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Introduction to Computer Networks
Networks
A A networknetwork is a set of devices (often referred to as is a set of devices (often referred to as nodesnodes) connected by communication ) connected by communication linkslinks. A node can . A node can be a computer, printer, or any other device capable of be a computer, printer, or any other device capable of sending and/or receiving data generated by other sending and/or receiving data generated by other nodes on the network.nodes on the network.
Introduction to Computer Networks
By: Jigar M. Pandya
Rules For CommunicationIntroduction to Computer Networks
Transmission should take place without error.
Transmission should be Less.
The cost of Transmission should be less.
The message should be safe and secure.
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5 Components For Communication
Introduction to Computer Networks
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Data Flow Of MessagesIntroduction to Computer Networks
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Applications of Networks
Resource SharingHardware (computing resources, disks, printers)Software (application software)
Information SharingEasy accessibility from anywhere (files, databases)Search Capability (WWW)
CommunicationEmailMessage broadcast
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Network Topology
The network topology defines the way in which computers, printers, and other devices are connected. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions.
Introduction to Computer Networks
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Bus Topology
Commonly referred to as a linear bus, all the devices on a bus topology are connected by one single cable.
Introduction to Computer Networks
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Star & Tree TopologyThe star topology is the most commonly used architecture in Ethernet LANs.
Larger networks use the extended star topology also called tree topology. When used with network devices that filter frames or packets, like bridges, switches, and routers, this topology significantly reduces the traffic on the wires by sending packets only to the wires of the destination host.
Introduction to Computer Networks
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Ring TopologyA frame travels around the ring, stopping at each node. If a node wants to transmit data, it adds the data as well as the destination address to the frame.
The frame then continues around the ring until it finds the destination node, which takes the data out of the frame.
Single ring – All the devices on the network share a single cable
Dual ring – The dual ring topology allows data to be sent in both directions.
Introduction to Computer Networks
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Mesh Topology
The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance.
It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions.
Implementing the mesh topology is expensive and difficult.
Introduction to Computer Networks
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Types of Connection
Introduction to Computer Networks
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Network Components
Introduction to Computer Networks
Physical Media
Interconnecting Devices
Computers
Networking Software
Applications
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LAN, MAN & WAN
Network in small geographical Area (Room, Building or a Campus) is called LAN (Local Area Network)
Network in a City is call MAN (Metropolitan Area Network)
Network spread geographically (Country or across Globe) is called WAN (Wide Area Network)
Introduction to Computer Networks
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Applications
E-mailSearchable Data (Web Sites)E-CommerceNews GroupsInternet Telephony (VoIP)Video ConferencingChat GroupsInstant Messengers Internet Radio
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Network Models
Two Types Of Connections are there Connection Oriented service Connectionless service1. Connection Oriented Service.
Similar to the telephone system1. Establish Connection 2. Use Connection 3. Release connection.
2. Connectionless service. Same as postal service, each message has full add. Order may differ of delivery. Five primitives are used.1. Listen 2. Connect3. Receive4. Send5. Disconnect
LAYERED TASKSLAYERED TASKS
We use the concept of We use the concept of layerslayers in our daily life. As an in our daily life. As an example, let us consider two friends who communicate example, let us consider two friends who communicate through postal mail. The process of sending a letter to a through postal mail. The process of sending a letter to a friend would be complex if there were no services friend would be complex if there were no services available from the post office. available from the post office.
Tasks involved in sending a letter
THE OSI MODELTHE OSI MODEL
Established in 1947, the International Standards Established in 1947, the International Standards Organization (Organization (ISOISO) is a multinational body dedicated to ) is a multinational body dedicated to worldwide agreement on international standards. An ISO worldwide agreement on international standards. An ISO standard that covers all aspects of network standard that covers all aspects of network communications is the Open Systems Interconnection communications is the Open Systems Interconnection ((OSIOSI) model. It was first introduced in the late 1970s. ) model. It was first introduced in the late 1970s.
ISO is the organization.OSI is the model.
Seven layers of the OSI model
The interaction between layers in the OSI model
Physical layer
The physical layer is responsible for movements ofindividual bits from one hop (node) to the next.
Data link layer
The data link layer is responsible for moving frames from one hop (node) to the next.
2.26
Figure 2.7 Hop-to-hop delivery
Network layer
The network layer is responsible for the delivery of individual packets from
the source host to the destination host.
Transport layer
The transport layer is responsible for the delivery of a message from one process to another.
Session layer
The session layer is responsible for dialog control and synchronization.
Presentation layer
The presentation layer is responsible for translation, compression, and encryption.
