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    SubjectRe: [PATCH] tcp: Implement a two-level initial RTO as per draft RFC 2988bis-02.
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    From: tsuna <tsunanet@gmail.com>
    Date: Wed, 18 May 2011 20:56:33 -0700

    > On Wed, May 18, 2011 at 7:36 PM, David Miller <davem@davemloft.net> wrote:
    >> From: Benoit Sigoure <tsunanet@gmail.com>
    >> Date: Wed, 18 May 2011 19:22:24 -0700
    >>
    >>> Prior to this patch, Linux would always use 3 seconds (compile-time
    >>> constant) as the initial RTO.  Draft RFC 2988bis-02 proposes to tune
    >>> this down to 1 second and, in case of a timeout during the TCP 3WHS,
    >>> revert the RTO back up to 3 seconds when data transmission begins.
    >>
    >> We just had a discussion where it was determined that changes to
    >> these settings are "network specific" and therefore that if it
    >> is appropriate at all (I'm still not convinced) it is only suitable
    >> as a routing metric.
    >
    > Fair enough. I'll take another stab at it and see if I can change
    > this to be on a per network basis. Do I need any patch that's not yet
    > in Linus' tree? I'm referring to this:

    Keep in mind another thing I do not like about this knob.

    The IETF draft has a requirement that we fallback to 3 seconds if the
    initial RTO is 1 second.

    Nothing in your facilities ensure this, or provide a way for the
    kernel to make sure this is the case.

    And for other values of initial RTO, what fallback is appropriate?

    As a result of all of this, I do not really think this is something
    the user should control at all.

    I really would rather see the initial RTO be static and be set to 1
    with fallback RTO of 3.
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