diff --git a/lib/diameter/s6a/message.h b/lib/diameter/s6a/message.h
index 573ad039f..707e0b085 100644
--- a/lib/diameter/s6a/message.h
+++ b/lib/diameter/s6a/message.h
@@ -168,8 +168,6 @@ typedef struct ogs_diam_s6a_message_s {
     uint32_t                        *err;
     uint32_t                        *exp_err;
 
-    bool                            isAnswer;
-
     ogs_diam_s6a_clr_message_t      clr_message;
     ogs_diam_s6a_aia_message_t      aia_message;
     ogs_diam_s6a_ula_message_t      ula_message;
diff --git a/lib/gtp/xact.h b/lib/gtp/xact.h
index efcc36135..8633f56dd 100644
--- a/lib/gtp/xact.h
+++ b/lib/gtp/xact.h
@@ -96,14 +96,15 @@ typedef struct ogs_gtp_xact_s {
 #define OGS_GTP_MODIFY_QOS_UPDATE ((uint64_t)1<<1)
     uint64_t        update_flags;
 
-#define OGS_GTP_DELETE_SEND_AUTHENTICATION_REQUEST 1
-#define OGS_GTP_DELETE_SEND_DETACH_ACCEPT 2
-#define OGS_GTP_DELETE_SEND_DEACTIVATE_BEARER_CONTEXT_REQUEST 3
-#define OGS_GTP_DELETE_SEND_UE_CONTEXT_RELEASE_COMMAND 4
-#define OGS_GTP_DELETE_HANDLE_PDN_CONNECTIVITY_REQUEST 5
-#define OGS_GTP_DELETE_UE_CONTEXT_REMOVE 6
-#define OGS_GTP_DELETE_IN_PATH_SWITCH_REQUEST 7
-#define OGS_GTP_DELETE_NO_ACTION 8
+#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
     int             delete_action;
 
 #define OGS_GTP_RELEASE_SEND_UE_CONTEXT_RELEASE_COMMAND     1
diff --git a/src/mme/emm-build.c b/src/mme/emm-build.c
index 67a15a315..1b7db9a3b 100644
--- a/src/mme/emm-build.c
+++ b/src/mme/emm-build.c
@@ -437,12 +437,11 @@ ogs_pkbuf_t *emm_build_security_mode_command(mme_ue_t *mme_ue)
     return nas_eps_security_encode(mme_ue, &message);
 }
 
-ogs_pkbuf_t *emm_build_detach_request(mme_ue_t *mme_ue, uint8_t detach_type)
+ogs_pkbuf_t *emm_build_detach_request(mme_ue_t *mme_ue)
 {
     ogs_nas_eps_message_t message;
 
     ogs_assert(mme_ue);
-    ogs_assert(detach_type);
 
     memset(&message, 0, sizeof(message));
     message.h.security_header_type = 
@@ -452,7 +451,8 @@ ogs_pkbuf_t *emm_build_detach_request(mme_ue_t *mme_ue, uint8_t detach_type)
     message.emm.h.protocol_discriminator = OGS_NAS_PROTOCOL_DISCRIMINATOR_EMM;
     message.emm.h.message_type = OGS_NAS_EPS_DETACH_REQUEST;
 
-    message.emm.detach_request_to_ue.detach_type.value = detach_type;
+    message.emm.detach_request_to_ue.detach_type.value =
+        mme_ue->nas_eps.detach.value;
 
     return nas_eps_security_encode(mme_ue, &message);
 }
diff --git a/src/mme/emm-build.h b/src/mme/emm-build.h
index ba2dc793d..14f01e888 100644
--- a/src/mme/emm-build.h
+++ b/src/mme/emm-build.h
@@ -37,7 +37,7 @@ ogs_pkbuf_t *emm_build_security_mode_command(mme_ue_t *mme_ue);
 ogs_pkbuf_t *emm_build_authentication_request(mme_ue_t *mme_ue);
 ogs_pkbuf_t *emm_build_authentication_reject(void);
 
