This is a small report in advance of the official notes, written from my
point of view. The key outcomes I noted from the PCN meeting were these:
1) The egress node will always report the measured rates of unmarked,
excess-traffic-marked, and, if applicable, threshold-marked traffic.
This is for two reasons: flexibility in the application of policy at the
decision point, and flexibility in future applications in general.
2) Two remarks apply to the signalling requirements draft. One has to do
with the current division into ingress vs. centralized control. Fortune
has sent notes on that topic. Probably more importantly, the draft has
to talk about how each end knows that the other end is alive, and how
long it is permissible for the system to proceed without some assurance
that the peer is still alive. Steven was going to write a note on this,
since he raised it.
3) The piggybacking behaviour draft needs fixing to match how RSVP and
NSIS actually work. I have to do some studying. Francois LeFaucheur gave
me a reference that should serve as a tutorial.
4) I don't think we came to a conclusion on how much memory/lag is
desirable in the measurements. Accumulating over an interval introduces
some lag. Exponential smoothing or moving averages introduce some lag.
These are both means to reducing very short-term oscillations in system
behaviour. I'm personally indifferent to the means used, but believe
that some damping is desirable.
4) The final point is, I think, the most important one for us to resolve
going forward. That is the question of when reports are issued. It could
be at the end of fixed intervals, or it could be when something
significant has changed. The question is tied up with whether reliable
transport is needed and also with the liveness question described in 2)
above.
Tom Taylor
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