OSI TCP model

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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



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



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.



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.



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.



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.



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.



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



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.



OSI Model:



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.





OSI Layers:



The Physical LayerResponsibility:

transmission of raw bits over acommunication channel.

Issues:mechanical and electrical interfaces

time per bit

distances



OSI Layers:

•Provides connectivity and path selection between two host

•Provides Logical address

•No error correction, best effort delivery.



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



The Data Link Layer -

The MAC sublayerMedium Access Control - needed by

mutiaccess networks.

MAC provides DLC with “virtual wires” onmultiaccess networks.



OSI Layers:



The Network Layer

Responsibilities:

path selection between end-systems (routing).

subnet flow control.

fragmentation & reassembly

translation between different network types.



OSI Layers:



The Transport LayerResponsibilities:provides virtual end-to-end links between

peer processes.

end-to-end flow control

Issues:

headers

error detection

reliable communication



OSI Layers:



The Session LayerResponsibilities:

establishes, manages, and terminates sessionsbetween applications.

service location lookup

Many protocol suites do not include a session

layer.



OSI Layers:



The Presentation LayerResponsibilities:

data encryption

data compressiondata conversion

Many protocol suites do not include aPresentation Layer.



OSI Layers:



The Application LayerResponsibilities:

anything not provided by any of the otherlayers

Issues:application level protocols

appropriate selection of “type of service”



Peer-to-Peer

Communication



Connecting Networks

Repeater: physical layer

Bridge: data link layer

Router: network layer

Gateway: network layer and

above.



RepeaterCopies bits from one network to another

Does not look at any bits

Allows the extension of a network beyondphysical length limitations

REPEATER



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



RouterCopies packets from one network to another.

Makes decisions about what route a packetshould take (looks at network headers).

ROUTERROUTER



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



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

http://bettscomputers.com/moodle/mod/resource/view.php?id=653

http://bettscomputers.com/moodle/mod/resource/view.php?id=653



TCP/IP MODEL



OSI & TCP/IP Models



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



Critique Of OSI & TCP/IP



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.



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



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



THANKS

OSI TCP model

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