The document summarizes the seven-layer OSI model and its purpose in standardizing network communication. It describes each layer's function, from the physical layer dealing with hardware up to the application layer interacting with software programs. Standards organizations like IEEE, ISO, and IANA help ensure compatibility by defining protocols for each OSI layer.

22. Figure 2.1 Flow of data through the OSI model

30. A Connection Oriented Session at Layer 4

31. Flow Control at Layer 4

32. Windowing Flow Control

33. Acknowledgements

35. Transport Layer (cont’d.) Figure 2-2 Segmentation and reassembly

36. Transport Layer (cont’d.) Figure 2-3 A TCP segment

37. Routing at Layer 3

38. Routers at Layer 3

42. Network Layer (cont’d.) Figure 2-4 An IP packet

46. Data Link Layer (cont’d.) Figure 2-5 The Data Link layer and its sublayers

47. Data Link Layer (cont’d.) Figure 2-6 A NIC’s Mac address

50. OSI Layer Functions

51. The Upper Layers

52. The Lower Layers

53. Data Encapsulation

57. Communication Between Two Systems (cont’d.) Figure 2-7 Data transformation through the OSI model

61. IEEE Networking Specifications (cont’d.) Table 2-2 IEEE 802 standards