Microsoft Corp. has made this an optional part of its Active Desktop under Internet Explorer 4.0 and Microsoft Windows 98. Another mode of distribution, called publish and subscribe, publishes the message to several central sites, and each client is configured to monitor one of the sites. When there is a change, the client downloads the new information. The most promising technology at the moment is IP Multicast, an Internet method for efficiently distributing multiple files and multimedia programs. As with most server-level products, choosing a push server is not simple.
Products differ quite a bit in features and price.
Starburst Multicast from Starburst Communications Corp. of Concord, Mass., is expensive and designed for large organizations, and it mainly does file transfers, but it's proven. Marimba's Castanet 3.1 and Rendezvous 4.2 from Tibco Inc. of Palo Alto, Calif., are good for refreshing volatile file content. PointCast excels at delivering small amounts of data quickly and efficiently. If distributions will focus on remote workers who aren't always online, consider RemoteWare Express from Xcellenet Inc. of Atlanta. First came the telephone.