Re: rate-limit

in final am gasit niste explicatii, cat or fi de bune nu stiu, dar na si
tie(voua):

When configuring the burst rate you need to take into account that some
protocols implement mechanisms
that reacti on packet loss. For instance, Transmission Control Protocol
(TCP) reduces the window by half for
each lost packet. This causes a "saw tooth" effect in the TCP traffic
when TCP tries to accelerate to the line
rate and is throttled by the policer. If the average rate of the saw
tooth traffic is calculated, it is much lower
than the policed rate. You can, however, increase the burst in order to
achieve better utilization. A good start
would be to set the burst equal to twice the amount of the traffic sent
with the desired rate during Round-Trip
Time (TCP RTT). If RTT is not known you can double the value of the burst
parameter.

The following example calculates the burst for a TCP session with a
policing rate of 64 Kbps and given the
TCP RTT is, 0.05 seconds:
<burst> = 2* * = 2 * 0.05 [sec] * 64000/8 [bytes/sec] = 800 [bytes]

<burst> = 2 * 0.05 [sec] * rate /8 [bytes/sec] = 2 * RTT [sec] * rate /8
[bytes/sec] = rate / 1000 * 12.5 [bytes]
RTT =~ 50ms

In the example above, <burst> is for one TCP session, so it should be
scaled to average the expected number
of sessions traveling through the policer.

C
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