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Papers by Bassouma Cristian Lay

Research paper thumbnail of Chord: A scalable peer-to-peer lookup service for internet applications

IEEE/ACM Transactions on Networking, 1995

A fundamental problem that confronts peer-to-peer applications is to efficiently locate the node ... more A fundamental problem that confronts peer-to-peer applications is to efficiently locate the node that stores a particular data item. This paper presents Chord, a distributed lookup protocol that addresses this problem. Chord provides support for just one operation: given a key, it maps the key onto a node. Data location can be easily implemented on top of Chord by associating a key with each data item, and storing the key/data item pair at the node to which the key maps. Chord adapts efficiently as nodes join and leave the system, and can answer queries even if the system is continuously changing. Results from theoretical analysis and simulations show that Chord is scalable, with communication cost and the state maintained by each node scaling logarithmically with the number of Chord nodes. of nearby servers, anonymity, search, authentication, and hierarchical naming. Despite this rich set of features, the core operation in most peer-to-peer systems is efficient location of data items. The contribution of this paper is a scalable protocol for lookup in a dynamic peer-to-peer system with frequent node arrivals and departures.

Research paper thumbnail of End-to-end Routing Behavior in the Internet

Computer Communication Review, 1996

The large-scale behavior of routing in the Internet has gone virtually without any formal study, ... more The large-scale behavior of routing in the Internet has gone virtually without any formal study, the exceptions being Chinoy's analysis of the dynamics of Internet routing information [Ch93], and recent work, similar in spirit, by Labovitz, Malan and Jahanian [LMJ97]. We report on an analysis of 40,000 end-to-end route measurements conducted using repeated "traceroutes" between 37 Internet sites. We analyze the routing behavior for pathological conditions, routing stability, and routing symmetry. For pathologies, we characterize the prevalence of routing loops, erroneous routing, infrastructure failures, and temporary outages. We find that the likelihood of encountering a major routing pathology more than doubled between the end of 1994 and the end of 1995, rising from 1.5% to 3.3%. For routing stability, we define two separate types of stability, "prevalence," meaning the overall likelihood that a particular route is encountered, and "persistence," the likelihood that a route remains unchanged over a long period of time. We find that Internet paths are heavily dominated by a single prevalent route, but that the time periods over which routes persist show wide variation, ranging from seconds up to days. About 2/3's of the Internet paths had routes persisting for either days or weeks. For routing symmetry, we look at the likelihood that a path through the Internet visits at least one different city in the two directions. At the end of 1995, this was the case half the time, and at least one different autonomous system was visited 30% of the time.

Research paper thumbnail of Mail and Internet Surveys: The Tailored Design Method

This book is printed on acid-free paper. Copyright © 2007 by John Wiley &... more This book is printed on acid-free paper. Copyright © 2007 by John Wiley & Sons, Inc. All rights reserved. Published by John Wiley & Sons, Inc., Hoboken, New Jersey. Published simultaneously in Canada. No part of this publication may be reproduced, stored in a retrieval system, or ...

Research paper thumbnail of A Hierarchical Internet Object Cache

This paper discusses the design and performance of a hierarchical proxy-cache designed to make In... more This paper discusses the design and performance of a hierarchical proxy-cache designed to make Internet information systems scale better. The design was motivated by our earlier trace-driven simulation study of Internet traffic. We challenge the conventional wisdom that the benefits of hierarchical file caching do not merit the costs, and believe the issue merits reconsideration in the Internet environment.

Research paper thumbnail of Life on the screen: identity in the age of the internet

... Life on the screen : identity in the age of the Internet / Sherry Turkle. p. cm. ... Page 9. ... more ... Life on the screen : identity in the age of the Internet / Sherry Turkle. p. cm. ... Page 9. Page 10. CONTENTS Introduction: Identity in the Age of the Internet 9 I. The SeducTioNS of TNE iNTERfACE 1. A Tale of Two Aesthetics 29 2. The Triumph of Tinkering 50 II. ...

Research paper thumbnail of Promoting the use of end-to-end congestion control in the Internet

IEEE/ACM Transactions on Networking, 1998

This paper considers the potentially negative impacts of an increasing deployment of non-congesti... more This paper considers the potentially negative impacts of an increasing deployment of non-congestion-controlled best-effort traffic on the Internet. 1 These negative impacts range from extreme unfairness against competing TCP traffic to the potential for congestion collapse. To promote the inclusion of end-to-end congestion control in the design of future protocols using best-effort traffic, we argue that router mechanisms are needed to identify and restrict the bandwidth of selected highbandwidth best-effort flows in times of congestion. The paper discusses several general approaches for identifying those flows suitable for bandwidth regulation. These approaches are to identify a high-bandwidth flow in times of congestion as unresponsive, "not TCP-friendly", or simply using disproportionate bandwidth. A flow that is not "TCP-friendly" is one whose long-term arrival rate exceeds that of any conformant TCP in the same circumstances. An unresponsive flow is one failing to reduce its offered load at a router in response to an increased packet drop rate, and a disproportionate-bandwidth flow is one that uses considerably more bandwidth than other flows in a time of congestion.

