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

[Toke Høiland-Jørgensen]

Sebastian Moeller <moeller0 at gmx.de> writes:

> 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?

Maybe? But actually lowering the MTU of the interface would have the
same effect, I guess? And what happens in the wild is anyone's guess, of
course... ;)

>> 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...

Sure, MSS clamping will work even for IPv6, but only for TCP...

-Toke