diff --git a/core/AmConfig.cpp b/core/AmConfig.cpp
index 1e060a0d..701d3f2d 100644
--- a/core/AmConfig.cpp
+++ b/core/AmConfig.cpp
@@ -97,6 +97,8 @@ unsigned int AmConfig::OptionsSessionLimit            = 0;
 unsigned int AmConfig::OptionsSessionLimitErrCode     = 503;
 string       AmConfig::OptionsSessionLimitErrReason   = "Server overload";
 
+bool         AmConfig::AcceptForkedDialogs     = true;
+
 bool         AmConfig::ShutdownMode            = false;
 unsigned int AmConfig::ShutdownModeErrCode     = 503;
 string       AmConfig::ShutdownModeErrReason   = "Server shutting down";
@@ -512,6 +514,9 @@ int AmConfig::readConfiguration()
     }
   }
 
+  if(cfg.hasParameter("accept_forked_dialogs"))
+    AcceptForkedDialogs = !(cfg.getParameter("accept_forked_dialogs") == "no");
+
   if(cfg.hasParameter("shutdown_mode_reply")){
     string c_reply = cfg.getParameter("shutdown_mode_reply");    
     size_t spos = c_reply.find(" ");
diff --git a/core/AmConfig.h b/core/AmConfig.h
index a8bf0f1e..3fa412a1 100644
--- a/core/AmConfig.h
+++ b/core/AmConfig.h
@@ -170,6 +170,8 @@ struct AmConfig
   static unsigned int OptionsSessionLimitErrCode;
   static string OptionsSessionLimitErrReason;
 
+  static bool AcceptForkedDialogs;
+
   static bool ShutdownMode;
   static unsigned int ShutdownModeErrCode;
   static string ShutdownModeErrReason;
diff --git a/core/AmEventDispatcher.cpp b/core/AmEventDispatcher.cpp
index 905d0391..b64155ca 100644
--- a/core/AmEventDispatcher.cpp
+++ b/core/AmEventDispatcher.cpp
@@ -27,6 +27,7 @@
 
 #include "AmEventDispatcher.h"
 #include "AmSipEvent.h"
+#include "AmConfig.h"
 #include "sip/hash.h"
 
 unsigned int AmEventDispatcher::hash(const string& s1)
@@ -52,12 +53,38 @@ AmEventDispatcher* AmEventDispatcher::instance()
   return _instance ? _instance : ((_instance = new AmEventDispatcher()));
 }
 
+
+bool AmEventDispatcher::addEventQueue(const string& local_tag,
+				      AmEventQueueInterface* q)
+{
+    unsigned int queue_bucket = hash(local_tag);
+
+    queues_mut[queue_bucket].lock();
+
+    if (queues[queue_bucket].find(local_tag) != queues[queue_bucket].end()) {
+      queues_mut[queue_bucket].unlock();
+      return false;
+    }
+
+    queues[queue_bucket][local_tag] = q;
+    queues_mut[queue_bucket].unlock();
+    
+    return true;
+}
+
+
 /** @return false on error */
 bool AmEventDispatcher::addEventQueue(const string& local_tag, 
 				      AmEventQueueInterface* q,
 				      const string& callid, 
-				      const string& remote_tag)
+				      const string& remote_tag,
+				      const string& via_branch)
 {
+    if(local_tag.empty () ||callid.empty() || remote_tag.empty() | via_branch.empty()) {
+      ERROR("local_tag, callid, remote_tag or via_branch is empty");
+      return false;
+    }
+
     unsigned int queue_bucket = hash(local_tag);
 
     queues_mut[queue_bucket].lock();
@@ -67,36 +94,54 @@ bool AmEventDispatcher::addEventQueue(const string& local_tag,
       return false;
     }
 
-    unsigned int id_bucket = 0;
-
-    if(!callid.empty() && !remote_tag.empty()) {
-      // try to find via id_lookup
-      id_bucket = hash(callid, remote_tag);
-      id_lookup_mut[id_bucket].lock();
-
-      if (id_lookup[id_bucket].find(callid+remote_tag) != 
-	  id_lookup[id_bucket].end()) {
-	id_lookup_mut[id_bucket].unlock();
-	queues_mut[queue_bucket].unlock();
-	return false;
-      }
+    // try to find via id_lookup
+    unsigned int id_bucket = hash(callid, remote_tag);
+    string id = callid+remote_tag;
+    if(AmConfig::AcceptForkedDialogs){
+      id += via_branch;
     }
 
-    queues[queue_bucket][local_tag] = q;
+    id_lookup_mut[id_bucket].lock();
     
