The modern ATM drivers shape the rate at the cell level. This, your IP
throughput must accoubt for cell tax during SAR.
Cell tax is ~15% (depending on packet sizes), and 26/31 is about 86%. This
makes sense.\
chris
> -----Original Message-----
> From: Strakadounas Kostas [mailto:strakad@forthnet.gr]
> Sent: Wednesday, February 07, 2001 8:22 AM
> To: cisco-nsp@puck.nether.net
> Cc: esar@forthnet.gr; achatz@forthnet.gr; kchatz@forthnet.gr
> Subject: [nsp] IP throughput over ATM link
>
>
>
> Does anyone know what is the IP throughput
> over an ATM VC with 80179 cps CBR capacity?
> Normaly I would expect this to be
> 80179cps X 48 bytes per cell X 8 = 30788736 bps.
> So we have made the following config:
> atm pvc 1 4 53 aal5snap 30789 30789
>
> However, the IP throughput I get is only 26Mbps and when
> I push traffic the number of output drops increases.
> Is this normal, or the ATM service is not operating as it should?
> Below you can find some output of the "sh int" and "sh atm vc"
> commands.
>
> Thank you in advance,
>
> Kostas Strakadounas
> FORTHnet SA
>
> forthnet#sh int atm4/0
> Input queue: 0/75/0 (size/max/drops); Total output drops: 198960
> Queueing strategy: Per VC Queueing
> 30 second input rate 12756000 bits/sec, 7451 packets/sec
> 30 second output rate 26138000 bits/sec, 5493 packets/sec
> 17326410 packets input, 3618820122 bytes, 0 no buffer
> Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
> 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
> 11828133 packets output, 2430453178 bytes, 0 underruns
> 0 output errors, 0 collisions, 0 interface resets
> 0 output buffer failures, 0 output buffers swapped out
>
>
> forthnet#sh atm vc
> VCD
> /
> Peak Avg/Min Burst
> Interface Name VPI VCI Type Encaps SC Kbps Kbps
> Cells Sts
> 4/0.1 1 4 53 PVC SNAP UBR
> 30789 UP
>
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