netdev - Re: When TCP keepalives tuned shorter than retransmission timeouts

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Message-ID: <1385482822.5352.3.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 26 Nov 2013 08:20:22 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Venkat Venkatsubra <venkat.x.venkatsubra@...cle.com>
Cc:	netdev@...r.kernel.org, David Miller <davem@...emloft.net>
Subject: Re: When TCP keepalives tuned shorter than retransmission timeouts

On Tue, 2013-11-26 at 07:51 -0800, Venkat Venkatsubra wrote:
> Some of our customers have tcp socket level options set to:
> TCP_KEEPIDLE 60
> TCP_KEEPINTVL 6 
> TCP_KEEPCNT 10
> 
> And when the peer is dead they expect the connection to timeout in 2 minutes instead of the
> 15 minutes from retransmission timeouts.
> (We know the tunables are set very low.)

Then change max number of retransmits : tcp_retries2 ?

Keepalive timer is not a way to defeat TCP exponential backoff.

Its really there to send probes when a session is idle.


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