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Bandwidth Estimation (Corvil Bandwidth)


Has anyone used the bandwidth estimation feature in IOS?

I have a question about the methodology that I'd like clarified, as follows:

Basically, what I think happens is that you define a bandwidth (% or whatever) and then define QoS targets (drop, delay, etc) and then you let it run for a while (or not? does it calculate immediately or perform traffic analysis?)

After you get the corvil bandwidth you change your original estimate (which could be too low or too high) to what the output suggests.

Is it a one-off process, or do you need to do it continuously?



Super Bronze

Re: Bandwidth Estimation (Corvil Bandwidth)

I've tried it.

You do need to let it "cook" for a little bit for it to compute stats. (It might tie into interface load interval.)

Stats are based on recent traffic, so you need to SNMP poll to see what's going on. (Much as you might for typical interface stats.)

If you change its parameters, it will provide different bandwidth estimates. (For same traffic, reducing delay or drops increases bandwidth estimate.)


I recall for one of the parameters, forget which (it might be documented in a tech note), doesn't compute its estimates too well.

I also recall you might need a separate feature license to use this feature.


Alhough the theory behind this technology is very interesting, I've found much the same information can be inferred using CBWFQ stats and knowing how different traffic behaves; this assuming there's additional cost to legally use this technology.

Re: Bandwidth Estimation (Corvil Bandwidth)

Thanks for the response - very interesting comments. As the feature is licensed I've just been wondering how much value for money it brings, as you say there are other ways to get some numbers.


Super Bronze

Re: Bandwidth Estimation (Corvil Bandwidth)

"As the feature is licensed I've just been wondering how much value for money it brings . . ."

IMO, not enough. It not supporting any type of histogram or even high water marks makes it difficult to instantly derive value from it. You need to tie it to defined CBWFQ classes, i.e. nothing similar to NBAR autodiscovery.

Its biggest advantages might be getting people to think about microbursts and being able to show people (e.g. management) a stat that shows you need X amount of bandwidth to support a class of traffic with defined constraints.

Perhaps Cisco will remove the feature license, as I believe then have done with Netflow. However, I recall I may have read Cisco intends to drop the technology from IOS.

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