Cyber security for everyone final project
- 2. LAYERED TASKS We use the concept of layers in our daily life. As an example, let us consider two friends who communicate through postal mail. The process of sending a letter to a friend would be complex if there were no services available from the post office. Sender, Receiver, and Carrier Hierarchy Topics discussed in this section:
- 3. Figure 1 Tasks involved in sending a letter
- 4. THE OSI MODEL Established in 1947, the International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards. An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. It was first introduced in the late 1970s. Layered Architecture Peer-to-Peer Processes Encapsulation Topics discussed in this section:
- 5. ISO is the organization. OSI is the model. Note
- 6. Figure 2 Seven layers of the OSI model
- 7. Figure 3 The interaction between layers in the OSI model
- 8. Figure 4 An exchange using the OSI model
- 9. LAYERS IN THE OSI MODEL In this section we briefly describe the functions of each layer in the OSI model. Physical Layer Data Link Layer Network Layer Transport Layer Session Layer Presentation Layer Application Layer Topics discussed in this section:
- 10. Figure 5 Physical layer
- 11. The physical layer is responsible for movements of individual bits from one hop (node) to the next. Note
- 12. Physical layer • The physical layer is also concerned with the following: 1. Physical characteristics of interface and medium 2. Representation of bits 3. Data rate 4. Synchronization of bits 5. Line configuration (point to point-multipoint) 6. Physical topology 7. Transmission mode (simplex-half duplex-full duplex)
- 13. Figure 6 Data link layer
- 14. The data link layer is responsible for moving frames from one hop (node) to the next. Note
- 15. Figure 7 Hop-to-hop delivery
- 16. Data link layer • The data link layer is also concerned with the following: 1. Framing 2. Physical addressing 3. Flow control 4. Error control 5. Access control
- 17. Figure 8 Network layer
- 18. The network layer is responsible for the delivery of individual packets from the source host to the destination host. Note
- 19. Figure 9 Source-to-destination delivery
- 20. Network layer • The network layer is also concerned with the following: 1. Logical addressing 2. Routing
- 21. Figure 10 Transport layer
- 22. The transport layer is responsible for the delivery of a message from one process to another. Note
- 23. Figure 11 Reliable process-to-process delivery of a message
- 24. Transport layer • The transport layer is also concerned with the following: 1. Service point addressing (port address) 2. Segmentation and reassembly 3. Connection control (connection less or connection oriented) 4. Flow control 5. Error control
- 25. Figure 12 Session layer
- 26. The session layer is responsible for dialog control and synchronization. Note
- 27. Session layer • The session layer is also concerned with the following: 1. Dialog control (half duplex-full duplex) 2. Synchronization (check point)
- 28. Figure 13 Presentation layer
- 29. The presentation layer is responsible for translation, compression, and encryption. Note
- 30. Presentation layer • The presentation layer is also concerned with the following: 1. Translation 2. Encryption 3. Compression
- 31. Figure 14 Application layer
- 32. The application layer is responsible for providing services to the user. Note
- 33. Application layer • The application layer is also concerned with the following: 1. Network virtual terminal 2. File transfer ,access, and management 3. Mail service 4. Directory service
- 34. Figure 15 Summary of layers