Both parties involved in a transaction must have faith in the currency's value. In contrast, notational checks, purchase orders and credit cards represent a commitment to exchange cash and exhibit no fundamental value. For data integrity, the protocol relies on time-outs and retransmissions. If an authorization request is not answered for any reason, the client prepares a reversal transaction. The terminal will not send another transaction until the host receives a reversal response.
Authentication is limited to carrier-assigned merchant and terminal fields.
This function is usually fulfilled by the payment module of the site's commerce package or by an intermediary, such as CyberCash. This integration of new and old lets consumers access random commerce sites without any special software. It also lets banks and financial institutions accept Internet-generated transactions using existing systems. Although it's not necessary to have an intimate knowledge of the link protocol, it's important to understand the fields that make up the authentication messages and responses. In addition, if you are designing a database for order capture, the industry-specific field definitions that extend the authentication messages are an excellent starting point.