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    On Sat, Sep 02, 2000 at 04:12:04PM +0200, Elmer Joandi wrote:
    ....
    > There is another big problem like that...
    > tunnels actually do not work on todays real internet...
    > MTU 1500 is so much a standard that it starts killing tunnels.
    > MTU < 1500 is not a working solution today thanks to (mostly
    > linux based ? ) broken firewalls

    It is due to knee-jerk ICMP blocking settings at firewalls/routers.

    From personal experience I can say that even cisco router training
    includes example of: "block ALL of ICMP", which of course makes
    TCP PMTU discovery non-functional.
    (That was 3 years ago when PMTU discovery was a new thing, but still..)

    Another issue are still existing SLIP links with mismatching
    link MTUs at each side.

    > elmer.

    /Matti Aarnio
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