Research paper thumbnail of Chord: A scalable peer-to-peer lookup service for internet applications

IEEE/ACM Transactions on Networking, 1995

A fundamental problem that confronts peer-to-peer applications is to efficiently locate the node ... more A fundamental problem that confronts peer-to-peer applications is to efficiently locate the node that stores a particular data item. This paper presents Chord, a distributed lookup protocol that addresses this problem. Chord provides support for just one operation: given a key, it maps the key onto a node. Data location can be easily implemented on top of Chord by associating a key with each data item, and storing the key/data item pair at the node to which the key maps. Chord adapts efficiently as nodes join and leave the system, and can answer queries even if the system is continuously changing. Results from theoretical analysis and simulations show that Chord is scalable, with communication cost and the state maintained by each node scaling logarithmically with the number of Chord nodes. of nearby servers, anonymity, search, authentication, and hierarchical naming. Despite this rich set of features, the core operation in most peer-to-peer systems is efficient location of data items. The contribution of this paper is a scalable protocol for lookup in a dynamic peer-to-peer system with frequent node arrivals and departures.

Research paper thumbnail of End-to-end Routing Behavior in the Internet

Computer Communication Review, 1996

The large-scale behavior of routing in the Internet has gone virtually without any formal study, ... more The large-scale behavior of routing in the Internet has gone virtually without any formal study, the exceptions being Chinoy's analysis of the dynamics of Internet routing information [Ch93], and recent work, similar in spirit, by Labovitz, Malan and Jahanian [LMJ97]. We report on an analysis of 40,000 end-to-end route measurements conducted using repeated "traceroutes" between 37 Internet sites. We analyze the routing behavior for pathological conditions, routing stability, and routing symmetry. For pathologies, we characterize the prevalence of routing loops, erroneous routing, infrastructure failures, and temporary outages. We find that the likelihood of encountering a major routing pathology more than doubled between the end of 1994 and the end of 1995, rising from 1.5% to 3.3%. For routing stability, we define two separate types of stability, "prevalence," meaning the overall likelihood that a particular route is encountered, and "persistence," the likelihood that a route remains unchanged over a long period of time. We find that Internet paths are heavily dominated by a single prevalent route, but that the time periods over which routes persist show wide variation, ranging from seconds up to days. About 2/3's of the Internet paths had routes persisting for either days or weeks. For routing symmetry, we look at the likelihood that a path through the Internet visits at least one different city in the two directions. At the end of 1995, this was the case half the time, and at least one different autonomous system was visited 30% of the time.

Research paper thumbnail of Mail and Internet Surveys: The Tailored Design Method

This book is printed on acid-free paper. Copyright © 2007 by John Wiley &... more This book is printed on acid-free paper. Copyright © 2007 by John Wiley & Sons, Inc. All rights reserved. Published by John Wiley & Sons, Inc., Hoboken, New Jersey. Published simultaneously in Canada. No part of this publication may be reproduced, stored in a retrieval system, or ...

Research paper thumbnail of A Hierarchical Internet Object Cache

This paper discusses the design and performance of a hierarchical proxy-cache designed to make In... more This paper discusses the design and performance of a hierarchical proxy-cache designed to make Internet information systems scale better. The design was motivated by our earlier trace-driven simulation study of Internet traffic. We challenge the conventional wisdom that the benefits of hierarchical file caching do not merit the costs, and believe the issue merits reconsideration in the Internet environment.

Research paper thumbnail of Life on the screen: identity in the age of the internet

... Life on the screen : identity in the age of the Internet / Sherry Turkle. p. cm. ... Page 9. ... more ... Life on the screen : identity in the age of the Internet / Sherry Turkle. p. cm. ... Page 9. Page 10. CONTENTS Introduction: Identity in the Age of the Internet 9 I. The SeducTioNS of TNE iNTERfACE 1. A Tale of Two Aesthetics 29 2. The Triumph of Tinkering 50 II. ...

Research paper thumbnail of Promoting the use of end-to-end congestion control in the Internet

IEEE/ACM Transactions on Networking, 1998

This paper considers the potentially negative impacts of an increasing deployment of non-congesti... more This paper considers the potentially negative impacts of an increasing deployment of non-congestion-controlled best-effort traffic on the Internet. 1 These negative impacts range from extreme unfairness against competing TCP traffic to the potential for congestion collapse. To promote the inclusion of end-to-end congestion control in the design of future protocols using best-effort traffic, we argue that router mechanisms are needed to identify and restrict the bandwidth of selected highbandwidth best-effort flows in times of congestion. The paper discusses several general approaches for identifying those flows suitable for bandwidth regulation. These approaches are to identify a high-bandwidth flow in times of congestion as unresponsive, "not TCP-friendly", or simply using disproportionate bandwidth. A flow that is not "TCP-friendly" is one whose long-term arrival rate exceeds that of any conformant TCP in the same circumstances. An unresponsive flow is one failing to reduce its offered load at a router in response to an increased packet drop rate, and a disproportionate-bandwidth flow is one that uses considerably more bandwidth than other flows in a time of congestion.