Explanation
An API gateway is a component that acts as a single point of entry for all cloud applications to access on-premise resources and services. It can provide security, routing, transformation, and other features to facilitate integration. An API gateway component should be deployable behind a DMZ or perimeter network, which is a subnetwork that separates the internal network from the external network and provides an additional layer of security. The middleware solution should also be capable of establishing a secure API gateway between cloud applications and on-premise resources, which may involve using protocols such as HTTPS, SSL/TLS, or VPN. The OAuth security protocol is not a requirement for choosing a middleware solution, as it is a standard for authorizing access to resources on behalf of a user. The middleware solution's ability to interface directly with databases via an ODBC connection string is also not a requirement, as it is a specific feature that may or may not be needed depending on the integration scenario. Reference: Salesforce Integration Architecture Designer Resource Guide, page 14-15