RE: [nsp] CBWFQ On frame relay Interfaces

From: Goodwin, Dustin T [IT] (dustin.t.goodwin@ssmb.com)
Date: Fri Aug 17 2001 - 11:21:00 EDT


-----Original Message-----
>From: Wortendyke, Ken [mailto:KWortendyke@Timebridge.com]
>Subject: RE: [nsp] CBWFQ On frame relay Interfaces
>
>Understood.
>Inquiring QoS minds want to know...
>
>Do you, or anyone else, know of any detrimental effects to having
>mis-matched Tc on opposite ends of a circuit? i.e. a 75xx with 4ms at the
>hub and 10ms on 26xx/36xx at the spokes? If no detriment, will there still
>be a benefit to running it this way? or would a network have to have a 75xx
>on both ends to see an improvement in jitter reduction?

A two way voip call is really two separate one way audio streams. So quality
of each audio path will be independent of the other. I guess it depends on
your total path jitter whether the difference between 4ms of jitter and 10ms
of jitter matters. I stumbled across a bug the Cisco Hoot n Holler feature
set which is really voip over multicast. Where the jitter buffers were set
to zero. So no jitter protection was in place. The small amount of jitter
introduce by actively shaping with a TC of 4ms destroyed voice quality.
Fixing the bug which enabled normal jitter buffer operation completely
masked the jitter introduced by the shaping. I am not sure that answered you
question but those are my thoughts on it.

- Dustin -



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