netdev - Re: [PATCH net 3/3] tcp: do not delay ACK in DCTCP upon CE status change

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Date:   Wed, 18 Jul 2018 14:44:05 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Yuchung Cheng <ycheng@...gle.com>, davem@...emloft.net
Cc:     netdev@...r.kernel.org, edumazet@...gle.com, ncardwell@...gle.com,
        brakmo@...com, ysseung@...gle.com
Subject: Re: [PATCH net 3/3] tcp: do not delay ACK in DCTCP upon CE status
 change



On 07/18/2018 01:56 PM, Yuchung Cheng wrote:
> Per DCTCP RFC8257 (Section 3.2) the ACK reflecting the CE status change
> has to be sent immediately so the sender can respond quickly:
> 
> """ When receiving packets, the CE codepoint MUST be processed as follows:
> 
>    1.  If the CE codepoint is set and DCTCP.CE is false, set DCTCP.CE to
>        true and send an immediate ACK.
> 
>    2.  If the CE codepoint is not set and DCTCP.CE is true, set DCTCP.CE
>        to false and send an immediate ACK.
> """
> 
> Previously DCTCP implementation may continue to delay the ACK. This
> patch fixes that to implement the RFC by forcing an immediate ACK.


Oh well, more ACK packets ;)

Signed-off-by: Eric Dumazet <edumazet@...gle.com>