Thanks jcl. I've seen the brief description in the manual, and would appreciate your further insights. I understand the philosophical perspective of wanting to trade against the market vs. against the broker, but at a practical level wonder:

a) In a supposedly NDD situation, we'd never really know if the broker had side deals with a liquidity partner(s) and actually traded against us, would we?

b) Another way of saying that: We have no way to know that every client gets the same ticks, do we?

c) All that aside, isn't a DD broker just another set of costs? In what way that matters to automated trading is a DD broker different?

Thanks.