如何对长期运行的ASPX请求执行浏览器更新以启用AJAX的WCF服务？

I've got a long running request on an ASPX page (.NET 3.5) to an AJAX-enabled WCF service. The set up basically works fine and I get the result back to my JavaScript callback after n seconds, but I'd like to know whether there is a way to keep the browser updated about the progress on the server while the process (i.e. the webservice method) is running.I've got a long running request on an ASPX page