Achieving 1500 MTU with PPPoE with BT FTTC / rfc4638

  • Mark Knight

    Mark Knight - 2013-07-04

    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. Luhtionov

    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
    Last edit: Dmitry S. Luhtionov 2013-07-19
  • Mark Knight

    Mark Knight - 2013-12-15

    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?

  • Dmitry S. Luhtionov

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

  • Mark Knight

    Mark Knight - 2013-12-16

    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

    Dinh Qui Tung - 2015-06-16

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

  • Dmitry S. Luhtionov

    Working in progress. But it is very slowly.

    Last edit: Dmitry S. Luhtionov 2015-08-18
  • Mark Knight

    Mark Knight - 2016-01-07

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

  • Dmitry S. Luhtionov

    Thanks for feedback.

  • Mark Knight

    Mark Knight - 2016-01-09

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


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