jndqadar@gmail.comjndqadar@gmail.com

Packet Switching, Layer Models Packet Switching, Layer Models and Protocol Suites and Protocol Suites

JUNAID QADARJUNAID QADARMSC ELECTRONICSMSC ELECTRONICS

Department of ElectronicsDepartment of ElectronicsUNIVERSITY OF PESHAWARUNIVERSITY OF PESHAWAR

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OutlineOutline Packet vs. circuit switchingPacket vs. circuit switching Layered tasksLayered tasks Internet protocol suitesInternet protocol suites ISO's OSI modelISO's OSI model

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Communication: Communication: App's ViewpointApp's Viewpoint Two network applications interact as if Two network applications interact as if

there is a dedicate pipe connecting themthere is a dedicate pipe connecting them

But what's going on underneath?But what's going on underneath? What is inside the "cloud"?What is inside the "cloud"?

InternetInternetAA

AppApp

BB

AppApp

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Circuit vs. Packet SwitchingCircuit vs. Packet Switching Dedicated circuitsDedicated circuits Circuit switchingCircuit switching

Telephone switchesTelephone switchesestablish circuitsestablish circuitsfor communicationfor communication

Packet switchingPacket switching Data are put intoData are put into

packetspackets Each stamped withEach stamped with

sourcesource and and destinationdestinationaddressesaddresses

RoutersRouters know where to know where toforward packetsforward packets

telephoneswitch

RouterPacket

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Layered TasksLayered Tasks Computer networks are complex systemsComputer networks are complex systems

Tasks involve varieties of hardware and Tasks involve varieties of hardware and software components, and protocolssoftware components, and protocols

Networking task is divided into several Networking task is divided into several subtasks, or layerssubtasks, or layers

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Real World ExampleReal World Example Communication between managers of two Communication between managers of two

companiescompanies

Communicate

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What Actually HappensWhat Actually Happens Communication takes place thru many layersCommunication takes place thru many layers

Logical communication

Secretary:types a letter

Delivery boy:drops the letter

Secretary:reads and reportsthe message

Delivery boy:takes the letter

Post office:Processes and routes the letter

Postal truck

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Internet Layer ModelInternet Layer Model The Internet Protocol StackThe Internet Protocol Stack

Application LayerApplication Layer

Transport LayerTransport Layer

Network LayerNetwork Layer

Data Link LayerData Link Layer

Physical LayerPhysical Layer

User

TransmissionMedium

Hardware

Software

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Application LayerApplication Layer

The only layer to interact with userThe only layer to interact with userResponsible for providing services to the userResponsible for providing services to the userResponsible for providing services to the userResponsible for providing services to the user

SMTP HTTP FTP SMTP HTTP FTP

Data

Data H5

ApplicationLayer

to Transport from Transport

Data H5

DataLogical communication

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Transport LayerTransport Layer

Duties/servicesDuties/services Port addressingPort addressing Segmentation and reassemblySegmentation and reassembly Connection controlConnection control Flow control (end-to-end)Flow control (end-to-end) Error control (end-to-end)Error control (end-to-end)

Responsible for delivery of a messageResponsible for delivery of a messagefrom one process to anotherfrom one process to another

Responsible for delivery of a messageResponsible for delivery of a messagefrom one process to anotherfrom one process to another

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Transport LayerTransport Layer

TransportLayer

Data

from Application

Data1 Data2 Data3H4 H4 H4

to Network

Data

to Application

Data1 Data2 Data3H4 H4 H4

from Network

(segments)

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Network LayerNetwork Layer

Duties/servicesDuties/services Logical addressingLogical addressing RoutingRouting

Responsible for the delivery of packetsResponsible for the delivery of packetsfrom the original source to the destinationfrom the original source to the destination

Responsible for the delivery of packetsResponsible for the delivery of packetsfrom the original source to the destinationfrom the original source to the destination

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Network LayerNetwork Layer

NetworkLayer

Data

from Transport

to Data Link

Data

to Transport

from Data Link

Data H3 Data H3(packet)

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Network LayerNetwork Layer

Network 1

Network 6

Network 5

1.1 1.2

6.6

6.1

6.3

5.7

5.2

Network 33.8

3.3Router

Data 1.1 5.7

1.1, 1.2, 6.1, 5.7, ... are logical addresses1.1, 1.2, 6.1, 5.7, ... are logical addresses

R1

R3R2

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Data Link LayerData Link Layer

Duties/servicesDuties/services FramingFraming Physical addressingPhysical addressing Flow control (hop-to-hop)Flow control (hop-to-hop) Error control (hop-to-hop)Error control (hop-to-hop) Access controlAccess control

Responsible for transmitting framesResponsible for transmitting framesfrom one node to the nextfrom one node to the next

Responsible for transmitting framesResponsible for transmitting framesfrom one node to the nextfrom one node to the next

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Data Link LayerData Link Layer

