diff --git a/core/AmRtpStream.cpp b/core/AmRtpStream.cpp
index 14813979..aa884eb7 100644
--- a/core/AmRtpStream.cpp
+++ b/core/AmRtpStream.cpp
@@ -162,6 +162,30 @@ void AmRtpStream::setLocalPort()
   DBG("local rtp port set to %i\n",l_port);
 }
 
+int AmRtpStream::ping()
+{
+  unsigned char ping_chr[2];
+
+  ping_chr[0] = 0;
+  ping_chr[1] = 0;
+
+  AmRtpPacket rp;
+  rp.payload = payload;
+  rp.marker = true;
+  rp.sequence = sequence++;
+  rp.timestamp = 0;   
+  rp.ssrc = l_ssrc;
+  rp.compile((unsigned char*)ping_chr,2);
+
+  rp.setAddr(&r_saddr);
+  if(rp.send(l_sd) < 0){
+    ERROR("while sending RTP packet.\n");
+    return -1;
+  }
+ 
+  return 2;
+}
+
 int AmRtpStream::send( unsigned int ts, unsigned char* buffer, unsigned int size )
 {
   if ((mute) || (hold))
diff --git a/core/AmRtpStream.h b/core/AmRtpStream.h
index c265fc62..46be880e 100644
--- a/core/AmRtpStream.h
+++ b/core/AmRtpStream.h
@@ -155,7 +155,10 @@ public:
 
   int receive( unsigned char* buffer, unsigned int size,
 	       unsigned int& ts, int& payload);
-    
+
+  /** ping the remote side, to open NATs and enable symmetric RTP */
+  int ping();
+
   /** Allocates resources for future use of RTP. */
   AmRtpStream(AmSession* _s=0);
   /** Stops the stream and frees all resources. */
diff --git a/core/AmSession.cpp b/core/AmSession.cpp
index 6253d91d..92d68314 100644
--- a/core/AmSession.cpp
+++ b/core/AmSession.cpp
@@ -648,6 +648,9 @@ void AmSession::onSipReply(const AmSipReply& reply)
 	      onEarlySessionStart(reply);
 
 	      rtp_str.setMonitorRTPTimeout(false);
+	      
+	      // ping the other side to open fw/NAT/symmetric RTP
+	      rtp_str.ping();
 
 	      if(input || output || local_input || local_output)
 		AmMediaProcessor::instance()->addSession(this,