The Networks
The four-party model, ISO 8583 field by field, the several numbers all called the transaction reference, and where the money goes.
The Four-Party Model
You will be able to name the five roles in a card payment and say which of them holds a contract with which others, and which pairs have no contract at…
8,216 words/36 min read24ISO 8583
You will be able to explain what the bitmap does, and read the shape of a transaction off eight bytes of hexadecimal before parsing a single value.
8,413 words/37 min read25The Bitmap
You will be able to read a sixteen-character hexadecimal string such as F23C448128E09200 and say, without a tool, which data elements the message carries.
8,465 words/37 min read26The Fields That Matter
You will be able to say, for each of the fifteen fields that carry a card authorisation, what it holds, who writes it and what specifically breaks when…
8,505 words/37 min read27A Transaction, Narrated
You will be able to narrate a contactless card authorisation from card presentation to receipt, naming every hop and what each party does in it.
8,495 words/37 min read28The Number You Were Given
You will be able to name the four identifiers a card payment leaves behind, say who created each one, where it appears and how long it lives.
7,916 words/34 min read29Response Codes
You will be able to point to the two-character field that carries the entire verdict of a card authorisation, name it as DE39, and say why a database…
8,692 words/38 min read30Authorisation, Clearing, Settlement
You will be able to explain why a customer's available balance falls in under two seconds while not one unit of currency has moved anywhere.
8,260 words/36 min read31Where the Money Goes
You will be able to say who pays interchange and who receives it, and explain why the merchant is neither of those parties despite being the one out of…
8,236 words/36 min read32ISO 20022
You will be able to explain why ISO 20022 is not a format but a method for producing formats, a dictionary of business concepts and a committee structure…
8,378 words/36 min read33The Physical Network
You will be able to name the five roles a card authorisation passes through, and say which two of them are scheme members and therefore the only parties…
8,631 words/38 min read