What is lag switching?

@Firegoat7 said in #9:

And? How difficult is is to measure a clients clock? Before, during and after a game. If an app can manipulate a clock then can that clock not be compared to another clock that is an independent variable?

It's a bit more complicated than that but the server side lag detection used now could certainly be used to help identify people trying to cheat with a timeseal-like solution. Without going into details, there are some other methods as well. Bottom line is that detecting people trying to cheat with hacks is always going to be easier than detecting people who are artificially creating lag... because that lag is in fact real lag.

@KenulL_76 Ah thank you, I've always wondered how they do it. I guess lag switching will be become more and more of a problem in the future.

Stupid question - Why can't Lichess make it so if anyone changes IP / turns the VPN on and off it auto resigns them? ...
Or is it much more complicated than just coding that?

https://www.youtube.com/watch?v=YyY_77lJrsY&t=37s this is lag switching what Andrew Tang means , its a extension.
But players have been banned for using it so its not accepted by lichess ^^. not many did make use of it i think
its bannable :) the 2 players in this video where who played are fair players they just wanna show how the lagscript works in a unrated game.
They are against it and show that even if you play "slow" that you can really make alot of moves and you keep so much time on the clock.

1234

@RickRenegade said in #12:

Stupid question - Why can't Lichess make it so if anyone changes IP / turns the VPN on and off it auto resigns them? ...
Or is it much more complicated than just coding that?

Lag switching does not change your IP address. And there is no way that lichess can tell if you are connecting and disconnecting from your VPN.

@wateenellende said in #13:

this is lag switching what Andrew Tang means , its a extension.

That extension was never released publicly, according to the author. It is not at all unlikely, however, that someone else has written one.

That said, lag switching doesn't require an extension but an extension can automate the switching and make it more precise.

@mrjbones said in #15:

Lag switching does not change your IP address. And there is no way that lichess can tell if you are connecting and disconnecting from your VPN.

I don't know anything about lag switching. I do know about VPNs.

Not only does a typical VPN change your IP address, that's one of the important features of it. It hides your IP address and therefore your ISP and by proxy, your identity. (but certainly not the only important feature of a VPN)

Not only can lichess detect your IP address changing, any persistent connections would stop working and would need to reconnect before traffic flows again, that might take 30 seconds for the old connection to timeout before it tries to reconnect.

You can easily introduce lag artificially without changing your IP address, though. I don't know when it's supposed to lag and not lag, potentially you could turn the lag on when you click your mouse button and off when you release it, or the opposite.

@h2b2 said in #17:

Not only does a typical VPN change your IP address, that's one of the important features of it. It hides your IP address and therefore your ISP and by proxy, your identity. (but certainly not the only important feature of a VPN)

This is absolutely true and nothing I said contradicts it.

Not only can lichess detect your IP address changing, any persistent connections would stop working and would need to reconnect before traffic flows again, that might take 30 seconds for the old connection to timeout before it tries to reconnect.

I think what you are missing is that connecting and disconnecting your VPN (fairly quickly btw... not long enough for your VPN to time out your connection) is not detectable by lichess because you aren't reconnecting to lichess with your provider-assigned IP; you are just going silent. As far as lichess is concerned your IP is the VPN-assigned IP and remains so, but they are still measuring the pings to your machine and cutting the connection between you and the VPN just looks like lag.

@mrjbones said in #18:

This is absolutely true and nothing I said contradicts it.

I think what you are missing is that connecting and disconnecting your VPN (fairly quickly btw... not long enough for your VPN to time out your connection) is not detectable by lichess because you aren't reconnecting to lichess with your provider-assigned IP; you are just going silent.

As far as lichess is concerned your IP is the VPN-assigned IP and remains so, but they are still measuring the pings to your machine and cutting the connection between you and the VPN just looks like lag.

I think I understand. turning the VPN off so lichess detects a disconnection and compensates you with time. the server is initiating the pings and detects a disconnection when it gets no reply.

Surely the client also initiates pings to detect if the server is alive?

If one of those pings hits lichess while the VPN is off, then it could be detected. To the server, it wouldn't be valid traffic, it would be a random tcp segment that doesn't belong to any connection the server knows about.

not that it would be needed for detection.

if someone plays a 30 move ultra bullet game and their connection drops out 30 times, that's a little suspicious. If that happens a second time, suspicion rises, after x times, ban.

@h2b2 said in #17:

any persistent connections would stop working and would need to reconnect before traffic flows again, that might take 30 seconds for the old connection to timeout before it tries to reconnect.

I thought I should add that you are correct on this point as well. Although there are different timeouts at different layers ... the shortest relevant one here would probably be the http keepalive timeout which defaults to 30 seconds. (I don't think lichess sets it lower.)