-ogs_pkbuf_t *emm_build_detach_request(mme_ue_t *mme_ue, uint8_t detach_type);
+ogs_pkbuf_t *emm_build_detach_request(mme_ue_t *mme_ue);
 ogs_pkbuf_t *emm_build_detach_accept(mme_ue_t *mme_ue);
 
 ogs_pkbuf_t *emm_build_tau_accept(mme_ue_t *mme_ue);
diff --git a/src/mme/emm-handler.c b/src/mme/emm-handler.c
index 34c89f733..9ed359185 100644
--- a/src/mme/emm-handler.c
+++ b/src/mme/emm-handler.c
@@ -64,13 +64,17 @@ int emm_handle_attach_request(mme_ue_t *mme_ue,
     /* HashMME */
     ogs_kdf_hash_mme(pkbuf->data, pkbuf->len, mme_ue->hash_mme);
 
-    /* Set EPS Attach Request Type */
+    /* Set EPS Attach */
     memcpy(&mme_ue->nas_eps.attach, eps_attach_type,
             sizeof(ogs_nas_eps_attach_type_t));
     mme_ue->nas_eps.type = MME_EPS_TYPE_ATTACH_REQUEST;
     mme_ue->nas_eps.ksi = eps_attach_type->nas_key_set_identifier;
-    ogs_debug("    OGS_NAS_EPS TYPE[%d] KSI[%d] ATTACH[0x%x]",
-            mme_ue->nas_eps.type, mme_ue->nas_eps.ksi, mme_ue->nas_eps.data);
+    ogs_debug("    OGS_NAS_EPS TYPE[%d] KSI[%d]",
+            mme_ue->nas_eps.type, mme_ue->nas_eps.ksi);
+    ogs_debug("    ATTACH TSC[%d] KSI[%d] VALUE[%d]",
+            mme_ue->nas_eps.attach.tsc,
+            mme_ue->nas_eps.attach.nas_key_set_identifier,
+            mme_ue->nas_eps.attach.value);
     switch(mme_ue->nas_eps.attach.value){
         case OGS_NAS_ATTACH_TYPE_EPS_ATTACH:
             ogs_debug("    Requested EPS_ATTACH_TYPE[1, EPS_ATTACH]");
@@ -373,12 +377,30 @@ int emm_handle_detach_request(
 
     detach_type = &detach_request->detach_type;
 
-    /* Set EPS Attach Type */
+    /* Set EPS Detach */
     memcpy(&mme_ue->nas_eps.detach, detach_type, sizeof(ogs_nas_detach_type_t));
-    mme_ue->nas_eps.type = MME_EPS_TYPE_DETACH_REQUEST_FROM_UE;
+
+    /* 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.  */
+    mme_ue->nas_eps.type = mme_ue->nas_eps.detach_type =
+        MME_EPS_TYPE_DETACH_REQUEST_FROM_UE;
+
     mme_ue->nas_eps.ksi = detach_type->nas_key_set_identifier;
-    ogs_debug("    OGS_NAS_EPS TYPE[%d] KSI[%d] DETACH[0x%x]",
-            mme_ue->nas_eps.type, mme_ue->nas_eps.ksi, mme_ue->nas_eps.data);
+    ogs_debug("    OGS_NAS_EPS TYPE[%d] KSI[%d]",
+            mme_ue->nas_eps.type, mme_ue->nas_eps.ksi);
+    ogs_debug("    DETACH TSC[%d] KSI[%d] SWITCH_OFF[%d] VALUE[%d]",
+            mme_ue->nas_eps.attach.tsc,
+            mme_ue->nas_eps.detach.nas_key_set_identifier,
+            mme_ue->nas_eps.detach.switch_off,
+            mme_ue->nas_eps.attach.value);
 
     switch (detach_request->detach_type.value) {
     /* 0 0 1 : EPS detach */
@@ -414,11 +436,15 @@ int emm_handle_service_request(
 
     ogs_assert(mme_ue);
 
-    /* Set EPS Update Type */
+    /* Set EPS Service */
     mme_ue->nas_eps.type = MME_EPS_TYPE_SERVICE_REQUEST;
     mme_ue->nas_eps.ksi = ksi_and_sequence_number->ksi;
     ogs_debug("    OGS_NAS_EPS TYPE[%d] KSI[%d]",
             mme_ue->nas_eps.type, mme_ue->nas_eps.ksi);
+    ogs_debug("    SERVICE TSC[%d] KSI[%d] VALUE[%d]",
+            mme_ue->nas_eps.service.tsc,
+            mme_ue->nas_eps.service.nas_key_set_identifier,
+            mme_ue->nas_eps.service.value);
 
