RE: [RPRWG] One question about the local add_rate
addRate refers to the actual flow rate that the node
was able to add. If this value is zero, the node
would then advertise a rate of zero in its SCFF. This
would cause all nodes to throttle their rates back to
that value (zero in this case) making room for the local
node to add more. All the nodes in the ring would then
start to increase their local fair rates using the rampCoef.
Let's say you have 4 stations on the ring A->B->C->D, where
each station, if active, tries to send traffic to D.
If A is the only active station, the way the increase
is computed will ensure that it never hits line rate.
There's always a little bandwidth remaining. If both
A and B are active, then station C can get to the point
where it's transit is active 100% of the time. So then
there are two cases:
Single transit queue - In this case, based on thresholds,
congestion will be detected prior to hitting 100% line
rate and zero will be advertised in the SCFF.
Dual transit queue - In this case, the local node will
be able to add traffic building it's STQ to stqLowThreshold.
This will cause it to detect congestion and advertise a
small value of what it was able to add in the SCFF.
This is a simplified example and assumes no classA0
traffic with shaperD set to line rate, and the fairness
scheme is use being the "aggressive mode". However, the
addRate of zero being advertised is just a transient
condition. As soon as congestion subsides, all nodes
will start ramping up their local fair rate values.
It should be possible to observe this behavior in the
simulations, although I can't point to any specific
simulation that shows something like this.
-Anoop
-----Original Message-----
From: X.B.Zhou
To: stds-802-17@xxxxxxxx
Sent: 4/27/03 10:00 AM
Subject: [RPRWG] One question about the local add_rate
Dear all,
I have a question about the local add_rate of a node. I don't know
whether this value refers to the actual flow rate of a
node or represents the flow rate required by the node?
If the local add_rate refers to the actual flow rate of a node,for
example, the upstream of a node occupied all the bandwidth of the link,
then the local add_rate of the node downstream would be zero at this
time. But the simulation results have not proved it.
Does it refer to the rate required by the hosts of the node?
Best Regards,
= = = = = = = = = = = = = = = = = = = =
----------------------
XiaoBo Zhou, Ph.D. Candidate
Dept. E.E., Tsinghua Univ., Beijing 100084, P.R.CHINA
Phone: +86-10-6278-1409
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2003-04-28