Thomas C. Bressoud

Wrapping server-side TCP to mask connection failures

We present an implementation of a fault-tolerant TCP (FT-TCP) that allows a faulty server to keep its TCP connections open until it either recovers or it is failed over to a backup. The failure and recovery of the server process are completely transparent to client processes connected with it via TCP. FT-TCP does not affect the software running on a client, does not require to change the servers TCP implementation, and does not use a proxy.

Optimal configuration for BGP route selection

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 providers 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.

Engineering fault-tolerant TCP/IP servers using FT-TCP

In a recent paper [2] we have proposed FT-TCP: an architecture that allows a replicated service to survive crashes without breaking its TCP connections. FT-TCP is attractive in principle because it does not require modifications to the TCP protocol and does not affect any of the software running on the clients; however, its practicality for realworld applications remains to be proven. In this paper, we report on our experience in engineering FT-TCP for two such applications—the Samba file server and a multimedia streaming server from Apple. We compare two implementations of FT-TCP, one based on primary-backup and another based on message logging, focusing on scalability, failover time, and application transparency. Our experiments suggest that FT-TCP is a practicable approach for replicating TCP/IP-based services that incurs low overhead on throughput, scales well as the number of clients increases, and allows recovery of the service in near-optimal time.

Seamless mobile computing on fixed infrastructure

The term mobile computing typically evokes images of a laptop, handheld, or wearable computer. However, the plummeting cost of hardware suggests that pervasive computing infrastructure could minimize the need to carry such devices in the near future. Personal computing will be available anywhere on demand, like light at the flip of a switch. Only when a user starts to use a computer will it acquire unique customization and state. When the user finishes using the computer, this customization and state will disappear from it. Thus, a user could travel hands-free yet be confident of making productive use of slivers of free time anywhere. For this to be a compelling vision from a users viewpoint, the customization and state acquisition process must be accurate and nearly instantaneous. For it to be a viable business model, the management and system administration costs of pervasive deployments of machines must be low. Internet Suspend/Resume is a thick-client approach to mobility in which hardware virtualization and file caching are the keys to rapid personalization of anonymous hardware for transient use.

Practical and low-overhead masking of failures of TCP-based servers

This article describes an architecture that allows a replicated service to survive crashes without breaking its TCP connections. Our approach does not require modifications to the TCP protocol, to the operating system on the server, or to any of the software running on the clients. Furthermore, it runs on commodity hardware. We compare two implementations of this architecture (one based on primary/backup replication and another based on message logging) focusing on scalability, failover time, and application transparency. We evaluate three types of services: a file server, a Web server, and a multimedia streaming server. Our experiments suggest that the approach incurs low overhead on throughput, scales well as the number of clients increases, and allows recovery of the service in near-optimal time.

Curriculum Guidelines for Undergraduate Programs in Data Science

The Park City Math Institute (PCMI) 2016 Summer Undergraduate Faculty Program met for the purpose of composing guidelines for undergraduate programs in Data Science. The group consisted of 25 undergraduate faculty from a variety of institutions in the U.S., primarily from the disciplines of mathematics, statistics and computer science. These guidelines are meant to provide some structure for institutions planning for or revising a major in Data Science.

Cluster fault-tolerance: An experimental evaluation of checkpointing and MapReduce through simulation

Traditionally, cluster computing has employed checkpointing to address fault tolerance. Recently, new models for parallel applications have grown in popularity — namely MapReduce and Dryad, with runtime systems providing their own reexecute-based fault-tolerance mechanisms, but with no analysis of their failure characteristics. Another development is the availability of failure data spanning years for systems of significant size at Los Alamos National Labs (LANL), but the Time Between Failure (TBF) for these systems is a poor fit to the exponential distribution assumed by optimization work in checkpointing, bringing these results into question. The work in this paper describes a discrete event simulation driven by the LANL data and by models of parallel checkpointing and MapReduce tasks. The simulation allows us to then evaluate and assess the fault tolerance characteristics of these tasks with the goal of minimizing the expected running time of a parallel program in a cluster in the presence of faults for both fault tolerance models.

Results of a Model for Hadoop YARN MapReduce Tasks

The performance of Hadoop YARN MapReduceapplications can be distilled down to a relatively small handfulof performance factors affecting the completion of the individualtask component times of map task time, shuffle time, mergetime, and reduce task time. These four components, coupledwith the operational policies of an application master and theresource management and scheduling ultimately determine theperformance of an application executing on a given cluster. Wepresent models for each of these task components and assess themodels against MapReduce applications to demonstrate their promise.

Session scribe notes for Twenty-First ACM Symposium on Operating Systems Principles

The following article is divided into nine sections, one for each of the sessions presented at SOSP 2007. For each session, two student volunteers took notes at the conference, capturing the questions and answers following each of the papers presented in that session. Note that the session order follows the program as given at the conference which, due to logistic necessity, differs slightly from the order in the proceedings.

Chairs' report on Twenty-First ACM Symposium on Operating Systems Principles

The 21st ACM Symposium on Operating Systems Principles (SOSP 2007) was held at the Skamania Lodge in Stevenson, Washington, USA from October 14th to October 17th 2007. The conference site is located in the Columbia River Gorge National Scenic Area, a spectacular canyon along the border between Oregon and Washington States in the Pacific Northwest, where the Columbia River cuts through the Cascades mountain range. Delegates were treated to breathtaking views of the gorge and mountains from the lodges rustic and warm common areas and the weather cooperated for the arrival and early parts of the conference, though the rains came in force in the latter part of the conference.