Web Services in Multimedia Communication Systems

These pages cover a variety of topics related to the concept of web services as they relate to ▲IP-based multimedia communication systems.

The W3C defines a web service as "a software system designed to support interoperable machine-to-machine interaction over a network." That can be broad, but being consistent with the purpose of Packetizer, we will narrow our focus on functionality and concepts that are directly related to communication systems, including communication between multimedia terminals (end systems) and supporting network services.

The W3C goes on to narrow the definition of web services as one that is defined via WSDL. While WSDL might be appropriate for many services, the supporters of the REST design approach have clearly indicated a preference for a competing service definition format called WADL. Like everything else, one size does not fit all. Or, as we have heard it said in standards work many times before, "The great thing about standards is that there are so many from which to choose."

Some have a view that a service is not a "web service" unless it utilizes ▲HTTP. We disagree with such a narrow definition of a web service. In fact, just as there is disagreement as to whether WSDL or WADL are both necessary, we would argue that narrowly fixating on HTTP means that we significantly limit our potential with the Internet. Consider the vast number of services already in existence like DNS, NTP, SMTP, and POP as evidence to the fact that a web service cannot and should not be constrained to HTTP.

Unlike a simple web service that fetches or stores information, multimedia communication systems are highly interactive, maintain state, and can produce a lot of bi-directional data traffic. Even so, communication systems operate over the Internet and may utilize many of the existing web services. It is reasonable, then, that such communication systems might also utilize such industry-standard syntax specification like ▲XML in order to facilitate communication.

None of the IPMC standards in existence today, including ▲SIP and ▲H.323, were truly engineered to take full advantage of the heterogeneous and distributed nature of the Internet. However, that is changing with new technologies like ▲AMS and, as such, it is important to explore the various web services technologies to understand how they related to multimedia communication.