Chapter-2.pdf
- 1. The Islamia University of Bahawalpur Network Models Chapter - 2
- 2. 2.2 LAYERED TASKS 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.
- 3. 2.3 Scenarios of Protocol Layering First Scenario Single Protocol Layer • • Maria and Ann Professor and Students
- 4. 2.4 Scenarios of Protocol Layering Second Scenario A Three-Layer Protocol
- 5. 2.5 Principles in Protocol Layering First Principle • Bi-directional Communication Second Principle • Two objects at each layer at both sites should be identical
- 6. 2.6 Open System Interconnection Model - OSI Model
- 7. 2.7 THE OSI MODEL 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.
- 8. 2.8 ISO is the organization. OSI is the model. Note
- 9. 2.9 Figure: Seven layers of the OSI model _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ All People Seems To Need Data Processing Signal
- 10. 2.10 Figure: Seven layers of the OSI model A B C D X Y Z _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 200 Pages Italian Document Italian to English 50 50 50 50
- 11. 2.11 Figure: Seven layers of the OSI model Translation/ Compression/ Encryption/NCP/NDR Authentication/ Session Management/PAP/SCP Provides Interface to User. HTTP, HTTPs, SMTP, FTP, TELNET, SSH Segmentation/flow control/error control . TCP/UDP Segments Logical Addressing/Routing/Path Determination IP/DHCP/ICMP/OSPF/BGP Packets Physical Addressing (Mac1/Mac2/Tail)/FDDI/PPP Frame Bits A B C D X Y Z
- 12. 2.12 Figure: The interaction between layers in the OSI model
- 13. LAYERS IN THE OSI MODEL LAYERS IN THE OSI MODEL In this section we briefly describe the functions of each layer in the OSI model. In this section we briefly describe the functions of each layer in the OSI model. In this section we briefly describe the functions of each layer in the OSI model. Application Layer Presentation Layer Session Layer Transport Layer Network Layer Data Link Layer Physical Layer Topics discussed in this section: Topics discussed in this section:
- 16. The application layer is responsible for providing services to the user. Note Application Layer
- 19. The presentation layer is responsible for Translation Compression Encryption Note Presentation Layer
- 20. Session layer
- 21. Session layer
- 22. The session layer is responsible for Dialog control Synchronization Note Session Layer
- 23. Transport layer
- 24. Transport layer
- 26. • • • • • The transport layer is responsible for the delivery of a message from one process to another. Service Point addressing Segmentation Error Control Flow Control Note Transport Layer
- 27. Reliable process-to-process delivery of a message
- 28. Network layer
- 29. IPV4 & IPV6 + Mask Network layer Logical Addressing Routing Path Determination
- 30. The network layer is responsible for the delivery of individual packets from the source host to the destination host. Note Network Layer
- 32. Data link layer
- 34. 2.34 • • • • • The data link layer is responsible for moving frames from one hop (node) to the next. Framing Physical addressing Flow Control Error Control Access Control Note Data Link Layer
- 36. Physical layer
- 37. Physical layer
- 38. • • • The physical layer is responsible for movements of individual bits from one hop (node) to the next. Data Rate Synchronization of bits Transmission mode Note Physical Layer
- 39. Summary of OSI Model layers
- 40. TCP/IP PROTOCOL SUITE TCP/IP PROTOCOL SUITE The layers in the TCP/IP protocol suite do not exactly match those in the OSI model. The original TCP/IP protocol suite was defined as having four layers: network interface, internet, transport, and application. However, when TCP/IP is compared to OSI, we can say that the TCP/IP protocol suite is made of five layers: physical, data link, network, transport, and application. Physical Layer Data Link Layer Network Layer Transport Layer Application Layer Topics discussed in this section: Topics discussed in this section:
- 42. Figure 2.16 Layer Architecture - TCP/IP Protocol Suite
- 43. Figure 2.16 TCP/IP and OSI model OSI Model TCP/IP Layers
- 44. Encapsulation and Decapsulation • • One of the important concepts in protocol layering in the Internet is Encapsulation Decapsulation
- 46. ADDRESSING ADDRESSING Four levels of addresses are used in an internet employing the TCP/IP protocols: physical, logical, port, and specific. Physical Addresses Logical Addresses Port Addresses Specific Addresses Topics discussed in this section: Topics discussed in this section:
- 47. Figure 2.17 Addresses in TCP/IP
- 48. Figure 2.18 Relationship of layers and addresses in TCP/IP
- 49. In Figure 2.19 a node with physical address 10 sends a frame to a node with physical address 87. The two nodes are connected by a link (bus topology LAN). As the figure shows, the computer with physical address 10 is the sender, and the computer with physical address 87 is the receiver. Example 2.1
- 50. Figure 2.19 Physical addresses
- 51. Figure 2.20 shows a part of an internet with two routers connecting three LANs. Each device (computer or router) has a pair of addresses (logical and physical) for each connection. In this case, each computer is connected to only one link and therefore has only one pair of addresses. Each router, however, is connected to three networks (only two are shown in the figure). So each router has three pairs of addresses, one for each connection. Example
- 52. 2.52 Figure 2.20 IP addresses
- 53. 2.53 Figure 2.21 shows two computers communicating via the Internet. The sending computer is running three processes at this time with port addresses a, b, and c. The receiving computer is running two processes at this time with port addresses j and k. Process a in the sending computer needs to communicate with process j in the receiving computer. Note that although physical addresses change from hop to hop, logical and port addresses remain the same from the source to destination. Example 2.4
- 54. 2.54 Figure 2.21 Port addresses
- 55. 2.55 The physical addresses will change from hop to hop, but the logical addresses usually remain the same. Note
- 56. Figure: Multiplexing and Demultiplexing
- 57. OSI versus TCP/IP Lack of OSI Model’s Success
- 58. Figure: OSI versus TCP/IP
- 59. Figure: Lack of OSI Model’s Success • • • OSI was completed when TCP/IP was fully in place and a lot of time and money had been spent on the suite; changing it would cost a lot. Some layers in the OSI model were never fully defined. OSI was implemented by an organization in a different application, it did not show a high enough level of performance