JUNAID QADAR MSC ELECTRONICS DEPARTMENT OF ELECTRONICS UNIVERSITY OF PESHAWAR

1. jndqadar@gmail.comjndqadar@gmail.com
Packet Switching, Layer ModelsPacket Switching, Layer Models
and Protocol Suitesand Protocol Suites
JUNAID QADARJUNAID QADAR
MSC ELECTRONICSMSC ELECTRONICS
Department of ElectronicsDepartment of Electronics
UNIVERSITY OF PESHAWARUNIVERSITY OF PESHAWAR

2. 22
OutlineOutline
 Packet vs. circuit switchingPacket vs. circuit switching
 Layered tasksLayered tasks
 Internet protocol suitesInternet protocol suites
 ISO's OSI modelISO's OSI model

3. 33
Communication:Communication: App's ViewpointApp's Viewpoint
 Two network applications interact as ifTwo 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"?
InternetInternet
AA
AppApp
BB
AppApp

4. 55
Circuit vs. Packet SwitchingCircuit vs. Packet Switching
 Dedicated circuitsDedicated circuits
 Circuit switchingCircuit switching
 Telephone switchesTelephone switches
establish circuitsestablish circuits
for communicationfor communication
 Packet switchingPacket switching
 Data are put intoData are put into
packetspackets
 Each stamped withEach stamped with
sourcesource andand destinationdestination
addressesaddresses
 RoutersRouters know where toknow where to
forward packetsforward packets
telephone
switch
RouterPacket

5. 66
Layered TasksLayered Tasks
 Computer networks are complex systemsComputer networks are complex systems
 Tasks involve varieties of hardware andTasks involve varieties of hardware and
software components, and protocolssoftware components, and protocols
 Networking task is divided into severalNetworking task is divided into several
subtasks, or layerssubtasks, or layers

6. 77
Real World ExampleReal World Example
 Communication between managers of twoCommunication between managers of two
companiescompanies
Communicate

7. 88
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 reports
the message
Delivery boy:
takes the letter
Post office:
Processes and routes the letter
Postal truck

8. 1111
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
Transmission
Medium
Hardware
Software

9. 1212
Application LayerApplication Layer
 The only layer to interact with userThe only layer to interact with user
Responsible 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
Application
Layer
to Transport from Transport
Data H5
Data
Logical communication

10. 1313
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 message
from one process to anotherfrom one process to another
Responsible for delivery of a messageResponsible for delivery of a message
from one process to anotherfrom one process to another

11. 1414
Transport LayerTransport Layer
Transport
Layer
Data
from Application
Data1 Data2 Data3H4 H4 H4
to Network
Data
to Application
Data1 Data2 Data3H4 H4 H4
from Network
(segments)

12. 1515
Network LayerNetwork Layer
 Duties/servicesDuties/services
 Logical addressingLogical addressing
 RoutingRouting
Responsible for the delivery of packetsResponsible for the delivery of packets
from the original source to the destinationfrom the original source to the destination
Responsible for the delivery of packetsResponsible for the delivery of packets
from the original source to the destinationfrom the original source to the destination

13. 1616
Network LayerNetwork Layer
Network
Layer
Data
from Transport
to Data Link
Data
to Transport
from Data Link
Data H3 Data H3
(packet)

14. 1717
Network LayerNetwork Layer
Network 1
Network 6
Network 5
1.1 1.2
6.6
6.1
6.3
5.7
5.2
Network 3
3.8
3.3
Router
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
R3
R2

15. 1818
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 frames
from one node to the nextfrom one node to the next
Responsible for transmitting framesResponsible for transmitting frames
from one node to the nextfrom one node to the next

16. 1919
Data Link LayerData Link Layer
Data Link
Layer
Data
from Network
to Physical
Data
to Network
from Physical
Data H2 Data H2
(frame)
T2 T2

17. 2020
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

18. 2121
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 3
3.8
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
R3
R2

19. 2222
Physical LayerPhysical Layer
 Duties/servicesDuties/services
 Physical characteristics of interfacesPhysical 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 bits
from one node to the nextfrom one node to the next
Responsible for transmitting individual bitsResponsible for transmitting individual bits
from one node to the nextfrom one node to the next

20. 2323
Physical LayerPhysical Layer
Physical
Layer
Data
from Data Link to Data Link
Data
01001011 01001011
Transmission medium
(bits)

21. 2424
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

22. 2525
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
sender
router
router
receiver

23. 262626
Protocol SuitesProtocol Suites
 A set of protocols must be constructedA set of protocols must be constructed
 to ensure that the resulting communicationto ensure that the resulting communication
system issystem is completecomplete andand efficientefficient
 Each protocol should handle a part ofEach protocol should handle a part of
communication not handled by othercommunication not handled by other
protocolsprotocols
 How can we guarantee that protocolsHow 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 calledcooperative sets called suitessuites oror familiesfamilies

24. 2727
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, ...

25. 2828
OSI ModelOSI Model
 OSI –OSI – OOpenpen SSystemsystems
IInterconnectionnterconnection
 Developed by theDeveloped by the IInternationalnternational
SStandardstandards OOrganizationsrganizations
(ISO)(ISO)
 Two additional layersTwo additional layers
 Presentation layerPresentation layer
 Session layerSession layer
7.Application Layer7.Application Layer
6.Presentation Layer6.Presentation Layer
5.Session Layer5.Session Layer
4.Transport Layer4.Transport Layer
3.Network Layer3.Network Layer
2.Data Link Layer2.Data Link Layer
1.Physical Layer1.Physical Layer
User
Transmission
Medium

26. 2929
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 andResponsible for establishing, managing and
terminating connections between applicationsterminating connections between applications
Responsible for establishing, managing andResponsible for establishing, managing and
terminating connections between applicationsterminating connections between applications

27. 3030
Presentation LayerPresentation Layer
 Duties/servicesDuties/services
 Data translationData translation
 EncryptionEncryption
 DecryptionDecryption
 CompressionCompression
Responsible for handling differences inResponsible for handling differences in
data representation to applicationsdata representation to applications
Responsible for handling differences inResponsible for handling differences in
data representation to applicationsdata representation to applications

28. THANKSTHANKS
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