DroptestRPC doesn't work with Cbench, When using more than 140 switches

Try to run Cbench with dropAllPacketsRpc On,

First round i get some returns but all test after return zero.

Error seen on OSGi console
2014-08-19 16:08:56.398 UTC [md-sal-binding-notification-12] ERROR o.o.o.droptest.AbstractDropTest - Failed to process packet
java.lang.IllegalStateException: No default provider is available
at org.opendaylight.yang.gen.v1.urn.opendaylight.flow.service.rev130819.SalFlowService$$Broker$DirectProxy.addFlow(SalFlowService$$Broker$DirectProxy.java) ~[na:na]
at org.opendaylight.openflowplugin.droptest.DropTestRpcSender.processPacket(DropTestRpcSender.java:71) ~[bundlefile:na]
at org.opendaylight.openflowplugin.droptest.AbstractDropTest.onPacketReceived(AbstractDropTest.java:121) ~[bundlefile:na]
at org.opendaylight.openflowplugin.droptest.DropTestRpcSender$$Broker$ListenerInvoker.onNotification(DropTestRpcSender$$Broker$ListenerInvoker.java) [bundlefile:na]
at org.opendaylight.controller.sal.binding.impl.AbstractNotificationListenerRegistration.notify(AbstractNotificationListenerRegistration.java:38) [bundlefile:na]
at org.opendaylight.controller.sal.binding.impl.NotifyTask.run(NotifyTask.java:42) [bundlefile:na]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471) [na:1.7.0_51]
at java.util.concurrent.FutureTask.run(FutureTask.java:262) [na:1.7.0_51]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [na:1.7.0_51]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [na:1.7.0_51]
at java.lang.Thread.run(Thread.java:744) [na:1.7.0_51]