Transport Layer Issue in Wireless Ad Hoc and Sensor Network

1. Transport Layer Issue in Wireless Ad Hoc and Sensor Network 1

2. Outline • Introduction • TCP Operation • Problem Statement • TCP Feedback • Ad hoc TCP • Conclusion • References • Questions 2

3. Transport Layer • Transport Layer is the fourth layer of OSI reference model. It provided transparent transfer of data between end system using the service of the network layer. • Two main protocols are • Transmission Control Protocol (TCP) • User Datagram Protocol (UDP) 3

4. TCP vs. UDP TCP • Connection oriented service • Provides end-to-end reliable communication • Congestion control • Connection management • Flow control • Wireless ad hoc and wireless sensor network • UDP • Is very simple connectionless protocol • Does not guarantee reliability and correctness of the sequence of the packet • IPTV, streaming media, VoIP, and online games 4

5. TCP vs. UDP 5

6. TCP vs. UDP 6

7. Mobile Ad hoc Network • Mobile Ad hoc network (MANET) is self-configured network which consist of mobile devices within a communication range of each other • Rapid topological change due to • Mobility of the nodes • Tradition TCP design is not suitable 7

8. Wireless Sensor Network • A wireless sensor network (WSN) is a collection of sensor network that are capable of sensing physical phenomena • Rapid topological change due to • Mobility of the nodes • Tradition TCP design is not suitable 8

9. TCP 9

10. TCP Open Operation 10

11. TCP Open Operation Active participant Passive participant (client) (server) SYN, SequenceNum = x , y 1 + SYN + ACK, SequenceNum = x Acknowledgment = ACK, Acknowledgment = y + 1 11

12. TCP Data Transfer Operation 12

13. TCP Termination Operation 13

14. Active participant Passive participant (server) (client) FIN, SequenceNum = x 1 + x Acknowledgment = y FIN, SequenceNum= Acknowledgment = y + 1 14

15. Problem Statement • TCP was originally designed and optimized for a wired network • In wired network route failure is not common • In mobile ad Hoc and sensor network route failure is frequent and it is unpredictable • Traditional TCP misinterpreted route failure as congestion problem 15

16. TCP misinterpretation • The sender TCP attempt to perform the following: • Invoke congestion control mechanism • Retransmit unacknowledged packet • Enter a slow rate recovery phase • Waste the scarce power and BW of the sender and intermediate nodes 16

17. Solution • TCP-feedback (TCP-F) • Ad hoc TCP or (ATCP) 17

18. TCP-F • Network layer provide feedback to the intermediate node and the source node’s TCP agent by notification packet • Route Failure Notification (RFN) packet • Rout Re-establishment Notification (RFN) packet • The point where the route is disconnected is called failed point (FP) • The source node changes from active state to snoozing state when it receives RFN • The route failure time (RFT) ensures the sender does not remain in the snoozing state forever 18

19. TCP-F D N RFN RFN S Failed Point A B C D E G New Route F 19

20. RFN RRN RRN RFN RFN RRN RRN S D A B C C TCP-F Failed Point Snoozing State 20

21. TCP-F issue • It does not re-calculation the congestion window upon establishing a new route • Out-of- order packet is not optimized • Bit error rate is not considered 21

22. A TCP • ATCP is a thin layer that is inserted between the IP and TCP • It listen the network state information provided by Explicit Congestion Notification (ECN) and by the ICMP “Destination Unreachable” message • The Source node change from active state to persist state when ICMP message is detected • ATCP change from connected to disconnected mode 22

23. ATCP • TCP generate probe packet while the source is in persist mode • Continuously probe the network until a new route is established • Destination node send ACK packet 23

24. ATCP Advantage • Standard TCP/IP is not modified • ATCP is invisible to TCP • ATCP does not interfere when TCP is delivering end-to-end message between a mobile node to a wired network • Congestion window is calculated to adapt with the new route BW requirement 24

25. ATCP Drawback • The source node can remain in the persist mode forever • The probing mechanism can generate problem in case of high load 25

26. TCP-F vs. ATCP 26

27. Conclusion • Traditional TCP misinterpret route failure as a congestion problem • It has to be optimized to work with wireless ad hoc and sensor network • TCP -F • Ad hoc TCP 27

28. References [1] K. Chandran, S. Raghunathan, S. Venkatesan, and R. Prakash, “A Feedback based scheme for improving TCP performance in ad hoc wireless networks,” in Conference on Distributed Computing Systems, Amsterdam, Netherlands, May 1998, pp. 472–479. [2] J. Liu and S. Singh, “ATCP: TCP for mobile ad hoc networks,” IEEE JSAC, vol. 19, no. 7, pp. 1300–1315, Jul. 2001. [3] H.AL.Ahmed,A.Eitan,and N.Philippe, “A Survey Of TCP over Ad Hoc Networks,” June, 2005 [4] “Networking Technology Layer 4,” class notes for ELG 5369, Departemnt of Electrical and computer Engineering, Univeristy of Ottawa, Ottawa, Fall 2010. [5] R.Eric, “TCP vs. UDP” May,2004 http://www.skullbox.net/tcpudp.php 28

29. Questions 1 • Why is the traditional TCP is not suitable in mobile ad hoc and sensor network • Because route failure or topological change is misinterpreted as a congestion problem 29

30. Question 2 • TCP three way handshaking open operation is shown in the diagram below. What is the value of x and y? • x=700, y=501 (client) (server) SYN, SequenceNum = 500 x SYN + ACK, SequenceNum = y Acknowledgment = ACK, Acknowledgment = 701 30

31. Question 3 • In TCP-F technique, the route failure notification (RFN) packet changes the source node’s TCP state from an active state to a snoozing state. Before receiving the RFN packet, the source was transmitting the packet at a rate of 100Kbit/sec. Upon receiving the route retransmission notification (RRN) packet, the sender node resumes transmission.  At what rate the source node resume transmitting?Answer: 100Kbit/sec 31