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Title : Single PCN Threshold Marking by using PCN baseline encoding for both admission and termination controls
Author(s) : D. Satoh, et al.
Filename : draft-satoh-pcn-st-marking-02.txt
Pages : 37
Date : 2009-09-10
Pre-congestion notification (PCN) gives early warning of congestion
by metering and marking packets in order to protect the quality of
service of inelastic flows. PCN traffic load is divide into three
pre-congestion states by two rates that [I-D.ietf.pcn.architecture]
defines per link: PCN-admissible- and PCN-supportable-rates. PCN
admission control and flow termination mechanisms operate in
accordance with these three states. [I-D.ietf.pcn.baseline.encoding]
defines two PCN encoding states. This document proposes an algorithm
for marking and metering by using PCN baseline encoding for both flow
admission and flow termination. The ratio of marked packets
determines the three link states: no packets marked, some packets
marked, and all packets marked. To achieve this marking behaviour,
we use two token buckets. One is not used for marking but for a
marking switch; the other is used for marking. The token bucket for
marking has two thresholds. One is TBthreshold.threshold, already
defined in [I-D.ietf-pcn-marking-behaviour], and the other is a new
threshold, which is set to be the number of bits of a metered-packet
smaller than the token bucket size. Therefore, the new threshold is
larger than TBthreshold.threshold. If the amount of tokens is less
than TBthreshold.threshold, all the packets are marked as defined in
[I-D.ietf-pcn-marking-behaviour]. If the amount of tokens is less
than the new threshold and greater than TBthreshold.threshold, one-
Nth packets are marked. We evaluated the performance of admission
control and flow termination using a simulation. For admission
control, the results show that the performance of the algorithm was
almost the same as, but slightly inferior to, that of CL
[draft-briscoe-tsvwg-cl-phb-03]. For flow termination, the
performance of the algorithm was almost the same as CL when the load
was 1.2 times the supportable rate, but it was superior to CL when
the load was high (two times the supportable rate). Furthermore, in
the algorithm, over termination percentages of all the bottleneck
links are almost the same in the case of multi-bottleneck. In CL,
the over termination percentages of all the bottleneck links are
different and those at upstream bottleneck links are higher than
those at downstream bottleneck links because of accumulation of
marked packets.
A URL for this Internet-Draft is:
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