The Order Protection Rule also established the National Best Bid and Offer (NBBO) requirement that mandates brokers to route orders to venues that offer the best displayed price.
The NBBO is distributed from the SIP to brokerages with latency. Moreover, incoming orders are received by the SIP with latency. As such, the last received NBBO may not be the true NBBO.
Is there only a "best-effort" requirement, where the last received NBBO is considered "good enough"? Or is there some delay mechanism, along with latency assumptions, which guarantee the true best price under the given assumptions?
Furthermore, suppose the brokerage routes the orders to a market maker. This market maker can either execute at NBBO or decline the transaction. Is the NBBO under which they operate given by the brokerage, or do they collect this information independently?