The customer is prohibited from stepping inside the bid/ask spread and thereby reducing its execution fees. Contrary to the CLOB model, customers can only trade with dealers. They can not trade with other customers, and importantly, they can not make markets themselves.
Customers are not allowed to enter the bid/ask spread, which helps in minimizing their trading costs. In contrast to the CLOB model, they can only trade with dealers and are not permitted to engage in direct trades or create market orders themselves.