of data from the start
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PRESENTATION LAYER
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L7 data
L7 data
Decode, encrypted and compressed data
H6
Presentation layer
L7 data
L7 data
Decode, encrypted and compressed data
H6
Presentation layer
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PRESENTATION LAYER
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The layer ensure the syntax and semantics of the information exchanged over the communication link
It ensures the format of data(translation of data into desired form) for the user and the system
It provide the mechanism for decryption at the receiver end and encryption at the transmitter end
Data compression and other mechanism can be implemented to reduce the bandwidth requirement of the data
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APPLICATION LAYER
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User
L7 data
FTAM
Application layer
User
L7 data
FTAM
Application layer
To presentation layer From presentation layer
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APPLICATION LAYER
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It is the upper or top layer in the OSI model
It endure the mechanism(services) to support the various user application such as e-mail, file transfer and database
The application layer provides a software emulation of a terminal at the host node located remotely across the geographical data
The user node communicate software terminal and via software terminal user node can communicate to the host terminal and vice versa
The software provide the elusion that the remote host can communicate to its own terminal
It ensure the mechanism of file access, management and its transfer
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TCP/IP REFERENCE MODEL
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OSI Model TCP/IP model
Application Application
Presentation
Session
Transport Transport
Network Internet
Data Link Host-to-network
Physical
These two layers are not present in this model
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NETWORK TOPOLOGY
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Network Topology
MeshTopology
StarTopology
BusTopology
RingTopology
TreeTopology
The topology of a network refers to geometric representation of the relationship existing between all the links via connecting devices or nodes
The various geometrical representation can be classified as follow :
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BUS TOPOLOGY
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Dropline
Dropline
Dropline
Dropline
Tap Tap TapTapCable end Cable end
The bus topology is a multipoint data communication circuit
The bus is a passive topology due to absence of electronics to amplify the signal
When the signal sends on the cable, all computer on the network receive the information i.e. information is broadcasted
One with the address matches the packet information, it receives the informations and other neglects it
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RING TOPOLOGY
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Ring TopologyRepeater
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STAR TOPOLOGY
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Hub
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MESH TOPOLOGY
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TREE TOPOLOGY
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HubHub
HUB
Hub
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LOCAL ACCESS NETWORKS
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Modem
Modem
Access links
Edge router
(a) Local network
(b) Company networkEnd systems
Edge router
Access links
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PHYSICAL LAYER TRANSMISSION MEDIUM
1/4/2017
The terminology medium represent the messages transmitted in the some space or in a communication channel
The different media show different properties and can be used in a different environment
The main function of physical layer is to provide mechanism for the transportation of stream of data from one device to another
We categorizes the transmission media as wireless or wired media, guided and unguided media and so on
A basic classification of transmission medium is shown on the next slide
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CLASSIFICATION OF TRANSMISSION MEDIUM
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Transmission Media
Guided or wired media
Unguided or wireless media
Twisted pair cable
Co-axial cable
Fibre-optic cable
Microwave links
Infrared
Air acts as medium
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SWITCHING METHODS
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Packet Switching
Switching
Message Switching
Circuit Switching
Switching methods provide the information regarding the connections and data flow in the network
Data is send via the public switch telephone network
Switching mechanism allows data to traverse between different routes
Switching can be mainly divided into following categories:
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ISDN
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ISDN stands for Integrated Services Digital Network (ISDN)
ISDN is a WAN (Wide Area Network)
ISDN can be understand as a resultant of the computer and communication technologies
A narrow band ISDN is the first generation of ISDN
The first generation of ISDN provide 64 kbps of user channel as the basic mode of switching with the circuit switching orientation
Frame relay is the important narrow band device in the first generation
The broadband ISDN is the second generation ISDN
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ISDN
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The advantage of broadband ISDN is its higher data rate, mainly in Mbps
ISDN is based on the standard define by the ITU – T
It provide the services over the wide range of application
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