Re: wire rate vs UDP throughput

[Marcelo M. <mar...@us...>]

Thank you Marc for your excelente input..

I did in fact solve the remaining question about the huge
loss rate at the PC2 receiver...

PC1: Fedora Core 1 - transmitter
PC2: Debian Linux - receiver

both PC with the exact same hardware...

I transmit from PC1 --> PC2 and there is aprox 90% loss rate.

I transmit from PC2 --> PC1 and there is aprox 0.5% loss rate.

The switch counters register no aparent loss, so I figure
that DEBIAN linux is the problem....not a stable release,
but the "development" one...

regards,

Marc Herbert wrote:

> On Fri, 30 Jul 2004, Marcelo Maraboli wrote:
> 
> 
>>Marc:
>>
>>how do you figure/calculate the number 22 Mbps from
>>what I am sending ??
>>
>>12/54 ?? this is the efficiency of USER-DATA v/s DATA-ON-WIRE
> 
> 
> Something like that...
> 
> 
> 
>>I think that would mean 22Mbps at the UDP level, but If I use
>>Iperf with -b 100m (UDP level desired byte rate),
>>then Iperf is not obeying me ?? ;)
> 
> 
> Since you are sending packets with approximately 80% headers and 20%
> data on a 100Mb/s Ethernet link (-l 12), iperf can obviously not
> achieve 100Mb/s throughput at the data-UDP level.
> 
> - If packets can be dropped _inside_ the networking stack of the
>   sender where throughputs are much higher than 100Mb/s (this is
>   system dependent, read my previous message concerning linux for
>   instance), then iperf will obey you and send 100Mb/s, but 80% of
>   them in the void inside the sender, and only 20% on the Ethernet
>   link. Is that what you want ?
> 
> - If no packets can be dropped inside the sender, it means iperf will
>   block waiting for the network interface and will be throttled down
>   to about 20%, not obeying you.
> 
> 
> 
>>I use:  iperf -c IP_PC2 -u -w 200k -l 12 -n 1785708 -b 100m
>>are some of these options mutually excluyent ??
> 
> 
> No, it's fine.
> 
> 
> 
>>     (which would lead to 148809 frames/s at 100mbps)
> 
> 
> No.
> 
> "-l 12"   means you send 12*8   = 96 bits of UDP data/frame.
> "-b 100M" means you send 100M bits of UDP data/second
> 
> So this would be about 1 million of frames per second.
> 
> But 100Mb/s of UDP data is not possible anyway on a 100Mb/s link (see
> above and before). You could try that on a 1Gb/s interface.
> 
> 
> 
> 
>>thanks for your input...
> 
> 
> You are welcome.
> 
> 

-- 
Marcelo Maraboli Rosselott
Jefe Area de Redes           (Network & UNIX Systems Administrator)
Ingeniero Civil Electronico                   (Electronic Engineer)

Direccion Central de Servicios Computacionales (DCSC)
Universidad Tecnica Federico Santa Maria, Chile.
phone: +56 32 654237
mailto:mar...@dc...	http://elqui.dcsc.utfsm.cl/