     /*
      * ATTACH_REQUEST
@@ -469,15 +495,19 @@ int emm_handle_tau_request(mme_ue_t *mme_ue,
     /* HashMME */
     ogs_kdf_hash_mme(pkbuf->data, pkbuf->len, mme_ue->hash_mme);
 
-    /* Set EPS Update Type */
+    /* Set EPS Update */
     memcpy(&mme_ue->nas_eps.update, eps_update_type,
             sizeof(ogs_nas_eps_update_type_t));
     mme_ue->nas_eps.type = MME_EPS_TYPE_TAU_REQUEST;
     mme_ue->nas_eps.ksi = eps_update_type->nas_key_set_identifier;
-    ogs_debug("    OGS_NAS_EPS TYPE[%d] KSI[%d] UPDATE[0x%x]",
-            mme_ue->nas_eps.type, mme_ue->nas_eps.ksi,
-            mme_ue->nas_eps.data);
-    
+    ogs_debug("    OGS_NAS_EPS TYPE[%d] KSI[%d]",
+            mme_ue->nas_eps.type, mme_ue->nas_eps.ksi);
+    ogs_debug("    UPDATE TSC[%d] KSI[%d] Active-flag[%d] VALUE[%d]",
+            mme_ue->nas_eps.update.tsc,
+            mme_ue->nas_eps.update.nas_key_set_identifier,
+            mme_ue->nas_eps.update.active_flag,
+            mme_ue->nas_eps.update.value);
+
     /*
      * ATTACH_REQUEST
      * TAU_REQUEST
@@ -598,9 +628,8 @@ int emm_handle_extended_service_request(mme_ue_t *mme_ue,
             sizeof(ogs_nas_service_type_t));
     mme_ue->nas_eps.type = MME_EPS_TYPE_EXTENDED_SERVICE_REQUEST;
     mme_ue->nas_eps.ksi = service_type->nas_key_set_identifier;
-    ogs_debug("    OGS_NAS_EPS TYPE[%d] KSI[%d] SERVICE[0x%x]",
-            mme_ue->nas_eps.type, mme_ue->nas_eps.ksi,
-            mme_ue->nas_eps.data);
+    ogs_debug("    OGS_NAS_EPS TYPE[%d] KSI[%d]",
+            mme_ue->nas_eps.type, mme_ue->nas_eps.ksi);
     
     /*
      * ATTACH_REQUEST
diff --git a/src/mme/emm-sm.c b/src/mme/emm-sm.c
index 6789620a0..4881297ec 100644
--- a/src/mme/emm-sm.c
+++ b/src/mme/emm-sm.c
@@ -128,11 +128,6 @@ static void common_register_state(ogs_fsm_t *s, mme_event_t *e)
                 OGS_FSM_TRAN(s, emm_state_exception);
                 break;
             }
-            
-            if(mme_ue->paging.type == MME_PAGING_TYPE_DETACH_TO_UE) {
-                mme_send_after_paging(mme_ue, false);
-                break;
-            }
 
             if (!MME_UE_HAVE_IMSI(mme_ue)) {
                 ogs_info("Service request : Unknown UE");
@@ -548,11 +543,10 @@ static void common_register_state(ogs_fsm_t *s, mme_event_t *e)
 
             CLEAR_MME_UE_TIMER(mme_ue->t3422);
 
-            if (MME_P_TMSI_IS_AVAILABLE(mme_ue)) {
-                ogs_assert(OGS_OK == sgsap_send_detach_indication(mme_ue));
-            } else {
-                mme_send_delete_session_or_mme_ue_context_release_detach(mme_ue);
-            }
+            rv = s1ap_send_ue_context_release_command(enb_ue,
+                    S1AP_Cause_PR_nas, S1AP_CauseNas_detach,
+                    S1AP_UE_CTX_REL_S1_REMOVE_AND_UNLINK, 0);
+            ogs_expect(rv == OGS_OK);
 
