You can send samples. E.g. the USD/EUR rate (or the price of an equities future) if it changes by more than x within the last 50ms. The difference of that rate to the "local" rate in London is enough to generate the trade. Same with equity indices. You'll know that if there's no movement, there's no opportunity. So it's enough to send a signal if there has been a significant move that's "young" enough so that the other side can't know it yet.
Your trades only make money on the difference of the public information in London and what you get faster from Chicago. Therefore sending trade instructions isn't helpful as Chicago doesn't know London prices. But just giving the London algorithm that bit of inside can help a lot.
I assume trade strategies are mostly very simple as well. Basically just anticipating a change in price and quickly buying/selling to make some money off it.
N.B.: I only talk about Chicago->London here but given that Chicago hosts one of the largest Futures markets, I'd assume a lot is actually done in reverse. Using local prices from London of an underlying instrument (e.g. London stock market) to "predict" the value of the future traded in Chicago. You can make a lot of money if you know the price of the underlying instrument of a future before others do.
Your trades only make money on the difference of the public information in London and what you get faster from Chicago. Therefore sending trade instructions isn't helpful as Chicago doesn't know London prices. But just giving the London algorithm that bit of inside can help a lot.
I assume trade strategies are mostly very simple as well. Basically just anticipating a change in price and quickly buying/selling to make some money off it.
N.B.: I only talk about Chicago->London here but given that Chicago hosts one of the largest Futures markets, I'd assume a lot is actually done in reverse. Using local prices from London of an underlying instrument (e.g. London stock market) to "predict" the value of the future traded in Chicago. You can make a lot of money if you know the price of the underlying instrument of a future before others do.