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Load Tolerant Queuing Mechanisms for Differentiated Services
2000 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Differentiated services is an architecture supporting differentiation between aggregates of flows. Since the architecture operates on aggregates, it has appealing scaling properties. Nodes within a differentiated services capable network implement standardized per-hop behaviors (PHBs) defining forwarding behaviors for aggregates by using specialized queuing mechanisms. Assured forwarding (AF) is a standardized set of PHBs containing four classes with three PHBs in each class. The PHBs are ordered by drop probability within a class. The aim of this work is to implement and evaluate a queuing mechanism for implementing the PHBs in an AF class, Weighted RED with Thresholds (WRT), in the FreeBSD operating system. WRT complies to the AF requirements even during times of overload. This property makes the queuing mechanism load-tolerant. The implementation is verified and its performance is evaluated in comparison with the performance of ordinary FIFO queuing. The results show that an implementation of WRT can be made efficient. For the implementation of WRT, it proved to be advantageous to use a recently proposed modification to RED (new RED) for early congestion signaling, and to measure drop rates and arrival rates for the aggregates to stabilize the relation between DPLs. The implementation also use a random-drop policy for dropping packets. It is, however, unclear wether this is worth the extra complexity.

Place, publisher, year, edition, pages
Keyword [en]
Technology, Communications, QoS, Differentiated services, queuing, mechanisms, RIO, WRED, WRT
Keyword [sv]
URN: urn:nbn:se:ltu:diva-44336ISRN: LTU-EX--00/114--SELocal ID: 21f5948f-732d-42a0-b682-be8939b5b7e1OAI: diva2:1017612
Subject / course
Student thesis, at least 30 credits
Educational program
Civil Engineering programmes 1997-2000, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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