             OGS_FSM_TRAN(s, &emm_state_de_registered);
             break;
@@ -644,7 +638,7 @@ static void common_register_state(ogs_fsm_t *s, mme_event_t *e)
                 OGS_FSM_TRAN(&mme_ue->sm, &emm_state_exception);
             } else {
                 ogs_assert(mme_ue->t3422.pkbuf);
-                rv = nas_eps_send_detach_request(mme_ue, 0);
+                rv = nas_eps_send_detach_request(mme_ue);
                 if (rv == OGS_OK) {
                     mme_ue->t3422.retry_count++;
                 } else {
diff --git a/src/mme/mme-context.h b/src/mme/mme-context.h
index 048f9f06c..11405b71b 100644
--- a/src/mme/mme-context.h
+++ b/src/mme/mme-context.h
@@ -312,13 +312,22 @@ struct mme_ue_s {
 #define MME_EPS_TYPE_DETACH_REQUEST_TO_UE           6
         uint8_t     type;
         uint8_t     ksi;
-        union {
-            ogs_nas_eps_attach_type_t attach;
-            ogs_nas_eps_update_type_t update;
-            ogs_nas_service_type_t service;
-            ogs_nas_detach_type_t detach;
-            uint8_t data;
-        };
+        ogs_nas_eps_attach_type_t attach;
+        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;
 
     /* UE identity */
diff --git a/src/mme/mme-fd-path.c b/src/mme/mme-fd-path.c
index ebb12ed1c..8f5ff5299 100644
--- a/src/mme/mme-fd-path.c
+++ b/src/mme/mme-fd-path.c
@@ -233,8 +233,6 @@ static void mme_s6a_aia_cb(void *data, struct msg **msg)
     ogs_assert(aia_message);
     e_utran_vector = &aia_message->e_utran_vector;
     ogs_assert(e_utran_vector);
-
-    s6a_message->isAnswer = true;
     
     /* Value of Result Code */
     ret = fd_msg_search_avp(*msg, ogs_diam_result_code, &avp);
@@ -644,8 +642,6 @@ static void mme_s6a_ula_cb(void *data, struct msg **msg)
     subscription_data = &ula_message->subscription_data;
     ogs_assert(subscription_data);
 
-    s6a_message->isAnswer = true;
-
     /* AVP: 'Result-Code'(268)
      * The Result-Code AVP indicates whether a particular request was completed
      * successfully or whether an error occurred. The Result-Code data field
@@ -1441,8 +1437,6 @@ static int mme_ogs_diam_s6a_clr_cb( struct msg **msg, struct avp *avp,
     clr_message = &s6a_message->clr_message;
     ogs_assert(clr_message);
 
-    s6a_message->isAnswer = false;
-
     /* Create answer header */
     qry = *msg;
     ret = fd_msg_new_answer_from_req(fd_g_config->cnf_dict, msg, 0);
diff --git a/src/mme/mme-path.c b/src/mme/mme-path.c
index 59848a30b..03c261cdf 100644
--- a/src/mme/mme-path.c
+++ b/src/mme/mme-path.c
@@ -28,32 +28,23 @@ void mme_send_delete_session_or_detach(mme_ue_t *mme_ue)
 {
     ogs_assert(mme_ue);
 
-    if (SESSION_CONTEXT_IS_AVAILABLE(mme_ue)) {
-        mme_gtp_send_delete_all_sessions(mme_ue,
-                OGS_GTP_DELETE_SEND_DETACH_ACCEPT);
-    } else {
-        ogs_assert(OGS_OK ==
-            nas_eps_send_detach_accept(mme_ue));
-    }
-}
-
-void mme_send_delete_session_or_mme_ue_context_release_detach(mme_ue_t *mme_ue)
-{
-    ogs_assert(mme_ue);
-
-    if (SESSION_CONTEXT_IS_AVAILABLE(mme_ue)) {
-        mme_gtp_send_delete_all_sessions(
-                mme_ue, OGS_GTP_DELETE_NO_ACTION);
-    } else {
-        enb_ue_t *enb_ue = enb_ue_cycle(mme_ue->enb_ue);
-        if (enb_ue) {
-            ogs_assert(OGS_OK ==
-                s1ap_send_ue_context_release_command(enb_ue,
-                    S1AP_Cause_PR_nas, S1AP_CauseNas_detach,
-                    S1AP_UE_CTX_REL_UE_CONTEXT_REMOVE, 0));
+    switch (mme_ue->nas_eps.detach_type) {
+    case MME_EPS_TYPE_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);
         } else {
-            ogs_warn("[%s] No S1 Context", mme_ue->imsi_bcd);
+            ogs_assert(OGS_OK == nas_eps_send_detach_accept(mme_ue));
         }
+        break;
+    case MME_EPS_TYPE_DETACH_REQUEST_TO_UE:
+        if (SESSION_CONTEXT_IS_AVAILABLE(mme_ue)) {
+            mme_gtp_send_delete_all_sessions(mme_ue, OGS_GTP_DELETE_NO_ACTION);
+        }
+        break;
+    default:
+        ogs_fatal("    Invalid OGS_NAS_EPS TYPE[%d]", mme_ue->nas_eps.type);
+        ogs_assert_if_reached();
     }
 }
 
