When moving on Warcraft I notice my movement is never delayed even when the network is lagged. Is this because they do client side verification of movement? Or do they do client side and also server side to prevent hackers from freely moving anywhere? In general do people verify every step with the server in a server-client architecture? Thanks.

While it may look like it is lagless, the opposite is true.

My wife and I play WoW in the same room. If we hit a lag burst, she'll see me sitting there, right in front of her. Meanwhile, I've gone and moved elsewhere. When the lag clears up, She sees me in my new position.


For predictive type control, google up Dead Reckoning.

I bet there is at least *some sort* of verification on server-side. Sadly, there must be tons of people trying to develop cheats for WoW.

You could check it that way: First, find how long you can cut your network without loosing your internet connection or your connection to WoW. Then put a weight on the forward key (dont use autorun). Then cut your connection for the longest you can without getting disconnected. Reconnect, and check if you get back a little. If you dont, it means either they really trust your client, or that your client sent the server a really good explanation about what happened in the black out.

Quote:Original post by Steadtler
I bet there is at least *some sort* of verification on server-side. Sadly, there must be tons of people trying to develop cheats for WoW.

Indeed. It does disconnect you if it thinks you've moved too far too fast. I've seen this behavior during a lag burst, but it's pretty forgiving. I'm sure that they dump you into a log file somewhere and periodically take a look at it, and probably ban the "freaks".

Other games have similar behavior. DAoC used to not do any validation and they later added it and its still pretty forgiving and easily hackable.

Interestingly, UO is the only MMO running that I know of where the client is not authoratative for the character's position. It gives you 4 steps of walk ahead but even those are server validated; that is, if you move somewhere you shouldn't have the server will bounce you.

Quote:
You could check it that way: First, find how long you can cut your network without loosing your internet connection or your connection to WoW.

I don't think there's an easy way of doing this without a lag hack, since WoW uses TCP; if the ethernet interface determines that its been disconnected, it will probably immediately close the connection the first time you try to send a packet to the interface.

AO does that too, at least it used to do in the first years. Makes it impossible to move when there is heavy lag, on the other side you dont see low-ping people "jumping" all over the place (just sitting around).

I remember in my networking class we could sever the connection for several seconds (by unpluging the wire) and replug it without loosing our TCP connection. (we did that to test our assignement FTP client). It depends on the adapter, I guess.