Service discovery spans platforms

ireless technologies allow a device to enter and leave multiple networks at will. The concept of a personal area network will let users be connected to information services anywhere through their personal communicators and wearable computers. For these technologies to be useful, however, they must be very easy to use.

In addition, such networks must be self-configuring, rendering them virtually transparent to consumers. Connections must work out of the box, without setup wizards, online settings or manuals.

The key to making these networks work is service discovery middleware. And to make the job easier, the Salutation Architecture was created to help solve the problems of service discovery and utilization among a broad set of appliances and equipment, and in an environment of widespread connectivity and mobility.

The architecture provides a standard method for applications, services and devices to describe and advertise their capabilities to other applications, services and devices, as well as to discover the capabilities of those other entities.

The architecture also helps applications, services and devices search other applications, services or devices for particular capabilities, and request and establish interoperable sessions to utilize those capabilities. Given the diverse nature of target appliances and equipment in an environment of widespread connectivity, the Salutation Architecture is processor, operating system, and communication protocol independent. It also allows for scalable implementations, even in very small, resourceconstrained devices.

Service discovery lets two disparate devices communicate their functional capabilities to one another. Information servers may customize interactions with devices to meet capabilities such as screen size and resolution. Or a service may search for a device that meets specific processing requirements such as document finishing. A device may also search a network to locate needed services.

To be successful, service discovery technology must provide more than the ability to advertise a device's class or a service's functionality. It is no longer enough to discover a printer. It is necessary to know a printer's color capability, the various resolutions it supports, the availability of a document finisher and collator, and the contents of the input drawers.

In traditional networks, a central directory contains detailed records about the network elements. In less- formal networks, a surrogate directory or look-up table may be constructed, with one node acting as the repository for the capabilities of the devices and services in a temporary network. Ad hoc, peer-to-peer networks don't require a directory at all, relying on direct interactions to determine the capabilities of other devices. In all of these cases, service discovery is used to identify the capabilities of things that enter the network.

With the wireless, mobile paradigm, the same device may take part in all three of these network types. A single service discovery technology is needed to support the mobile device as it migrates from traditional directory-centric and peer-to-peer networks and back again. Not only should the service discovery technology have the ability to determine the capabilities of the devices that enter a network, they should also have the ability to find a specific device or service and bind to it.

Finally, service discovery technology must be independent of operating systems and protocols. If not, islands of interconnectivity will be created without the means to bridge from one to another. For example, Sun's service discovery technology, called Jini, does not interact with Universal Plug and Play, Microsoft's offering.

The Salutation Architecture has implementations modeled in TCP/IP, InfraRed Data Association standards, Bluetooth and Service Location Protocol. It is available free through the Salutation Consortium, a nonprofit corporation. The architecture supports Windows, WindowsCE, Java, VXWorks and Tornado, with ports to Palm in the works.

While Salutation-enabled products are shipping in support of office automation, the technology is equally suited to meet the diverse product mix and network requirements presented in wireless networking.

Pascoe, president of the Salutation Consortium, currently works for IBM. He is also founder of XtraWorX based in Highland, Utah. He can be reached at rpascoe@salutation.org.

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