1. Reference Model 1

2. Layered network Why network are layered ?! -Easy to change -Easy to troubleshoot -Give general idea of each layer 2

3. OSI Reference Model 3 TCP/IP

4. OSI History : -Developed By ISO (international standard organization) -OSI shortened from ( open system Inter connection) -OSI has 7 layers and there were principle to arrive to these seven layers 1)- layers should be created where different abstraction is needed. 2) Each layer should perform specific function. 4

5. OSI (cont) 3) The function of each layer should defined looking to protocol. 4) Minimize information flow 5) Not too small not too large 5

6. Figure 1-20: The OSI reference Model. 6

7. Physical layer Where the actual connection happens 7

8. Data link layer Transform row data into data frames and send it to receiver and the receiver will send acknowledgment frame. Flow control. 8

9. Network Layer Routing packets from source to destination Control congestion. Solve problems of addressing. 9

10. Transport Layer Accept data from above split it up into smaller units pass these to network layer and ensure all these pieces arrives correctly to other end. Error free point-to-point connection End – to – end layer 10

11. Session layer Start or establish the connection between users of different machines, and it offers: 1-dialog control. 2-token management. 3-syncronization. 11

12. Presentation layer Concerned with data presentation. 12

13. The application layer Contains protocol needed by users : HTTP _ SMTP _ FTP 13

14. TCP/IP History: ARPANET “research network sponsored by D.O.D to connect universities and governments institution using leased telephone line. What led's to producing TCP/IP ? 14

15. TCP/IP has 4 Layers Figure 1-21: The TCP/IP reference Model. 15

16. 1) Internet layer -Deliver packet to desired destination. -Defining official packet format and protocol called (IP)“internet protocol”. 16

17. 2)Transport Layer Main job to allow peer entities in source and destination to carry on conversation. has two protocols: 1) TCP _ transmission control protocol. -Reliable connection oriented protocol -Flow control 2)UDP _ User Datagram Protocol - Unreliable connection protocol. 17

18. The application layer Contains protocol needed by users : HTTP _ SMTP _ FTP 18

19. Host_To_Network Main job to connect host to network. Rarely discussed on TCP/IP papers. 19

20. Comparison Between OSI and TCP/IP Similarities - both based on concept of stack of independent protocols. - layers in both models have the same function. 20

21. Comparison Between OSI and TCP/IP Differences 1)there are Three concepts that are centralized to OSI Model: 1- services 2- interfaces 3- protocols 2)number of layers. 3)Connectionless and connection oriented 21

22. Critique of OSI Model and protocols 1.Bad timing. 2.Bad technology. 3.Bad implementation. 4.Bad politics. 22

23. Figure 1-23: The apocalypse of the two elephants Bad Timing 23

24. Critique of TCP/IP reference model First: does not distinguish between services interface and protocol. Second: it is not all general. Third: host to network layer. Fourth: physical and data link layer. Last: many other protocol were ad hoc. 24