Re: [PATCH] tcp: Implement a two-level initial RTO as per draft RFC 2988bis-02.

From: tsuna
Date: Thu May 19 2011 - 02:42:56 EST

On Wed, May 18, 2011 at 11:36 PM, Alexander Zimmermann
<alexander.zimmermann@xxxxxxxxxxxxxxxxxxxxx> wrote:
> If you set the initRTO=0.1s, it's good for me but bad for the rest of the
> world. That's the difference.
> Or do you want to implement a lower barrier of 1sec so that you can ensure
> that nobody set the initRTO lower than 1s?

Oh, I see. Yes, there is a lower bound (and an upper bound) on what
values the kernel will accept as initRTO. In the patch "Implement a
two-level initial RTO as per draft RFC 2988bis-02" above, I re-used
TCP_RTO_MIN and TCP_RTO_MAX in net/ipv4/sysctl_net_ipv4.c in order to
prevent users from setting a minRTO that's outside this range. They
are defined as follows in tcp.h:

#define TCP_RTO_MAX ((unsigned)(120*HZ))
#define TCP_RTO_MIN ((unsigned)(HZ/5))

So we're talking about a [200ms ; 120s] range no matter what.

Benoit "tsuna" Sigoure
Software Engineer @
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