Title:
On the Computational Complexity of Maintaining GPS Clock and Providing Tight Delay Bounds in Packet Schedule
On the Computational Complexity of Maintaining GPS Clock and Providing Tight Delay Bounds in Packet Schedule
Author(s)
Xu, Jun
Zhao, Qi
Zhao, Qi
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Abstract
Packet scheduling is an important mechanism
for providing QoS guarantees in data networks.
A scheduling algorithm in general consists of two
functions: one estimates how the GPS (General Processor
Sharing) clock progresses with respect to the
real time, and the other decides the order of serving
the packets based on the estimation of their GPS
start/finish times. In this work, we answer important
open questions concerning the computational complexity
of performing both functions. The first part
of our work systematically studies the complexity of
computing the GPS virtual start/finish times of the
packets, which is long believed to be Ω(n) per packet
but has never been proved or explicitly refuted. It also
answers several other related open questions such as
“whether the complexity can be lower if we only want
to compute the relative order of the GPS finish times
of the packets rather than their exact values?” The
second part of our work studies the inherent complexity
for scheduling algorithms to guarantee tight delay
bounds. We extend the prior work by Xu and Lipton
to a stronger and more practical computational model
and explore related issues. We show rigorously that
existing methodologies used in prior work will not be
suitable for establishing lower bound results under the new model.
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Date Issued
2003
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Resource Subtype
Technical Report