I'm creating a map at the moment where I have to really think about the trigger structure to avoid lag issues. So I have a simple question that I need answering...

WHAT HUMAN PLAYERS PROCESS THE COMPUTER-PLAYER TRIGGERS?

I've had a few thoughts, and I'm guessing that only 1 human player (i.e. the host) processes the computer-player triggers, because surely they only have to be processed by 1 player? Let me clarify this some more... If player 1, 2, & 3 are human players, and player 4 is a computer player, then does only player 1 process the triggers for player 4 in each trigger cycle, or do players 1, 2, and 3 all have to process triggers for player 4?

Sorry for the newbness, but I need to know this!

All triggers are processed by all players equally. If only one player processed them and then shared the result, it'd be way too exploitable. With the current system, every computer figures out independently what should be happening, and those that disagree are desynced.

Confirm what Azrael said. I tested this out empirically when I was doing my PC - mac EUD triggers. Each computer will process all triggers for all players in the game.

Only player input data is transferred on b.net between trigger cycles, like mouse clicks or keyboard presses, in order to reduce the load on the network. Remember SC1 was developed for like 32kbit modems lol. Everything else is calculated on each PC independantly.

If you're asking how trigger cycles work, read the article, located here: http://www.staredit.net/starcraft/Triggers

Yeah, each computer processes them seperately, because they should always get the same result.
If they don't get the same result, there's something different in the data of one of the computers, and they desync.
Also, it would be more ineficcient for one computer to process all the triggers, and then share the results with the others, because the information would have to be sent over bnet.

It's not the internet that is causing the lag when triggers are lagging, it's the computer itself, more specifically starcraft, which wasn't designed for the triggers used in some maps nowadays.

There are two possibilities

The speed of the computer used by the player is to blame.
(They are probably still running microsoft 95)
OR
Starcraft can't handle the load of triggers?
(it's such an old game that computer speed isn't a factor)
OR
The player lagging is using dialup, or some other crappy internet, or a crappy router, or is sharing said crappy router/internet with someone else, or is downloading movies.

Most networked games try and transmit as little as possible between the player and the server (or each other player).

WoW uses about 10mb of bandwidth per hour. That's really not very much at all.

well that pretty much sums it up for me. thank you very much.