Hirschmann MACH 4000 Series, User Manual

Page: 143 / 236

Traffic control
Basic - L3P
Release 3.1 06/07
8.4 Prioritization
143
D
Strict priority
D
Weighted Fair Queuing
D
Strict Priority combined with Weighted Fair Queuing
Default: Strict Priority.
U
Description Strict Priority
With Strict priority, the Switch sends all data packets with a higher priority
level before it sends a data packet with the next lower priority level. Thus
the Switch does not send a data packet with the next lower priority until
there are no other data packets waiting in the queue. In some cases, a
high level of data traffic can prevent packets with lower priority 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.
U
Description of Weighted Fair Queuing
With Weighted Fair Queuing, also known as Weighted Round Robin
(WRR), the user can assign every priority class a minimal or guaranteed
bandwidth. This ensures that when the network is very busy, even data
packets with a low priority have a chance of being transmitted.
The values for weighting are in the range of 0 % to 100 % of the available
bandwidth in jumps of 5 %.
D
The weighting “0” corresponds to the setting “no bandwidth
guarantee”.
D
The total of the individual bandwidths may be up to 100 %.
If you combine Weighted Fair Queuing with Strict Priority, then make
sure that the highest priority class for Weighted Fair Queuing is smaller
than the lowest priority class for Strict Priority.
In this case, a high Strict Priority network load can significantly reduce
the bandwidth available for Weighted Fair Queuing.