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Re: [tcpm] draft-ietf-tcpm-rfc8312bis questions

Vidhi Goel <vidhi_goel@apple.com> Wed, 28 July 2021 07:30 UTC

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From: Vidhi Goel <vidhi_goel@apple.com>
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Date: Wed, 28 Jul 2021 00:30:12 -0700
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Cc: Praveen Balasubramanian <pravb=40microsoft.com@dmarc.ietf.org>, "tcpm@ietf.org" <tcpm@ietf.org>
To: Yuchung Cheng <ycheng@google.com>
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Subject: Re: [tcpm] draft-ietf-tcpm-rfc8312bis questions
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> btw it seems RFC5681 is even more conservative in dealing with stretched acks in terms of ABC adoption. 

Thanks Yuchung for double checking.

> "During slow start,....  While
>    traditionally TCP implementations have increased cwnd by precisely
>    SMSS bytes upon receipt of an ACK covering new data, we RECOMMEND
>    that TCP implementations increase cwnd, per:
> 
>       cwnd += min (N, SMSS)                      (2)

This is mentioned as a recommendation and not a MUST.

>    where N is the number of previously unacknowledged bytes acknowledged
>    in the incoming ACK.  This adjustment is part of Appropriate Byte
>    Counting [RFC3465] and provides robustness against misbehaving
>    receivers that may attempt to induce a sender to artificially inflate

Later, 5681 references RFC 3465 - although not for any guidance on the max limit. I am not sure if RFC 5681 needs any update but it would be good to update 3465 to reflect today’s practices.

Thanks,
Vidhi

> On Jul 27, 2021, at 5:57 PM, Yuchung Cheng <ycheng@google.com> wrote:
> 
> btw it seems RFC5681 is even more conservative in dealing with stretched acks in terms of ABC adoption. 
> 
> sec 3.1
> 
> "During slow start,....  While
>    traditionally TCP implementations have increased cwnd by precisely
>    SMSS bytes upon receipt of an ACK covering new data, we RECOMMEND
>    that TCP implementations increase cwnd, per:
> 
>       cwnd += min (N, SMSS)                      (2)
> 
>    where N is the number of previously unacknowledged bytes acknowledged
>    in the incoming ACK.  This adjustment is part of Appropriate Byte
>    Counting [RFC3465] and provides robustness against misbehaving
>    receivers that may attempt to induce a sender to artificially inflate
>    cwnd using a mechanism known as "ACK Division" [SCWA99]."
> 
> 
> 
> On Tue, Jul 27, 2021 at 5:54 PM Praveen Balasubramanian <pravb=40microsoft.com@dmarc.ietf.org <mailto:40microsoft.com@dmarc.ietf.org>> wrote:
> As discussed in the working group meeting, can you please clarify what behavior changes an implementation will see as a result of adopting 8312-bis versus RFC 8312? Particularly interested to know which changes will result in improved performance.
> 
>  
> 
> Thanks!
> 
>  
> 
>  
> 
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