weighted fair-queue

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I have a 10Mbps down and 1Mbps up cable circuit with Cisco 851 router. Only QOS available is WFQ. That is fine if I can make a vonage call be stable during an ftp download. Class based Fair Queuing should work, but WFQ should at least limit ftp. I've read this only helps with slower serial links. I want to apply it to the ethernet interface connected to the cable modem. Will this work? What options for congestive discard threshold and dynamic queues do I need for a 1Mbps upload circuit?

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fair-queue

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Correct Answer by Joseph W. Doherty about 7 years 5 months ago

I'm don't know the 851 QoS features, but unless there's some shaper to match your 1 Mbps up, WFQ alone won't help you if the router "sees" the interface as 10 or 100 Mbps.

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Correct Answer
Joseph W. Doherty Thu, 06/18/2009 - 17:02

I'm don't know the 851 QoS features, but unless there's some shaper to match your 1 Mbps up, WFQ alone won't help you if the router "sees" the interface as 10 or 100 Mbps.

Joseph W. Doherty Fri, 06/19/2009 - 09:02

Yes, correct. The router's WFQ will only activate when it "sees" congestion. If the interface is 100 Mbps, but if there's a downstream bandwidth bottleneck, e.g. Cable 1 Mbps, the congestion will form there where you often can't manage it. The "normal" solution is a shaper that "mimics" the downstream bottleneck such that we can prioritize traffic as we desire.

I just took a quick look at the 850's documentation. Documention is sparse when it comes to describing CBWFQ (not WFQ) features. Full CBWFQ often supports shaping, but unclear whether this feature is supported on this platform.

You might try:

policy-map somename

class-default

shape average 1000000

If that "takes", try it on your outbound facing interface, e.g.:

interface FastEthernet x

service-policy outbound somename

Also if the above "takes", there even other "better" CBWFQ statements to support voice, but more involved to configure.

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