For every quote message received from a market center, CQS calculates a National Best Bid and Offer (NBBO) based on a price, size and time priority scheme. If the quote is a NASDAQ market maker quote, CQS also calculates a NASDAQ BBO. CQS disseminates the Market center's root quote with an appendage that includes the National and NASDAQ BBOs. In the event that a market center is experiencing technical difficulties in providing quote information, CQS also has a facility that, at the direction of the market center, disseminates zero quotes in its securities thus eliminating any stale quotes and taking that market center out of the BBO calculations.