A new version of SOES (Small Order Execution System).
Orders can be directed on not directed (to a specific market maker). There are binding and non-binding orders. Binding orders forces ECNs to fill the order based on NASDAQ rules. In case of non-binding orders, market makers have 5 seconds to decide. Orders are filled in 0.8 sec. Large trading volume can slow SuperSOES.
There are 9 ECNs: INCA, MSCO, BTRD, GSCO, ARCA, MASH, ATTN, SBSH, REDI, ISLD, MLCO, LEHM. And more to come.
Archipelago is not considered ECN but an exchange itself.
Archipelago is active, Island is passive. Means archipelago arcitvily try to match the order at other firms. In case of Island, it just put in the order book which makes it faster.