WS-Discovery

Oh my, WS-Discovery is a Web service spec I might actually use! Horror! 8-)

When I heard what it was, and that it was written by BEA, I was sure that Yaron Goland would be involved, after all his related work on UPnP. He wasn’t, nor was he even acknowledged. Odd.

But there’s not really too much to say about it (at least until I do a detailed review). Link local discovery is a pretty well understood domain, and the authors of this spec seem to grok it at least as well as I do. The use of SOAP/XML is unfortunate, I’d say, because of its bloat; you really need to keep things lean for multicast discovery so as to fit everything in a single datagram. Some kind of binary-encoded SOAP would be useful here.

I sort of wonder why Rendezvous or LLMNR weren’t adopted; the former has a whole lot of support and running code behind it, while the latter has MS and should be published as an RFC shortly. But I suppose that nothing’s really close to critical mass in this space, so I can’t blame them for starting from scratch.

There’s also mention of a “SOAP/UDP” spec, which is “To be published”. That’ll be interesting to see, especially if there’s a compact (but still extensible) binary encoding. What’s suggested in the spec, re “UNICAST_UDP_REPEAT” and “APP_MAX_DELAY”, and comments such as “waiting for timers” suggests that it might be more a case of trying to reinvent parts of TCP rather than embracing the message-per-datagram model which seems to work so well. But my experience there is rather limited, so I’d be happy to be proven wrong.

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