Data LinkLayer

Data

from Network

to Physical

Data

to Network

from Physical

Data H2 Data H2(frame)

T2 T2

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Data Link LayerData Link Layer

3B

A3, 3B, 82, 9F, ... are physical addressesA3, 3B, 82, 9F, ... are physical addresses

9F 82 A3

Data 9FT2 A3

Data

H2

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Data Link LayerData Link Layer

Network 1

Network 6

Network 5

1.1 1.2

6.6

B1

6.3

5.7

5.2

Network 33.8

3.3

Data 1.15.7

97 32

25

79

62

54

74

12

88

Data 1.15.7 2597

Data 1.15.7 6279

Data 1.15.7 7454

R1

R3R2

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Physical LayerPhysical Layer

Duties/servicesDuties/services Physical characteristics of interfaces Physical characteristics of interfaces

and mediaand media Representation of bitsRepresentation of bits Data rate (transmission rate)Data rate (transmission rate) Synchronization of bitsSynchronization of bits

Responsible for transmitting individual bitsResponsible for transmitting individual bitsfrom one node to the nextfrom one node to the next

Responsible for transmitting individual bitsResponsible for transmitting individual bitsfrom one node to the nextfrom one node to the next

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Physical LayerPhysical Layer

PhysicalLayer

Data

from Data Link to Data Link

Data

01001011 01001011

Transmission medium

(bits)

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The Big PictureThe Big Picture

L5 data H5

L4 data H4

L3 data H3

L2 dataT2 H2

0111011010101001010101001

L5 data H5

L4 data H4

L3 data H3

L2 dataT2 H2

0111010101010010101010101

5

4

3

2

1

5

4

3

2

1

Transmission medium

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Internet ModelInternet Model

ApplicationApplication

TransportTransport

NetworkNetwork

Data LinkData Link

PhysicalPhysical

NetworkNetwork

Data LinkData Link

PhysicalPhysical

NetworkNetwork

Data LinkData Link

PhysicalPhysical

ApplicationApplication

TransportTransport

NetworkNetwork

Data LinkData Link

PhysicalPhysical

Transmission medium

senderrouter

routerreceiver

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Protocol SuitesProtocol Suites A set of protocols must be constructedA set of protocols must be constructed

to ensure that the resulting communication to ensure that the resulting communication system is system is completecomplete and and efficientefficient

Each protocol should handle a part of Each protocol should handle a part of communication not handled by other communication not handled by other protocolsprotocols

How can we guarantee that protocols How can we guarantee that protocols work well together?work well together? Instead of creating each protocol in isolation, Instead of creating each protocol in isolation,

protocols are designed in complete, protocols are designed in complete, cooperative sets called cooperative sets called suitessuites or or familiesfamilies

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Internet Protocol SuiteInternet Protocol Suite

LayerLayer ProtocolsProtocols

ApplicationApplication HTTP, FTP, Telnet, SMTP, ...HTTP, FTP, Telnet, SMTP, ...

TransportTransport TCP, UDP, SCTP, ...TCP, UDP, SCTP, ...

NetworkNetwork IP (IPv4), IPv6, ICMP, IGMP, ...IP (IPv4), IPv6, ICMP, IGMP, ...

Data LinkData Link Ethernet, Wi-Fi, PPP, ...Ethernet, Wi-Fi, PPP, ...

PhysicalPhysical RS-232, DSL, 10Base-T, ...RS-232, DSL, 10Base-T, ...

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OSI ModelOSI Model

OSI – OSI – OO pen pen SSystems ystems II nterconnectionnterconnection

Developed by the Developed by the II nternational nternational SS tandards tandards OO rganizations rganizations (ISO)(ISO)

Two additional layersTwo additional layers Presentation layerPresentation layer Session layerSession layer

7.Application Layer7.Application Layer6.Presentation Layer6.Presentation Layer

5.Session Layer5.Session Layer4.Transport Layer4.Transport Layer3.Network Layer3.Network Layer

2.Data Link Layer2.Data Link Layer1.Physical Layer1.Physical Layer

User

TransmissionMedium

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Session LayerSession Layer

Duties/servicesDuties/services Interaction managementInteraction management

Simplex, half-duplex, full-duplexSimplex, half-duplex, full-duplex Session recoverySession recovery

Responsible for establishing, managing and Responsible for establishing, managing and terminating connections between applicationsterminating connections between applicationsResponsible for establishing, managing and Responsible for establishing, managing and

terminating connections between applicationsterminating connections between applications

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Presentation LayerPresentation Layer

Duties/servicesDuties/services Data translationData translation EncryptionEncryption DecryptionDecryption CompressionCompression

Responsible for handling differences inResponsible for handling differences indata representation to applicationsdata representation to applications

Responsible for handling differences inResponsible for handling differences indata representation to applicationsdata representation to applications

THANKSTHANKS??????????????????????????????

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