Quote from PocketChange:
Define High frequency?
Do you want to process and place orders in microseconds, milliseconds or seconds, minutes etc?
With Standard PC hardware, connecting to your broker's back office and price feeds over the internet you can build a reliable trading system with redundancy and precision to 200 ms.
By precision I mean the ability to reliably process price feeds, place orders, confirm fills and manage fail overs.
If you need precision inside of 200 ms you should look at co-locating at the exchange/broker data center. You should be able to run as fast as they can.
For < 3 ms to microsecond precision you need some experts and serious hardware. Your trading application should interface directly with the exchange and clearing house. Try contacting Advantage Futures, they have the infrastructure to support these types of efforts.
What my trading algo does is placing limit orders and preferably complete the trade after a fill in less than 30 seconds. Obviously, getting my limit orders filled is the crucial part of this strategy. I thought this means being as fast as possible, but maybe, after reading all the replies, I was wrong.