From: Carlos G Mendioroz (tron@huapi.ba.ar)
Date: Wed Sep 11 2002 - 22:01:55 GMT-3
I would say these are tail drops because of queue filling.
Default queue size is 64 packets... may be you have a big pipe
coming into the router and you are pumping a lot of packets
at once ? Even if the mean 5 min rate is below your service rate,
you may have peak rates well above that.
Just some thoughts...
Brennan_Murphy@NAI.com wrote:
>
> I am having trouble understanding when/why CBWFQ drops packets.
> I've got 5054 packet drops on a PVC but they started incrementing
> even when the 5 minute offered rate was well below the shape
> adaptive command. See config below.
>
> More info:
> This is on a 7505, CBWFQ, IP CEF Disti is on. Frame relay links
>
> Any insights are appreciated.
>
> class-map match-all gold
> match ip precedence 2
> !
> !
> policy-map CBWFQ
> class gold
> bandwidth percent 30
> fair-queue
> policy-map 256CIR
> class class-default
> shape average 768000 3072 3072
> shape adaptive 384000
> service-policy CBWFQ
>
> rt1#sh pol int hss0/0/0.3
> Hssi0/0/0.3: DLCI 320 -
>
> Service-policy output: 256CIR (1231)
>
> Class-map: class-default (match-any) (1251/0)
> 124803 packets, 109774228 bytes
> 5 minute offered rate 417000 bps, drop rate 0 bps
> Match: any (1255)
> queue size 0, queue limit 17
> packets output 134504, packet drops 5054
> tail/random drops 5054, no buffer drops 0, other drops 0
> Shape: cir 768000, Bc 3072, Be 3072
> lower bound cir 384000, adapt to fecn 0
> output bytes 82134895, shape rate 437000 bps
>
> Service-policy : CBWFQ (1233)
>
> Class-map: gold (match-all) (1235/2)
> 0 packets, 0 bytes
> 5 minute offered rate 0 bps, drop rate 0 bps
> Match: ip precedence 2 (1239)
> queue size 0, queue limit 5
> packets output 0, packet drops 0
> tail/random drops 0, no buffer drops 0, other drops 0
> Bandwidth: 30%, kbps 230
> Fair-queue: per-flow queue limit 2
>
> Class-map: class-default (match-any) (1245/0)
> 124803 packets, 109774228 bytes
> 5 minute offered rate 417000 bps, drop rate 0 bps
> Match: any (1249)
> queue size 0, queue limit 11
> packets output 134504, packet drops 5054
> tail/random drops 5054, no buffer drops 0, other drops 0
>
> -BM
-- Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
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