Handling Jumbo Packets

[soumya panigrahi]

On Mon, Mar 24, 2014 at 2:45 PM, Luigi Rizzo <rizzo at iet.unipi.it> wrote:

>
>
>
> On Mon, Mar 24, 2014 at 7:40 AM, soumya panigrahi <
> soumyapanigrahi at gmail.com> wrote:
>
>> Hi,
>>
>> First of all I would like to thank you all for developing an awesome
>> packet capturing framework.
>> I have been using it recently and find it very very fast and efficient.
>>
>> However off late I am trying to capture Jumbo packets on the network for
>> the following scenario's but that doesn't seem to be working.
>>
>
> the sysctl tree dev.netmap (on FreeBSD)
> or the filesystem
> /sys/module/netmap_lin/parameters
> (on Linux)
> have a number of parameters that control buffer numbers and sizes.
> In particular "buf_size" is used to allocate packet buffers and
> you can bump it up from 2048 to something larger to accommodate
> jumbo buffers.
>
> Depending on the NIC you may need to do something in the initialization
> of the NIC itself to allow sending/receiving frames larger than 1518 bytes,
> but I'd just try and see whether it works for you now.
>
> cheers
> luigi
>

Thanks a lot for the quick response.
I will also try to see if we can handle Jumbo frames by tweaking the
buf_size parameter on Linux.
In addition can you advice if NetMap can de-fragment Jumbo packets that
were fragmented as IP packets by intermediate IP device because of MTU size
limitation?
For example a 9000 Bytes single ethernet frame was fragmented into 1516
Bytes multiple ethernet frames at IP layer.
Can netmap re-assemble these fragmented ethernet frames into a single Jumbo
frame before passing it the application?
If so how?

Thanks,
Soumya

>
>

>
>> Please suggest in its present form is NetMap capable of handling the
>> below scenario's w.r.t Jumbo frames? If how do we have to some special
>> handling w.r.t to this?
>>
>> 1) Netmap is receiving un-fragmented Jumbo frame. In this case is NetMap
>> capable of passing on the Jumbo packet to the user?
>> 2) Netmap receving fragmented Jumbo frames. In this case is NetMap
>> capable of reassembling the fragmented packets and deliver the assembled
>> packet to the user?
>>
>> I have been stuck with this issue for some time now. A quick response
>> would help a great deal.
>>
>> Thanks,
>> Soumya Panigrahi
>>
>
>
>
> --
> -----------------------------------------+-------------------------------
>  Prof. Luigi RIZZO, rizzo at iet.unipi.it  . Dip. di Ing. dell'Informazione
>  http://www.iet.unipi.it/~luigi/        . Universita` di Pisa
>  TEL      +39-050-2211611               . via Diotisalvi 2
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