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Upcoming Seminars
Past Seminars - 2006,
2005, 2004, 2003
Martin
Lukac
UCLA
hosted by Aaron Falk
Thu, December 7
1:30 pm PT
11th floor large conference room (1137)
System Management in Challenged Networks
Wireless network technology is being applied to a wide range
of scientific and engineering problems and across a wide
dynamic range of spatial scales. When node placement is
constrained by the application (e.g, coupled to sensor
placement needs), and can not rely on pre-existing
infrastructure (e.g., cellular infrastructure or
power-lines), such systems may experience erratic link
qualities and intermittent node disconnection. These
characteristics, combined with unpredictable environmental
conditions, make it difficult to rely upon traditional end
to end connections for regular high bandwidth data
acquisition and for system management and configuration.
We have implemented and deployed such a "challenged network"
system of 50 nodes for use by seismologists along a part of
the Mesoamerican Subduction Experiment (MASE) broadband
seismic array, stretching 500 KM from Acapulco to Tampico
through Mexico city. The deployed system supports Delay
Tolerant data transfer of relatively high bandwidth seismic
data. Our system includes a reliable asynchronous remote
shell interface called the Disruption Tolerant Shell (DTS)
to accomplish management on this type of system. We present
the implementation of this solution and its evaluation on a
13 node portion of the MASE network.
Bio:
Martin Lukac is a graduate student in Computer Science at
UCLA. He is working on his PhD degree in the CENS System Lab
under Prof. Deborah Estrin. His research interests include
high data rate sensor networks, rapidly deployable systems,
and challenged networks. Prior to coming to UCLA, Martin received
his BS from Haverford College.
Vasilis
Pappas
UCLA
hosted by Aaron Falk
Wed, April 5
1:30 pm PT
11th floor large conference room (1137)
A Resilient Domain Name System
The Domain Name System (DNS) is a critical part of the Internet
infrastructure. Its main functionality is to map human readable
identifiers, such as names, to machine identifiers, such as
IP addresses.
The first part of this talk will focus on two major operational
issues that the DNS currently faces. I will discuss the problem
of denial of service (DoS) attacks targeting the DNS, and
I will show their impact on the DNS operations. Then, I will
present four types of DNS configuration errors and I will
provide the main results of an Internet-wide measurement study,
which show the pervasiveness of these errors and their impact
on the DNS performance. The second part of the talk will focus
on improving the resilience of the DNS. I will present our
DNS configuration verifier with which operators can identify
DNS misconfigurations. Then, I will show an alternative DNS
implementation that is based on structured peer-to-peer systems,
and I will explain why certain aspects of its performance
fall behind the current DNS. Finally, I will show how to improve
the resilience of the DNS by introducing minimal changes in
the DNS caching servers.
Bio:
Vasileios Pappas is a PhD student in the Computer Science
Department at the University of California, Los Angeles. His
research interest include computer networks and distributed
systems and more specifically the dependability and management
issues that arise in large scale systems. Before arriving
to UCLA, he received his B.Eng. degree from National Technical
University of Athens in 2001. Two years later he got the MS
degree from UCLA and he is expected to graduate from the PhD
program in the summer of 2006.
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Purushotham Kamath
ISI
PhD defense practice talk
Advisors: Joe Bannister, Joe Touch
Thu, May 4
2:00pm PT
11th floor large conference room (1137)
Media Access Control for Optical
CDMA Networks through Interference Avoidance
Interference Avoidance is a contention media access control
protocol for optical Code Division Multiple Access (CDMA)
Local Area Networks (LANs). Optical CDMA is a direct sequence
spread spectrum based technology for multiplexing transmissions
on an optical fiber. It can be used as the physical layer
of a high speed, all optical, shared medium LAN. The throughput
of such a network collapses at high offered load due to multi-user
interference. This work shows that Optical CDMA LANs possess
two properties: non mutually destructive interference and
coherence of state. By exploiting these properties, Interference
Avoidance reduces packet loss due to interference and prevents
throughput collapse. Interference Avoidance is an extension
of the Carrier Sensing media access control protocol to high
speed, shared medium, optical LANs. It consists of state estimation
and transmission scheduling. This work proposes algorithms
for state estimation and transmission scheduling. It shows
that they stabilize network throughput at around 30% of the
maximum throughput at high offered load when used with large
length, low weight codesets. The throughput without media
access control tends to zero. The throughput performance of
the algorithms is within 20% of corresponding optimal estimation
and scheduling algorithms. Measurements from a laboratory
testbed demonstrate that transmission scheduling reduces the
bit error rate in the presence of severe physical layer noise.
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Past Seminars - 2006,
2005, 2004, 2003
2006
- Joseph Bannister (5/12/05) - Properties of the
IPv6 Address Space Occupancy
- Clifford Neuman (5/5/05) - DETER Project Overview
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2004
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2003
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