-    if(!callid.empty() && !remote_tag.empty()) {
-      id_lookup[id_bucket][callid+remote_tag] = local_tag;
+    if (id_lookup[id_bucket].find(id) != 
+	id_lookup[id_bucket].end()) {
       id_lookup_mut[id_bucket].unlock();
+      queues_mut[queue_bucket].unlock();
+      return false;
     }
-   
+
+    queues[queue_bucket][local_tag] = q;
+    id_lookup[id_bucket][id] = local_tag;
+
+    id_lookup_mut[id_bucket].unlock();
     queues_mut[queue_bucket].unlock();
     
     return true;
 }
 
+AmEventQueueInterface* AmEventDispatcher::delEventQueue(const string& local_tag)
+{
+    AmEventQueueInterface* q = NULL;
+    
+    unsigned int queue_bucket = hash(local_tag);
+
+    queues_mut[queue_bucket].lock();
+    
+    EvQueueMapIter qi = queues[queue_bucket].find(local_tag);
+    if(qi != queues[queue_bucket].end()) {
+
+	q = qi->second;
+	queues[queue_bucket].erase(qi);
+    }
+    queues_mut[queue_bucket].unlock();
+    
+    return q;
+}
+
 AmEventQueueInterface* AmEventDispatcher::delEventQueue(const string& local_tag,
 							const string& callid, 
-							const string& remote_tag)
+							const string& remote_tag,
+							const string& via_branch)
 {
     AmEventQueueInterface* q = NULL;
     
@@ -110,11 +155,16 @@ AmEventQueueInterface* AmEventDispatcher::delEventQueue(const string& local_tag,
 	q = qi->second;
 	queues[queue_bucket].erase(qi);
 
-	if(!callid.empty() && !remote_tag.empty()) {
+	if(!callid.empty() && !remote_tag.empty() && !via_branch.empty()) {
 	  unsigned int id_bucket = hash(callid, remote_tag);
+	  string id = callid+remote_tag;
+	  if(AmConfig::AcceptForkedDialogs){
+	    id += via_branch;
+	  }
+
 	  id_lookup_mut[id_bucket].lock();
 
-	  DictIter di = id_lookup[id_bucket].find(callid+remote_tag);
+	  DictIter di = id_lookup[id_bucket].find(id);
 	  if(di != id_lookup[id_bucket].end()) {	    
 	    id_lookup[id_bucket].erase(di);
 	  }
@@ -147,11 +197,20 @@ bool AmEventDispatcher::post(const string& local_tag, AmEvent* ev)
 }
 
 
-bool AmEventDispatcher::post(const string& callid, const string& remote_tag, AmEvent* ev)
+bool AmEventDispatcher::post(const string& callid, 
+			     const string& remote_tag, 
+			     const string& via_branch,
+			     AmEvent* ev)
 {
     unsigned int id_bucket = hash(callid, remote_tag);
+    string id = callid+remote_tag;
+    if(AmConfig::AcceptForkedDialogs){
+      id += via_branch;
+    }
+
     id_lookup_mut[id_bucket].lock();
-    DictIter di = id_lookup[id_bucket].find(callid+remote_tag);
+
+    DictIter di = id_lookup[id_bucket].find(id);
     if (di == id_lookup[id_bucket].end()) {
       id_lookup_mut[id_bucket].unlock();
       return false;
@@ -208,16 +267,24 @@ void AmEventDispatcher::dispose()
     _instance = NULL;
   }
 }
+
 /** this function optimizes posting of SIP Requests 
     - if the session does not exist, no event need to be created (req copied) */
-bool AmEventDispatcher::postSipRequest(const string& callid, const string& remote_tag, 
-				       const AmSipRequest& req)
+bool AmEventDispatcher::postSipRequest(const AmSipRequest& req)
 {
     // get local tag
     bool posted = false;
+    string callid = req.callid;
+    string remote_tag = req.from_tag;
     unsigned int id_bucket = hash(callid, remote_tag);
+    string id = callid+remote_tag;
+    if(AmConfig::AcceptForkedDialogs){
+      id += req.via_branch;
+    }
+
     id_lookup_mut[id_bucket].lock();
-    DictIter di = id_lookup[id_bucket].find(callid+remote_tag);
+
+    DictIter di = id_lookup[id_bucket].find(id);
     if (di == id_lookup[id_bucket].end()) {
       id_lookup_mut[id_bucket].unlock();
       return false;
diff --git a/core/AmEventDispatcher.h b/core/AmEventDispatcher.h
index f545790d..8fb53ce0 100644
--- a/core/AmEventDispatcher.h
+++ b/core/AmEventDispatcher.h
@@ -59,8 +59,8 @@ private:
     AmMutex queues_mut[EVENT_DISPATCHER_BUCKETS];
 
