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

[Toke Høiland-Jørgensen via Bloat]

Sebastian Moeller  writes:

> Hi Toke,
>
>
>> On Dec 9, 2020, at 12:20, Toke Høiland-Jørgensen  wrote:
>> 
>> Sebastian Moeller  writes:
>> 
>>> Hi Toke,
>>> 
>>> 
 On Dec 9, 2020, at 11:52, Toke Høiland-Jørgensen via Bloat 
  wrote:
 
 Kenneth Porter  writes:
 
> 
> 
> Upstream article:
> 
> 
 
 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
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Re: [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  wrote:
> 
> Sebastian Moeller  writes:
> 
>> Hi Toke,
>> 
>> 
>>> On Dec 9, 2020, at 11:52, Toke Høiland-Jørgensen via Bloat 
>>>  wrote:
>>> 
>>> Kenneth Porter  writes:
>>> 
 
 
 Upstream article:
 
 
>>> 
>>> 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

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

[Toke Høiland-Jørgensen via Bloat]

Sebastian Moeller  writes:

> Hi Toke,
>
>
>> On Dec 9, 2020, at 11:52, Toke Høiland-Jørgensen via Bloat 
>>  wrote:
>> 
>> Kenneth Porter  writes:
>> 
>>> 
>>> 
>>> Upstream article:
>>> 
>>> 
>> 
>> 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...

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

-Toke
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Re: [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 11:52, Toke Høiland-Jørgensen via Bloat 
>  wrote:
> 
> Kenneth Porter  writes:
> 
>> 
>> 
>> Upstream article:
>> 
>> 
> 
> 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:

https://github.com/dlakelan/routerperf/blob/master/SimpleHFSCgamerscript.sh


iptables -t mangle -F FORWARD # to flush the openwrt default MSS clamping 
rule
if [ $UPRATE -lt 3000 ]; then
ipt64 -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -o $LAN -j 
TCPMSS --set-mss 540
fi
if [ $DOWNRATE -lt 3000 ]; then
## need to clamp MSS to 540 bytes in both directions to reduce
## the latency increase caused by 1 packet ahead of us in the
## queue since rates are too low to send 1500 byte packets at 
acceptable delay
ipt64 -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN -o $WAN -j 
TCPMSS --set-mss 540
fi


We are actually trying to get something along that lines packaged as a script 
for sqm-scripts, but that is delayed since I need to fix some iptables stuff 
that seems to not work anymore first


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

[Toke Høiland-Jørgensen via Bloat]

Kenneth Porter  writes:

> 
>
> Upstream article:
>
> 

Good points, but doesn't mention options to decrease the packet size
(lower MTU/MSS clamping)... :)

-Toke
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