A key part of any Asynchronous JavaScript and XML (Ajax)-based web application is the communication layer between the client and the server. To implement this layer, you need to understand the various communication mechanisms that browsers provide, as well as each mechanism's pros and cons. In this article, learn to make the correct match between the specific communication needs of an application and the appropriate mechanism. Detailed examples show you how to create a communication layer that can meet these different client-server communication needs.