Electronic communications networks (ECNs) are order execution systems networked into the Nasdaq Level 2 quotes. The 4-letter symbols following the names are the "market maker
identifiers" under which their quotes are displayed on the Nasdaq Level 2 screen.
Archipelago (ARCA) Merging with the Pacific Exchange.
Owned by All-Tech Direct, Inc.
Brut (BRUT) (No web site. This is the surviving ECN of the recent merger of two of the original nine ECNs, Brass Utility and Strike Technologies.
Instinet (INCA) The largest and oldest ECN.
Island (ISLD) Displays its limit order book in real time.
MarketXT (MKXT) The "after-hours" ECN.
NexTrade (NTRD) Affiliated with MatchBookFX, an electronic matching system for spot foreign currency trading. Offers 24-hour access to the markets.
OptiMark(OPTI) Not really an ECN, OptiMark is a "market optimization system that
matches buy and sell orders on a variable pricing basis. No direct access by individual traders at this time.
REDIBook (REDI) Owned by Spear, Leeds & Kellogg. The ECN itself does not have a web site, although REDI products can be found at redi.com.