592 research outputs found
Global Fairness of additive-increase and multiplicative-decrease with heterogeneous round-trip times
Consider a network with an arbitrary topology and arbitrary communication delays, in which congestion control is based on additive-increase and multiplicative-decrease. We show that the source rates tend to be distributed in order to maximize an objective function called (`` fairness). We derive this result under the assumption of rate proportional negative feedback and for the regime of rare negative feedback. This applies to TCP in moderately loaded networks, and to those TCP implementations that are designed to interpret multiple packet losses within one RTT as a single congestion indication and do not rely on re-transmission timeout. This result provides some insight into the distribution of rates, and hence of packet loss ratios, which can be expected in a given network with a number of competing TCP or TCP-friendly sources. We validate our findings by analyzing the parking lot scenario, and comparing with previous results \cite{floyd-91-b,mathis-97-a}, and an extensive numerical simulation with realistic parameter settings. We apply fairness to gain a more accurate understanding of the bias of TCP against long round trip times
STAIR: Practical AIMD Multirate Congestion Control
Existing approaches for multirate multicast congestion control are either friendly to TCP only over large time scales or introduce unfortunate side effects, such as significant control traffic, wasted bandwidth, or the need for modifications to existing routers. We advocate a layered multicast approach in which steady-state receiver reception rates emulate the classical TCP sawtooth derived from additive-increase, multiplicative decrease (AIMD) principles. Our approach introduces the concept of dynamic stair layers to simulate various rates of additive increase for receivers with heterogeneous round-trip times (RTTs), facilitated by a minimal amount of IGMP control traffic. We employ a mix of cumulative and non-cumulative layering to minimize the amount of excess bandwidth consumed by receivers operating asynchronously behind a shared bottleneck. We integrate these techniques together into a congestion control scheme called STAIR which is amenable to those multicast applications which can make effective use of arbitrary and time-varying subscription levels.National Science Foundation (CAREER ANI-0093296, ANI-9986397
Evaluation Study for Delay and Link Utilization with the New-Additive Increase Multiplicative Decrease Congestion Avoidance and Control Algorithm
As the Internet becomes increasingly heterogeneous, the issue of congestion
avoidance and control becomes ever more important. And the queue length,
end-to-end delays and link utilization is some of the important things in term
of congestion avoidance and control mechanisms. In this work we continue to
study the performances of the New-AIMD (Additive Increase Multiplicative
Decrease) mechanism as one of the core protocols for TCP congestion avoidance
and control algorithm, we want to evaluate the effect of using the AIMD
algorithm after developing it to find a new approach, as we called it the
New-AIMD algorithm to measure the Queue length, delay and bottleneck link
utilization, and use the NCTUns simulator to get the results after make the
modification for the mechanism. And we will use the Droptail mechanism as the
active queue management mechanism (AQM) in the bottleneck router. After
implementation of our new approach with different number of flows, we expect
the delay will less when we measure the delay dependent on the throughput for
all the system, and also we expect to get end-to-end delay less. And we will
measure the second type of delay a (queuing delay), as we shown in the figure 1
bellow. Also we will measure the bottleneck link utilization, and we expect to
get high utilization for bottleneck link with using this mechanism, and avoid
the collisions in the link
On-Line End-to-End Congestion Control
Congestion control in the current Internet is accomplished mainly by TCP/IP.
To understand the macroscopic network behavior that results from TCP/IP and
similar end-to-end protocols, one main analytic technique is to show that the
the protocol maximizes some global objective function of the network traffic.
Here we analyze a particular end-to-end, MIMD (multiplicative-increase,
multiplicative-decrease) protocol. We show that if all users of the network use
the protocol, and all connections last for at least logarithmically many
rounds, then the total weighted throughput (value of all packets received) is
near the maximum possible. Our analysis includes round-trip-times, and (in
contrast to most previous analyses) gives explicit convergence rates, allows
connections to start and stop, and allows capacities to change.Comment: Proceedings IEEE Symp. Foundations of Computer Science, 200
Distributed Rate Allocation Policies for Multi-Homed Video Streaming over Heterogeneous Access Networks
We consider the problem of rate allocation among multiple simultaneous video
streams sharing multiple heterogeneous access networks. We develop and evaluate
an analytical framework for optimal rate allocation based on observed available
bit rate (ABR) and round-trip time (RTT) over each access network and video
distortion-rate (DR) characteristics. The rate allocation is formulated as a
convex optimization problem that minimizes the total expected distortion of all
video streams. We present a distributed approximation of its solution and
compare its performance against H-infinity optimal control and two heuristic
schemes based on TCP-style additive-increase-multiplicative decrease (AIMD)
principles. The various rate allocation schemes are evaluated in simulations of
multiple high-definition (HD) video streams sharing multiple access networks.
Our results demonstrate that, in comparison with heuristic AIMD-based schemes,
both media-aware allocation and H-infinity optimal control benefit from
proactive congestion avoidance and reduce the average packet loss rate from 45%
to below 2%. Improvement in average received video quality ranges between 1.5
to 10.7 dB in PSNR for various background traffic loads and video playout
deadlines. Media-aware allocation further exploits its knowledge of the video
DR characteristics to achieve a more balanced video quality among all streams.Comment: 12 pages, 22 figure
Bandwidth Sharing Scheme of End-to-End Congestion Control Protocols
In a general network, it is not easy to find according to which
criterion the available bandwidth would be shared between
competing flows. In this paper, we propose a technique to find the
bandwidth sharing scheme of end-to-end congestion control
protocols. This technique divides the analysis work into two
separate steps. In the first step, one should find the rate
function, which expresses the relation between the throughput and
the congestion measure. In the second step, the utility function
can be obtained from the rate function
Comparative Study Of Congestion Control Techniques In High Speed Networks
Congestion in network occurs due to exceed in aggregate demand as compared to
the accessible capacity of the resources. Network congestion will increase as
network speed increases and new effective congestion control methods are
needed, especially to handle bursty traffic of todays very high speed networks.
Since late 90s numerous schemes i.e. [1]...[10] etc. have been proposed. This
paper concentrates on comparative study of the different congestion control
schemes based on some key performance metrics. An effort has been made to judge
the performance of Maximum Entropy (ME) based solution for a steady state
GE/GE/1/N censored queues with partial buffer sharing scheme against these key
performance metrics.Comment: 10 pages IEEE format, International Journal of Computer Science and
Information Security, IJCSIS November 2009, ISSN 1947 5500,
http://sites.google.com/site/ijcsis
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