@@ -201,20 +192,17 @@ void mme_send_after_paging(mme_ue_t *mme_ue, bool failed)
         break;
     case MME_PAGING_TYPE_DETACH_TO_UE:
         if (failed == true) {
+            /* Nothing */
+            ogs_fatal("MME-initiated Detach should not be invoked "
+                        "if Paging failed");
+            ogs_assert_if_reached();
+        } 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);
             }
-
-            OGS_FSM_TRAN(&mme_ue->sm, &emm_state_de_registered);
-        } else {
-            uint8_t detach_type = (uintptr_t)mme_ue->paging.data;
-            ogs_assert(detach_type);
-
-            ogs_assert(OGS_OK ==
-                    nas_eps_send_detach_request(mme_ue, detach_type));
-            mme_send_delete_session_or_mme_ue_context_release_detach(mme_ue);
         }
         break;
     default:
diff --git a/src/mme/mme-path.h b/src/mme/mme-path.h
index b9887bb46..afc6f13e8 100644
--- a/src/mme/mme-path.h
+++ b/src/mme/mme-path.h
@@ -27,7 +27,6 @@ extern "C" {
 #endif
 
 void mme_send_delete_session_or_detach(mme_ue_t *mme_ue);
-void mme_send_delete_session_or_mme_ue_context_release_detach(mme_ue_t *mme_ue);
 void mme_send_delete_session_or_mme_ue_context_release(mme_ue_t *mme_ue);
 void mme_send_release_access_bearer_or_ue_context_release(enb_ue_t *enb_ue);
 
diff --git a/src/mme/mme-s11-handler.c b/src/mme/mme-s11-handler.c
index 8191c99b0..db80c976f 100644
--- a/src/mme/mme-s11-handler.c
+++ b/src/mme/mme-s11-handler.c
@@ -562,7 +562,11 @@ void mme_s11_handle_delete_session_response(
     ogs_debug("    MME_S11_TEID[%d] SGW_S11_TEID[%d]",
             mme_ue->mme_s11_teid, source_ue->sgw_s11_teid);
 
-    if (action == OGS_GTP_DELETE_SEND_AUTHENTICATION_REQUEST) {
+    if (action == OGS_GTP_DELETE_NO_ACTION) {
+        /* No Action to be taken after sessions are deleted during
+         * MME Initiated detach. S1 will be cleared after receipt
+         * of the detach accept from UE */
+    } else if (action == OGS_GTP_DELETE_SEND_AUTHENTICATION_REQUEST) {
         if (mme_sess_count(mme_ue) == 1) /* Last Session */ {
             mme_s6a_send_air(mme_ue, NULL);
         }
@@ -603,6 +607,20 @@ void mme_s11_handle_delete_session_response(
                 ogs_error("ENB-S1 Context has already been removed");
         }
 
+    } else if (action == OGS_GTP_DELETE_SEND_S1_REMOVE_AND_UNLINK) {
+        if (mme_sess_count(mme_ue) == 1) /* Last Session */ {
+            enb_ue_t *enb_ue = NULL;
+
+            enb_ue = enb_ue_cycle(mme_ue->enb_ue);
+            if (enb_ue) {
+                ogs_assert(OGS_OK ==
+                    s1ap_send_ue_context_release_command(enb_ue,
+                        S1AP_Cause_PR_nas, S1AP_CauseNas_normal_release,
+                        S1AP_UE_CTX_REL_S1_REMOVE_AND_UNLINK, 0));
+            } else
+                ogs_error("ENB-S1 Context has already been removed");
+        }
+
     } else if (action == OGS_GTP_DELETE_HANDLE_PDN_CONNECTIVITY_REQUEST) {
         if (mme_sess_count(mme_ue) == 1) /* Last Session */ {
             rv = nas_eps_send_emm_to_esm(mme_ue,
@@ -636,12 +654,6 @@ void mme_s11_handle_delete_session_response(
 
         return;
 
