WAN Configuration 2-23
•
Enter a value from 60 to 100 (percent) in the
Lo/Hi Ratio
field.
Differentiated Ser vices uses the low-to-high priority queue ratio to regulate traffic flow. For example, to
provide the least possible latency and highest possible throughput for high priority traffic, you could set the
ratio to 100(%). This would cause the Router to for ward low priority data
only after
the high priority queue is
completely empty. In practice, you should set it to something less than 100%, since the low priority traffic
might have to wait too long to be passed, and consequently be subject to time-outs.
When the LoHi value is 50 or below, it is equivalent to turning off the ser vice.
Note:
Low to High Priority Queue Asymmetry Field (lohi-asymmetry)
This parameter is a percentage between 50 and 100 used to regulate the level of packets allowed to be pending in the low
priority queue. It can be used to some degree to adjust the relative throughput bandwidth for low vs. high priority traffic.
For example, to provide for least possible latency and highest throughput for high priority packets, you can set the
lohi-asymmetr y to 100%. This will cause the gateway to for ward low priority packets only when the high priority queue is
completely empty. If the high priority stream throughput is such that it fully loads the Gateway, the low priority stream will in
this case be completely suppressed. If it is a TCP stream, it probably will time out. To keep low priority TCP connections
“alive” with minimal throughput while other applications are loading the Gateway with high priority traffic, you might tr y
setting the parameter to 90%. The means a low priority packet will be for warded whenever the relative packet count
asymmetr y, defined as (low)/(high + low) with is greater than .90.
Lowering the lohi-asymmetr y value will lower the throughput and widen the latency distribution of the high priority streams,
so for best results, especially during heavy high priority loading, the value should be left high. Setting the field to 50%, for
example, is almost equivalent to turning off the ser vice as far as the Gateway's behavior is concerned.
Much of the benefit of DiffSer ve is a cumulative one obser ved as packets traverse the nodes on a network from endpoint to
endpoint. A small improvement in the latency distribution for the flow through a single network node (such as a Motorola
Netopia
®
“edge” Gateway) may not be especially noticeable in a VoIP conversation, for example. If the latency for the VoIP
packets in a stream can be minimized through 10 or 20 nodes in the route to the other end of the conversation, however,
the cumulative difference may be ver y noticeable.
In general, a VoIP call, for example, is low bandwidth – bi-directional UDP streams totaling about 20 packets/sec, or
Diffserv Options
Diffserv Enabled: Yes
Lo/Hi Ratio: 0
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Summary of Contents for Netopia Embedded Software
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