Direct Feeds Versus The SIP

In US equities, every exchange is required to send its trades and quotes to a Securities Information Processor (SIP), which combines feeds from all the exchanges into one official "consolidated" price and quote stream — the National Best Bid and Offer, or NBBO. That consolidated feed is what most retail brokers, news services, and slower institutional systems actually watch. But building it takes time: each exchange has to transmit its data to the SIP, the SIP has to collect updates from a dozen-plus venues and merge them in the right order, and only then does it republish the result. Every one of those steps adds delay that simply doesn't exist if you instead subscribe directly to a single exchange's own data feed.

Two feeds, two speeds, one price

A direct feed is the raw data an exchange sells straight from its own matching engine, with no aggregation step — often delivered in single-digit microseconds from generation to a colocated subscriber. The SIP feed carries the same underlying trades and quotes but arrives after the extra hop through the exchange-to-SIP link and the SIP's own consolidation process, historically adding low-single-digit milliseconds of extra delay, sometimes more during busy periods. A millisecond sounds negligible next to a human reaction time, but it is an eternity relative to how fast a modern matching engine can process an order — enough time for a firm watching the direct feed to already know a price has moved and act on it before a SIP-based participant even sees the update.

This gap isn't a bug or a conspiracy; it's a structural consequence of the SIP's job being aggregation across many venues, which necessarily takes longer than reading one venue's own wire. But it means two participants can have legally accurate, simultaneously "current" views of the market that actually differ by milliseconds, and only one of them is really current in the sense of matching what's tradeable right now.

Worked example: a stale-NBBO trade

An exchange's own direct feed shows the best offer just improved from $100.05 to $100.02, generated by its matching engine at time $T$. Because of the exchange-to-SIP link and SIP processing, the consolidated NBBO doesn't reflect $100.02 until $T + 2$ milliseconds. A market-making firm on the direct feed can, within microseconds of $T$, cancel a stale quote or lift the new best offer before a SIP-only participant even sees a change. If a SIP-only trader submits a marketable order at $T + 0.5$ ms believing the best offer is still $100.05, that order arrives into a book where the real best offer is already $100.02 — the direct-feed participant captures whatever spread that stale belief creates, entirely legally, purely through information timing.

What this means in practice

Any strategy that competes on speed pays for direct feeds and colocation precisely to avoid the SIP's extra delay, and regulators have repeatedly examined this speed gap as a fairness question without banning it, since direct feeds are for sale to anyone willing to pay. For slower, longer-horizon strategies the gap is irrelevant — a fund holding positions for weeks doesn't care about two milliseconds — but for anything that trades on the arrival of new information, watching the SIP instead of a direct feed means, structurally, always being a beat behind.