fixed iperf rate API json return format
diff --git a/web/topology_rest.py b/web/topology_rest.py
index ac96026..ab1c053 100755
--- a/web/topology_rest.py
+++ b/web/topology_rest.py
@@ -871,8 +871,7 @@
     print "REST IF has issue"
     exit
 
-  js = json.dumps(result)
-  resp = Response(js, status=200, mimetype='application/json')
+  resp = Response(result, status=200, mimetype='application/json')
   return resp