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Web services: pump up the volume: bandwidth consumption and network latency challenges must be addressed

Communications News, Feb, 2004 by Zohar Pearl

Web services is one of the hottest topics in the IT business. This new distributed computing model enables applications to be deployed as services that can be accessed by anyone, inside or outside of the enterprise. This creates new opportunities to increase revenue and establish tighter relationships with customers and business partners, but it also creates some new challenges for network managers.

Most IT managers have focused on the potential benefits of Web services, while largely overlooking the impact on enterprise networks and the resulting cost of upgrades that may be needed. A basic understanding of Web services is needed in order to understand its impact on enterprise networks, particularly WANs.

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The Web services framework is a set of industry-standard protocols, and message formats that enable developers to build applications that provide services to other applications across the Web. Web services are self-contained, self-defining applications. These services can range from simple stock quotes or weather forecasts to complex business processes, and multiple set lambs can be loosely coupled in build more complex services. Unlike the original Web model, Web services enable automated program-to-program communications and not just human access to server-based content.

The goal of Web services is to enable any authorized user to access, any available service. To meet this objective, the Web services initiative has standardized three sets of functions:

* standard transport and messaging protocols;

* directory services; and

* standard service-description language.

The most basic requirement is to enable communications between Web services and service requesters. The Web services messaging protocols are designed to be independent of the underlying transport protocols, but, as a practical matter, most implementations use the Web's HTTP protocol. From a network point-of-view, Web services looks like ordinary Web traffic.

The next requirement is to define a standard format for the messages that flow between requesters and Weir services. To meet this requirement, Welt services uses the extensible markup language (XML) standard. XML is an industry-standard, platform independent syntax for describing and structuring data. In the Web services architecture, XML describes not only application data but also the simple object access protocol (SOAP) message envelopes that carry the data between requesters and Web services.

Both the XML and SOAP standards are developed and maintained by the World Wide Web Consortium (W3C).

SOAP/XML messages are self-defining, which means that they not only contain data, but also the definition of that data-metadata. The large amount of XML metadata contained in SOAP messages is the main reason that Web services will require more network bandwidth than traditional distributed computing models. The XML metatags that are the building blocks of SOAP messages can be many times the size of the data that they define.

In one example taken from a SOAP primer produced by the W3C, about 75% of the code is not related to the original message, but is taken up by optional and required elements of SOAP messages. It shows why Web services that use SOAP/XML will require more network bandwidth than traditional distributed application models. In fact, Web services can consume 10 times as much bandwidth as legacy client-server computing.

None of this diminishes the benefits and importance of SOAP/ XML within the Web services architecture, but it does mean that network managers must be prepared to handle higher traffic volumes. Application developers may not even be aware of the increased overhead because SOAP messages are generally built by development tools, not by the developers themselves.

PROTOCOLS ADD TO CONSUMPTION

In addition to the overhead of SOAP/XML messaging between requesters and services, Web services also introduces some additional protocols that enable requesters to dynamically find the services they need. In order to use a Web service, a requester:

* uses the universal description, discovery' and integration (UDDI) protocol to determine if the needed service is available and where it is located; and

* uses the Web scrvice definition language (WSDL) to learn how to interact with the service.

Both of these SOAP/XML-based protocols enable dynamic access to Web services, but they also contribute to the increased bandwidth consumption.

Network managers face two key challenges in supporting Web services. First, Web services can consume much more bandwidth than traditional distributed applications. The result is increased network congestion, particularly on enterprise WAN links where bandwidth is scarce and expensive. Web services proponents (application people, not network people), however, discount SOAP/ XML overhead by stating that "bandwidth is cheap." That may be the case on LANs and on the Internet, but it is certainly not the case on private enterprise WANs.

Technology Industry

Web services: pump up the volume: bandwidth consumption and network latency challenges must be addressed

Communications News, Feb, 2004 by Zohar Pearl

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