     /** 
-     * Call ID + remote tag -> local tag 
-     *  (needed for CANCELs and some provisionnal answers)
+     * Call ID + remote tag + via_branch -> local tag 
+     *  (needed for CANCELs)
      *  (UAS sessions only)
      */
     Dictionnary id_lookup[EVENT_DISPATCHER_BUCKETS];
@@ -74,23 +74,32 @@ public:
     static AmEventDispatcher* instance();
     static void dispose();
 
-    bool postSipRequest(const string& callid, const string& remote_tag, 
-			const AmSipRequest& req);
+    bool postSipRequest(const AmSipRequest& req);
 
     bool post(const string& local_tag, AmEvent* ev);
-    bool post(const string& callid, const string& remote_tag, AmEvent* ev);
+    bool post(const string& callid, 
+	      const string& remote_tag, 
+	      const string& via_branch,
+	      AmEvent* ev);
 
     /* send event to all event queues. Note: event instances will be cloned */
     bool broadcast(AmEvent* ev);
 
+    bool addEventQueue(const string& local_tag,
+		       AmEventQueueInterface* q);
+
     bool addEventQueue(const string& local_tag, 
 		       AmEventQueueInterface* q,
-		       const string& callid="", 
-		       const string& remote_tag="");
+		       const string& callid, 
+		       const string& remote_tag,
+		       const string& via_branch);
+
+    AmEventQueueInterface* delEventQueue(const string& local_tag);
 
     AmEventQueueInterface* delEventQueue(const string& local_tag,
-					 const string& callid="", 
-					 const string& remote_tag="");
+					 const string& callid, 
+					 const string& remote_tag,
+					 const string& via_branch);
 
     bool empty();
 };
diff --git a/core/AmSession.cpp b/core/AmSession.cpp
index 2b3718a4..f5429467 100644
--- a/core/AmSession.cpp
+++ b/core/AmSession.cpp
@@ -210,6 +210,11 @@ const string& AmSession::getLocalTag() const
   return dlg.local_tag;
 }
 
+const string& AmSession::getFirstBranch() const
+{
+  return dlg.first_branch;
+}
+
 void AmSession::setUri(const string& uri)
 {
   DBG("AmSession::setUri(%s)\n",uri.c_str());
diff --git a/core/AmSession.h b/core/AmSession.h
index ca60b2a5..81a239e3 100644
--- a/core/AmSession.h
+++ b/core/AmSession.h
@@ -334,6 +334,9 @@ public:
   /** Gets the Session's local tag */
   const string& getLocalTag() const;
 
+  /** Gets the branch param of the first via in the original INVITE*/
+  const string& getFirstBranch() const;
+
   /** Sets the Session's local tag if not set already */
   void setLocalTag();
 
diff --git a/core/AmSessionContainer.cpp b/core/AmSessionContainer.cpp
index bff01ed9..aa69882e 100644
--- a/core/AmSessionContainer.cpp
+++ b/core/AmSessionContainer.cpp
@@ -195,9 +195,10 @@ void AmSessionContainer::destroySession(AmSession* s)
     AmEventQueueInterface* q = AmEventDispatcher::instance()->
 	delEventQueue(s->getLocalTag(),
 		      s->getCallID(),
-		      s->getRemoteTag());
+		      s->getRemoteTag(),
+		      s->getFirstBranch());
     
-    if(q) {	
+    if(q) {
 	stopAndQueue(s);
     }
     else {
@@ -300,7 +301,7 @@ void AmSessionContainer::startSessionUAS(AmSipRequest& req)
 	}
 
 	switch(addSession(req.callid,req.from_tag,local_tag,
-			  session.get())) {
+			  req.via_branch,session.get())) {
 
 	case AmSessionContainer::Inserted:
 	  // successful case
@@ -330,7 +331,8 @@ void AmSessionContainer::startSessionUAS(AmSipRequest& req)
 	  session->start();
 	} catch (...) {
 	  AmEventDispatcher::instance()->
-	    delEventQueue(req.callid,req.from_tag,local_tag);
+	    delEventQueue(req.callid,req.from_tag,local_tag,
+			  req.via_branch);
 	  throw;
 	}
 
@@ -355,11 +357,12 @@ void AmSessionContainer::startSessionUAS(AmSipRequest& req)
 
 bool AmSessionContainer::postEvent(const string& callid, 
 				   const string& remote_tag,
+				   const string& via_branch,
 				   AmEvent* event)
 {
     bool posted =
-	AmEventDispatcher::instance()->
-	post(callid,remote_tag,event);
+      AmEventDispatcher::instance()->
+        post(callid,remote_tag,via_branch,event);
 
     if(!posted)
 	delete event;
@@ -446,6 +449,7 @@ AmSessionContainer::AddSessionStatus
 AmSessionContainer::addSession(const string& callid,
 			       const string& remote_tag,
 			       const string& local_tag,
+			       const string& via_branch,
 			       AmSession* session)
 {
   if(_container_closed.get())
@@ -453,7 +457,7 @@ AmSessionContainer::addSession(const string& callid,
   
