diff --git a/apps/announcement/Announcement.cpp b/apps/announcement/Announcement.cpp
index 0b458487..f860d4c6 100644
--- a/apps/announcement/Announcement.cpp
+++ b/apps/announcement/Announcement.cpp
@@ -100,7 +100,7 @@ AmSession* AnnouncementFactory::onInvite(const AmSipRequest& req, const string&
 }
 
 AmSession* AnnouncementFactory::onInvite(const AmSipRequest& req, const string& app_name,
-					 AmArg& session_params)
+					 const AmArg& session_params)
 {
   UACAuthCred* cred = AmUACAuth::unpackCredentials(session_params);
   AmSession* s = new AnnouncementDialog(getAnnounceFile(req), cred);
diff --git a/apps/announcement/Announcement.h b/apps/announcement/Announcement.h
index 6aabb9c9..14f8f812 100644
--- a/apps/announcement/Announcement.h
+++ b/apps/announcement/Announcement.h
@@ -52,7 +52,7 @@ public:
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
 		      const map<string,string>& app_params);
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
-		      AmArg& session_params);
+		      const AmArg& session_params);
 
 };
 
diff --git a/apps/annrecorder/AnnRecorder.cpp b/apps/annrecorder/AnnRecorder.cpp
index 11b6f1fb..f50b0777 100644
--- a/apps/annrecorder/AnnRecorder.cpp
+++ b/apps/annrecorder/AnnRecorder.cpp
@@ -207,7 +207,7 @@ AmSession* AnnRecorderFactory::onInvite(const AmSipRequest& req, const string& a
 }
 
 AmSession* AnnRecorderFactory::onInvite(const AmSipRequest& req, const string& app_name,
-					 AmArg& session_params)
+					 const AmArg& session_params)
 {
   UACAuthCred* cred = AmUACAuth::unpackCredentials(session_params);
 
diff --git a/apps/annrecorder/AnnRecorder.h b/apps/annrecorder/AnnRecorder.h
index 93b5b952..6cc7c16d 100644
--- a/apps/annrecorder/AnnRecorder.h
+++ b/apps/annrecorder/AnnRecorder.h
@@ -77,7 +77,7 @@ public:
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
 		      const map<string,string>& app_params);
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
-		      AmArg& session_params);
+		      const AmArg& session_params);
 
 };
 
diff --git a/apps/callback/CallBack.cpp b/apps/callback/CallBack.cpp
index 4e93b5c4..ea7a27ca 100644
--- a/apps/callback/CallBack.cpp
+++ b/apps/callback/CallBack.cpp
@@ -158,7 +158,7 @@ AmSession* CallBackFactory::onInvite(const AmSipRequest& req, const string& app_
 
 // outgoing calls 
 AmSession* CallBackFactory::onInvite(const AmSipRequest& req, const string& app_name,
-				     AmArg& session_params)
+				     const AmArg& session_params)
 {
   UACAuthCred* cred = NULL;
   if (session_params.getType() == AmArg::AObject) {
diff --git a/apps/callback/CallBack.h b/apps/callback/CallBack.h
index c9dbd846..1069e975 100644
--- a/apps/callback/CallBack.h
+++ b/apps/callback/CallBack.h
@@ -75,7 +75,7 @@ public:
   AmSession* onInvite(const AmSipRequest&, const string& app_name,
 		      const map<string,string>& app_params);
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
-		      AmArg& session_params);
+		      const AmArg& session_params);
   int onLoad();
 
   void run();
diff --git a/apps/click2dial/Click2Dial.cpp b/apps/click2dial/Click2Dial.cpp
index 6678cb36..808005f6 100644
--- a/apps/click2dial/Click2Dial.cpp
+++ b/apps/click2dial/Click2Dial.cpp
@@ -102,7 +102,7 @@ string Click2DialFactory::getAnnounceFile(const AmSipRequest& req)
 }
 
 
-AmSession* Click2DialFactory::onInvite(const AmSipRequest& req, const string& app_name, AmArg& session_params)
+AmSession* Click2DialFactory::onInvite(const AmSipRequest& req, const string& app_name, const AmArg& session_params)
 {
   string callee_uri, a_realm, a_user, a_pwd;
 
diff --git a/apps/click2dial/Click2Dial.h b/apps/click2dial/Click2Dial.h
index 57bdfe38..15acdd5c 100644
--- a/apps/click2dial/Click2Dial.h
+++ b/apps/click2dial/Click2Dial.h
@@ -54,7 +54,7 @@ class Click2DialFactory: public AmSessionFactory
     int onLoad();
     AmSession* onInvite(const AmSipRequest& req, const string& app_name,
 			const map<string,string>& app_params);
-    AmSession* onInvite(const AmSipRequest& req, const string& app_name, AmArg& session_params);
+    AmSession* onInvite(const AmSipRequest& req, const string& app_name, const AmArg& session_params);
 };
 
