// window id. needed for asyncronous data like images loaded
// todo maybe better delegate window registry to the windowbackoffice?
URLBuilder ubu = new URLBuilder(uriPrefix, resWindow.getInstanceId(), String.valueOf(resWindow.timestamp), resWindow.wbackofficeImpl);
StringOutput sout = new StringOutput(30);
ubu.buildURI(sout, null, null);
mr = new RedirectMediaResource(sout.toString());
ServletUtil.serveResource(request, response, mr);
if (isDebugLog) {
long diff = System.currentTimeMillis() - debug_start;
debugMsg.append("rdirnw:").append(diff).append(LOG_SEPARATOR);