The binary output of each data feed are provided in pcap format. Data is captured by IEX when the feed is disseminated by the System via the lower level IEX Transport Protocol (IEX-TP). Historical data files are named in a manner to identify the version of IEX-TP and the data feed specification used to produce the data. Firms must use appropriate specification versions to decode each pcap. For example, 20170515_IEXTP1_DEEP1.0.pcap.gz is the DEEP data file from May 15, 2017 which is formatted in accordance with IEX-TP v1 and DEEP v1.0.