 class C2DCallerDialog: public AmB2BCallerSession, public CredentialHolder
diff --git a/apps/dsm/DSM.cpp b/apps/dsm/DSM.cpp
index 775498f1..cdc46a39 100644
--- a/apps/dsm/DSM.cpp
+++ b/apps/dsm/DSM.cpp
@@ -729,7 +729,7 @@ AmSession* DSMFactory::onInvite(const AmSipRequest& req, const string& app_name,
 
 // outgoing call
 AmSession* DSMFactory::onInvite(const AmSipRequest& req, const string& app_name,
-				AmArg& session_params) 
+				const AmArg& session_params)
 {
 
   string start_diag;
diff --git a/apps/dsm/DSM.h b/apps/dsm/DSM.h
index 20933fba..3cc30ba2 100644
--- a/apps/dsm/DSM.h
+++ b/apps/dsm/DSM.h
@@ -139,7 +139,7 @@ public:
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
 		      const map<string,string>& app_params);
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
-		      AmArg& session_params);
+		      const AmArg& session_params);
   // DI
   // DI factory
   AmDynInvoke* getInstance() { return instance(); }
diff --git a/apps/examples/call_gen/CallGen.cpp b/apps/examples/call_gen/CallGen.cpp
index 4c11b34d..2b5689c4 100644
--- a/apps/examples/call_gen/CallGen.cpp
+++ b/apps/examples/call_gen/CallGen.cpp
@@ -172,7 +172,7 @@ AmSession* CallGenFactory::onInvite(const AmSipRequest& req, const string& app_n
 
 // outgoing calls 
 AmSession* CallGenFactory::onInvite(const AmSipRequest& req, const string& app_name,
-				    AmArg& args)
+				    const AmArg& args)
 {  
   size_t cnt = 0; 
   cnt++; // int    ncalls           = args.get(cnt++).asInt();
diff --git a/apps/examples/call_gen/CallGen.h b/apps/examples/call_gen/CallGen.h
index cbcfa435..b981a613 100644
--- a/apps/examples/call_gen/CallGen.h
+++ b/apps/examples/call_gen/CallGen.h
@@ -89,7 +89,7 @@ public:
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
 		      const map<string,string>& app_params);
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
-		      AmArg& args);
+		      const AmArg& args);
 
   int onLoad();
 
diff --git a/apps/examples/di_dialer/DIDial.cpp b/apps/examples/di_dialer/DIDial.cpp
index 2b2bd020..b8a5cbdf 100644
--- a/apps/examples/di_dialer/DIDial.cpp
+++ b/apps/examples/di_dialer/DIDial.cpp
@@ -128,7 +128,7 @@ string DIDial::dialout(const string& application,
 		       const string& user, 
 		       const string& from, 
 		       const string& to,
-		       AmArg* extra_params) {
+		       const AmArg* extra_params) {
   DBG("dialout application '%s', user '%s', from '%s', to '%s'\n", 
       application.c_str(), user.c_str(), from.c_str(), to.c_str());
 
@@ -148,7 +148,7 @@ string DIDial::dialout_auth(const string& application,
 			    const string& a_realm, 
 			    const string& a_user, 
 			    const string& a_pwd,
-			    AmArg* extra_params
+			    const AmArg* extra_params
 		       ) {
   DBG("dialout application '%s', user '%s', from '%s', to '%s', authrealm '%s', authuser '%s', authpass '%s'", 
       application.c_str(), user.c_str(), from.c_str(), to.c_str(), a_realm.c_str(), a_user.c_str(), a_pwd.c_str());
diff --git a/apps/examples/di_dialer/DIDial.h b/apps/examples/di_dialer/DIDial.h
index 26d8a1e6..d15d7bca 100644
--- a/apps/examples/di_dialer/DIDial.h
+++ b/apps/examples/di_dialer/DIDial.h
@@ -24,7 +24,7 @@ class DIDial : public AmDynInvoke
 		 const string& user,
 		 const string& from, 
 		 const string& to,
-		 AmArg* extra_params);
+		 const AmArg* extra_params);
 
   string dialout_auth(const string& application, 
 		      const string& user,
@@ -33,7 +33,7 @@ class DIDial : public AmDynInvoke
 		      const string& realm, 
 		      const string& a_user,
 		      const string& pwd,
-		      AmArg* extra_params);
+		      const AmArg* extra_params);
 
   string dialout_auth_b2b(const string& application, 
 		       const string& announcement, 
diff --git a/apps/examples/dtmftester/DtmfTester.cpp b/apps/examples/dtmftester/DtmfTester.cpp
index ec59ebc7..69292709 100644
--- a/apps/examples/dtmftester/DtmfTester.cpp
+++ b/apps/examples/dtmftester/DtmfTester.cpp
@@ -96,7 +96,7 @@ AmSession* DtmfTesterFactory::onInvite(const AmSipRequest& req, const string& ap
 }
 
