Re: OT: FR fragment size consideration

From: Alexei Monastyrnyi (alexeim@orcsoftware.com)
Date: Tue Nov 14 2006 - 12:41:05 ART


Just a quick example here - physical interface with AIR 128, one PVC
with shaping to CIR 64.

map-class frame-relay FRF
 frame-relay cir 64000
 frame-relay bc 640
 frame-relay be 0
 frame-relay fair-queue
 frame-relay fragment 80 <- based on CIR

vs

map-class frame-relay FRF
 frame-relay cir 64000
 frame-relay bc 640
 frame-relay be 0
 frame-relay fair-queue
 frame-relay fragment 160 <- based on AIR

Why second one is usually said to be recommended?

Thanks in advance,
A.

Alexei Monastyrnyi wrote:
> Hi Group.
>
> I have checked discussions happened to be on this topic starting from
> April but haven't found any clear understanding of how one should pick
> a fragment size with regards to CIR/AIR of the interface.
>
> DocCD and Odom's QoS Guide say that one should consider AIR of the
> slowest end. In some scenarios CIR (shaping rate) is considered when
> picking fragment size.
>
> Could someone point to pros and cons of either approach?
>
> TIA,
> A.
>
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