[Bloat] Comcast & L4S

[David Collier-Brown]

What Comcast/L4S is doing was once called, by a Polish colleague, 
"Peeing in the soup, so it smells more like me."

--dave

On 1/31/25 18:57, Dave Taht via Bloat wrote:
> Here are the positives:
>
> For the first time, a major ISP has deployed the PIE AQM on all
> traffic. Before now Comcast was only doing that on the upstream.
> That´s 99.99% of all current comcast traffic getting an AQM on it. WIN.
>
> The L4S side being enabled will also result in some applications
> actually trying to use it for cloud gaming. There is a partnership
> with valve,
> meta, and apple, that implies that we will perhaps see some VR and AR
> applications trying to use it. I look forward to a killer app.
>
> Negatives include explicit marking and potential DOS vectors as often
> discussed.  I do feel that in order to keep up with the jonesies,
> we will have to add optional l4s marking to CAKE, which should
> outperform pie (mark-head), I just wish I knew what the right
> level was - at 100Mbit it seemed at 2ms was best. We also need to
> remove classic RFC3168 style marking and drop instead when the L4S bit
> is present - across the entire linux and BSD ecosystem.
>
> There was an abortive attempt last year to get dualpi, accecn, and
> prague into mainstream linux, but it stumbled over GSO handing, and
> has not been resubmitted. ACCECN seems to be making some progress.
> This makes it really hard to fool with this stuff.
>
>
>
>
>
>
>
>
> On Fri, Jan 31, 2025 at 5:27 AM Sebastian Moeller via Bloat
> <bloat at lists.bufferbloat.net> wrote:
>> Hi Rich,
>>
>>
>>> On 31. Jan 2025, at 14:20, Rich Brown via Bloat <bloat at lists.bufferbloat.net> wrote:
>>>
>>> Google Alerts sent me this: https://www.webpronews.com/comcasts-latency-leap-a-game-changer-in-network-performance/
>>>
>>> Key quote: "Compatibility and Ecosystem: For L4S to have a significant impact, it requires an ecosystem where both the network infrastructure and the end-user devices support the standard..."
>>>
>>> Can anyone spell "boil the ocean"? :-)
>>>
>>> Or am I missing someting?
>> Well, the whole safety mechanisms in L4$ are laughably inadequate... this "design" essentially exposes a priority scheduler* without meaningful admission control to the open internet. This is so optimistically naive that it almost is funny again. I wish all the effort and hard work to make L4$ happen, would have been put in a reasonable design... but at least I learned one of the IETF's failure modes, and that is at least something valuable ;)
>>
>>
>> *) Just because something is not a strict preempting priority scheduler does not make it a good idea to expose it blindly... a conditional priority scheduler with e.g. L4$'  weight share of 10:1 already can do a lot of harm.
>>
>>
>>>
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>
-- 
David Collier-Brown,         | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
davecb at spamcop.net           |              -- Mark Twain