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Re: [tsvwg] L4S and the RACK requirement

Wesley Eddy <wes@mti-systems.com> Sat, 23 February 2019 00:03 UTC

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To: lloyd.wood@yahoo.co.uk, Tsvwg IETF List <tsvwg@ietf.org>
References: <fb6d2979-a6a4-b122-a90e-4a0732ee89fa@mti-systems.com> <1316285020.1534460.1550493368197@mail.yahoo.com>
From: Wesley Eddy <wes@mti-systems.com>
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Date: Fri, 22 Feb 2019 19:03:36 -0500
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Subject: Re: [tsvwg] L4S and the RACK requirement
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On 2/18/2019 7:36 AM, lloyd.wood@yahoo.co.uk wrote:
> Am I the only person who remembers Savage attacks from ack splitting 
> and packet counting?
>
> http://cseweb.ucsd.edu/~savage/papers/CCR99.pdf
>
> there's the support for the MUST NOT, at least. I's not the lack of 
> scale that is the major issue there, it's being open to abuse. ack 
> counting didn't work...
>
I think it's only sort-of related, but not really.

The tricks described there are ways to get a sender to be overly 
aggressive if it doesn't implement ABC (or other mitigations) so is 
growing a congestion window based on units of packets rather than 
bytes.  The L4S requirement here is about retransmission / loss 
detection though (reducing the window) happening based on units of time 
vs packets (rather than bytes vs packets).

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