1. Network Models

2. 2.1 what is the Protocol? A protocol defines the rules that both the sender and receiver and all intermediate devices need to follow, to be able to communicate effectively. In the network telecommunication, we need to divide the communication task between different layers, in which case we need a protocol or more at each layer.

3. 2.3 Figure 2.16 Layers and protocols in the reference protocol model

4. Communication through an internet

5. Communication through an internet () bits frames packets Segments or datagrams messages Data units of each layer

7. 2.7 Figure 2.5 Physical layer The physical layer is responsible for movements of individual bits from one hop (node) to the next.

8. 2.8 Figure 2.6 Data link layer The data link layer is responsible for moving frames from one hop (node) to the next.

9. 2.9 Figure 2.7 Hop-to-hop delivery

10. 2.10 Figure 2.8 Network layer The network layer is responsible for the delivery of individual packets from the source host to the destination host.

11. 2.11 Figure 2.9 Source-to-destination delivery

12. 2.12 Figure 2.10 Transport layer The transport layer is responsible for the delivery of a message from one process to another.

13. 2.13 Figure 2.11 Reliable process-to-process delivery of a message

14. 2.14 Figure 2.14 Application layer

15. 2.15 The application layer is responsible for 1- providing services to the user. 2- dialog control and synchronization. 3- translation, compression, and encryption.

16. 2.16 Figure 2.17 Addresses in TCP/IP

17. 2.17 Figure 2.18 Relationship of layers and addresses in TCP/IP

18. 2.18 Figure 2.19 Physical addresses

19. 2.19 Figure 2.20 IP addresses

20. 2.20 Figure 2.21 Port addresses

21. THE DATA LINK LAYER

22. 3.1 DATA LINK LAYER functions 1.Providing a well-defined service interface to the network layer. 2.Error control 3.Flow control: Regulating the flow of data so that slow receivers are not swamped by fast senders. 4.Framing: breaking up the bit stream into discrete frames

23. Packets and Frames Relationship between packets and frames.

24. 3.1.2 Framing A good design of framing must make it easy for a receiver to find the start of new frames while using little of the channel bandwidth. We will look at three methods: – 1. Byte count. – 2. Flag bytes with byte stuffing. – 3. Flag bytes with bit stuffing.

25. 2. Flag bytes with byte stuffing.

26. 3. Flag bytes with bit stuffing.