[P4-dev] P4 issues on mininet with multiple switches

Md. Islam mislam4 at kent.edu
Sat May 6 17:20:28 EDT 2017


It works for multiple routers.

On Sat, May 6, 2017 at 5:08 PM, Hassan Ali Khan <18100116 at lums.edu.pk>

> Thank you, Amedeo, for your reply.
> One other issue that we are facing in mininet is that although the
> simple_router implementation works for one switch, it doesn't work for
> multiple switches. The reason, I assume, is that the table entries caters
> the case where the packet's next hop for the switch is the receiving host
> since there are no switches in between ; however, with multiple switches,
> new entries have to be added where we need the IPs of the switch ports,
> linked with each switch. Maybe that is why, our packets are not being
> forwarded properly.
> What's your view about that?
> Regards,
> Hassan Ali Khan
> 2018-10-0116
> ------------------------------
> *From:* Amedeo Sapio <amedeo.sapio at polito.it>
> *Sent:* Sunday, May 7, 2017 1:29:07 AM
> *To:* Hassan Ali Khan
> *Cc:* p4-dev; Haseeb Naseem
> *Subject:* Re: [P4-dev] P4 issues on mininet with multiple switches
> ​Hi,
> since you talk about acks, I assume you meant TCP and not UDP.
> I had a similar experience using network namespaces (similar to what
> mininet does). The destination host was receiving all the packets but it
> did not send any ACK. The problem was that TCP offloading was active on the
> virtual interfaces, so TCP packets had the wrong checksum. You can disable
> it in each virtual interface used by mininet with the following 2 commands:
> ethtool --offload ethX rx off tx off
> ethtool -K ethX gso off
> ​using the name of your interface instead of ethX.
> Hope this helps,
> Amedeo
> ---
> Amedeo Sapio
> e-mail: amedeo.sapio at polito.it
> Mobile: +39 3291564391
> [image: View Amedeo Sapio's profile on LinkedIn]
> <https://it.linkedin.com/pub/amedeo-sapio/50/153/25>
>> We have been trying to test the P4 implementation of ecmp for quite a
>> while and have failed due to mininet causing problems with topologies
>> containing multiple switches. For example, in our case, Host 1 is sending
>> UDP packets and is Host 2 is receiving packets but not sending ACKS and
>> hence , we cannot evaluate the performance of the protocol. Can you please
>> guide us how to approach this problem?
>> Regards,
>> Hassan Ali Khan
>> 2018-10-0116
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PhD Student/Graduate Assistant
CS Department, Kent State University
Kent, OH 44240
http://web.cs.kent.edu/~mislam4/ <https://web.cs.kent.edu/~mislam4/>
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