private int checkOne(String sender,MultiCastMessage msg, int senderSeq)
        {
        	
        	AtomicInteger lastSeqNum =  recvSeqTracker.get(msg.getGroupID()).get(sender);
        	String groupID = msg.getGroupID();
        	if(senderSeq == lastSeqNum.get()+1)
        	{	
	       		return 1;
       		}
        	
	       	else if(senderSeq > lastSeqNum.get()+1)
	       	{
	       		System.out.println("multicast missing, seq->"+senderSeq);
	       		// some previous msg missing, 
	       		
	       	// set Seq and Src
	       		MultiCastMessage message = new MultiCastMessage(" ", " ", new NACKRequest(sender,lastSeqNum.get()+1,senderSeq-1), null);
	            message.set_seqNum(currentSeqNum);
	            message.set_source(local_name);
	        	
	            List<String> groupList = conf.groupMap.get(groupID);
	        	Iterator<String> it = groupList.iterator();
	        	
	        	//Add Clock to message
	        	message.setTimeStamp(multiVectorClockMap.get(groupID).getCurrentTimeStamp());

	        	
	        	//Send MultiCastMessage to each node in group including yourself
	        	while(it.hasNext())
	        	{
	        		message.setDest(it.next());
	        		MultiCastMessage M = new MultiCastMessage(message);
	        		M.setGroupID(groupID);
	        		M.setACKs(new HashMap<String,AtomicInteger>(recvSeqTracker.get(groupID)));
	        		M.setMessageType(MessageType.MULTICAST);
	        		M.setControlType(ControlType.NACK);
	        		M.setMulticastSeq(groupSendSeqTracker.get(groupID).intValue());
	        		try {
	    				InternalSend(M);
	    				System.out.println(M.toString());
	    			} catch (UnknownHostException e) 
	    			{
	    				System.out.println("Remote Peer Unknown");
	    				e.printStackTrace();
	    			}
	        	}
	        	
	       		
	       		// in receiver thread, when you recv NACK  , then what?? to do
	       		
	       		return 2;
	       	
	       	}
	       	
	       	else
	       	{
		       	System.out.println("multicast duplicate, disgard it ");
	       		// S<=R, has already received this msg, just disgard it
	       		// 
	       		return 3;
       		}
        }