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    SubjectRe: Linux 2.4.27 SECURITY BUG - TCP Local and REMOTE(verified) Denial of Service Attack
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    * David S. Miller:

    > On Tue, 21 Sep 2004 20:32:12 +0200
    > Florian Weimer <fw@deneb.enyo.de> wrote:
    >
    >> > But then you get PMTU problems...
    >>
    >> PMTU discovery is not an issue because it's turned off anyway, at
    >> least by default.
    >
    > It's on by default, for both TCP and UDP in the kernel,
    > and has been so for a long time.

    Linux is not the reference TCP/IP stack for routers. 8-)

    > Why would it be off by default?

    Probably because PMTUD is just a DRAFT STANDARD, and these router
    folks are usually extremely conservative. Switching the default is
    dangerous because it's likely to break existing setups, as Herbert
    noted.

    > If you disable PMTU discovery, say goodbye to TCP performance.

    Indeed. On those platforms, the CPU impact is also significant, and
    the overall increase in BGP convergence time is measurable.
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