diff --git a/lib/diameter/s6a/message.h b/lib/diameter/s6a/message.h
index cb5ae6108..a347365d3 100644
--- a/lib/diameter/s6a/message.h
+++ b/lib/diameter/s6a/message.h
@@ -179,6 +179,7 @@ typedef struct ogs_diam_s6a_clr_message_s {
 #define OGS_DIAM_S6A_CLR_FLAGS_S6A_S6D_INDICATOR            (1)
 #define OGS_DIAM_S6A_CLR_FLAGS_REATTACH_REQUIRED            (1 << 1)
     uint32_t clr_flags;
+    uint32_t cancellation_type;
 } ogs_diam_s6a_clr_message_t;
 
 typedef struct ogs_diam_s6a_idr_message_s {
diff --git a/lib/gtp/xact.h b/lib/gtp/xact.h
index 8633f56dd..455e8372a 100644
--- a/lib/gtp/xact.h
+++ b/lib/gtp/xact.h
@@ -96,15 +96,17 @@ typedef struct ogs_gtp_xact_s {
 #define OGS_GTP_MODIFY_QOS_UPDATE ((uint64_t)1<<1)
     uint64_t        update_flags;
 
-#define OGS_GTP_DELETE_NO_ACTION 1
-#define OGS_GTP_DELETE_SEND_AUTHENTICATION_REQUEST 2
-#define OGS_GTP_DELETE_SEND_DETACH_ACCEPT 3
+#define OGS_GTP_DELETE_NO_ACTION                              1
+#define OGS_GTP_DELETE_SEND_AUTHENTICATION_REQUEST            2
+#define OGS_GTP_DELETE_SEND_DETACH_ACCEPT                     3
 #define OGS_GTP_DELETE_SEND_DEACTIVATE_BEARER_CONTEXT_REQUEST 4
-#define OGS_GTP_DELETE_SEND_UE_CONTEXT_RELEASE_COMMAND 5
-#define OGS_GTP_DELETE_SEND_S1_REMOVE_AND_UNLINK 6
-#define OGS_GTP_DELETE_HANDLE_PDN_CONNECTIVITY_REQUEST 7
-#define OGS_GTP_DELETE_UE_CONTEXT_REMOVE 8
-#define OGS_GTP_DELETE_IN_PATH_SWITCH_REQUEST 9
+#define OGS_GTP_DELETE_SEND_UE_CONTEXT_RELEASE_COMMAND        5
+#define OGS_GTP_DELETE_SEND_S1_REMOVE_AND_UNLINK              6
+#define OGS_GTP_DELETE_HANDLE_PDN_CONNECTIVITY_REQUEST        7
+#define OGS_GTP_DELETE_UE_CONTEXT_REMOVE                      8
+#define OGS_GTP_DELETE_UE_CONTEXT_COMPLETE_REMOVE             9
+#define OGS_GTP_DELETE_IN_PATH_SWITCH_REQUEST                10
+
     int             delete_action;
 
 #define OGS_GTP_RELEASE_SEND_UE_CONTEXT_RELEASE_COMMAND     1
diff --git a/src/mme/emm-handler.c b/src/mme/emm-handler.c
index 9838db80b..435887d8f 100644
--- a/src/mme/emm-handler.c
+++ b/src/mme/emm-handler.c
@@ -389,10 +389,10 @@ int emm_handle_detach_request(
      *
      * So, we will lose the MME_EPS_TYPE_DETACH_REQUEST_TO_UE.
      *
-     * We need more variable(nas_eps.detach_type)
+     * We need more variable(detach_type)
      * to keep Detach-Type whether UE-initiated or MME-initiaed.  */
-    mme_ue->nas_eps.type = mme_ue->nas_eps.detach_type =
-        MME_EPS_TYPE_DETACH_REQUEST_FROM_UE;
+    mme_ue->nas_eps.type = MME_EPS_TYPE_DETACH_REQUEST_FROM_UE;
+    mme_ue->detach_type = MME_DETACH_TYPE_REQUEST_FROM_UE;
 