Presentation layer
• Data translation ,compression and encryption.• Encrypt data to hide it.• Compress data from last message to small no of
messages.
Application layer
The application layer is responsible for providing services to the user.
Application layer
• Login password checking, file transfer are some of the application.
• Provide direct access to network device.• Interface between user and system.
Examples• File transfer• Emails• www
• Protocols• ftp, smtp, telnet….
Summary of layers
QUESTIONS
1. What is Connection Oriented Service ?2. What Is Connection Less Service ?3. Example Of Connation Less ?4. Example Of Connection Oriented ?5. Full Form Of OSI 6. Full Form OF ISO7. What is OSI Model ?8. How many Layers are there in OSI Model ?9. Task Of Application layer ?10. Task Of Presentation layer ?11. Task Of Session layer ?12. Task Of Transport layer ?13. Task Of Network layer ?14. Task Of Data-link layer ?15. Task Of Physical layer ?
TCP/IP ModelTCP/IP Model
The layers in the The layers in the TCP/IP MODEL TCP/IP MODEL do not exactly match do not exactly match those in the OSI model.those in the OSI model.
The original TCP/IP protocol suite was defined as The original TCP/IP protocol suite was defined as having four layers: having four layers: host-to-networkhost-to-network, , internetinternet, , transporttransport, , and and applicationapplication. .
However, when TCP/IP is compared to OSI, we can say However, when TCP/IP is compared to OSI, we can say that the TCP/IP protocol suite is made of five layers: that the TCP/IP protocol suite is made of five layers: physicalphysical, , data linkdata link, , networknetwork, , transporttransport, and , and applicationapplication..
TCP/IP ModelTCP/IP Model( Transmission control protocol / internet protocol )
The TCP/IP reference model.
TCP/IP ModelTCP/IP Model
• IT Was earlier used by ARPA(Advanced Research Project Agency)
• Used to connect Military networks together.
• Basically work for the internet .
• TCP/IP offers a simple naming and addressing scheme.
• Info is carried in packets.
• IP is used to put message in Packet.
• Each packet has address of sender and receiver (IP Address)
• Divide large message in to small packets.
• It is not necessary for all packets to follow same route.
• HTTP helps it to Share HTML Doc with the help of WWW.
( Transmission control protocol / internet protocol )
TCP/IP Model LayersTCP/IP Model LayersHost – to – Network LayerHost – to – Network Layer
• Lowest Layer in model
• Combination of Physical and Data-link Layer.
• The host has to connect to the network using some protocol, so
it can send IP packets over it.
• Protocol may vary based on host or network.
TCP/IP Model LayersTCP/IP Model LayersInternet LayerInternet Layer
• It holds whole architecture together.
• The task is to insert packet into any network and make them
travel.
• The order of packets may differ ,the higher layer support it to
arrange packets.
• It Defines Packet format and protocol called IP.
• Routing of packets and congestion control are important issues.
• Almost same as the network layer in OSI model.
TCP/IP Model LayersTCP/IP Model LayersTransport LayerTransport Layer
• Same Function as Transport layer in OSI layer.
• It allows entities to converse with each other.
• The Protocols Used Are TCP & UDP.
• TCP is Connection Oriented Service, No Error ,Handles Flow
of control.
• UDP is Connection less service, Chances Of Error , Prompt
delivery is more important then accurate.
TCP/IP Model LayersTCP/IP Model LayersApplication LayerApplication Layer
• IT Doesn't Have Session or Presentation Layer.
• All upper level protocols are supported by This layer.
• Main task is to provide user interface.
• Provide services that can be used by other services.
• For Example .
• SMTP :- Mailing Service
• Telnet :- Remote Logon Service
• FTP :- File Transfer Service.
TCP/IP and OSI model
Comparing OSI and TCP/IP Models
Concepts central to the OSI model• Services• Interfaces• Protocols
Comparing OSI and TCP/IP Models
Why OSI did not take over the world• Bad timing• Bad technology• Bad implementations• Bad politics
Comparing OSI and TCP/IP Models
Problems In TCP / IP :• Service, interface, and protocol not distinguished• Not a general model• Host-to-network “layer” not really a layer• No mention of physical and data link layers• Minor protocols deeply embedded, hard to
replace
Hybrid Model
• Addressing - whom am I going to talk to? i.e., how do we identify
senders and receivers?
• Rules for data transfer: Simplex ,half-duplex and full duplex
• Error control: This is all about communicating along imperfect
channels and error correction in such cases.
• Large messages: Procedures for disassembling, transmitting and
reassembling.
Design Issues For Layers