diff --git a/proxy/lib/snowflake.go b/proxy/lib/snowflake.go
index e39fcfb..7d237de 100644
--- a/proxy/lib/snowflake.go
+++ b/proxy/lib/snowflake.go
@@ -73,6 +73,10 @@ const readLimit = 100000 //Maximum number of bytes to be read from an HTTP reque
 
 var broker *SignalingServer
 
+var currentNATTypeAccess = &sync.RWMutex{}
+
+// currentNATType describes local network environment.
+// Obtain currentNATTypeAccess before access.
 var currentNATType = NATUnknown
 
 const (
@@ -183,7 +187,10 @@ func (s *SignalingServer) pollOffer(sid string, shutdown chan struct{}) *webrtc.
 			return nil
 		default:
 			numClients := int((tokens.count() / 8) * 8) // Round down to 8
-			body, err := messages.EncodePollRequest(sid, "standalone", currentNATType, numClients)
+			currentNATTypeAccess.RLock()
+			currentNATTypeLoaded := currentNATType
+			currentNATTypeAccess.RUnlock()
+			body, err := messages.EncodePollRequest(sid, "standalone", currentNATTypeLoaded, numClients)
 			if err != nil {
 				log.Printf("Error encoding poll message: %s", err.Error())
 				return nil
@@ -530,7 +537,12 @@ func (sf *SnowflakeProxy) Start() error {
 
 	// use probetest to determine NAT compatability
 	sf.checkNATType(config, sf.NATProbeURL)
-	log.Printf("NAT type: %s", currentNATType)
+
+	currentNATTypeAccess.RLock()
+	currentNATTypeLoaded := currentNATType
+	currentNATTypeAccess.RUnlock()
+
+	log.Printf("NAT type: %s", currentNATTypeLoaded)
 
 	ticker := time.NewTicker(pollInterval)
 	defer ticker.Stop()
@@ -604,12 +616,54 @@ func (sf *SnowflakeProxy) checkNATType(config webrtc.Configuration, probeURL str
 		return
 	}
 
+	currentNATTypeAccess.RLock()
+	currentNATTypeLoaded := currentNATType
+	currentNATTypeAccess.RUnlock()
+
+	currentNATTypeTestResult := NATUnknown
 	select {
 	case <-dataChan:
-		currentNATType = NATUnrestricted
+		currentNATTypeTestResult = NATUnrestricted
 	case <-time.After(dataChannelTimeout):
-		currentNATType = NATRestricted
+		currentNATTypeTestResult = NATRestricted
 	}
+
+	currentNATTypeToStore := NATUnknown
+	switch currentNATTypeLoaded + "->" + currentNATTypeTestResult {
+	case NATUnknown + "->" + NATUnknown:
+		currentNATTypeToStore = NATUnknown
+
+	case NATUnknown + "->" + NATUnrestricted:
+		currentNATTypeToStore = NATUnrestricted
+
+	case NATUnknown + "->" + NATRestricted:
+		currentNATTypeToStore = NATRestricted
+
+	case NATUnrestricted + "->" + NATUnknown:
+		currentNATTypeToStore = NATUnrestricted
+
+	case NATUnrestricted + "->" + NATUnrestricted:
+		currentNATTypeToStore = NATUnrestricted
+
+	case NATUnrestricted + "->" + NATRestricted:
+		currentNATTypeToStore = NATRestricted
+
+	case NATRestricted + "->" + NATUnknown:
+		currentNATTypeToStore = NATRestricted
+
+	case NATRestricted + "->" + NATUnrestricted:
+		currentNATTypeToStore = NATUnrestricted
+
+	case NATRestricted + "->" + NATRestricted:
+		currentNATTypeToStore = NATRestricted
+	}
+
+	log.Printf("NAT Type measurement: %v -> %v = %v\n", currentNATTypeLoaded, currentNATTypeTestResult, currentNATTypeToStore)
+
+	currentNATTypeAccess.Lock()
+	currentNATType = currentNATTypeToStore
+	currentNATTypeAccess.Unlock()
+
 	if err := pc.Close(); err != nil {
 		log.Printf("error calling pc.Close: %v", err)
 	}