Title page for ETD etd-12122004-202307

Type of Document

Dissertation

Author

Akin, Ozdemir ,

Author's Email Address

ozdemirakin@gmail.com

URN

etd-12122004-202307

Title

Active Queue Management and Scheduling Methods for Packet-Switched Networks

Degree

PhD

Graduate Program

Electrical Engineering

Advisory Committee

Advisor Name	Title
J. Keith Townsend	Committee Chair
George Rouskas	Committee Member
Mihail Devetsikiotis	Committee Member
Yannis Viniotis	Committee Member

Keywords

quality of service
TCP/IP
scheduling
active queue management

Date of Defense

2004-12-09

Availability

unrestricted

Abstract

To support the myriad of envisioned communication products of the future,
there is a need to develop a network infrastructure that can provide
larger bandwidth, with better control of quality of service (QoS).
However, with increasing demand for applications running over packet networks,
congestion at the intermediate nodes (e.g., routers and switches) can be a
serious problem. Consequences include long delays, large delay variation
and high packet loss rates. Different solutions requiring varying levels of
modification to the currently used algorithms have been proposed both for
responsive (e.g., TCP) and
unresponsive (e.g., UDP) protocols. However, most
of the solutions are either
too complicated to implement in real life or not
general enough to be applicable to an arbitrary network topology. In this
thesis, we investigate two
mechanisms - active queue management (AQM), and
scheduling - that can improve QoS in the packet networks. AQM techniques
attempt to prevent congestion
and regulate the queue length by sending
congestion signals (i.e., dropping and/or marking packets) in a proactive
manner, which would eventually cause
the senders to decrease their sending
rates. We use an analytic model derived for TCP in the literature to develop
an AQM scheme that not only controls the queue length at the intermediate
nodes but also distributes the
resources fairly between the users. We
present two different schemes that
have different levels of complexity
and performance. We also propose a distributed networking scheme that
improves the performance of our new AQM algorithms. Although AQM schemes
work well with responsive protocols such as TCP, the performance degrades
for unresponsive protocols since unresponsive
protocols do not change
their packet sending rate in response to
the congestion notifications sent
by the network. Scheduling algorithms can regulate both responsive and
unresponsive flows and can also provide guarantees on some QoS parameters,
such as latency and fairness. We propose a new scheduling algorithm that
can guarantee a better latency and fairness bound than the previous schemes
with a similar complexity. This new scheme uses different queues for each
round to simplify the common sorting problem with the scheduling schemes.
Also a new notion, virtual round, is used to time-stamp incoming packets.

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