Considerations When Advertising Legacy Services

Generally, modifying the source code to add SLP is preferable to either writing a stand-alone SA or using proxy registration. By modifying the source code, it is possible to add service-specific features and to closely track service availability. If the source code is unavailable, writing a stand-alone SA is preferable to using proxy registration. A stand-alone SA allows the SA to track service availability by being integrated into the service start/stop procedure. Proxy advertising is generally the third choice, when no source code is available and writing a stand-alone SA is impractical.

Proxy advertisements are maintained only as long as slpd that reads the proxy registration file is running. If an advertisement times out or slpd is halted, the proxy advertisement is no longer available. Conversely, there is no direct connection between the proxy advertisement and the service itself.

If the service is brought down, slpd must be brought down, the serialized registration file edited to comment out or remove the proxy advertisement, and slpd brought up again. You must follow the same procedure when the service is restarted or reinstalled. The lack of connection between the proxy advertisement and the service is a major drawback of proxy advertisements, in comparison with the two other techniques of legacy advertising.