7,836 research outputs found
Traffic measurement and analysis
Measurement and analysis of real traffic is important to gain knowledge
about the characteristics of the traffic. Without measurement, it is
impossible to build realistic traffic models. It is recent that data
traffic was found to have self-similar properties. In this thesis work
traffic captured on the network at SICS and on the Supernet, is shown to
have this fractal-like behaviour. The traffic is also examined with
respect to which protocols and packet sizes are present and in what
proportions. In the SICS trace most packets are small, TCP is shown to be
the predominant transport protocol and NNTP the most common application.
In contrast to this, large UDP packets sent between not well-known ports
dominates the Supernet traffic. Finally, characteristics of the client
side of the WWW traffic are examined more closely. In order to extract
useful information from the packet trace, web browsers use of TCP and HTTP
is investigated including new features in HTTP/1.1 such as persistent
connections and pipelining. Empirical probability distributions are
derived describing session lengths, time between user clicks and the
amount of data transferred due to a single user click. These probability
distributions make up a simple model of WWW-sessions
Traffic engineering in ambient networks: challenges and approaches
The focus of this paper is on traffic engineering in ambient networks.
We describe and categorize different alternatives for making the routing more adaptive to the current traffic situation and discuss the challenges that ambient networks pose on traffic engineering methods. One of the main objectives of traffic engineering is to avoid congestion by controlling and optimising the routing function, or in short, to put the traffic where the capacity is. The main challenge for traffic engineering in ambient networks is to cope with the dynamics of both topology and traffic demands. Mechanisms are needed that can handle traffic load dynamics in scenarios with sudden changes in traffic demand and dynamically distribute traffic to benefit from available resources. Trade-offs between optimality, stability and signaling overhead that are important for traffic engineering methods in the fixed Internet becomes even more critical in a dynamic ambient environment
DTMsim - DTM channel simulation in ns
Dynamic Transfer Mode (DTM) is a ring based MAN technology that
provides a channel abstraction with a dynamically adjustable capacity.
TCP is a reliable end to end transport protocol capable of adjusting
its rate. The primary goal of this work is investigate the coupling
of dynamically allocating bandwidth to TCP flows with the affect this
has on the congestion control mechanism of TCP. In particular we
wanted to find scenerios where this scheme does not work, where either
all the link capacity is allocated to TCP or congestion collapse
occurs and no capacity is allocated to TCP. We have created a
simulation environment using ns-2 to investigate TCP over networks
which have a variable capacity link. We begin with a single TCP Tahoe
flow over a fixed bandwidth link and progressively add more complexity
to understand the behaviour of dynamically adjusting link capacity to
TCP and vice versa
Happy software developers solve problems better: psychological measurements in empirical software engineering
For more than 30 years, it has been claimed that a way to improve software
developers' productivity and software quality is to focus on people and to
provide incentives to make developers satisfied and happy. This claim has
rarely been verified in software engineering research, which faces an
additional challenge in comparison to more traditional engineering fields:
software development is an intellectual activity and is dominated by
often-neglected human aspects. Among the skills required for software
development, developers must possess high analytical problem-solving skills and
creativity for the software construction process. According to psychology
research, affects-emotions and moods-deeply influence the cognitive processing
abilities and performance of workers, including creativity and analytical
problem solving. Nonetheless, little research has investigated the correlation
between the affective states, creativity, and analytical problem-solving
performance of programmers. This article echoes the call to employ
psychological measurements in software engineering research. We report a study
with 42 participants to investigate the relationship between the affective
states, creativity, and analytical problem-solving skills of software
developers. The results offer support for the claim that happy developers are
indeed better problem solvers in terms of their analytical abilities. The
following contributions are made by this study: (1) providing a better
understanding of the impact of affective states on the creativity and
analytical problem-solving capacities of developers, (2) introducing and
validating psychological measurements, theories, and concepts of affective
states, creativity, and analytical-problem-solving skills in empirical software
engineering, and (3) raising the need for studying the human factors of
software engineering by employing a multidisciplinary viewpoint.Comment: 33 pages, 11 figures, published at Peer
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