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Lecture Business data communications: Chapter 3 - Behrouz A. Forouzan

Chapter 3 - Transport layer. After reading this chapter, the reader should be able to: Understand the position of the transport layer in the internet model; understand the rationale for the existence of the transport layer; understand the concept of application-to-application delivery; understand the duties of the transport layer: packetizing, addressing, connection creation, and reliable delivery. | Chapter 3 Transport Layer Understand the position of the transport layer in the Internet model. Understand the rationale for the existence of the transport layer. Understand the concept of application-to-application delivery. Understand the duties of the transport layer: packetizing, addressing, connection creation, and reliable delivery. After reading this chapter, the reader should be able to: OBJECTIVES Know which application layer program can use UDP and which can use TCP. Distinguish between the two transport-layer protocols used in the Internet: UDP and TCP. APPLICATION-TO- APPLICATION DELIVERY 3.1 Figure 3-1 Transport layer in the Internet model Figure 3-2 Application-to-application delivery DUTIES 3.2 Figure 3-3 Duties of the transport layer Figure 3-4 Connection establishment Figure 3-5 Connection termination Connection is closely related to reliability: A connectionless protocol cannot be reliable because the relationship between packets provides reliability. Note: Figure . | Chapter 3 Transport Layer Understand the position of the transport layer in the Internet model. Understand the rationale for the existence of the transport layer. Understand the concept of application-to-application delivery. Understand the duties of the transport layer: packetizing, addressing, connection creation, and reliable delivery. After reading this chapter, the reader should be able to: OBJECTIVES Know which application layer program can use UDP and which can use TCP. Distinguish between the two transport-layer protocols used in the Internet: UDP and TCP. APPLICATION-TO- APPLICATION DELIVERY 3.1 Figure 3-1 Transport layer in the Internet model Figure 3-2 Application-to-application delivery DUTIES 3.2 Figure 3-3 Duties of the transport layer Figure 3-4 Connection establishment Figure 3-5 Connection termination Connection is closely related to reliability: A connectionless protocol cannot be reliable because the relationship between packets provides reliability. Note: Figure 3-6 Application programs The addresses of client and server programs are defined at the transport layer. These addresses are local to the computer running the programs. The addresses must be unique locally but not universally. Note: Figure 3-7 Port numbers Technical Focus: Range of Port Numbers The port numbers range from 0 to 65535 and are divided into three ranges: Well-known ports: 0 to 1023 Temporary ports: 49,152 to 66,535 Registered ports: 1,024 to 49,151 Business Focus: Well-Known Ports Some well-known port numbers are shown below: SMTP: 25 TFTP: 69 HTTP: 80 FTP: 20 and 21 TELNET: 23 A client uses a temporary port number; a server uses a well-known port number. Note: Figure 3-8 Damage control For reliable service, the transport layer needs to number packets belonging to a connection using sequence numbers. Note: A reliable transport protocol provides damage control, loss control, order control, and duplicate control even if the underlying networking technology and lower-level .