diff --git a/src/tools/ServeErrors.java b/src/tools/ServeErrors.java
index ff083f9..4392aa6 100644
--- a/src/tools/ServeErrors.java
+++ b/src/tools/ServeErrors.java
@@ -79,4 +79,15 @@ public abstract class ServeErrors {
 		}
 	}
 
+	/** Send an unknown host message.
+	 * @param pd	Request received
+	 */
+	protected < T extends ProtocolP2PPacket<?> > void sendUnknownHost(T pd) {
+		try {
+			pd.sendResponse(createProtocolP2PPacket(new Payload(RequestResponseCode.UNKNOWN_HOST)));
+		} catch (Exception e) {
+			writeLog(e, LogLevel.Error);
+		}
+	}
+
 }
diff --git a/src/tracker/TrackerManagement.java b/src/tracker/TrackerManagement.java
index b4a51fc..617f101 100644
--- a/src/tracker/TrackerManagement.java
+++ b/src/tracker/TrackerManagement.java
@@ -17,6 +17,7 @@ import protocolP2P.Register;
 import protocolP2P.RequestResponseCode;
 import protocolP2P.RatioRequest;
 import protocolP2P.RatioResponse;
+import protocolP2P.UpdateRatio;
 import localException.InternalError;
 import remoteException.EmptyDirectory;
 import exception.LocalException;
@@ -154,6 +155,29 @@ public abstract class TrackerManagement extends ServeErrors implements Runnable
 	 */
 	protected abstract void closeHostItemSocket(HostItem hostItem);
 
+	/** Handle Update Ratio
+	 * @param pd	Received request
+	 * @throws	InternalError
+	 */
+	protected < T extends ProtocolP2PPacket<?> > void handleUpdateRatio(T pd) throws InternalError {
+		Payload p = pd.getPayload();
+		assert p instanceof UpdateRatio : "payload must be an instance of UpdateRatio";
+		if (!(p instanceof UpdateRatio)) {
+			throw new InternalError();
+		}
+
+		UpdateRatio updateRatio = (UpdateRatio) p;
+		HostItem updateRatioServer = updateRatio.getServer();
+		HostItem updateRatioClient = updateRatio.getClient();
+		long ratioSize = updateRatio.getDataSize();
+		if (!ratioDown.containsKey(updateRatioClient) || ! ratioUp.containsKey(updateRatioServer)) {
+			sendUnknownHost(pd);
+		} else {
+			ratioDown.put(updateRatioClient, Long.valueOf(ratioDown.get(updateRatioClient).longValue() + ratioSize));
+			ratioUp.put(updateRatioServer, Long.valueOf(ratioUp.get(updateRatioServer).longValue() + ratioSize));
+		}
+	}
+
 	/** Handle Registering
 	 * @param pd	Received request
 	 * @throws	InternalError
@@ -171,12 +195,9 @@ public abstract class TrackerManagement extends ServeErrors implements Runnable
 		}
 
 		// initialize ratios if this is a new host
-		if (!ratioUp.containsKey(host)) {
-			ratioUp.put(host, Long.valueOf(0));
-		}
-		if (!ratioDown.containsKey(host)) {
-			ratioDown.put(host, Long.valueOf(0));
-		}
+		ratioUp.putIfAbsent(host, Long.valueOf(0));
+		ratioDown.putIfAbsent(host, Long.valueOf(0));
+		
 		// send a list request
 		try {
 			ProtocolP2PPacket<?> pLReq = createProtocolP2PPacket(new Payload(RequestResponseCode.LIST_REQUEST));
@@ -232,6 +253,10 @@ public abstract class TrackerManagement extends ServeErrors implements Runnable
 				writeLog("Received RATIO REQUEST from host " + pd.getHostItem(), LogLevel.Action);
 				handleRatio(pd);
 				break;
+			case UPDATE_RATIO:
+				writeLog("Received UPDATE RATIO from host " + pd.getHostItem(), LogLevel.Action);
+				handleUpdateRatio(pd);
+				break;
 			default:
 				writeLog("Received grabbage from host " + pd.getHostItem(), LogLevel.Action);
 				sendInternalError(pd);