Web service protocol stack

A web service implementation depends on technologies often organized in a layered stack. The implementation itself defines a standard protocol for each technology layer, with each layer depending on the layers appearing below it in the stack.

Figure 1. Web service protocol stack
This image represents the protocol stack for web services. From the bottom up, the stack includes a transport layer, a packaging layer, and a description layer. HTTP and HTTPS are associated with the transport layer. SOAP is associated with the packaging layer. WSDL is associated with the description layer.

Beginning at the bottom of the stack, the Transport layer defines the technology standards for communication, allowing information to move across the network. HTTP or HTTPS are often used as the standard for the transport layer.

The Packaging layer rests on top of Transport and defines the standard for structuring information for transport across the network. The SOAP format is commonly used, which offers an XML structure for packaging the data. See the topic Simple Object Access Protocol for more information.

The topmost layer is Description and identifies the standards used by the layers below it in the stack, as well as providing the definition of the interface available for client use. The most common means of conveying this information is through the use of a WSDL file. See the topic Web Service Description Language for more information.