Financial transaction systems, such as those utilizing the Financial Information Exchange (FIX) protocol, must make buy/sell decisions based on information received over a network interface. However, at the time that a decision to buy or sell is made, some data on the system may not yet be visible to the financial engine software because it has not yet completed being processing by the network protocol stack. This data is hidden from a FIX engine running in user space until the network protocol processing (in the kernel) is fully completed and the message contents are copied from kernel space to user space. This hidden data may contain information that would lead to a more advantageous transaction if it were available to the financial application at the time that the trade decision is made. We have made several modifications to the TCP/IP protocol stack in the Linux operating system. Our protocol modifications allow a user application to determine if there are pertinent pending messages currently being processed in the kernel. If this is the case, the user application may then choose to delay the buy/sell decision by a short time until these additional messages have completed kernel processing and become available to the user application. We have implemented this mechanism under Linux 2.6.27.24 and are evaluating alternate implementations and the significance of the decision improvements that result from this enhancement.

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.

The performance of IP telephony systems is highly dependent on the audio codecs and their reaction to packet loss and instantaneous delays. Understanding the interaction between audio encoding and the dynamic behavior of the Internet is significant for designing adaptive audio transport mechanisms. For this purpose, we conducted a large-scale audio transmission experiment over the Internet in a 12-month period using various Internet sites. As a result of this experiment, we have made a number of new observations to assess the audio quality of G.711 and G.728 codes under different loss and delay conditions. The paper also states a number of recommendations for implementing efficient adaptive FEC and playout mechanisms.

We analyze 12 traces of round-trip Internet packet delay. We find that these traces, when viewed as time series data, often exhibit Hurst parameter (H) estimates greater than 0.5, indicating long-range dependence. Several traces, however, are not well-modeled with a constant H. We discuss in detail our analytical methods and the robustness of empirical estimators of H under conditions of non-negligible packet loss. Our results indicate that Internet delay is bursty across multiple time scales, which implies that end-user duality of service in the Internet is likely to be impacted by long periods of very large and/or highly variable delays.

In this paper we present results which suggest that Internet packet delay, when viewed as a time series, is self-similar in nature. A self-similar phenomenon displays the same or similar statistical properties across a wide range of time scales. Self-similarity has previously been observed in the magnitude of traffic transmitted on local-area and wide-area networks. Our research is the first to explore the self-similarity of traffic delay rather than traffic magnitude. Our results imply that the delay experienced by application layer protocols is extremely bursty and that traditional Poisson models cannot accurately predict the degree of burstiness. Furthermore, we present evidence that the degree of self-similarity for a round-trip path in the Internet may be correlated with the packet loss observed on that path.

We propose an efficient algorithm for constructing multicast trees in the Shufflenet. Although the Shufflenet has been shown to be an important network topology for wavelength division multiplexed (WDM) local optical networks, no algorithm has previously been proposed for multicasting in this network. We present a single-pass algorithm that constructs minimum-delay multicast trees, and show how a second pass can be added to reduce tree cost while maintaining very low delay.