1. Transport Layer Issue in Wireless Ad Hoc and Sensor Network1

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 UDP 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 Operation12

13. TCP Termination Operation13

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

20. TCP-F RFN RFN RFN Failed Point S A B C C D Snoozing State RRN RRN RRN20

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 TCP-F ATCP High BER packet lost Not handled Handled
Route Failures detection
RFN packet freezes TCP sender state
ICMP message freezes TCP sender state
Route reconstruction detection
RRN packet resumes TCP to normal state
Probing mechanism
Packet reordering
Congestion window and RTO after RR
Old CW and RTO
Reset for each new route 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
[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 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