[ovs-discuss] Tunnel path MTU discovery deprecated in 1.9 and what't the substitution?

[Jesse Gross]

Please keep this on the mailing list.

The best place to apply clamping depends on your network topology.  If
you can do it on the VMs, then that is fine although you probably
would be able to just directly change the MTU at that point.
Otherwise, you could also contribute MSS clamping support to OVS,
which is the long term solution to this problem.

On Mon, Mar 11, 2013 at 12:38 AM, Yeming Zhao <zhaoyeming at gmail.com> wrote:
> Thank you Jesse.
> In my case, I'm connecting VMs to an OVS running on a host machine. You
> suggest using MSS clamping inside my guest VMs, right? Because I don't see
> how I can fiddle with the tunnel on the host machine.
>
> Thanks,
> Bryan
>
>
> On Sat, Mar 9, 2013 at 12:34 AM, Jesse Gross <jesse at nicira.com> wrote:
>>
>> On Thu, Mar 7, 2013 at 10:05 PM, Yeming Zhao <zhaoyeming at gmail.com> wrote:
>> > I saw the tunnel path mtu discovery featured deprecated and will be
>> > removed
>> > soon.
>> >
>> > This feature is quite handy for me actually. I'm wondering what's the
>> > work
>> > around after its removal, assuming I cannot go and manually change all
>> > the
>> > mtu values on the hosts.
>>
>> There's no direct substitute for it at the moment in OVS.  MSS
>> clamping is the best solution, which you may be able to implement
>> using iptables in some situations.  Otherwise, tunnels will continue
>> to work although large packets may result in IP fragmentation.
>
>