QoS Configuration - b/w command not working?

[ospfrouter]

Dear all,

I have a problem when configuring a simple QoS scenario.

I have 2 routers, both 2901's running IOS15.1(4)M1.

As the starting point for a larger QoS config I need to configure the network as shown in the attached schematic to prioritse traffic, in times of congestion, from PC 10.0.0.2 to PC 20.0.0.2.

The 'WAN' link between each routers gi0/1 interface is 100Mbps.

I can run a 'bandwidth test' between PC 10.0.0.3 and 20.0.0.3 and this consumes 97.7Mbps (ie 100% WAN bandwdith).

I can then run an 'iperf' TCP throughput test between PC 10.0.0.2 and 20.0.0.2 and this yields a throughput of 94Mbps, again consuming all the available bandwidth - once IP and Ethernet overheads are considered.

When however I run the 'iperf' test in conjunction with the 'bandwdith test' my Iperf is reduced to 1.7Mbps while the bandwidth test reduces to 96Mbps.

So i want to develop a QoS config that asigns 75% of available bandwdith to the iperf test in times of congestion.

So on router A I have configured :-

access-list 160 permit ip host 10.0.0.2 host 20.0.0.2

class-map match-all iperf

     match access-group 160

policy-map iperf_policy

     class iperf

     bandwdith percent 75

interface gi0/1

     service-policy output iperf_policy

But the above appears to have no effect - the iperf test still yields a throughput of 1.7Mbps while the bandwidth test is running.

To verify that my access-list and to some extent that other QoS tools are working I can successfully use the 'police' and 'shape' commands to restict traffic. But the 'bandwidth' and 'priority' commands both do not appear to have any effect.

Perhaps this problem centres around iperf being a TCP throughput test - I'm not sure?

Please can anyone offer any ideas ?

Regards

TP

[Joseph W. Doherty · Accepted solution]

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Posting

Perhaps this problem centres around iperf being a TCP throughput test - I'm not sure?

Yes, that's likely the cause.

b/w command doesn't guarantee bandwidth, it just adjusts flow's weight.

Try two flows, of the same kind, between the two classes and see if you obtain the bandwidth split that's configured.

[ospfrouter]

Many thanks Joseph for your prompt reply - very helpful.