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SubjectRe: RTO [was Re: my broken TCP is faster on broken networks [Re: Very poor TCP/SACK performance]]
   Date: 	Sat, 12 Sep 1998 18:01:59 +0200 (CEST)
From: Andrea Arcangeli <>

And I just seen that 2.0 increase srtt of 2*MDEV and not of 4*MDEV:

--- 2.0.35 ---
} else {
/* no previous measure. */
sk->rtt = m<<3; /* take the measured time to be
rtt */
sk->mdev = m<<1; /* make sure rto = 3*rtt */

2.1 instead calc mdev as m<<2.

And this probably is the cause of the stalls reported by many people on
the list.

No, the real fix for the stalls will be in 2.1.122, the linear
increase case of congestion window calculations was completely wrong
due to a change I made circa 2.1.92 which is reverted now in 2.1.122

Setting the initial mdev to m<<1 is a bug in the BSD code which we
just copied blindly in 2.0.x, the calculation in 2.1.x (m<<2) is the
correct one, check the RFCs :-). I believe this is mentioned in
Steven's books and the tcp-impl "known TCP implementation problems"
draft, amongst other places.

David S. Miller

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