An ad hoc network is a group of mobile computers (or nodes) using wireless network interfaces, in which individual nodes cooperate by forwarding packets for each other to allow nodes to communicate beyond direct wireless transmission range. Ad hoc networks require no centralized administration or fixed network infrastructure such as base stations, and can be quickly and inexpensively set up as needed. Examples of applications for ad hoc networks range from military operations and emergency disaster relief, to community networking and interaction between attendees at a meeting. In this tutorial, I will describe some of the research challenges and current solutions in this rapidly growing research area. We will cover protocols at the Medium Access Control (MAC), routing, and transport layers, as well as issues in the simulation and experimental implementation evaluation of ad hoc networking systems. I will also describe the current state and future plans for standardizing routing protocols for ad hoc networks, going on within the Internet Engineering Task Force (IETF), the principal protocol standards development organization for the Internet.

David B. Johnson is an Associate Professor of Computer Science and Electrical and Computer Engineering at Rice University. Prior to joining the faculty at Rice in 2000, he was an Associate Professor of Computer Science at Carnegie Mellon University, where he had been on the faculty for eight years. Professor Johnson is leading the Monarch Project at Rice University, developing adaptive networking protocols and architectures to allow truly seamless wireless and mobile networking. Related to this research, he has also been very active in the Internet Engineering Task Force (IETF), the principal protocol standards development body for the Internet, were he was one of the main designers of the IETF Mobile IP protocol for IPv4 and is the primary designer of Mobile IP for IPv6. He is currently serving as the General Chair for MobiCom 2003; he has served as a member of the Technical Program Committee for over 30 international conferences and workshops and is an editor for several journals. He is also an Executive Committee member and the Treasurer for SIGMOBILE, the ACM Special Interest Group on Mobility of Systems, Users, Data, and Computing.

Quinta-feira, 13:00h - 18:00h, Sala Tambaú (Thursday - 1:00 PM - 6:00 PM)

Over the past few years, we have seen the emergence of distributed, peer-peer application-level networks that provide functionality that has often been the responsibility of lower layers of the network protocol stack. These functions include multicasting, routing for ad hoc and overlay networks, and data storage, discovery, and retrieval. This tutorial will provide a taxonomy of peer-to-peer systems, ranging from the basic file sharing of Napster and Gnutella and variants, through to the persistent storage of freenet, and to Content Addressable Networks, such as CAN, Chord, Pastry. These systems differ in the complexity and distributedness of their service discovery and topology organization, and subsequent indexing, searching, routing. They also provide a wide range of levels of anonymity, availability, and integrity. We will also look at the differences between P2P and pure overlay systems, and how they interact. We'll look at how P2P and overlay services may merge into the current Internet infrastructure. Throughout this tutorial we will try to point out opportunities for performance related research. These fall in the area of workload characterization and modeling and analysis of system behavior.

Don Towsley is currently a Distinguished Professor of Computer Science and co-director of the Computer Networks Laboratory at the University of Massachusetts. He has been working on issues related to modeling, analysis, and control of networks. His current interests include, congestion control, integrated control in wireless networks, and peer-to-peer networks. Don Towsley is the co-recipient of the 1998 IEEE Communications Society William Bennett outstanding paper award and runner up for the same prize in 2000. He has also been the co-recipient of three ACM SIGMETRICS best paper awardsin 1987, 1996, and 2000. He has been elected Fellow of the IEEE and of the ACM for his contributions to network modeling and analysis. He has been on the Editorial Boards of numerous journals including the IEEE Transactions on Communications and the IEEE/ACM Transactions on Networking. Last, he is the Chair of the IFIP Working Group 7.3 on Modeling and Analysis of Computer and Communication systems.

Terça-feira, 13:00h - 18:00h, Sala Iracema (Tuesday - 1:00 PM - 6:00 PM)

Agreements problems are among the most important problems designers of distributed systems have to cope with. Atomic Broadcast, Atomic Multicast and Weak Non-Blocking Atomic Commitment (NBAC) are typical examples of agreement problems encountered in the design and implementation of fault-tolerant distributed systems. An agreement problem involves a set of processes. It is characterized by the fact that these processes have to agree on a common value. For example, in the atomic Broadcast problem, processes have to agree on a single delivery order for a set of messages. In the NBAC problem, processes have to agree on a single outcome for a transaction (Commit or Abort).

In many systems, each agreement problem is solved using a specific protocol. It appears, however, that agreement problems can be perceived as instances of a more abstract problem, namely the Consensus problem. In the consensus problem, each process proposes an initial value to the others and, despite failures, all correct processes have to eventually agree on a common value (called the decision value) that has to be one of the proposed values.

During this tutorial, we will show the interest of providing such a basic Consensus service. We will also describes several protocols that allows to solve the Consensus problem. This problem is apparently simple yet it has no deterministic solution in asynchronous distributed systems that are subject to even a single process crash failure (Fisher-Lynch-Paterson's impossibility result). This impossibility result has motivated researchers to find a set of minimal assumptions that, when satisfied by a distributed system, makes consensus solvable in this system. In particular, the concept of unreliable failure detector introduced by Chandra and Toueg constitutes an answer to this challenge.

Michel Hurfin conducts his scientific research activities at the INRIA laboratory located in Rennes (Brittany, France) where he acts currently as the leader of a project team called ADEPT (Asynchronous Distributed Environments, Protocols and Time). His research interests include distributed systems, software engineering and middleware for distributed operating systems. Recently, he has initiated researches on resource management in Grid computing and also on distributed fault-tolerant middleware. Michel received a Ph.D. degree in Computer Science from the Rennes University. His dissertation topic addressed the problems of execution replay and property detection in distributed applications. In 1994, he has spent a post-doctoral year at Kansas State University in the research group of Professor Mizuno.

Quarta-feira, 13:00h - 18:00h, Sala Ponta Verde (Wednesday - 1:00 PM - 6:00 PM)