linux-kernel - Re: [PATCH] tcp: Fix RFC reference in comment

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Date:	Tue, 13 Jan 2015 17:01:28 -0500
From:	John Heffner <johnwheffner@...il.com>
To:	"Banerjee, Debabrata" <dbanerje@...mai.com>
Cc:	Yuchung Cheng <ycheng@...gle.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tcp: Fix RFC reference in comment

On Tue, Jan 13, 2015 at 4:42 PM, Banerjee, Debabrata
<dbanerje@...mai.com> wrote:
> On 1/13/15, 4:36 PM, "Yuchung Cheng" <ycheng@...gle.com> wrote:
>
>>On Tue, Jan 13, 2015 at 1:10 PM, Debabrata Banerjee <dbanerje@...mai.com>
>>wrote:
>>>
>>> -/* RFC2861. Reset CWND after idle period longer RTO to "restart
>>>window".
>>> +/* RFC2581 4.1. Reset CWND after idle period longer RTO to "restart
>>>window".
>>>   * This is the first part of cwnd validation mechanism. */
>>>  static void tcp_cwnd_restart(struct sock *sk, const struct dst_entry
>>>*dst)
>>>  {
>>
>>RFC2861 resets the cwnd like in RFC2581, but the rest of the code
>>implements RFC2861. So I think the current comment is fine.
>
>
> No RFC2861 is an experimental RFC that's implemented in
> tcp_cwnd_application_limited(). RFC2861 Recommends reducing the cwnd by
> averaging the current cwnd and the used cwnd as the new cwnd.
>
>
> RFC2581 4.1 Says to set cwnd to initial cwnd if more than one rto has
> passed since the last send. This is what is implemented in the function
> above.

Look at the code a little closer -- it's decaying cwnd based on number
of timeouts as described in 2861, not resetting to IW as recommended
in 2581.

  -John
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