[dpdk-users] TimeStamping Packets Generated and Received via Pktgen Application

Ajinkya D Kadam ajinkya.kadam at nyu.edu
Mon Oct 17 10:01:17 CEST 2016


Hi Paul,

Thanks a lot for your help.

I was reading through your paper and I think this tool will be much more
helpful to me. Btw I am using quad X710 and dual X520 NICs.

Is this [1] the right code to look at if i want to see how you have
achieved hardware based time stamping ?

In addition, I want to confirm my understanding of why MoonGen is better
than PktGen in time stamping context.
PktGen reads the value of rdtsc which it then appends to packet, this adds
more delay and hence the precision is bad.

In case of MoonGen how does this work ? I am not sure. Could you please
elaborate ?

Thanks,
Ajinkya


[1]
https://github.com/libmoon/libmoon/blob/b5f6c2cac42c02db64073b57dd8ca82692d3858c/examples/hardware-timestamping.lua

ᐧ

On Sun, Oct 16, 2016 at 6:55 PM, Paul Emmerich <emmericp at net.in.tum.de>
wrote:

> Hi,
>
>
> Ajinkya D Kadam:
>
>> If yes I would like to modify the pktgen code so that each transmitting
>> and
>> received packet is timestamped.  Right now I am exploring the example
>> applications  like rxtx_callbacks which timestamps packets in DPDK, Is
>> this
>> the right direction to go ?
>>
>
> Check out my packet generator MoonGen
> https://github.com/emmericp/MoonGen
>
> It uses the hardware timestamping features (PTP) to do latency
> measurements in the nanosecond-range.
>
> However, if you will run into hardware limitations if you want to
> timestamp *all* packets. This is sometimes supported on RX (e.g., i310,
> X550) but I don't know a NIC that supports this on TX.
>
> As for the precision that is achievable: ~10ns (depending on the NIC) with
> hardware support. Software timestamping will typically result in a standard
> deviation of 200-300ns under load and there will be huge outliers.
>
>
>  Paul
>


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