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9.14 PROBLEMS

  1. Assume that when the current size of the congestion window is 48 KB, the TCP sender experiences a timeout. What will be the congestion window size if the next three transmission bursts are successful? Assume that MSS is 1 KB. Consider (a) TCP Tahoe and (b) TCP Reno.

  2. Find out the probability of a path break for an eight-hop path, given that the probability of a link break is 0.2.

  3. Discuss the effects of multiple breaks on a single path at the TCP-F sender.

  4. What additional state information is to be maintained at the FP in TCP-F?

  5. Mention one advantage and one disadvantage of using probe packets for detection of a new path.

  6. Mention one advantage and one disadvantage of using LQ and REPLY for finding partial paths in TCP-BuS.

  7. What is the impact of the failure of proxy nodes in split-TCP?

  8. During a research discussion, one of your colleagues suggested an extension of split-TCP where every intermediate node acts as a proxy node. What do you think would be the implications of such a protocol?

  9. What are the pros and cons of assigning the responsibility of end-to-end reliability to the application layer?

  10. What is the default value of β used for handling induced traffic in ATP and why is such a value chosen?

  11. Explain how network security requirements vary in the following application scenarios of ad hoc wireless networks:

    1. Home networks

    2. Classroom networks

    3. Emergency search-and-rescue networks

    4. Military networks

  12. Explain how security provisioning in ad hoc wireless networks differs from that in infrastructure-based networks?

  13. Explain the key encrypting key (KEK) method.

  14. Nodes A and B want to establish a secure communication, and node A generates a random key 11001001. Suppose the function used by both nodes A and B for encryption is XOR, and let node A generate a random transport key 10010101, and let node B generate 00101011. Explain the three-pass Shamir protocol exchanges.

  15. Why is it not advisable to use natural-language passwords directly for cryptographic algorithms?

  16. Consider the certificate graph shown in Figure 9.17, with the local certificate repositories of nodes A and B as indicated. Find the possible paths of trust from node A to node B which can be obtained using a chain of keys.

    09fig17.gifFigure 9.17 Certificate graph.

  17. List a few inherent security flaws present in the following types of routing protocols: (a) table-driven and (b) on-demand routing.

  18. List and explain how some of the inherent properties of the wireless ad hoc networks introduce difficulties while implementing security in routing protocols.

  19. Mark the paths chosen by the following secure-routing protocols for the network topology shown in Figure 9.18: (a) Shortest path routing and (b) SAR protocol. Assume that node 2 is a secure node. (c) If node 2 (which lies in the path chosen by SAR protocol) is suddenly attacked and becomes a malicious node, then mark an alternative path chosen by SAODV protocol.

    09fig18.gifFigure 9.18 Example network topology.

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