 AmSession* DtmfTesterFactory::onInvite(const AmSipRequest& req, const string& app_name,
-				       AmArg& session_params)
+				       const AmArg& session_params)
 {
   UACAuthCred* cred = AmUACAuth::unpackCredentials(session_params);
 
diff --git a/apps/examples/dtmftester/DtmfTester.h b/apps/examples/dtmftester/DtmfTester.h
index 41b5b8ad..ffcc6d9e 100644
--- a/apps/examples/dtmftester/DtmfTester.h
+++ b/apps/examples/dtmftester/DtmfTester.h
@@ -52,7 +52,7 @@ public:
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
 		      const map<string,string>& app_params);
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
-		      AmArg& session_params);
+		      const AmArg& session_params);
 
 };
 
diff --git a/apps/examples/early_record/EarlyRecord.cpp b/apps/examples/early_record/EarlyRecord.cpp
index a4569c39..0c19381d 100644
--- a/apps/examples/early_record/EarlyRecord.cpp
+++ b/apps/examples/early_record/EarlyRecord.cpp
@@ -30,7 +30,7 @@ AmSession* EarlyRecordFactory::onInvite(const AmSipRequest& req, const string& a
 
 // auth with di_dial
 AmSession* EarlyRecordFactory::onInvite(const AmSipRequest& req, const string& app_name,
-					AmArg& session_params)
+					const AmArg& session_params)
 {
   UACAuthCred* cred = AmUACAuth::unpackCredentials(session_params);
   
diff --git a/apps/examples/early_record/EarlyRecord.h b/apps/examples/early_record/EarlyRecord.h
index 47de9c7a..c1e60a0f 100644
--- a/apps/examples/early_record/EarlyRecord.h
+++ b/apps/examples/early_record/EarlyRecord.h
@@ -19,7 +19,7 @@ public:
     AmSession* onInvite(const AmSipRequest& req, const string& app_name,
 			const map<string,string>& app_params);
     AmSession* onInvite(const AmSipRequest& req, const string& app_name,
-			AmArg& session_params);
+			const AmArg& session_params);
 
 };
 
diff --git a/apps/examples/pinauthconference/PinAuthConference.cpp b/apps/examples/pinauthconference/PinAuthConference.cpp
index 8240bd96..937490b8 100644
--- a/apps/examples/pinauthconference/PinAuthConference.cpp
+++ b/apps/examples/pinauthconference/PinAuthConference.cpp
@@ -92,7 +92,7 @@ AmSession* PinAuthConferenceFactory::onInvite(const AmSipRequest&, const string&
 
 // outgoing calls
 AmSession* PinAuthConferenceFactory::onInvite(const AmSipRequest& req, const string& app_name,
-					      AmArg& session_params)
+					      const AmArg& session_params)
 {
   return new PinAuthConferenceDialog(prompts);
 }
diff --git a/apps/examples/pinauthconference/PinAuthConference.h b/apps/examples/pinauthconference/PinAuthConference.h
index 108a65bd..132a1263 100644
--- a/apps/examples/pinauthconference/PinAuthConference.h
+++ b/apps/examples/pinauthconference/PinAuthConference.h
@@ -63,7 +63,7 @@ public:
   AmSession* onInvite(const AmSipRequest&, const string& app_name,
 		      const map<string,string>& app_params);
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
-		      AmArg& session_params);
+		      const AmArg& session_params);
   int onLoad();
 };
 
diff --git a/apps/examples/simple_conference/SimpleConference.cpp b/apps/examples/simple_conference/SimpleConference.cpp
index b07fd47c..30b2027f 100644
--- a/apps/examples/simple_conference/SimpleConference.cpp
+++ b/apps/examples/simple_conference/SimpleConference.cpp
@@ -51,7 +51,7 @@ AmSession* SimpleConferenceFactory::onInvite(const AmSipRequest& req, const stri
 
