2,341 research outputs found
Analysis and Decentralised Optimal Flow Control of Heterogeneous Computer Communication Network Models
General closed queueing networks are used to model the local flow
control in multiclass computer communication networks with single and
multiple transmission links. The problem of analysing multiclass
general closed queueing network models with single server and
multiserver is presented followed by the problem of decentralised
optimal local flow control of multiclass general computer
communication networks with single and multiple transmission links.
The generalised exponential (GE) distributional model with known first
two moments has been used to represent general interarrival and
transmission time distributions as various users have various traffic
characteristics.
A new method of general model reduction using the Norton' s
theorem for general queueing networks in conjunction with the
universal maximum entropy algorithm is proposed for the analysis of large general closed queueing networks. This extension to Norton's
theorem has an advantage over the direct application of the universal
maximum entropy approach whereby the study of a subset of queueing
centres of interest can be done without repeatedly solving the entire
network.
The principle of maximum entropy is used to derive new
approximate solutions for the joint queue length distributions of
multiclass general queueing network models with single server and
multiserver and favourable comparisons with other methods are made.
The decentralised optimal local flow control of the multiclass
computer communication networks with single and multiple transmission
links is shown to be a state dependent window type mechanism that has
been traditionally used in practice
Concave Switching in Single and Multihop Networks
Switched queueing networks model wireless networks, input queued switches and
numerous other networked communications systems. For single-hop networks, we
consider a {()-switch policy} which combines the MaxWeight policies
with bandwidth sharing networks -- a further well studied model of Internet
congestion. We prove the maximum stability property for this class of
randomized policies. Thus these policies have the same first order behavior as
the MaxWeight policies. However, for multihop networks some of these
generalized polices address a number of critical weakness of the
MaxWeight/BackPressure policies.
For multihop networks with fixed routing, we consider the Proportional
Scheduler (or (1,log)-policy). In this setting, the BackPressure policy is
maximum stable, but must maintain a queue for every route-destination, which
typically grows rapidly with a network's size. However, this proportionally
fair policy only needs to maintain a queue for each outgoing link, which is
typically bounded in number. As is common with Internet routing, by maintaining
per-link queueing each node only needs to know the next hop for each packet and
not its entire route. Further, in contrast to BackPressure, the Proportional
Scheduler does not compare downstream queue lengths to determine weights, only
local link information is required. This leads to greater potential for
decomposed implementations of the policy. Through a reduction argument and an
entropy argument, we demonstrate that, whilst maintaining substantially less
queueing overhead, the Proportional Scheduler achieves maximum throughput
stability.Comment: 28 page
Closed queueing networks under congestion: non-bottleneck independence and bottleneck convergence
We analyze the behavior of closed product-form queueing networks when the
number of customers grows to infinity and remains proportionate on each route
(or class). First, we focus on the stationary behavior and prove the conjecture
that the stationary distribution at non-bottleneck queues converges weakly to
the stationary distribution of an ergodic, open product-form queueing network.
This open network is obtained by replacing bottleneck queues with per-route
Poissonian sources whose rates are determined by the solution of a strictly
concave optimization problem. Then, we focus on the transient behavior of the
network and use fluid limits to prove that the amount of fluid, or customers,
on each route eventually concentrates on the bottleneck queues only, and that
the long-term proportions of fluid in each route and in each queue solve the
dual of the concave optimization problem that determines the throughputs of the
previous open network.Comment: 22 page
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Improving the network transmission cost of differentiated web services
This paper investigates into the transmission cost of web services related messages which is affected by network
latency. Web services enable seamless interaction and integration of e-business applications. Web services contain a
collection of operations so as to interact with outside world over the Internet through XML messaging. Though XML
effectively describe message related information and is fairly human readable, it badly affects the performance of Web
services in terms of transmission cost, processing cost, and so on. This paper aims to minimize network latency of message
communication of Web services by employing pre-emptive resume scheduling. Fundamental principle of this approach is the
provision of preferential treatment to some messages as compared to others. This approach assigns different priorities to
distinct classes of messages given the fact that some messages may tolerate longer delays than others. For instance, shorter
messages may be given higher priority than longer messages, or the Web service provider may give higher priority to the
messages of paying subscribers
A Fixed-Point Algorithm for Closed Queueing Networks
In this paper we propose a new efficient iterative scheme for solving closed queueing networks with phase-type service time distributions. The method is especially efficient and accurate in case of large numbers of nodes and large customer populations. We present the method, put it in perspective, and validate it through a large number of test scenarios. In most cases, the method provides accuracies within 5% relative error (in comparison to discrete-event simulation)
Nonlinear Markov Processes in Big Networks
Big networks express various large-scale networks in many practical areas
such as computer networks, internet of things, cloud computation, manufacturing
systems, transportation networks, and healthcare systems. This paper analyzes
such big networks, and applies the mean-field theory and the nonlinear Markov
processes to set up a broad class of nonlinear continuous-time block-structured
Markov processes, which can be applied to deal with many practical stochastic
systems. Firstly, a nonlinear Markov process is derived from a large number of
interacting big networks with symmetric interactions, each of which is
described as a continuous-time block-structured Markov process. Secondly, some
effective algorithms are given for computing the fixed points of the nonlinear
Markov process by means of the UL-type RG-factorization. Finally, the Birkhoff
center, the Lyapunov functions and the relative entropy are used to analyze
stability or metastability of the big network, and several interesting open
problems are proposed with detailed interpretation. We believe that the results
given in this paper can be useful and effective in the study of big networks.Comment: 28 pages in Special Matrices; 201
Store-Forward and its implications for Proportional Scheduling
The Proportional Scheduler was recently proposed as a scheduling algorithm
for multi-hop switch networks. For these networks, the BackPressure scheduler
is the classical benchmark. For networks with fixed routing, the Proportional
Scheduler is maximum stable, myopic and, furthermore, will alleviate certain
scaling issued found in BackPressure for large networks. Nonetheless, the
equilibrium and delay properties of the Proportional Scheduler has not been
fully characterized.
In this article, we postulate on the equilibrium behaviour of the
Proportional Scheduler though the analysis of an analogous rule called the
Store-Forward allocation. It has been shown that Store-Forward has
asymptotically allocates according to the Proportional Scheduler. Further, for
Store-Forward networks, numerous equilibrium quantities are explicitly
calculable. For FIFO networks under Store-Forward, we calculate the policies
stationary distribution and end-to-end route delay. We discuss network
topologies when the stationary distribution is product-form, a phenomenon which
we call \emph{product form resource pooling}. We extend this product form
notion to independent set scheduling on perfect graphs, where we show that
non-neighbouring queues are statistically independent. Finally, we analyse the
large deviations behaviour of the equilibrium distribution of Store-Forward
networks in order to construct Lyapunov functions for FIFO switch networks
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Performance modelling of wormhole-routed hypercubes with bursty traffice and finite buffers
An open queueing network model (QNM) is proposed for wormhole-routed hypercubes with finite
buffers and deterministic routing subject to a compound Poisson arrival process (CPP) with geometrically
distributed batches or, equivalently, a generalised exponential (GE) interarrival time distribution. The GE/G/1/K
queue and appropriate GE-type flow formulae are adopted, as cost-effective building blocks, in a queue-by-queue
decomposition of the entire network. Consequently, analytic expressions for the channel holding time, buffering
delay, contention blocking and mean message latency are determined. The validity of the analytic approximations
is demonstrated against results obtained through simulation experiments. Moreover, it is shown that the wormholerouted
hypercubes suffer progressive performance degradation with increasing traffic variability (burstiness)
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