Re: [tsvwg] David Black (individual) on safety of L4S for the Internet

[Jonathan Morton <[e-mail]>]

> On 8 May, 2020, at 11:01 pm, Black, David <[e-mail]> wrote:
> 
> In contrast to reliance on TCP Prague, that combination of FQ and bleaching looks like it could provide a robust safety case.  It would be most unfortunate if things wind up depending on this, especially bleaching, as the fact that ECT(1) is not bleached at network boundaries was a major reason for selection of ECT(1) as the identifier for low-latency L4S traffic.  Among the implications is that if the L4S experiment fails, that bleaching could be around much longer, making it infeasible to use ECT(1) for anything else Internet-wide.  In my view, it is the responsibility of the L4S proponents to design the L4S  technology and structure the experiment in a fashion that makes ECT(1) bleaching unlikely and/or likely to be limited in scope if it happens.

This point bears emphasis: if ECT(1) is bleached or blackholed, it will become *unavailable* for a future Internet experiment.  And I think that if network operators feel a need to do that, it will represent a failure of the L4S experiment sufficient to justify its termination, and attempt the reclamation of ECT(1).

The combination of these two facts suggests that if the L4S experiment goes ahead, it will permanently consume ECT(1).  Any choice to do so should therefore not be made lightly.

 - Jonathan Morton