[Bloat] Why you need at least 3Mbps upload to get good game performance with ~1500byte packets: Doing the math

[Sebastian Moeller]

Hi Toke,


> On Dec 9, 2020, at 12:20, Toke Høiland-Jørgensen <toke at toke.dk> wrote:
> 
> Sebastian Moeller <moeller0 at gmx.de> writes:
> 
>> Hi Toke,
>> 
>> 
>>> On Dec 9, 2020, at 11:52, Toke Høiland-Jørgensen via Bloat <bloat at lists.bufferbloat.net> wrote:
>>> 
>>> Kenneth Porter <shiva at sewingwitch.com> writes:
>>> 
>>>> <https://forum.openwrt.org/t/why-you-need-at-least-3mbps-upload-to-get-good-game-performance-with-1500byte-packets-doing-the-math/81240>
>>>> 
>>>> Upstream article:
>>>> 
>>>> <http://models.street-artists.org/2020/12/05/why-gaming-on-a-dsl-line-is-terrible-and-the-math-says-theres-nothing-you-can-do-about-it/>
>>> 
>>> Good points, but doesn't mention options to decrease the packet size
>>> (lower MTU/MSS clamping)... :)
>> 
>> 	But he is doing exactly that in the script he developed for OpenWrt games on poor links:
> 
> Ah, cool! May be necessary to actually decrease the interface MTU as
> well, though, since TCP MSS clamping won't work for QUIC...

	Mmmh, QUIC does pMPUd, no? IN that case a "simple" filter to drop QUIC packets along a certain size might already do the trick?


> 
> And of course, for IPv6 you can't decrease the MTU below 1280 bytes
> without breaking spec :(

	Jepp, but MSS clamping still works, except there are limits how low OS will go, Macos will not go below ~200, and I believe Linux also recently got increased values for min MSS to counter some DOS issues with SACK and friends, no? That said, it is well possible that even IPv6 might work with smaller MTUs...

Best Regards
	Sebastian

> 
> -Toke