     mme_ue->nas_eps.ksi = detach_type->nas_key_set_identifier;
     ogs_debug("    OGS_NAS_EPS TYPE[%d] KSI[%d]",
diff --git a/src/mme/mme-context.h b/src/mme/mme-context.h
index d407e77e6..58f1cdfd7 100644
--- a/src/mme/mme-context.h
+++ b/src/mme/mme-context.h
@@ -316,20 +316,25 @@ struct mme_ue_s {
         ogs_nas_eps_update_type_t update;
         ogs_nas_service_type_t service;
         ogs_nas_detach_type_t detach;
-
-        /* 1. MME initiated detach request to the UE.
-         *    (nas_eps.type = MME_EPS_TYPE_DETACH_REQUEST_TO_UE)
-         * 2. If UE is IDLE, Paging sent to the UE
-         * 3. If UE is wake-up, UE will send Server Request.
-         *    (nas_eps.type = MME_EPS_TYPE_SERVICE_REQUEST)
-         *
-         * So, we will lose the MME_EPS_TYPE_DETACH_REQUEST_TO_UE.
-         *
-         * We need more variable(nas_eps.detach_type)
-         * to keep Detach-Type whether UE-initiated or MME-initiaed.  */
-        uint8_t     detach_type;
     } nas_eps;
 
+    /* 1. MME initiated detach request to the UE.
+     *    (nas_eps.type = MME_EPS_TYPE_DETACH_REQUEST_TO_UE)
+     * 2. If UE is IDLE, Paging sent to the UE
+     * 3. If UE is wake-up, UE will send Server Request.
+     *    (nas_eps.type = MME_EPS_TYPE_SERVICE_REQUEST)
+     *
+     * So, we will lose the MME_EPS_TYPE_DETACH_REQUEST_TO_UE.
+     *
+     * We need more variable(detach_type)
+     * to keep Detach-Type whether UE-initiated or MME-initiaed.  */
+#define MME_DETACH_TYPE_REQUEST_FROM_UE             1
+#define MME_DETACH_TYPE_MME_EXPLICIT                2
+#define MME_DETACH_TYPE_HSS_EXPLICIT                3
+#define MME_DETACH_TYPE_MME_IMPLICIT                4
+#define MME_DETACH_TYPE_HSS_IMPLICIT                5
+    uint8_t     detach_type;
+
     /* UE identity */
 #define MME_UE_HAVE_IMSI(__mME) \
     ((__mME) && ((__mME)->imsi_len))
diff --git a/src/mme/mme-fd-path.c b/src/mme/mme-fd-path.c
index 281be44b5..c7eb0bf93 100644
--- a/src/mme/mme-fd-path.c
+++ b/src/mme/mme-fd-path.c
@@ -1510,6 +1510,7 @@ static int mme_ogs_diam_s6a_clr_cb( struct msg **msg, struct avp *avp,
     ogs_assert(ret == 0);
     ret = fd_msg_avp_hdr(avp, &hdr);
     ogs_assert(ret == 0);
+    clr_message->cancellation_type = hdr->avp_value->i32;
 
     /* Set the Origin-Host, Origin-Realm, andResult-Code AVPs */
     ret = fd_msg_rescode_set(ans, (char*)"DIAMETER_SUCCESS", NULL, NULL, 1);
@@ -1583,7 +1584,9 @@ out:
 
     /* Send the answer */
     ret = fd_msg_send(msg, NULL, NULL);
-    ogs_assert(ret == 0);    
+    ogs_assert(ret == 0);
+
+    ogs_free(s6a_message);
 
     return 0;
 }
diff --git a/src/mme/mme-path.c b/src/mme/mme-path.c
index 32b439376..211465a22 100644
--- a/src/mme/mme-path.c
+++ b/src/mme/mme-path.c
@@ -28,8 +28,9 @@ void mme_send_delete_session_or_detach(mme_ue_t *mme_ue)
 {
     ogs_assert(mme_ue);
 
