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QoS - Min and Max Thresholds

Hello Everyone,

I'm studying QoS and I'm wondering how does a Cisco Engineer find out what the best Minimum and Maximum Threshold rates are when using WRED?

Where would one find these values?

I'm under the impression that it requires a study that's based on the size of the queues, is that correct?

But then, I come to the conclusion that even if the queues are big enough, application critical data like (VOIP) would suffer from delay..

So, how do you calculate the min and max threshold values..

Thanks ahead of time..

PR

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VIP Expert

Re: QoS - Min and Max Thresholds

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

Setting WRED parameters, for optimal performance, is (IMO) very tedious.  Lots of variables involved.

For starters, it shouldn't normally be applied to traffic that's not rate-adaptive, such as VoIP.

It works best for multiple large bulk data transfer TCP streams that are using dropped packets for their principle flow control.  Then it can be optimized to maximize their "goodput".

To answer your question, you might study RED literature, and its many variants, found on the Internet.

You also want to study, if you're not already very familiar, with how adaptive flow rate protocols, such as TCP, behave when packets are dropped.  (With TCP also be mindful of the different "flavors", i.e. Tahoe, Reno, New-Reno, etc.)

If you have specific questions, post again to this thread, and I might be able to help.

View solution in original post

1 REPLY 1
VIP Expert

Re: QoS - Min and Max Thresholds

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

Setting WRED parameters, for optimal performance, is (IMO) very tedious.  Lots of variables involved.

For starters, it shouldn't normally be applied to traffic that's not rate-adaptive, such as VoIP.

It works best for multiple large bulk data transfer TCP streams that are using dropped packets for their principle flow control.  Then it can be optimized to maximize their "goodput".

To answer your question, you might study RED literature, and its many variants, found on the Internet.

You also want to study, if you're not already very familiar, with how adaptive flow rate protocols, such as TCP, behave when packets are dropped.  (With TCP also be mindful of the different "flavors", i.e. Tahoe, Reno, New-Reno, etc.)

If you have specific questions, post again to this thread, and I might be able to help.

View solution in original post

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