Samsung Ubigate iBG3026 Configuration Manual page 237

Ubigate iBG3026 Configuration Guide/Ed.00
Therefore it is important to select an optimum value. MPD is entered is
entered as a power of 2 and has a default value of 5. This means the actual
value of MPD = 32 and the Mark Probability = 1/32.
The minth and maxth, are the configured minimum and maximum thresholds
respectively, represents packet queue depth levels at which RED algorithm
changes its course of action, i.e. no-drop, probabilistic-drop, and tail-drop,
depending on whether the average queue size is below minth, in between
minth and maxth, and at or above maxth respectively.
Minth is given a default value of N packets, where N corresponds to ¼ of
maximum of(3 * Ts) msec of buffering(at 100 byte packets) at a rate of
interface bandwidth or 20.(For larger packets, this will result in larger amount
of buffering). This means that, if a interface is receiving not more than it's
bandwidth, on an average at least ¼xTs msec of traffic will be buffered before
RED starts dropping. Note that these buffering requirements are calculated for
100 byte packets which are conservative. The average internet packet size is
probably between 100-200 bytes, for which the buffering would be up to twice
the amount mentioned above. The minimum permissible value for minth is L,
where L corresponds to ¼xTs msec of buffering(for 100 byte packets) at rate
of interface bandwidth or L = 5, whichever is lower.
Maxth is given a default value of N packets, where N corresponds to ¾ of
maximum of(3 * Ts) msec of buffering(at 100 byte packets) at a rate of
interface bandwidth or 20. However it is recommended to set maxth to at least
2 times the minth. Too small a difference between minth and maxth will reduce
the effectiveness of RED by causing frequent tail drops. The maximum permissible
value for maxth is H, where H corresponds to(3*Ts) msec of buffering(for 100 byte
packets) at the rate interface bandwidth or 20, whichever is higher.
Class Queue RED parameters
The EWF and MPD parameters considerations are same as described in the
section Interface RED parameters.
The minth and maxth, are the configured minimum and maximum thresholds
respectively, represents packet queue depth levels at which RED algorithm
changes its course of action, i.e. no-drop, probabilistic-drop, and tail-drop,
depending on whether the average queue size is below minimum threshold, in
between minimum and maximum thresholds, and at or above maximum
threshold respectively.
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