EtherHaul Operation, Administration and Maintenance Manual
Page 90
occur as multiple TCP hosts reduce their transmission rates). If the difference is
too small, many packets may be dropped at the same time, resulting in global
synchronization.
“n” the average factor
-
“n” is the user
-configurable exponential weight factor.
The previous
average
is more important for the higher n values. Peaks and Lows
in queue length are smoothed by a high value. Lower n values allow the value of
the average queue size to remain similar to the value of the close to the current
queue size.
If the value of n is too high, WRED does not react to congestion. Packets are
sent or dropped as if WRED is not enabled.
Packet Drop Probability
- The mark probability denominator is the fraction of
packets dropped when the average queue size reaches the maximum threshold.
For example, if the denominator is 512, one out of every 512 packets is dropped
when the average queue reaches the maximum threshold.
9.8.6.3
TCP Performance Example
The following images display how the system behaves with and without WRED:
Figure 9-11 TCP Performance without WRED
