HTTP 503 when calling long-running ASP.NET web service

We have ASP.NET Web Service running on IIS6 that has long-running methods (processing takes about 5 minutes).

When we call the web service from Win 2003 Server, our client gets HTTP 503 error after waiting for the response for couple of minutes. So we never get the response data back to the client, even though, the call is actually completed on the server (our application logging shows that the whole method gets executed). So the execution on the server side is not stopped, client just stops waiting for the response.

However, when we call the same method with the same parameters and the same client from Win XP workstation, everything works as expected and we don't get any HTTP errors.

D开发者_如何学Coes anyone got any ideas why this error happens only when calling from Server OS? Is there some registry or other setting where you can control how long OS waits for HTTP responses?