1. 思科网络技术学院理事会. http://www.catc.edu.cn 1 OSI Transport Layer Network Fundamentals – Chapter 4

2. 2 思科网络技术学院理事会. http://www.catc.edu.cn Objectives  Explain the need for the Transport layer.  Identify the role of the Transport layer as it provides the end-to-end transfer of data between applications.  Describe the role of two TCP/IP Transport layer protocols: TCP and UDP.  Explain the key functions of the Transport layer, including reliability, port addressing, and segmentation.  Explain how TCP and UDP each handle key functions.  Identify when it is appropriate to use TCP or UDP and provide examples of applications that use each protocol.

3. 3 思科网络技术学院理事会. http://www.catc.edu.cn Course Index  4.1 Roles of the Transport Layer  4.2 The TCP Protocol – Communicating with Reliability  4.3 Managing TCP Sessions  4.4 The UDP Protocol - Communicating with Low Overhead  4.5 Lab Activities

4. 思科网络技术学院理事会. http://www.catc.edu.cn 4 4.1 Roles of the Transport Layer

5. 5 思科网络技术学院理事会. http://www.catc.edu.cn 4.1.1 Purpose of the Transport Layer  Tracking Individual Conversations  Segmenting Data  Reassembling Segments  Identifying the Applications

6. 6 思科网络技术学院理事会. http://www.catc.edu.cn 4.1.2 Controlling the Conversations  The Primary function of Transport layer protocols Segmentation and Reassembly Conversation Multiplexing  Other function of Transport layer protocols Connection-oriented conversations Reliable delivery Ordered data reconstruction Flow control

7. 7 思科网络技术学院理事会. http://www.catc.edu.cn 4.1.3 Supporting Reliable Communication

8. 8 思科网络技术学院理事会. http://www.catc.edu.cn 4.1.4 TCP and UDP  TCP Connection-oriented Reliable delivery Flow control Applications that use TCP: Web Browsers; E-mail File Transfers  UDP Simple Connectionless Low overhead Best effort Applications that use UDP: Domain Name System (DNS); Video Streaming; Voice over IP (VoIP)

9. 9 思科网络技术学院理事会. http://www.catc.edu.cn 4.1.5 Port Addressing  Used for Identifying the Conversations

10. 10 思科网络技术学院理事会. http://www.catc.edu.cn 4.1.5 Port Addressing  Types of port numbers

11. 11 思科网络技术学院理事会. http://www.catc.edu.cn 4.1.5 Port Addressing  netstat Command

12. 12 思科网络技术学院理事会. http://www.catc.edu.cn 4.1.6 Segmentation and Reassembly  Ensures that data is transmitted within the limits of the media  Ensures that data from different applications can be multiplexed on to the media  TCP and UDP Handle Segmentation Differently

13. 思科网络技术学院理事会. http://www.catc.edu.cn 13 4.2 The TCP Protocol – Communicating with Reliability

14. 14 思科网络技术学院理事会. http://www.catc.edu.cn 4.2.1 TCP – Making Conversations Reliable  TCP segment

15. 15 思科网络技术学院理事会. http://www.catc.edu.cn 4.2.2 TCP Server Process

16. 16 思科网络技术学院理事会. http://www.catc.edu.cn 4.2.3 TCP Connection Establishment and Termination  Establishment of TCP sessions

17. 17 思科网络技术学院理事会. http://www.catc.edu.cn 4.2.3 TCP Connection Establishment and Termination  Termination of TCP sessions

18. 思科网络技术学院理事会. http://www.catc.edu.cn 18 4.3 Managing TCP Sessions

19. 19 思科网络技术学院理事会. http://www.catc.edu.cn 4.3.1 TCP Segment Reassembly  Use the sequence number

20. 20 思科网络技术学院理事会. http://www.catc.edu.cn 4.3.2 TCP Acknowledgement with Windowing  Use the acknowledgement number  It’s expectational acknowledgement

21. 21 思科网络技术学院理事会. http://www.catc.edu.cn 4.3.3 TCP retransmission  TCP usually only acknowledges data for contiguous sequence bytes  Selective Acknowledgements is an optional feature

22. 22 思科网络技术学院理事会. http://www.catc.edu.cn 4.3.4 TCP Congestion Control – Minimizing Segment Loss  Window size—flow and congestion control

23. 思科网络技术学院理事会. http://www.catc.edu.cn 23 4.4 The UDP Protocol - Communicating with Low Overhead

24. 24 思科网络技术学院理事会. http://www.catc.edu.cn 4.4.1 UDP – Low Overhead vs. Reliability  UDP Provides the basic Transport layer functions Lower overhead It is not connection-oriented and does not provide the sophisticated retransmission, sequencing, and flow control mechanisms Application that use UDP include: Domain Name System (DNS) Simple Network Management Protocol (SNMP) Dynamic Host Configuration Protocol (DHCP) Routing Information Protocol (RIP) Trivial File Transfer Protocol (TFTP) Online games

25. 25 思科网络技术学院理事会. http://www.catc.edu.cn 4.4.2 UDP Datagram Reassembly  UDP protocol reassembles PDUs in the order that it was received.

26. 26 思科网络技术学院理事会. http://www.catc.edu.cn 4.4.3 & 4.4.4 UDP Processes  Also use port numbers to identify a specified application layer process and direct segments to the proper service or application

27. 27 思科网络技术学院理事会. http://www.catc.edu.cn Summary

28. 28 思科网络技术学院理事会. http://www.catc.edu.cn