-    switch (mme_ue->nas_eps.detach_type) {
-    case MME_EPS_TYPE_DETACH_REQUEST_FROM_UE:
+    switch (mme_ue->detach_type) {
+    case MME_DETACH_TYPE_REQUEST_FROM_UE:
+        ogs_debug("Detach Request from UE");
         if (SESSION_CONTEXT_IS_AVAILABLE(mme_ue)) {
             mme_gtp_send_delete_all_sessions(
                     mme_ue, OGS_GTP_DELETE_SEND_DETACH_ACCEPT);
@@ -37,11 +38,37 @@ void mme_send_delete_session_or_detach(mme_ue_t *mme_ue)
             ogs_assert(OGS_OK == nas_eps_send_detach_accept(mme_ue));
         }
         break;
-    case MME_EPS_TYPE_DETACH_REQUEST_TO_UE:
+
+    /* MME Explicit Detach, ie: O&M Procedures */
+    case MME_DETACH_TYPE_MME_EXPLICIT:
+        break;
+
+    /* HSS Explicit Detach, ie: Subscription Withdrawl Cancel Location */
+    case MME_DETACH_TYPE_HSS_EXPLICIT:
+        ogs_debug("Explicit HSS Detach");
         if (SESSION_CONTEXT_IS_AVAILABLE(mme_ue)) {
             mme_gtp_send_delete_all_sessions(mme_ue, OGS_GTP_DELETE_NO_ACTION);
         }
         break;
+
+    /* MME Implicit Detach, ie: Lost Communication */
+    case MME_DETACH_TYPE_MME_IMPLICIT:
+        break;
+
+    /* HSS Implicit Detach, ie: MME-UPDATE-PROCEDURE */
+    case MME_DETACH_TYPE_HSS_IMPLICIT:
+        ogs_debug("Implicit HSS Detach");
+        if (SESSION_CONTEXT_IS_AVAILABLE(mme_ue)) {
+            if (ECM_IDLE(mme_ue)) {
+                mme_gtp_send_delete_all_sessions(mme_ue,
+                    OGS_GTP_DELETE_UE_CONTEXT_COMPLETE_REMOVE);
+            } else {
+                mme_gtp_send_delete_all_sessions(mme_ue,
+                    OGS_GTP_DELETE_SEND_UE_CONTEXT_RELEASE_COMMAND);
+            }
+        }
+        break;
+
     default:
         ogs_fatal("    Invalid OGS_NAS_EPS TYPE[%d]", mme_ue->nas_eps.type);
         ogs_assert_if_reached();
diff --git a/src/mme/mme-s11-handler.c b/src/mme/mme-s11-handler.c
index c6febf92b..6d2497d2d 100644
--- a/src/mme/mme-s11-handler.c
+++ b/src/mme/mme-s11-handler.c
@@ -639,6 +639,12 @@ void mme_s11_handle_delete_session_response(
         mme_ue_remove(mme_ue);
         return;
 
+    } else if (action == OGS_GTP_DELETE_UE_CONTEXT_COMPLETE_REMOVE) {
+        /* Remove MME-UE Context and hash after Implicit Detach */
+        mme_ue_hash_remove(mme_ue);
+        mme_ue_remove(mme_ue);
+        return;
+
     } else if (action == OGS_GTP_DELETE_IN_PATH_SWITCH_REQUEST) {
 
         /* Don't have to remove Session in X2 Handover with SGW relocation */
diff --git a/src/mme/mme-s6a-handler.c b/src/mme/mme-s6a-handler.c
index 7dcf52678..78183f882 100644
--- a/src/mme/mme-s6a-handler.c
+++ b/src/mme/mme-s6a-handler.c
@@ -170,11 +170,13 @@ uint8_t mme_s6a_handle_idr(
     return OGS_OK;
 }
 
-void mme_s6a_handle_clr(
-        mme_ue_t *mme_ue, ogs_diam_s6a_clr_message_t *clr_message)
+void mme_s6a_handle_clr(mme_ue_t *mme_ue, ogs_diam_s6a_message_t *s6a_message)
 {
+    ogs_diam_s6a_clr_message_t *clr_message = NULL;
     ogs_assert(mme_ue);
-    ogs_assert(clr_message);    
+    ogs_assert(s6a_message);
+    clr_message = &s6a_message->clr_message;
+    ogs_assert(clr_message);
 
