Handling Of Traffic Classes - Hirschmann MACH 4000 User Manual

Network load control

8.4.6 Handling of traffic classes

For the handling of traffic classes, the Switch provides:
Strict Priority
Weighted Fair Queuing
Strict Priority combined with Weighted Fair Queuing
Default setting: Strict Priority.
Description of Strict Priority
With the Strict Priority setting, the Switch first transmits all data packets
that have a higher traffic class before transmitting a data packet with the
next highest traffic class. The Switch transmits a data packet with the low-
est traffic class only when there are no other data packets remaining in
the queue. In some cases, a high level of data traffic can prevent packets
with lower traffic classes from being sent.
In applications that are time- or latency-critical, such as VoIP or video, this
method ensures that high-priority data is sent immediately.
Description of Weighted Fair Queuing
With Weighted Fair Queuing, also known as Weighted Round Robin
(WRR), the user can assign a minimum or guaranteed bandwidth to each
traffic class. The result of this is that when the network is very busy, even
data packets with a low priority are transmitted.
The weighting values range from 0% to 100% of the available bandwidth,
in steps of 5%.
A weighting of 0 is equivalent to a "no bandwidth" setting.
The sum of the individual bandwidths may be up to 100%.
If you assign Weighted Fair Queuing to all traffic classes, the entire band-
width for the corresponding port is available to you.
When you combine Weighted Fair Queuing with Strict Priority, make sure
that the highest traffic class of Weighted Fair Queuing is smaller than the
lowest traffic class of Strict Priority.
In this case, a high Strict Priority network load can significantly reduce the
bandwidth available for Weighted Fair Queuing.
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8.4 QoS/Priority
Basic - L3P
Release 4.0 11/07