netdev - Re: [PATCH] TCP_USER_TIMEOUT: a new socket option to specify max timeout before a TCP connection is aborted

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Date:	Sun, 29 Aug 2010 23:54:48 -0700
From:	Jerry Chu <hkchu@...gle.com>
To:	David Miller <davem@...emloft.net>
Cc:	eric.dumazet@...il.com, hannemann@...s.rwth-aachen.de,
	hagen@...u.net, lars.eggert@...ia.com, netdev@...r.kernel.org
Subject: Re: [PATCH] TCP_USER_TIMEOUT: a new socket option to specify max
 timeout before a TCP connection is aborted

On Sun, Aug 29, 2010 at 9:19 PM, David Miller <davem@...emloft.net> wrote:
> From: Jerry Chu <hkchu@...gle.com>
> Date: Sun, 29 Aug 2010 17:23:05 -0700
>
>> Personally I think as an API, it's easier for an application to
>> grasp the concept of a time quantity than # of
>> retransmissions. (E.g., how will an app determine it needs 10
>> retries vs 20 retries?)
>
> Conversely how can the user grasp how many actual attempts will
> be made if backoff is employed?
>
> It's very easy to under-cap the number of actual packet send
> attempts that will be made specifying just a timeout, in the
> presence of backoff.

My previous statement presumes applications care less about exactly
how many times retransmission attempts have been made because
that's more of "implementation detail" for a reliable transport. But I can
see one can argue either way effectively so I'm ok with both. If people
prefer timeout in # of retries then it just needs to be converted to time
units when used in conjunction with the USER TIMEOUT option (and
one can readily use the existing "retransmits_timed_out()" function,
although the latter presents only an approximation).

Jerry

>
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