   if(AmEventDispatcher::instance()->
      addEventQueue(local_tag,(AmEventQueue*)session,
-		   callid,remote_tag)) {
+		   callid,remote_tag,via_branch)) {
     return Inserted;
   }
 
diff --git a/core/AmSessionContainer.h b/core/AmSessionContainer.h
index 6f95f9c4..d482660c 100644
--- a/core/AmSessionContainer.h
+++ b/core/AmSessionContainer.h
@@ -108,6 +108,7 @@ class AmSessionContainer : public AmThread
   AddSessionStatus addSession(const string& callid,
 			      const string& remote_tag,
 			      const string& local_tag,
+			      const string& via_branch,
 			      AmSession* session);
 
   /**
@@ -139,7 +140,9 @@ class AmSessionContainer : public AmThread
    * post an event into the event queue of the identified dialog.
    * @return false if session doesn't exist 
    */
-  bool postEvent(const string& callid, const string& remote_tag,
+  bool postEvent(const string& callid, 
+		 const string& remote_tag,
+		 const string& via_branch,
 		 AmEvent* event);
 
   /**
diff --git a/core/AmSipDialog.cpp b/core/AmSipDialog.cpp
index 5a37e87d..32aa05cc 100644
--- a/core/AmSipDialog.cpp
+++ b/core/AmSipDialog.cpp
@@ -155,6 +155,7 @@ void AmSipDialog::updateStatus(const AmSipRequest& req)
     remote_party = req.from;
     local_party  = req.to;
     route        = req.route;
+    first_branch = req.via_branch;
   }
 
   int cont = rel100OnRequestIn(req);
diff --git a/core/AmSipDialog.h b/core/AmSipDialog.h
index b94623a6..78704f82 100644
--- a/core/AmSipDialog.h
+++ b/core/AmSipDialog.h
@@ -173,6 +173,8 @@ class AmSipDialog
   string remote_tag;
   string local_tag;
 
+  string first_branch;
+
   string remote_party; // To/From
   string local_party;  // To/From
 
diff --git a/core/AmSipDispatcher.cpp b/core/AmSipDispatcher.cpp
index 12f54357..6bb122ac 100644
--- a/core/AmSipDispatcher.cpp
+++ b/core/AmSipDispatcher.cpp
@@ -92,7 +92,7 @@ void AmSipDispatcher::handleSipMsg(AmSipRequest &req)
   }
   else if(req.method == "CANCEL"){
       
-    if(ev_disp->postSipRequest(callid, remote_tag, req)){
+    if(ev_disp->postSipRequest(req)){
       return;
     }
   
diff --git a/core/AmSipMsg.h b/core/AmSipMsg.h
index 48de2960..a57e0f63 100644
--- a/core/AmSipMsg.h
+++ b/core/AmSipMsg.h
@@ -73,6 +73,7 @@ class AmSipRequest : public _AmSipMsgInDlg
 
   string rack_method;
   unsigned int rack_cseq;
+  string via_branch;
 
  AmSipRequest() : _AmSipMsgInDlg() { }
   ~AmSipRequest() { }
diff --git a/core/SipCtrlInterface.cpp b/core/SipCtrlInterface.cpp
index ee5c3052..f11ed455 100644
--- a/core/SipCtrlInterface.cpp
+++ b/core/SipCtrlInterface.cpp
@@ -471,6 +471,7 @@ inline void SipCtrlInterface::sip_msg2am_request(const sip_msg *msg,
     req.from_tag = c2stlstr(((sip_from_to*)msg->from->p)->tag);
     req.to_tag   = c2stlstr(((sip_from_to*)msg->to->p)->tag);
     req.cseq     = get_cseq(msg)->num;
+    req.via_branch = c2stlstr(msg->via_p1->branch);
     req.body     = c2stlstr(msg->body);
 
     if (msg->rack) {
diff --git a/core/etc/sems.conf.sample b/core/etc/sems.conf.sample
index 47673e14..3a845dc9 100644
--- a/core/etc/sems.conf.sample
+++ b/core/etc/sems.conf.sample
@@ -476,6 +476,17 @@ use_default_signature=yes
 #
 #100rel=require
 
+#
+# accept forked dialogs on UAS side? [yes|no]
+#
+#  no - INVITE with existing callid+remote_tag is replied with 482.
+# yes - INVITE with existing callid+remote_tag+via_branch is replied with 482.
+#       Forked INVITEs (!= via-branch) are accepted. 
+#
+# Default: yes
+#
+#accept_forked_dialogs=no
+
 # Make SIP authenticated requests sticky to the proxy? [yes | no]
 #
 # If enabled, host of request-URI of out-of-dialog requests that are