Achieving 1500 MTU with PPPoE with BT FTTC / rfc4638

[Mark Knight]

Hi, are there any plans to enable the MPD pppoe dialer to implement the rfc4538 PPP-Max-Payload tag to enable it to negotiate 1500 rather than 1492 MTU please?

This would be really useful in the United Kingdom where BT's fibre to the cabinet (FTTC) service supports PPPoE with "baby" jumbo frames at 1508 MTU. Alternatively are there any workarounds?

I'm currently using FreeBSD 9.1-RELEASE-p2.

Many thanks for advice and feedback!

[Dmitry S. Lukhtionov]

This is not mpd, this is a ng_pppoe stuff. I try to resolve it.

Try this workaround

set link enable multilink
set link mtu 1460
set link mru 1460
set link mrru 1500

[Mark Knight]

Thanks. I've tried this but unfortunately once I've brought up one link the telco supplied modem/bridge doesn't seem to pass or allow any additional links at the PPPoE layer so I don't seem to be able to use the multilink hack.

I see there's been a commit upstream to add the max-payload tag; presumably the work to support this needs changes both in netgraph/ng_pppoe.c and mpd5? Before I hack up my local version to try and get this working, is anyone else working on this?

http://lists.freebsd.org/pipermail/svn-src-all/2013-July/072089.html

[Dmitry S. Lukhtionov]

This is only a first stage to implement ppp-max-payload tag. I now working on it.

[Mark Knight]

Brilliant thanks. If you need a beta tester I'd be happy to try patches on either of my FreeBSD 8.4 or 9.2 boxes and I'll back-port if necessary. Please let me know if I can do anything to help! Thanks, Mark

[Dinh Qui Tung]

Hi what's the news on this one? I'd be happy to beta test.

[Dmitry S. Lukhtionov]

Working in progress. But it is very slowly.

[Mark Knight]

Great - looks like this is in mpd5.8 - thank you - will try it shortly :)

[Dmitry S. Lukhtionov]

Thanks for feedback.

[Mark Knight]

Works beautifully - once I remembered to set the MTU of the parent Ethernet inteface to 1508 :)