Networking Class 3

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2. OSI Model
• OSI means Open System Interconnect model.
• Developed by the International Organization for
Standardization in 1974.
• It consists of seven layers.
• Each layer has a different but specific processing
function.
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3. OSI Model Layers
Layer - 7 Application
Application
Layer - 6 Presentation
Presentation
Layer - 5 Session
Session
Layer - 4 Transport
Transport
Layer - 3 Network
Network
Layer - 2 Data Link
Data Link
Layer - 1 Physical
Physical
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4. Application Layer
Application Layer is
Application
Application responsible for providing
Networking Services to user.
Presentation
Presentation It also known as Desktop Layer.
Identification of Services is
Session
Session done using Port Numbers.
Transport
Transport Ports are nothing but Socket i.e.
Entry and Exit Point to the Layer
Network
Network
Data Link Total No. Ports 0 – 65535
Data Link
Reserved Ports 0 – 1023
Physical
Physical Open Ports 1024 – 65535
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5. Examples of Networking Services
Service Port No.
HTTP 80
FTP 21
SMTP 25
TELNET 23
TFTP 69
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6. How data flows from Application Layer
Application
Application Data
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Presentation
Presentation
Session
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
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7. Presentation Layer
Presentation Layer is
Application
Application responsible for converting data
into standard format.
Presentation
Presentation
Presentation
Presentation
Examples : ASCII, EBCDIC, JPEG,
Session
Session MPEG, BMP, MIDI, WAV, MP3
Transport
Transport
Following tasks are perform at
Network Presentation layer :
Network
Data Link
Data Link Encoding – Decoding
Encryption – Decryption
Physical
Physical Compression – Decompression
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8. How data flows from Presentation Layer
Application
Application Data
Presentation
Presentation Data
Session
Session
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
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9. Session Layer
Session Layer is responsible
Application
Application establishing, maintaining and
terminating session.
Presentation
Presentation Session ID also works at Session
Layer.
Session
Session
Transport Examples :
Transport
Network
Network RPC  Remote Procedure Call
SQL  Structured Query language
Data Link
Data Link NFS  Network File System
Physical
Physical
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10. How data flows from Session Layer
Application
Application Data
Presentation
Presentation Data
Session
Session Data
Transport
Transport
Network
Network
Data Link
Data Link
Physical
Physical
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11. Transport Layer
Transport Layer is
Application
Application responsible for end-to-end
connectivity. It is also known as
Presentation
Presentation heart of OSI Layers. Following
task are performed at Transport
Session
Session Layer : -
Transport
Transport
Transport • Identifying Service
Network
Network • Multiplexing & De-multiplexing
• Segmentation
Data Link
Data Link
• Sequencing & Reassembling
Physical
Physical • Flow Control
• Error Correction
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12. Identifying Service
TCP UDP
• Transmission Control • User Datagram
Protocol Protocol
• Connection Oriented • Connection Less
• Acknowledgement • No Acknowledgement
• Reliable • Unreliable
• Slower • Faster
• Port No. 6 • Port No. 17
• e.g. HTTP, FTP, SMTP • e.g. DNS, DHCP, TFTP
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13. Multiplexing & De-multiplexing
Application
Application
Presentation
Presentation
Session
Session
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Transport
Transport
TCP - 6 UDP - 17
Network
Network
Data Link
Data Link
Physical
Physical 13

14. How data flows from Transport Layer
Application
Application Data
Presentation
Presentation Data
Session
Session Data
Transport TH
Segment
Data
Transport
Network
Network
Data Link
Data Link
Physical
Physical
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15. Network Layer
Network Layer is
Application
Application responsible for providing best
path to data to reach destination.
Presentation
Presentation Logical Addressing sits on this
layer. Device working on Network
Session
Session Layer is Router.
Transport
Transport It is divided into two parts
• Routed Protocols
Network
Network
e.g. IP, IPX, Apple Talk.
Data Link
Data Link • Routing Protocols
Physical e.g. RIP, IGRP, OSPF, EIGRP
Physical
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16. How data flows from Network Layer
Application
Application Data
Presentation
Presentation Data
Session
Session Data
e.g. Router Transport
Transport Segment
Network
Network Packet
NH Segment
Data Link
Data Link
Physical
Physical
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17. Datalink Layer
Datalink Layer is
Application
Application divided into two Sub Layers :
Presentation
Presentation • LLC – Logical Link Control
Session It talks about Wan protocols e.g.
Session
PPP, HDLC, Frame-relay
Transport
Transport
• MAC – Media Access Control
Network
Network It talks about Physical Address.
It is 48 bit Addressing
Data Link
Data Link
Data
Data i.e. 12 digit Hexadecimal No.
It is also responsible for Error
Physical
Physical Detection
Device working on Data Link
Layer is Switch, Bridge, NIC.
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18. How data flows from Data Link Layer
Application
Application Data
Presentation
Presentation Data
Session
Session Data
Transport
Transport Segment
e.g. Switch Network
Network Packet
Data Link
Data Link DH Frame DT
Packet
Physical
Physical
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19. Physical Layer
Physical Layer is
Application
Application responsible for electrical,
mechanical or procedural checks.
Presentation
Presentation Data will be converted in Binary
that is 0’s & 1’s. Data will be in the
Session
Session form of electrical pulses if it is
Coaxial or Twisted Pair cable and in
Transport
Transport the form of Light if it is Fiber Optic
Cable.
Network
Network
Devices working at Physical Layer
Data Link
Data Link are Hubs, Repeaters, Cables,
Modems etc.
Physical
Physical
Physical
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20. How data flows from Physical Layer
Application
Application Data
Presentation
Presentation Data
Session
Session Data
Transport
Transport Segment
Network
Network Packet
e.g. Hub Data Link
Data Link Frame
Physical
Physical Bits
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21. Data Encapsulation & De-capsulation
A B
Application Data Data Application
Application Application
Presentation
Presentation Data Data Presentation
Presentation
Session
Session Data Data Session
Session
Transport TH Segment TH
Transport
Transport Data
Segment TH Data Transport
Network
Network NH Segment
Packet NH Segment
Packet Network
Network NH
Data Link
Data Link DHFrameDT
Packet DTFrameDH
Packet
Packet DH
Data LinkDT
Data Link
Physical
Physical Bits Bits Physical
Physical
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22. Comparing OSI with TCP/IP Layers
OSI Layers TCP/IP Layers
Application
Application
Presentation
Presentation Application
Application
Session
Session
Transport
Transport Transport
Transport
Network
Network Internet
Internet
Data Link
Data Link Network
Network
Access
Access
Physical
Physical
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