     /* Set EPS Detach */
     memset(&mme_ue->nas_eps.detach, 0, sizeof(ogs_nas_detach_type_t));
@@ -194,26 +196,42 @@ void mme_s6a_handle_clr(
      *
      * So, we will lose the MME_EPS_TYPE_DETACH_REQUEST_TO_UE.
      *
-     * We need more variable(nas_eps.detach_type)
+     * We need more variable(detach_type)
      * to keep Detach-Type whether UE-initiated or MME-initiaed.  */
-    mme_ue->nas_eps.type = mme_ue->nas_eps.detach_type =
-        MME_EPS_TYPE_DETACH_REQUEST_TO_UE;
+    mme_ue->nas_eps.type = MME_EPS_TYPE_DETACH_REQUEST_TO_UE;
+
     ogs_debug("    OGS_NAS_EPS TYPE[%d]", mme_ue->nas_eps.type);
 
     if (OGS_FSM_CHECK(&mme_ue->sm, emm_state_de_registered)) {
         /* Remove all trace of subscriber even when detached. */
         mme_ue_hash_remove(mme_ue);
         mme_ue_remove(mme_ue);
-    } else if (ECM_IDLE(mme_ue)) {
-        MME_STORE_PAGING_INFO(mme_ue, MME_PAGING_TYPE_DETACH_TO_UE, NULL);
-        ogs_assert(OGS_OK == s1ap_send_paging(mme_ue, S1AP_CNDomain_ps));
-    } else {
-        ogs_assert(OGS_OK == nas_eps_send_detach_request(mme_ue));
+        return;
+    } else if (clr_message->cancellation_type ==
+            OGS_DIAM_S6A_CT_MME_UPDATE_PROCEDURE) {
+        mme_ue->detach_type = MME_DETACH_TYPE_HSS_IMPLICIT;
         if (MME_P_TMSI_IS_AVAILABLE(mme_ue)) {
             ogs_assert(OGS_OK == sgsap_send_detach_indication(mme_ue));
         } else {
             mme_send_delete_session_or_detach(mme_ue);
         }
+    } else if (clr_message->cancellation_type ==
+            OGS_DIAM_S6A_CT_SUBSCRIPTION_WITHDRAWL) {
+        mme_ue->detach_type = MME_DETACH_TYPE_HSS_EXPLICIT;
+        if (ECM_IDLE(mme_ue)) {
+            MME_STORE_PAGING_INFO(mme_ue, MME_PAGING_TYPE_DETACH_TO_UE, NULL);
+            ogs_assert(OGS_OK == s1ap_send_paging(mme_ue, S1AP_CNDomain_ps));
+        } else {
+            ogs_assert(OGS_OK == nas_eps_send_detach_request(mme_ue));
+            if (MME_P_TMSI_IS_AVAILABLE(mme_ue)) {
+                ogs_assert(OGS_OK == sgsap_send_detach_indication(mme_ue));
+            } else {
+                mme_send_delete_session_or_detach(mme_ue);
+            }
+        }
+    } else {
+        ogs_error("Unsupported Cancellation-Type [%d]", 
+            clr_message->cancellation_type);
     }
 }
 
diff --git a/src/mme/mme-s6a-handler.h b/src/mme/mme-s6a-handler.h
index 33094ea8a..3cf0a3463 100644
--- a/src/mme/mme-s6a-handler.h
+++ b/src/mme/mme-s6a-handler.h
@@ -33,7 +33,7 @@ uint8_t mme_s6a_handle_ula(
 uint8_t mme_s6a_handle_idr(
         mme_ue_t *mme_ue, ogs_diam_s6a_message_t *s6a_message);
 void mme_s6a_handle_clr(
-        mme_ue_t *mme_ue, ogs_diam_s6a_clr_message_t *clr_message);
+        mme_ue_t *mme_ue, ogs_diam_s6a_message_t *s6a_message);
 
 #ifdef __cplusplus
 }
diff --git a/src/mme/mme-sm.c b/src/mme/mme-sm.c
index 22aeca369..259623c20 100644
--- a/src/mme/mme-sm.c
+++ b/src/mme/mme-sm.c
@@ -432,7 +432,7 @@ void mme_state_operational(ogs_fsm_t *s, mme_event_t *e)
             }
             break;
         case OGS_DIAM_S6A_CMD_CODE_CANCEL_LOCATION:
-            mme_s6a_handle_clr(mme_ue, &s6a_message->clr_message);
+            mme_s6a_handle_clr(mme_ue, s6a_message);
             break;
         case OGS_DIAM_S6A_CMD_CODE_INSERT_SUBSCRIBER_DATA:
             mme_s6a_handle_idr(mme_ue, s6a_message);