diff --git a/src/modules/topos/topos_mod.c b/src/modules/topos/topos_mod.c
index 0d36058188c..8bde83ba826 100644
--- a/src/modules/topos/topos_mod.c
+++ b/src/modules/topos/topos_mod.c
@@ -56,12 +56,15 @@
 #include "../../core/onsend.h"
 #include "../../core/mod_fix.h"
 #include "../../core/kemi.h"
+#include "../../core/data_lump.h"
 
 #include "../../lib/srdb1/db.h"
 #include "../../core/utils/sruid.h"
 
 #include "../../modules/sanity/api.h"
 
+#include "../topoh/api.h"
+
 #include "tps_storage.h"
 #include "tps_msg.h"
 #include "api.h"
@@ -91,6 +94,8 @@ str _tps_methods_nocontact_list = str_init("");
 extern unsigned int _tps_methods_noinitial;
 str _tps_methods_noinitial_list = str_init("");
 
+static topoh_api_t thb = {0};
+
 int _tps_clean_interval = 60;
 
 #define TPS_EVENTRT_OUTGOING 1
@@ -276,6 +281,14 @@ static int mod_init(void)
 				" but a_contact or b_contact xavu fields not defined\n");
 		return -1;
 	}
+	
+	if(_tps_param_mask_callid == 1) {
+		/* bind the topoh API */
+		if(topoh_load_api(&thb) != 0) {
+			LM_ERR("cannot bind to topoh API\n");
+			return -1;
+		}
+	}
 
 	sr_event_register_cb(SREV_NET_DATA_IN,  tps_msg_received);
 	sr_event_register_cb(SREV_NET_DATA_OUT, tps_msg_sent);
@@ -737,4 +750,110 @@ int mod_register(char *path, int *dlflags, void *p1, void *p2)
 	return 0;
 }
 
+/**
+ *  MASK CallID
+ */
+
+int tps_mask_callid(sip_msg_t *msg)
+{
+	struct lump* l;
+	str out;
+	str in;
+
+	if(_tps_param_mask_callid==0)
+		return 0;
+
+	if(msg->callid==NULL)
+	{
+		LM_ERR("cannot get Call-Id header\n");
+		return -1;
+	}
+	LM_DBG("CALL-ID : [%.*s]\n", msg->callid->body.len, msg->callid->body.s);
+	in=msg->callid->body;
+	
+	if(thb.mask_callid(&in, &out) != 0) {
+			LM_ERR("cannot encode callid\n");
+			return -1;
+	}
+	
+	
+	LM_DBG("Updated CALL-ID : [%.*s]\n",out.len, out.s);
+	if(out.s==NULL)
+	{
+		LM_ERR("cannot encode callid\n");
+		return -1;
+	}
+
+	l=del_lump(msg, msg->callid->body.s-msg->buf, msg->callid->body.len, 0);
+	if (l==0)
+	{
+		LM_ERR("failed deleting callid\n");
+		pkg_free(out.s);
+		return -1;
+	}
+	if (insert_new_lump_after(l, out.s, out.len, 0)==0) {
+		LM_ERR("could not insert new lump\n");
+		pkg_free(out.s);
+		return -1;
+	}
+
+	return 0;
+}
+
+/**
+ *  UNMASK CallID
+ */
+int tps_unmask_callid(sip_msg_t *msg)
+{
+	struct lump* l;
+	str out;
+	str in;
+	int umask_ret;
+	
+
+	if(_tps_param_mask_callid==0)
+		return 0;
+
+	if(msg->callid==NULL)
+	{
+		LM_ERR("cannot get Call-Id header\n");
+		return -1;
+	}
+
+	
+
+	LM_DBG("CALL-ID : [%.*s]\n", msg->callid->body.len, msg->callid->body.s);
+	in=msg->callid->body;
+	umask_ret=thb.unmask_callid(&in, &out);
+	if(umask_ret == 1) {
+		LM_DBG("Unmask not required\n");
+		return 0;
+	}else if(umask_ret != 0) {
+			LM_ERR("cannot decode callid\n");
+			return -1;
+	}
+	LM_DBG("Updated (unmasked) CALL-ID : [%.*s]\n",out.len, out.s);
+	if(out.s==NULL)
+	{
+		LM_ERR("cannot decode callid\n");
+		return -1;
+	}
+
+	l=del_lump(msg, msg->callid->body.s-msg->buf, msg->callid->body.len, 0);
+	if (l==0)
+	{
+		LM_ERR("failed deleting callid\n");
+		pkg_free(out.s);
+		return -1;
+	}
+	if (insert_new_lump_after(l, out.s, out.len, 0)==0) {
+		LM_ERR("could not insert new lump\n");
+		pkg_free(out.s);
+		return -1;
+	}
+
+	return 0;
+}
+
+
 /** @} */
diff --git a/src/modules/topos/tps_msg.c b/src/modules/topos/tps_msg.c
index a11d544f777..4e5491366f4 100644
--- a/src/modules/topos/tps_msg.c
+++ b/src/modules/topos/tps_msg.c
@@ -43,6 +43,8 @@
 #include "../../core/parser/parse_via.h"
 #include "../../core/parser/contact/parse_contact.h"
 #include "../../core/parser/parse_refer_to.h"
+
+
 #include "tps_msg.h"
 #include "tps_storage.h"
 
