This is a payload from a single ethernet packet taken off the wire and decoded by a packet sniffer. To accommodate the extremely high volume of data streamed by the exchange in real-time, the simple binary encoding and the MDP specification define a streaming format with no duplication of data, and a self-referencing beginning and end of message encapsulation that implies related parts of the message by its internal and order and reference. This streaming entanglement makes the raw decoded file relatively useless to analytic processing.

An example of this is where a trade on the book takes Implied liquidity. The TradeID for the implied match will be for thje Implies book. For analytic purposes we want both the direct book's TradeID and the Implied Book's TradeID within a single record so that we can accurately source the liquidity for a given direct trade on the book.

Some purveyors of Tick Data do not use the actual recorded PCAPs, but instead download full replay files at the end of the trading session. These replay files are a subset of the actual PCAP files and contain incomplete information.