-    } else if (action == OGS_GTP_DELETE_NO_ACTION) {
-        /* 
-        * No Action to be taken after sessions are deleted during
-        * MME Initiated detach.  S1 will be cleared after receipt
-        * of the detach accept from UE */
-        
     } else {
         ogs_fatal("Invalid action = %d", action);
         ogs_assert_if_reached();
diff --git a/src/mme/mme-s6a-handler.c b/src/mme/mme-s6a-handler.c
index a094ab48d..6c54b9bf7 100644
--- a/src/mme/mme-s6a-handler.c
+++ b/src/mme/mme-s6a-handler.c
@@ -18,8 +18,9 @@
  */
 
 #include "nas-path.h"
-#include "mme-path.h"
 #include "s1ap-path.h"
+#include "sgsap-path.h"
+#include "mme-path.h"
 
 #include "mme-sm.h"
 #include "mme-s6a-handler.h"
@@ -140,16 +141,9 @@ uint8_t mme_s6a_handle_ula(
         ogs_assert(OGS_OK ==
             nas_eps_send_tau_accept(mme_ue,
                 S1AP_ProcedureCode_id_InitialContextSetup));
-    } else if (mme_ue->nas_eps.type == MME_EPS_TYPE_SERVICE_REQUEST) {
-        ogs_error("[%s] Service request", mme_ue->imsi_bcd);
-        return OGS_NAS_EMM_CAUSE_PROTOCOL_ERROR_UNSPECIFIED;
-    } else if (mme_ue->nas_eps.type ==
-            MME_EPS_TYPE_DETACH_REQUEST_FROM_UE) {
-        ogs_error("[%s] Detach request", mme_ue->imsi_bcd);
-        return OGS_NAS_EMM_CAUSE_PROTOCOL_ERROR_UNSPECIFIED;
     } else {
-        ogs_fatal("Invalid Type[%d]", mme_ue->nas_eps.type);
-        ogs_assert_if_reached();
+        ogs_error("Invalid Type[%d]", mme_ue->nas_eps.type);
+        return OGS_NAS_EMM_CAUSE_PROTOCOL_ERROR_UNSPECIFIED;
     }
 
     return OGS_NAS_EMM_CAUSE_REQUEST_ACCEPTED;
@@ -158,31 +152,47 @@ uint8_t mme_s6a_handle_ula(
 void mme_s6a_handle_clr(
         mme_ue_t *mme_ue, ogs_diam_s6a_clr_message_t *clr_message)
 {
-    uint8_t detach_type = 0;
-
     ogs_assert(mme_ue);
     ogs_assert(clr_message);    
 
-    /* Set NAS EPS Type */
-    mme_ue->nas_eps.type = MME_EPS_TYPE_DETACH_REQUEST_TO_UE;
-    ogs_debug("    OGS_NAS_EPS TYPE[%d]", mme_ue->nas_eps.type);
+    /* Set EPS Detach */
+    memset(&mme_ue->nas_eps.detach, 0, sizeof(ogs_nas_detach_type_t));
 
     if (clr_message->clr_flags & OGS_DIAM_S6A_CLR_FLAGS_REATTACH_REQUIRED)
-        detach_type = OGS_NAS_DETACH_TYPE_TO_UE_RE_ATTACH_REQUIRED;
+        mme_ue->nas_eps.detach.value =
+            OGS_NAS_DETACH_TYPE_TO_UE_RE_ATTACH_REQUIRED;
     else
-        detach_type = OGS_NAS_DETACH_TYPE_TO_UE_RE_ATTACH_NOT_REQUIRED;
-    
+        mme_ue->nas_eps.detach.value =
+            OGS_NAS_DETACH_TYPE_TO_UE_RE_ATTACH_NOT_REQUIRED;
+
+    /* 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.  */
+    mme_ue->nas_eps.type = mme_ue->nas_eps.detach_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, (void *)(uintptr_t)detach_type);
+        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, detach_type));
-        mme_send_delete_session_or_mme_ue_context_release_detach(mme_ue);
+        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);
+        }
     }
 }
 
diff --git a/src/mme/mme-sm.c b/src/mme/mme-sm.c
index f4796bbd3..5ebc666bb 100644
--- a/src/mme/mme-sm.c
+++ b/src/mme/mme-sm.c
@@ -390,24 +390,17 @@ void mme_state_operational(ogs_fsm_t *s, mme_event_t *e)
         s6a_message = e->s6a_message;
         ogs_assert(s6a_message);
 