 // outgoing calls - rep is 200 class response to INVITE
 AmSession* SimpleConferenceFactory::onInvite(const AmSipRequest& req, const string& app_name,
-					     AmArg& session_params)
+					     const AmArg& session_params)
 {
   return new SimpleConferenceDialog();
 }
diff --git a/apps/examples/simple_conference/SimpleConference.h b/apps/examples/simple_conference/SimpleConference.h
index 7c80c245..0562662f 100644
--- a/apps/examples/simple_conference/SimpleConference.h
+++ b/apps/examples/simple_conference/SimpleConference.h
@@ -50,7 +50,7 @@ public:
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
 		      const map<string,string>& app_params);
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
-		      AmArg& session_params);
+		      const AmArg& session_params);
   int onLoad();
 };
 
diff --git a/apps/sw_vsc/SW_Vsc.cpp b/apps/sw_vsc/SW_Vsc.cpp
index cb0715ba..c33897ba 100644
--- a/apps/sw_vsc/SW_Vsc.cpp
+++ b/apps/sw_vsc/SW_Vsc.cpp
@@ -246,7 +246,7 @@ AmSession *SW_VscFactory::onInvite(const AmSipRequest &req,
 
 AmSession *SW_VscFactory::onInvite(const AmSipRequest &req,
                                    const string &app_name,
-                                   AmArg &session_params)
+                                   const AmArg &session_params)
 {
     UACAuthCred *cred = AmUACAuth::unpackCredentials(session_params);
     AmSession *s = new SW_VscDialog(&m_patterns, cred);
diff --git a/apps/sw_vsc/SW_Vsc.h b/apps/sw_vsc/SW_Vsc.h
index 0595c278..7165edc4 100644
--- a/apps/sw_vsc/SW_Vsc.h
+++ b/apps/sw_vsc/SW_Vsc.h
@@ -87,8 +87,7 @@ public:
     AmSession *onInvite(const AmSipRequest &req, const string &app_name,
                         const map<string, string> &app_params);
     AmSession *onInvite(const AmSipRequest &req, const string &app_name,
-                        AmArg &session_params);
-
+                        const AmArg &session_params);
 };
 
 class SW_VscDialog : public AmSession,
diff --git a/apps/webconference/WebConference.cpp b/apps/webconference/WebConference.cpp
index 69aa13b3..9bdfa1b0 100644
--- a/apps/webconference/WebConference.cpp
+++ b/apps/webconference/WebConference.cpp
@@ -445,7 +445,7 @@ AmSession* WebConferenceFactory::onInvite(const AmSipRequest& req, const string&
 
 // outgoing calls 
 AmSession* WebConferenceFactory::onInvite(const AmSipRequest& req, const string& app_name,
-					  AmArg& session_params)
+					  const AmArg& session_params)
 {
   UACAuthCred* cred = AmUACAuth::unpackCredentials(session_params);
   AmSession* s = new WebConferenceDialog(prompts, getInstance(), cred); 
diff --git a/apps/webconference/WebConference.h b/apps/webconference/WebConference.h
index b226a91c..94572c42 100644
--- a/apps/webconference/WebConference.h
+++ b/apps/webconference/WebConference.h
@@ -154,7 +154,7 @@ public:
   AmSession* onInvite(const AmSipRequest&, const string& app_name,
 		      const map<string,string>& app_params);
   AmSession* onInvite(const AmSipRequest& req, const string& app_name,
-		      AmArg& session_params);
+		      const AmArg& session_params);
   int onLoad();
 
   bool isValidConference(const string& conf_id, const string& participant_id);
diff --git a/core/AmApi.cpp b/core/AmApi.cpp
index 4a9986ec..79f5b1df 100644
--- a/core/AmApi.cpp
+++ b/core/AmApi.cpp
@@ -50,7 +50,7 @@ AmSessionFactory::AmSessionFactory(const string& name)
 }
 
 AmSession* AmSessionFactory::onInvite(const AmSipRequest& req, const string& app_name,
-				      AmArg& session_params) {
+				      const AmArg& session_params) {
   WARN(" discarding session parameters to new session.\n");
   map<string,string> app_params;
   return onInvite(req,app_name,app_params);
@@ -62,7 +62,7 @@ AmSession* AmSessionFactory::onRefer(const AmSipRequest& req, const string& app_
 }
 
