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By limit order, I don't mean just send out an order at that exact price. The limit would be sort of internal to the algorithm. For example, suppose the inside ask is at 50 with no ECNs there. If I send out a Super Smart Order at 50.10, it should look for the nearest ECN from 50.01 to 50.10 and send out an order at the price that ECN is at. So if the nearest ECN is ARCA at 50.02, the order should try to hit ARCA at 50.02, not 50.10. However, I've always assumed that I can post an ECN buy order higher than the lowest price on that ECN and I would 'sweep up' that lowest price, like how it works on ISLD. I guess this is not true for some ECNs. Which ECNs would this not be true?