CSCE 990 Networks Systems Seminar
Fall 1999
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Abstract:
In this talk I will address the problem of key distribution for large
dynamic multicast groups. I specially consider the problem of key change
on membership change (join/leave operation). I will present a framework
for developing algorithms for secure multicast communications, and
propose algorithms that require O(log(|M|)) messages instead of O(|M|)
(where |M| denotes the size of the group) when a member leaves the
group. These algorithms have the advantage that they can be implemented
in a centralized manner. This makes them suitable for multicast over
satellite links.
This work is the result of a project sponsored by the European Space Agency during year 1998.
Abstract:
Server responsiveness and scalability are more important than ever in
today's client/server dominated network environments. Recently,
researchers have begun to consider cluster-based computers using
commodity hardware as an alternative to expensive specialized hardware
for building scalable Web servers. In this paper, we present
performance results comparing two cluster-based Web servers based on
different server infrastructures: MAC-based dispatching (LSMAC) and
IP-based dispatching (LSNAT). Both cluster-based server systems were
implemented as application-space programs running on commodity hardware.
We point out the advantages and disadvantages of both systems. We also
identify when servers should be clustered and when clustering will not
improve performance.
Abstract:
SIMON is an object oriented simulation package implementated in C++ which
incorporates optical device charecteristics in the measurement of
network-level blocking statictics. SIMON is suitable for studying the
performance of large wavelength-routed optical networks, in which a call
is setup for a specific duration on a predetermined lightpath. currently
the physical layer models allow for modelling phenomena such as signal
attenuation in fiber and other components, amplifier gain saturation and
homowavelength crosstalk in switches. Simulation experiments can be
performned with a user-specified bit-error rate(BER) limit, which must be
satsified by all calls set up in the network.
Abstract:
Group communication occurs when there are a group of participants
in a session and any one in the group can send messages to and receive
messages from all the other participants in the group. It is becoming
an important and hot research area because of diverse applications
such as teleconferencing, real-time information services, distributed
interactive simulations, and collaborative work. There has been a lot
work done in this area.
In particular, we focus on "Group communication with hierarchical access control," when a group is divided into a number of subgroups at several levels and a high-level subgroup can receive and decrypt the messages from lower-level subgroups; but the reverse is not allowed. Even though there have existed several research results, they are not completely satisfactory. We propose two new schemes , one of which not only solves the problem, effectively and efficiently, but also provides the following properties: hiding of receivers and authentication of sender. Hiding receivers is useful in some situations such as (1) outsiders are not allowed to know who the receivers are, (2) the sender is not allowed to know who the receivers are, (3) or when the sender finds it difficult to know who the receivers are. The authentication of the sender can prevent masquerading attack.
In this talk, we will discuss
Abstract:
Optical network architectures have emerged that exploit more than just the
point-to-point transmission capabilities of optical fibers. Wavelength
division multiplexing and reconfigurability are the key characteristics of
such networks. In this presentation, we shall discuss traffic optimization
and reconfiguration management in MM broadcast optical networks and MM
wavelength routed optical networks. Architecture, notation, and a
mathematical model to represent broadcast networks will be discussed.
Reconfiguration as applicable to both these network architectures will
also be discussed.
Abstract:
While there is currently great interest in the problem of providing
real-time communication and computation services in general purpose
operating systems, the issue of real-time scheduling of internal
operating system activities has received relatively little
attention. Without real-time scheduling of the operating system
itself, the system is susceptible to conditions such as receiver
livelock -- a situation in which an operating system spends all its
time processing arriving network packets, and application processes,
even if scheduled with a real-time scheduler, are starved. We
investigate the problem of scheduling operating system activities
such as network protocol processing in a proportional share manner.
We describe a proportional share implementation of the FreeBSD
operating system and demonstrate that it solves the receiver
livelock problem. Packets are processed within the operating system
only at the cumulative rate at which the destination applications
are prepared to receive them. Our solution ensures that if a packet
is processed by the operating system, it is delivered to the
application and processed in real-time. If packets arrive faster
than an application is prepared to process them, they are discarded
after consuming minimal system resources. In this manner the
performance of "well behaved" applications is unaffected by
"misbehaving" applications. We demonstrate this effect by running a
set of multimedia applications under a variety of network conditions
on a set of increasingly sophisticated proportional share
implementations of FreeBSD and comparing their performance. This
work contributes to our knowledge of the engineering of proportional
share real-time systems.
Abstract:
Recent technological advances in photonics have made optical
interconnects an attractive alternative to electronic interconnects
in multiprocessor and multicomputer systems where communication
bandwidth and latency are of paramount importance. The clear
advantage of optical interconnects over their electronic
counterparts is the massive bandwidth of the former compared to
that of the latter. The ratio of optical I/O bandwidth and
electrical I/O bandwidth is in the order of 10s to 100s in current
technology and could be higher in the future. The challenges, it
seems, have been to find effective ways for the electronic
components that made up most of the processors and network
interfaces to tap into the abundant optical bandwidth while
maintaining the architectural and systems integrity, given the
existing technological differences between electronics and optics.
In this talk, while breif discussions will be given on integrating
an optical interconnection network (IN) into an otherwise entirely
electronic framework, our focus will be on the architectural and
performance aspects of a particular optical IN, hierarchical-ring
IN.