@@ -882,7 +884,10 @@ int tps_request_received(sip_msg_t *msg, int dialog)
 		LM_ERR("failed to extract and pack the headers\n");
 		return -1;
 	}
-
+	
+	tps_unmask_callid(msg);
+	LM_DBG("Request message after CALLID Unmask-> [%.*s] \n",msg->len,msg->buf);
+	
 	ret = tps_dlg_message_update(msg, &mtsd, _tps_contact_mode);
 	if(ret<0) {
 		LM_ERR("failed to update on dlg message\n");
@@ -1017,13 +1022,16 @@ int tps_response_received(sip_msg_t *msg)
 	memset(&mtsd, 0, sizeof(tps_data_t));
 	memset(&stsd, 0, sizeof(tps_data_t));
 	memset(&btsd, 0, sizeof(tps_data_t));
-
-	lkey = msg->callid->body;
-
+	
 	if(tps_pack_message(msg, &mtsd)<0) {
 		LM_ERR("failed to extract and pack the headers\n");
 		return -1;
 	}
+	tps_unmask_callid(msg);
+	LM_DBG("Response message after CALLID Unmask-> [%.*s] \n",msg->len,msg->buf);
+	
+	lkey = msg->callid->body;
+	
 	tps_storage_lock_get(&lkey);
 	if(tps_storage_load_branch(msg, &mtsd, &btsd, 0)<0) {
 		goto error;
@@ -1089,7 +1097,12 @@ int tps_request_sent(sip_msg_t *msg, int dialog, int local)
 
 	if(dialog!=0) {
 		if(tps_get_xuuid(msg, &xuuid)<0) {
-			LM_DBG("no x-uuid header - nothing to do\n");
+			LM_DBG("no x-uuid header -Local message only Call-ID Mask if downstream \n");
+			/* ACK and CANCEL go downstream so Call-ID mask required*/
+			if(get_cseq(msg)->method_id==METHOD_ACK
+					|| get_cseq(msg)->method_id==METHOD_CANCEL) {
+				tps_mask_callid(msg);
+			}
 			return 0;
 		}
 		mtsd.a_uuid = xuuid;
@@ -1157,6 +1170,13 @@ int tps_request_sent(sip_msg_t *msg, int dialog, int local)
 
 done:
 	tps_storage_lock_release(&lkey);
+	/*DownStream Request sent MASK CALLID */
+	if(direction == TPS_DIR_DOWNSTREAM) {
+	    /*  mask CallID */
+	    tps_mask_callid(msg);
+	    LM_DBG("SENT message after CALLID CHG->[%.*s] \n",msg->len,msg->buf);
+	}
+	
 	return 0;
 
 error:
@@ -1253,6 +1273,13 @@ int tps_response_sent(sip_msg_t *msg)
 	if(tps_storage_update_dialog(msg, &mtsd, &stsd, TPS_DBU_CONTACT)<0) {
 		goto error1;
 	}
+	
+	/*DownStream Response sent MASK CALLID */
+	if(direction == TPS_DIR_UPSTREAM) {
+	    /*  mask CallID */
+	    tps_mask_callid(msg);
+	    LM_DBG("SENT Response message after CALLID CHG->[%.*s] \n",msg->len,msg->buf);
+	}
 	return 0;
 
 error:
diff --git a/src/modules/topos/tps_msg.h b/src/modules/topos/tps_msg.h
index 93f768462fe..3ff06894759 100644
--- a/src/modules/topos/tps_msg.h
+++ b/src/modules/topos/tps_msg.h
@@ -43,4 +43,6 @@ int tps_request_received(sip_msg_t *msg, int dialog);
 int tps_response_received(sip_msg_t *msg);
 int tps_request_sent(sip_msg_t *msg, int dialog, int local);
 int tps_response_sent(sip_msg_t *msg);
+int tps_mask_callid(sip_msg_t *msg);
+int tps_unmask_callid(sip_msg_t *msg);
 #endif