In computing, an Ajax Service Bus (ASB) refers to a software architecture construct that describes a communication mechanism between an AJAX application running in a web browser to a web application server. The ASB manages an application's network communication, and provides a channel for optimizing application web messaging needs. Current Ajax applications asynchronously communicate with a browser using XMLHttpRequest (XHR). An ASB oversees XHR and provides functionality such as two-way multiplexing, "once-and-only once" guaranteed delivery,[clarification needed] publish/subscribe exchanges, and asynchronous push events.
The ASB is perpendicular, and connects directly from a browser running an AJAX application into one or more services running in a datacenter. An Enterprise service bus (ESB) provides horizontal communication between all of those services; an ASB can connect directly into the ESB as it would with a single service and extend the combined functionality to an AJAX application.