More specifically, analytical queueing network models for expected message delay in 2-level and 3-level hierarchical-ring INs are developed. Such networks have recently been used in commercial and research prototype multiprocessors. A major class of traffic carried by these INs consists of cache line transfers, and associated coherency control messages, between processor caches and remote memory modules in shared-memory multiprocessors. Memory modules are assumed to be evenly distributed over the processor nodes. Such traffic consists of short, fixed-length messages. They can be conveniently transported using the slotted ring transmission technique, which is studied here. The message delay results derived from the models are shown to be quite accurate when checked against a simulation study. The comparisons to simulations include heavy traffic situations where queueing delays in ring crossover switches are significant for ring utilization levels of $80$ to $90\%$. As well as facilitating analysis, the analytical models can be used to determine optimal sizes for the rings at different levels in the hierarchy under specified traffic distributions in a system with a given total number of processor nodes. Optimality is in terms of minimizing average message delay. A specific example of such a design exercise is provided for the uniform traffic case. Architectural implications of a more "purely" optical hierarchical-ring IN will also be briefly discussed.
Abstract:
Ad Hoc wireless networks consist of large population of mobile stations
that are interconnected by a multihop wireless links. The key
characteristics of such a network are large number of users, mobility of
the users, and ability to operate without a fixed base station. The last
feature makes the routing problem more challenging and interesting.
Traditional routing strategies cannot be applied as the links between the
mobile hosts are dynamic in nature. A hierarchical routing algorithm
proposed by Atsushi Iwata et al will be described.
Abstract:
In this talk, we will discuss the issue of providing
Quality of Service on today's Internet (Web) Servers.
The first paper [Chen and Mohapatra] provides a
model for supporting differentiated services.
If time permits, we will discuss the second paper
[Pandey, Barnes, and Olsson] which describes the
design and implementation of a QoS Web Server.
First Paper: Providing Differentiated Service from an Internet Server
Authors: Xiangping Chen and Prasant Mohapatra
Paper Abstract:
Differentiated service been proposed as a potential solution for bandwidth
allocation and expect to be supported in next generation Internet. However, a
service differentiating Internet with best-effort servers may not meet the
overall goals of the differentiated service. In this paper, approaches and
performance issues on providing differentiated services from an Internet server
are studied. Experimental study and analyses prove that under near-saturation
of server utilization, differentiating service provides significantly better
performance to high priority tasks compared to a traditional service mode.
Quantitative performance estimation of different priority levels of tasks is
presented. It is also observed that an enhanced shortest queue first task
assignment scheme helps in decreasing the average response time of the server
system.
Second Paper: Supporting Quality of Service in HTTP Servers
Authors: Raju Pandey, J. Fritz Barnes, and Ronald Olsson
Paper Abstract:
Most implementation of HTTP servers do not distinguish among requests
to different pages. This has the implication that requests for popular pages
have the tendency to overwhelm the requests for other pages. In addition, HTTP
servers do not allow a site to specify polices for server resource allocation.
This paper presents a notion of quality of service that enables a site to
customize how an HTTP server should respond to external requests by setting
priorities among page requests and allocating server resources. It also
describes a design and an implementation of a distributed HEEP server, QoS Web
Server, that enforces the quality of service constraints. The performance
analysis of the prototype server indicates that the server provides the desired
quality of service with minimal overhead.
Abstract:
Most implementation of HTTP servers do not distinguish
among requests to different pages. This has the implication that requests
for popular pages have the tendency to overwhelm the requests for other
pages. In addition, HTTP servers do not allow a site to specify polices
for server resource allocation. This paper presents a notion of quality of
service that enables a site to customize how an HTTP server should respond
to external requests by setting priorities among page requests and
allocating server resources. It also describes a design and an
implementation of a distributed HEEP server, QoS Web Server, that enforces
the quality of service constraints. The performance analysis of the
prototype server indicates that the server provides the desired quality of
service with minimal overhead.
Abstract:
Continuous growth of the Internet and emerging multimedia applications
place demands for higher bandwidth within the Internet Service Providers
(ISPs). This requires higher forwarding performance (packets per second)
by routers, for both multicast and unicast traffic. Along with the need to
improve forwarding performance there is also the need for adding routing
functionality to support multicast, allowing more flexible control over
how traffic is routed, and providing the ability to build a hierarchy of
routing knowledge. Label Switching is a technology that provides an
efficient solution to these challenges. It blends the flexibility and rich
functionality provided by Network Layer routing with the simplicity
provided by the label swapping forwarding paradigm. I intend to talk about
a novel approach to network layer packet forwarding, called Multiprotocol
Label Switching (MPLS) and also about a specific implementation of this
technology - Tag switching architecture.
Reference: RFC 2105: Cisco Systems Tag Switching Architecture Overview: Y Rekhter, B. Davie, D.Katz, E.Rosen, G.Swallow.
Abstract:
Intrusion detection is the problem of identifying unauthorized
use, misuse, and abuse of computer systems by both system insiders and
external penetrators. The proliferation of heterogeneous computer
networks provides additional implications for the intrusion detection.
Namely, the increased connectivity of computer systems gives greater
access to outsiders, and makes it easier for intruders to avoid detection.
DIDS combines distributed monitoring and data reduction with centralized
data analysis to monitor a heterogeneous network of computers. The main
problem considered in the paper is Network user identification problem,
which is concerned with tracking a user moving across the network,
possibly with a new user-id on each computer. This paper provides an
overview of the motivation behind DIDS, the system architecture and
capabilities.