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We study and compare topology aggregation techniques used in QoS routing. Topology Aggregation (TA) is defined as a set of techniques that abstract or summarize the state information about the network topology to be exchanged, processed and maintained by network nodes for routing purposes. Due to scalability, aggregation techniques have been an integral part of some routing protocols. However, TA has not been studied extensively except under a rather limited context. Under the continuing growth of the Internet, scalability issues of QoS routing have been gaining more importance. Therefore, we survey the current TA techniques, provide methodology to classify, evaluate, and compare their complexities and efficiencies.

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The growing popularity of 802.11-based wireless LANs (WLAN) also increases the risk of security attacks. Most studies of WLAN security are on the protection of data integrity, and few studies are addressing the issue of Denial of Service (DoS) attacks. This paper studies two major DoS attacks of authentication request flooding (AuthRF) and association request flooding (AssRF). Our studies show that these DoS attacks cause significant performance degradations and may disconnect the communications. A queuing model is presented to study the attacking mechanisms, and the causes of performance degradations. The analytical results of the queuing model are validated by the simulation model, and both results are consistent with the empirical data. The queuing model analysis leads to the development of four solutions: Request Authentication (RA), Reduction of Duplicate Requests (RDR), Reduction of Response Retransmissions (RRR), and Round Robin Transmission (RRT). We tested these four solutions and collected empirical data to validate the effectiveness of the solutions. A comparison of these four solutions is presented to show their strengths and weaknesses in resolving the attacks.