[ovs-discuss] packets getting dropped at egress

[Dave Waters]

In my case all my NIC cards can support jumbo frames. So i can really send
a 1600 byte packet. However, i am being restricted by the OVS's internal
port's MTU which is fixed to 1500. As a result i am unable to send out
larger packets (because of the VXLAN header addition). Can somebody please
help me here?

Dave

On Fri, Jul 24, 2015 at 10:39 PM, Dave Waters <davewaters1970 at gmail.com>
wrote:

> That wouldnt work since anybody connected to portA and sending a 1500 byte
> packet, would be unable to do so.
>
> Is there a known limitation wherein i can increase the MTU of an internal
> bridge port?
>
> Dave
>
> On Fri, Jul 24, 2015 at 10:32 PM, Joe Stringer <joestringer at nicira.com>
> wrote:
>
>> Have you tried decreasing the MTU of portA such that packets are
>> encapsulated they're <=1500B?
>>
>> On 23 July 2015 at 08:19, Dave Waters <davewaters1970 at gmail.com> wrote:
>> > Its not. But how do i ensure that my packet does not get dropped
>> somewhere
>> > downstream, since i have now increased it beyond the original value?
>> >
>> > On Thu, Jul 23, 2015 at 7:49 PM, gowrishankar
>> > <gowrishankar.m at linux.vnet.ibm.com> wrote:
>> >>
>> >> On Thursday 23 July 2015 04:16 AM, Dave Waters wrote:
>> >>>
>> >>> Hi,
>> >>>
>> >>> I have two ports in my OVS bridge. I receive packets from one port
>> >>> (portA) and i send them out of the other (portB). When i send out the
>> >>> packets, they are VXLAN tunneled to the other end.
>> >>>
>> >>> Now, the default MTU of all ports (including the bridge port) is 1500
>> in
>> >>> my setup.
>> >>>
>> >>> The issue is that when i get a 1500 byte packet on portA, i try to
>> push
>> >>> it out on portB after slapping on the VXLAN headers. This results in a
>> >>> packet size thats greater than what portB can handle, and hence the
>> packets
>> >>> are dropped.
>> >>>
>> >>
>> >> Is increasing MTU of portB to 1550 (to accommodate additional 50 bytes
>> >> when no vlan taged) a constraint in your setup ?
>> >>
>> >>
>> >>> I know that OVS does not handle IP fragmentation/reassembly, so how
>> do we
>> >>> deal with this situation? I dont think we can rely on path MTU
>> discovery
>> >>> since not all applications do PMTU before spewing out packets. Any
>> ideas,
>> >>> anybody?
>> >>>
>> >>> Warm regards,
>> >>> Dave
>> >>>
>> >>
>> >> --
>> >> Regards,
>> >> Gowrishankar M
>> >>
>> >
>> >
>> > _______________________________________________
>> > discuss mailing list
>> > discuss at openvswitch.org
>> > http://openvswitch.org/mailman/listinfo/discuss
>> >
>>
>
>
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