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1. OSI ARCHITECTURE
BALU MAHENDRAN.R
JANUARY,20 2017

2. What is osi?
• OSI “ Open System Interconnection”
• International Organization for standardization(ISO) defines
is a way to connect computer by architecture
• Network functionality is divided into SEVEN LAYER

3. SEVEN LAYERS

4. FUNCTIONS OF LAYER:
Application Data
Presentation Data
Session Data
Transport Segment
Network Packet
Data Link Frame
Physical Bits
• The mode of
transforminng information
from one layer to another
layer is shown in the table

5. Layer 1: The Physical Layer
➢ Convert the logical 1’s and 0’s coming from layer 2
into electrical signals.
➢ It is responsible for electical ,mechanical and
procedural check.
➢ Data will be in the form of electrical pulses
Devices: hubs, cables, connectors, etc…
Services : HTTP,FTP,SMTP,TELNET,TFTP......

6. Responsiblities:
▪ Data Rate
▪ Synchronization
of Bit
▪ Line
Configuration
▪ Physical
Topology
▪ Transmission
mode

7. Layer 2: The Data Link Layer
➢The data link layer is responsible for moving frames from one
node to the next node.
➢It is divided into two sub layer
link control
Examples :- Ethernet, Frame Relay, FDDI,NIC.....
Logical Link Control (LLC) Media Access Control (MAC)
• It talks about WAN protocols.
Eg: PPP,HDLC.....
• It talks about physical address .
• It is of 48 bit address i.e. 12 bit
hexa decimal number.

8. Responsiblities:
▪ Framing
▪ Physical addressing
▪ Flow control
▪ Error control
▪ Access control

9. Layer 3: The Network Layer
➢The network layer is responsible for the delivery of individual
packets from the source host to the destination host.
➢It provides the Best path for data to reach the destination
Protocols :-
Routed: IP, IPx,Apple Talk...
Routing: RIP,EIGRP, OSPF,EIGRP.....
Devices: routers, firewalls,etc......

10. Responsiblities:
▪Logical
addressing
▪Routing

11. Layer 4: The Transport Layer
➢ The transport layer is responsible for the delivery of a message
from process -to- process .
➢ Ensures that data units are delivered in sequence.
Transmission control
protocol(TCP)
User datagram
protocol(UDP)
• Connection oriented
• Acknowledgement
• Reliable
• Slower
• Port no: 6
Eg: HTTP,FTP,SMTP...
• Connection less
• No Acknowledgement
• Reliable
• Faster
• Port no: 17
Eg: DNS,DHCP,TFTP...

12. Responsiblities:
▪ Multiplexing &
Demultiplexing
▪ Port Addressing
▪ Segementation
& Reassembling
▪ Error correction
▪ Flow control

13. Layer 5: The Session Layer
➢ It is responsible for establishing ,
maintaining and terminating
connection
➢ Session Id works on this layer
Eg:-
RPC-Remote Procedure Call
NTS-Network File System

14. Layer 6: The Presentation Layer
➢It is responsibile for converting for converting data into
standard formats.
Eg: ASCII,EBCDIC,JPEG,MPEG..
➢ The following task are performed in this layer
Encryption - Decryption
Encoding - Decoding
Compression-Decomposition

15. LAYER 7: APPLICATION
➢It provides networking
services to the user.
➢It is also known as Desktop
layer.
➢Identification of services is
done using Port number.
➢Port are entry and exit point
to the layer
Total number of port
Reserved ports
Open client ports
0 - 65535
0 - 1023
1024 - 65535

16. Responsiblities:
▪ FTAM(file transfer
access
management)
▪ Mail services
▪ Directory services
Services: HTTP,FTM,
SMTP,TELNET...

17. Interconnection between layers in the OSI model

18. OSI MODEL REFERENCE WITH TCP PROTOCOL

19. THE END
ALL THE BEST