-        if (s6a_message->isAnswer) {
-            enb_ue = enb_ue_cycle(mme_ue->enb_ue);
-            if (!enb_ue) {
-                ogs_error("S1 context has already been removed");
-
-                ogs_subscription_data_free(
-                        &s6a_message->ula_message.subscription_data);
-                ogs_free(s6a_message);
-                break;
-            }
-        }
-
         switch (s6a_message->cmd_code) {
         case OGS_DIAM_S6A_CMD_CODE_AUTHENTICATION_INFORMATION:
             emm_cause = mme_s6a_handle_aia(mme_ue, s6a_message);
             if (emm_cause != OGS_NAS_EMM_CAUSE_REQUEST_ACCEPTED) {
                 ogs_info("[%s] Attach reject [OGS_NAS_EMM_CAUSE:%d]",
                         mme_ue->imsi_bcd, emm_cause);
+                enb_ue = enb_ue_cycle(mme_ue->enb_ue);
+                if (!enb_ue) {
+                    ogs_error("S1 context has already been removed");
+                    break;
+                }
                 ogs_assert(OGS_OK ==
                     nas_eps_send_attach_reject(mme_ue, emm_cause,
                         OGS_NAS_ESM_CAUSE_PROTOCOL_ERROR_UNSPECIFIED));
@@ -423,6 +416,11 @@ void mme_state_operational(ogs_fsm_t *s, mme_event_t *e)
             if (emm_cause != OGS_NAS_EMM_CAUSE_REQUEST_ACCEPTED) {
                 ogs_info("[%s] Attach reject [OGS_NAS_EMM_CAUSE:%d]",
                         mme_ue->imsi_bcd, emm_cause);
+                enb_ue = enb_ue_cycle(mme_ue->enb_ue);
+                if (!enb_ue) {
+                    ogs_error("S1 context has already been removed");
+                    break;
+                }
                 ogs_assert(OGS_OK ==
                     nas_eps_send_attach_reject(mme_ue, emm_cause,
                         OGS_NAS_ESM_CAUSE_PROTOCOL_ERROR_UNSPECIFIED));
diff --git a/src/mme/nas-path.c b/src/mme/nas-path.c
index d822174ef..a14a817fc 100644
--- a/src/mme/nas-path.c
+++ b/src/mme/nas-path.c
@@ -256,7 +256,7 @@ int nas_eps_send_authentication_reject(mme_ue_t *mme_ue)
     return rv;
 }
 
-int nas_eps_send_detach_request(mme_ue_t *mme_ue, uint8_t detach_type)
+int nas_eps_send_detach_request(mme_ue_t *mme_ue)
 {
     int rv;
     ogs_pkbuf_t *emmbuf = NULL;
@@ -267,8 +267,7 @@ int nas_eps_send_detach_request(mme_ue_t *mme_ue, uint8_t detach_type)
         emmbuf = mme_ue->t3422.pkbuf;
         ogs_expect_or_return_val(emmbuf, OGS_ERROR);
     } else {
-        ogs_assert(detach_type);
-        emmbuf = emm_build_detach_request(mme_ue, detach_type);
+        emmbuf = emm_build_detach_request(mme_ue);
         ogs_expect_or_return_val(emmbuf, OGS_ERROR);
     }
 
diff --git a/src/mme/nas-path.h b/src/mme/nas-path.h
index 56138d12d..3e3183485 100644
--- a/src/mme/nas-path.h
+++ b/src/mme/nas-path.h
@@ -43,7 +43,7 @@ int nas_eps_send_authentication_reject(mme_ue_t *mme_ue);
 
 int nas_eps_send_security_mode_command(mme_ue_t *mme_ue);
 
-int nas_eps_send_detach_request(mme_ue_t *mme_ue, uint8_t detach_type);
+int nas_eps_send_detach_request(mme_ue_t *mme_ue);
 int nas_eps_send_detach_accept(mme_ue_t *mme_ue);
 
 int nas_eps_send_pdn_connectivity_reject(