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Presentation onOSI Model & TCP/ IP Model
Presented By:Aditya Vikram Singh
Gaurav Mehta
Laxmi Priya Budek
Shruti Kashyap
Sumit Gill
Sunit Kumar
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Contents:
• Introduction
• Communication Architecture
• Layer Architecture
• OSI Model
• Layers Of OSI Model
• TCP/IP Model
• Layers Of TCP/IP• Critique Of OSI & TCP/IP model
• Comparison Of OSI & TCP/IP model
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Communication Architecture
Strategy for connecting host computers and othercommunicating equipment.
Defines necessary elements for data communicationbetween devices.
A communication architecture, therefore, defines astandard for the communicating hosts.
A programmer formats data in a manner defined by thecommunication architecture and passes it on to thecommunication software.
Separating communication functions adds flexibility,for example, we do not need to modify the entire hostsoftware to include more communication devices.
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Layer Architecture
Layer architecture simplifies the network designand helps in troubleshooting.
It is easy to debug network applications in a
layered architecture network.The network management is easier due to thelayered architecture.
Network layers follow a set of rules, calledprotocol.
The protocol defines the format of the data beingexchanged, and the control and timing for thehandshake between layers.
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Open Systems
Interconnection ModelInternational standard organization (ISO)established a committee in 1977 to develop anarchitecture for computer communication.
Open Systems Interconnection (OSI) referencemodel is the result of this effort.
In 1984, the Open Systems Interconnection (OSI)reference model was approved as an internationalstandard for communications architecture.
Term “open” denotes the ability to connect anytwo systems which conform to the reference modeland associated standards.
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OSI Reference ModelThe OSI model is now considered the primaryArchitectural model for inter-computercommunications.
The OSI model describes how information or datamakes its way from application programmes(such as spreadsheets) through a network medium (such as wire) to another applicationprogramme located on another network.
The OSI reference model divides the problem of moving information between computers over anetwork medium into SEVEN smaller and moremanageable problems .
This separation into smaller more manageable
functions is known as layering.
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OSI: A Layered Network
ModelThe process of breaking up the functions or tasksof networking into layers reduces complexity.
Each layer provides a service to the layer aboveit in the protocol specification.
Each layer communicates with the same layer’ssoftware or hardware on other computers.The lower 4 layers (transport, network, data link and physical —Layers 4, 3, 2, and 1) areconcerned with the flow of data from end to endthrough the network.
The upper three layers of the OSI model
(application, presentation and session—Layers 7,6 and 5) are orientated more toward services tothe applications.
Data is Encapsulated with the necessary protocolinformation as it moves down the layers beforenetwork transit.
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PACKET
Packets
Transmissions are broken up into smallerunits or data transmissions called packets
PACKET PACKET PACKET
Example
A file (might be an mp3 sound file) is divided into packets.
It does not matter what the transmission is. It could be Worddocument, a PowerPoint or an MP3
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Packets and OSI
After transmission is divided into packetsextra information required to make sure it allgoes back together correctly. The OSI modelhelps to look after this.
The OSI model also provides much moreinformation which is included with each
package.
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OSI Model:
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OSI in ActionA message begins at the topapplication layer and moves downthe OSI layers to the bottomphysical layer.
As the message descends, each
successive OSI model layer addsa header to it.
A header is layer-specificinformation that basicallyexplains what functions the layercarried out.
Conversely, at the receiving end,headers are striped from themessage as it travels up thecorresponding layers.
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OSI Layers:
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The Physical LayerResponsibility:
transmission of raw bits over acommunication channel.
Issues:mechanical and electrical interfaces
time per bit
distances
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OSI Layers:
•Provides connectivity and path selection between two host
•Provides Logical address
•No error correction, best effort delivery.
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The Data Link Layer -
Data Link ControlResponsibility:provide an error-free communication link
Issues:framing (dividing data into chunks) header & trailer bits
addressing
10110110101 01100010011 10110000001
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The Data Link Layer -
The MAC sublayerMedium Access Control - needed by
mutiaccess networks.
MAC provides DLC with “virtual wires” onmultiaccess networks.
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OSI Layers:
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The Network Layer
Responsibilities:
path selection between end-systems (routing).
subnet flow control.
fragmentation & reassembly
translation between different network types.
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OSI Layers:
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The Transport LayerResponsibilities:provides virtual end-to-end links between
peer processes.
end-to-end flow control
Issues:
headers
error detection
reliable communication
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OSI Layers:
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The Session LayerResponsibilities:
establishes, manages, and terminates sessionsbetween applications.
service location lookup
Many protocol suites do not include a session
layer.
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OSI Layers:
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The Presentation LayerResponsibilities:
data encryption
data compressiondata conversion
Many protocol suites do not include aPresentation Layer.
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OSI Layers:
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The Application LayerResponsibilities:
anything not provided by any of the otherlayers
Issues:application level protocols
appropriate selection of “type of service”
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Peer-to-Peer
Communication
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Connecting Networks
Repeater: physical layer
Bridge: data link layer
Router: network layer
Gateway: network layer and
above.
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RepeaterCopies bits from one network to another
Does not look at any bits
Allows the extension of a network beyondphysical length limitations
REPEATER
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BridgeCopies frames from one network to another
Can operate selectively - does not copy all
frames (must look at data-link headers).Extends the network beyond physical length
limitations.
BRIDGE
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RouterCopies packets from one network to another.
Makes decisions about what route a packetshould take (looks at network headers).
ROUTERROUTER
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GatewayOperates as a router
Data conversions above the network layer.
Conversions:encapsulation - use an intermediate network
translation - connect different applicationprotocols
encrpyption - could be done by a gateway
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Examples of protocols
Layer 7 application
Layer 6presentation
Layer 5 sessionLayer 4 transport
Layer 3 network
Layer 2 data link
Layer 1 physical
E-mail, Web browser, Directory
POP, SMTP, FTP, HTTP, DNS
Sockets
TCP
IP
PPP, Ethernet, Token ring
100baseT
More on Protocols
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TCP/IP MODEL
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OSI & TCP/IP Models
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TCP/IP ModelApplication Layer Application programs using the network
Transport Layer (TCP/UDP)
Management of end-to-end message transmission,
error detection and error correction
Network Layer (IP)
Handling of datagrams : routing and congestion
Data Link Layer Management of cost effective and reliable data delivery,
access to physical networks
Physical Layer
Physical Media
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Critique Of OSI & TCP/IP
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Critique Of OSI & TCP/IPModel:OSI Model:
• Bad Timing
• Bad Technology• Bad Implementation
• Bad Politics
TCP/IP Model:
• Doesnot distinguish the conceptof service, interface andprotocol.
• Model is not suited for any otherprotocol.
• Host-To-Network: Dummy Layer.
• Doesnot distinguish betweenphysical & datalink layers.
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Comparison:OSI Model:
• Services, Interface,Protocols.
• Model was devisedbefore the advent of protocols.
• Number of layers.
• Connectionless &Connection Oriented.
TCP/IP Model:
• Services, Interfaces,Protocols.
• Model was devisedkeeping in view theprotocols.
• Number of layers.
• Connectionless &Connection Oriented.
The OSI Reference Model
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END
The OSI Reference Model
A convenient aid for remembering the OSI layer
names is to use the first letter of each word in the
phrase:
All People Seem To Need Data Processing
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