A combined delay and throughput proportional scheduling scheme for Differentiated Services

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Sankaran, Samyukta
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Electrical and Computer Engineering

The Department of Electrical and Computer Engineering (ECpE) contains two focuses. The focus on Electrical Engineering teaches students in the fields of control systems, electromagnetics and non-destructive evaluation, microelectronics, electric power & energy systems, and the like. The Computer Engineering focus teaches in the fields of software systems, embedded systems, networking, information security, computer architecture, etc.

The Department of Electrical Engineering was formed in 1909 from the division of the Department of Physics and Electrical Engineering. In 1985 its name changed to Department of Electrical Engineering and Computer Engineering. In 1995 it became the Department of Electrical and Computer Engineering.

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  • Department of Electrical Engineering (1909-1985)
  • Department of Electrical Engineering and Computer Engineering (1985-1995)

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Traditionally, the Internet has provided the same level of service (best effort service) to all users. However, newer applications have wider Quality of Service (QoS) needs, which makes the current scenario inadequate and restrictive. The IETF has proposed two main approaches for achieving QoS - Integrated Services (IntServ) and Differentiated Services (Diffserv). Although the IntServ model offers absolute per-flow performance guarantees, the associated overhead contributes to a lack of scalability in the Internet. Diffserv proposes a more lightweight approach of grouping flows into few classes, offering more scalability at the expense of absolute guarantees. Differentiated Services can take several forms, such as absolute, relative, and proportional differentiation. Proportional Differentiation can be regarded as a general model, which can encompass other models as special cases, in which the performance metrics of classes are ratioed according to their weights. This thesis proposes and evaluates a scheduling mechanism for controlling per-hop performance metrics according to the proportional differentiation model. Classes may specify a weight, and the per-hop aggregate throughput and mean delay of the classes may be controllable according to those weights. The scheme uses the well-known Little's Law to design such a system. A moving window averaging mechanism and an active queue management scheme are simultaneously and respectively used to achieve control over the relative throughputs as well as the relative delays between classes. This scheme ensures that computationally intensive measurement of actual packet delays is not required, and very little state information must be kept. Mathematical bounds for the feasible conditions under which throughput and delay differentiation is achievable are also presented, and extensive simulations show the effectiveness of the scheme.

Tue Jan 01 00:00:00 UTC 2002