As flight deck touchscreen implementation continues to rise, more research is required to understand how task performance is impacted by turbulence. Previous work found that for basic dragging gestures on a touchscreen, performance and usability declined, and workload increased, with rising levels of turbulence. The current study extended on this work by examining common flight deck tasks using various gestures and input methods. Twenty-six participants completed two tasks (panning and number entry), in different formats, at four levels of turbulent vibration (control, light chop, light turbulence, and moderate turbulence). Performance was assessed objectively (time to completion and additional interactions with the screen), and subjectively (workload, usability, and comfort). Across the tasks, increased turbulence negatively impacted performance, overall workload, and usability. Design recommendations are made for how to best implement pan and number entry tasks on a touchscreen in the flight deck.

We propose a new intra-domain IP routing algorithm called trail blazer (TB) that alleviates network congestion by local decisions based on latency measurements collected by scout packets. TB is a member of a class of traffic-aware routing algorithms based on the behavior of ants. TB maintains in every router a probability table that controls the selection of outgoing links for a given destination. This table is modified by passing scout packets. Some scout packets follow existing high probability paths, and other scout packets explore new paths by making random "mistakes" in order to find detours around congested areas of the network. Scout packets do not have global knowledge of the network topology. Rather, they are influenced by probability trails left by previous scout packets, and leave a trail of updated probability information. TB is meant to be an extension of existing link-state protocols such as OSPF or IS-IS, which provide shortest-path information to initialize the probability table. Simulations of UDP traffic in congested networks show a reduction of packet drops by factors of 3.4-38.4 and 1.8-8.2, for single-path and multi-path shortest-path routing, respectively, with a bounded reordering window. Even though TB may cause packet reordering which may affect the congesting control mechanisms of TCP, TCP traffic sent over TB has a similar bandwidth to shortest-path routing. Simulation of a hybrid routing algorithm that routes TCP traffic over shortest paths and UDP traffic over TB show reduced interference between TCP and UDP traffic.

An Internet Service Provider must provide transit service for traffic between its customers and its providers and, at the same time, attempt to minimize network utilization and balance traffic according to the capacities of its border routers. Central to the selection of border routers for transit traffic flows is the Border Gateway Protocol (BGP) between Autonomous System (AS) peers, through which route advertisements for network prefixes determine the selection of border routers for each traffic flow. This paper examines the problem of determining an optimal set of border routers for the advertisement of network prefixes so as to minimize the cost of traffic across a transit service provider's network while maintaining egress bandwidth constraints at the border routers. Egress bandwidth constraints are considered because there is anecdotal evidence to suggest that the peering links between ASs are often bottleneck links in the Internet, and so the optimal utilization of these links is also critical. After precisely formulating the optimization problem in accordance with the operation of BGP, we relate the problem to the generalized assignment problem and develop heuristic solutions for solving it. Simulation results from an implementation show up to a 37% improvement in the utilization of the peering links when compared to hot potato routing.

A central problem in personal communication systems is to optimize bandwidth usage, while providing Quality of Service (QoS) guarantees to mobile users. Network mobility management, and in particular, location management, consumes a significant portion of bandwidth, which is a necessary overhead for supporting mobile users. We focus our efforts on minimizing this overhead. Unlike previous works, we concentrate on optimizing existing schemes, and so the algorithms we present are easily incorporated into current networks. We present the first polynomial time approximation algorithms for minimum bandwidth location management. In planar graphs, our algorithm provably generates a solution that uses no more than a constant factor more bandwidth than the optimal solution. In general graphs, our algorithm provably generates a solution that uses just a factor O(logn) more bandwidth than optimal where n is the number of base stations in the network. We show that, in practice, our algorithm produces near-optimal results and outperforms other schemes that are described in the literature. For the important case of the line graph, we present a polynomial-time optimal algorithm. Finally, we illustrate that our algorithm can also be used for optimizing the handoff mechanism.

We present a formal specification of the selective acknowledgment (SACK) mechanism that is being proposed as a new standard option for TCP. The formal specification allows one to reason about the SACK protocol; thus, we are able to formally prove that the SACK mechanism does not violate the safety properties (reliable, at most once, and in order message delivery) of the acknowledgment (ACK) mechanism that is currently used with TCP. The new mechanism is being proposed to improve the performance of TCP when multiple packets are lost from one window of data. The proposed mechanism for implementing the SACK option for TCP is sufficiently complicated that it is not obvious that it is indeed safe, so we think it is important to formally verify its safety properties. In addition to safety, we are also able to show that SACK can improve the time it takes for the sender to recover from multiple packet losses. With the additional information available at a SACK sender, the round-trip time that a cumulative ACK sender waits before retransmitting each subsequent packet lost after the very first loss can be saved. We also show that SACK can improve performance even with window sizes as small as four packets and in situations where acknowledgment packets are lost.

The strong correlation between the frequency of words and their naming latency has been well documented. However, as early as 1973, the Age of Acquisition (AoA) of a word was alleged to be the actual variable of interest, but these studies seem to have been ignored in most of the lit(cid:173) erature. Recently, there has been a resurgence of interest in AoA. While some studies have shown that frequency has no effect when AoA is con(cid:173) trolled for, more recent studies have found independent contributions of frequency and AoA. Connectionist models have repeatedly shown strong effects of frequency, but little attention has been paid to whether they can also show AoA effects. Indeed, several researchers have explicitly claimed that they cannot show AoA effects. In this work, we explore these claims using a simple feed forward neural network. We find a sig(cid:173) nificant contribution of AoA to naming latency, as well as conditions under which frequency provides an independent contribution.

Article Reliable message delivery and conditionally-fast transactions are not possible without accurate clocks Share on Author: Mark A. Smith AT&T Labs Research, 180 Park Ave., Florham Park, NJ AT&T Labs Research, 180 Park Ave., Florham Park, NJView Profile Authors Info & Claims PODC '98: Proceedings of the seventeenth annual ACM symposium on Principles of distributed computingJune 1998 Pages 163–171https://doi.org/10.1145/277697.277728Online:01 June 1998Publication History 4citation87DownloadsMetricsTotal Citations4Total Downloads87Last 12 Months4Last 6 weeks0 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

Thw paper considers symmetry-breakhg in an aaynchronoue d~tributed network.We present and analyze a randomized protocol that constructs a maximal independent set in O(log n) expected time, and also a protocol for the dining philosophers problem that schedules a job that competes with 6 other jobs in expected 0(6) time, which is optimal.The beat previous algorithms for dining philosophers achieved only 0(62).In addition, the new protocols are 2-wait-/iwe which means that delays at a process are only dependent on processors or links at most distance two in the communication graph.1. Design a round-based protocol that performs well in a synchronous distributed network.