 AmSession* AmSessionFactory::onRefer(const AmSipRequest& req, const string& app_name,
-				     AmArg& session_params)
+				     const AmArg& session_params)
 {
   WARN(" discarding session parameters to new session.\n");
   map<string,string> app_params;
@@ -146,7 +146,7 @@ AmSessionEventHandlerFactory::AmSessionEventHandlerFactory(const string& name)
 }
 
 bool AmSessionEventHandlerFactory::onInvite(const AmSipRequest& req, 
-					    AmArg& session_params,
+					    const AmArg& session_params,
 					    AmConfigReader& cfg) {
   WARN("discarding session parameters for new session.\n");
   return onInvite(req, cfg);
diff --git a/core/AmApi.h b/core/AmApi.h
index c5a01983..16a87293 100644
--- a/core/AmApi.h
+++ b/core/AmApi.h
@@ -115,7 +115,7 @@ class AmSessionEventHandlerFactory: public AmPluginFactory
    * @return false if session creation should be stopped
    */
   virtual bool onInvite(const AmSipRequest& req, AmConfigReader& cfg)=0;
-  virtual bool onInvite(const AmSipRequest& req, AmArg& session_params, AmConfigReader& cfg);
+  virtual bool onInvite(const AmSipRequest& req, const AmArg& session_params, AmConfigReader& cfg);
 };
 
 /** \brief Interface for plugins to create sessions */
@@ -162,7 +162,7 @@ class AmSessionFactory: public AmPluginFactory
    *   processing as it would block the server.
    */
   virtual AmSession* onInvite(const AmSipRequest& req, const string& app_name,
-			      AmArg& session_params);
+			      const AmArg& session_params);
 
   /**
    * Creates a dialog state on new REFER with local-tag.
@@ -185,7 +185,7 @@ class AmSessionFactory: public AmPluginFactory
    *   processing as it would block the server.
    */
   virtual AmSession* onRefer(const AmSipRequest& req, const string& app_name,
-			     AmArg& session_params);
+			     const AmArg& session_params);
 
   /**
    * Method to receive any out-of-dialog request 
diff --git a/core/AmSessionContainer.cpp b/core/AmSessionContainer.cpp
index ae6e6cbd..befb2672 100644
--- a/core/AmSessionContainer.cpp
+++ b/core/AmSessionContainer.cpp
@@ -205,7 +205,7 @@ void AmSessionContainer::destroySession(AmSession* s)
     }
 }
 
-string AmSessionContainer::startSessionUAC(const AmSipRequest& req, string& app_name, AmArg* session_params) {
+string AmSessionContainer::startSessionUAC(const AmSipRequest& req, string& app_name, const AmArg* session_params) {
 
   unique_ptr<AmSession> session;
   try {
@@ -490,7 +490,7 @@ bool AmSessionContainer::check_and_add_cps(bool emergency_flag)
 
 AmSession* AmSessionContainer::createSession(const AmSipRequest& req,
 					     string& app_name,
-					     AmArg* session_params)
+					     const AmArg* session_params)
 {
   if (AmConfig::ShutdownMode) {
     _run_cond.set(true); // so that thread stops
diff --git a/core/AmSessionContainer.h b/core/AmSessionContainer.h
index 348bdd22..98094a6a 100644
--- a/core/AmSessionContainer.h
+++ b/core/AmSessionContainer.h
@@ -119,7 +119,7 @@ class AmSessionContainer : public AmThread
    */
   AmSession* createSession(const AmSipRequest& req, 
 			   string& app_name,
-			   AmArg* session_params = NULL);
+			   const AmArg* session_params = NULL);
 
   /**
    * Adds a session to the container (UAS only).
@@ -150,7 +150,7 @@ class AmSessionContainer : public AmThread
    */
   string startSessionUAC(const AmSipRequest& req, 
 			 string& app_name,
-			 AmArg* session_params = NULL);
+			 const AmArg* session_params = NULL);
 
   /**
    * Detroys a session.
diff --git a/core/AmUAC.cpp b/core/AmUAC.cpp
index e9ba5e9a..fca685a1 100644
--- a/core/AmUAC.cpp
+++ b/core/AmUAC.cpp
@@ -39,7 +39,7 @@ string AmUAC::dialout(const string& user,
 		      const string& to,
 		      const string& local_tag,
 		      const string& hdrs,
-		      AmArg*  session_params) {
+		      const AmArg*  session_params) {
  
   AmSipRequest req;
   string m_app_name = app_name;
diff --git a/core/AmUAC.h b/core/AmUAC.h
index a1d4ae72..c3c3a0ba 100644
--- a/core/AmUAC.h
+++ b/core/AmUAC.h
@@ -46,7 +46,7 @@ class AmUAC {
 			const string& to,
 			const string& local_tag = "",
 			const string& hdrs = "",
-			AmArg*  session_params = NULL);
+			const AmArg*  session_params = NULL);
 
 };