doi:10.1016/j.peva.2007.03.001
Copyright © 2007 Elsevier Ltd All rights reserved.
Decomposition properties in fluid queues
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Yujing Wua,
,
, Weibo Gongb,
and Don Towsleyc, 
aDepartment of Computer Science, University of Calgary, Calgary AB, Canada T2N 1N4
bDepartment of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA 01003, USA
cDepartment of Computer Science, University of Massachusetts, Amherst, MA 01003, USA
Received 1 October 2005;
revised 15 August 2006;
accepted 7 March 2007.
Available online 18 March 2007.
Abstract
We discover two decomposition properties in certain fluid queues. In a queue fed by burst flows, the impact of flow dynamics over shorter timescales on the mean buffer length can be separated from the impact of flow dynamics over larger timescales. A queue with multiple inputs can be decomposed into multiple simpler queues and the two systems have the same mean buffer length. This study may find applications in fast evaluation and resource management of computer networks.
Keywords: Queues; Decomposition; Mean buffer length; Fluid flows
Fig. 1. A fluid burst flow.
Fig. 2. Two special burst flows.
Fig. 3. An active–idle flow.
Fig. 4. Inflow and silent periods in the sample path of a burst flow.
(a) Original queue (System A).
(b) Decomposed queues (System C).
Fig. 5. Flow decomposition illustration.
(a) Tandem queues (System A).
(b) Decomposed tandem queues (System C).
Fig. 6. Flow decomposition in a tandem system.
(a) System A.
(b) System C (decomposed System A).
(c) System D (virtual queue of System A).
(d) System E (decomposed System D and virtual queues of System C).
Fig. 7. Illustration of the proof of Theorem 4.6.
Fig. 8. Flow decomposition of a tandem queue with a flow attached in the middle node.

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