diff --git a/src/s1ap/handlers/detach_accept.c b/src/s1ap/handlers/detach_accept.c
new file mode 100644
index 0000000..b0e8c1f
--- /dev/null
+++ b/src/s1ap/handlers/detach_accept.c
@@ -0,0 +1,328 @@
+/*
+ * Copyright (c) 2003-2018, Great Software Laboratory Pvt. Ltd.
+ * Copyright (c) 2017 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdint.h>
+
+#include "log.h"
+#include "err_codes.h"
+#include "message_queues.h"
+#include "ipc_api.h"
+#include "s1ap.h"
+#include "s1ap_config.h"
+#include "main.h"
+#include "msgType.h"
+
+static int
+get_detach_accept_protoie_value(struct proto_IE *value, struct detach_accept_Q_msg *g_acptReqInfo)
+{
+	uint8_t ieCnt = 0;
+
+	value->no_of_IEs = DTCH_ACCEPT_NO_OF_IES;
+
+	value->data = (proto_IEs *) malloc(DTCH_ACCEPT_NO_OF_IES *
+			sizeof(proto_IEs));
+
+	value->data[ieCnt].val.mme_ue_s1ap_id = g_acptReqInfo->ue_idx;
+	ieCnt++;
+
+	value->data[ieCnt].val.enb_ue_s1ap_id = g_acptReqInfo->enb_s1ap_ue_id;
+	ieCnt++;
+
+	struct nasPDU *nas = &(value->data[ieCnt].val.nas);
+	nas->header.security_header_type = IntegrityProtectedCiphered;
+	nas->header.proto_discriminator = EPSMobilityManagementMessages;
+
+	/* placeholder for mac. mac value will be calculated later */
+	uint8_t mac[MAC_SIZE] = {0};
+	memcpy(nas->header.mac, mac, MAC_SIZE);
+
+	nas->header.seq_no = g_acptReqInfo->dl_seq_no;
+	nas->header.message_type = DetachAccept;
+
+	ieCnt++;
+
+	return SUCCESS;
+}
+
+/**
+* Stage specific message processing.
+*/
+static int
+detach_accept_processing(struct detach_accept_Q_msg *g_acptReqInfo)
+{
+	unsigned char tmpStr[4];
+	struct s1ap_PDU s1apPDU= {0};
+	uint16_t protocolIe_Id;
+	uint8_t protocolIe_criticality = CRITICALITY_REJECT;
+	uint8_t initiating_msg = 0;
+	uint8_t datalen = 0;
+	uint8_t s1ap_len_pos;
+	uint8_t nas_len_pos;
+	uint8_t u8value = 0;
+	uint8_t mac_data_pos;
+
+	Buffer g_acpt_buffer;
+
+	s1apPDU.procedurecode = id_downlinkNASTransport;
+	s1apPDU.criticality = CRITICALITY_IGNORE;
+
+	get_detach_accept_protoie_value(&s1apPDU.value, g_acptReqInfo);
+
+	g_acpt_buffer.pos = 0;
+
+	buffer_copy(&g_acpt_buffer, &initiating_msg,
+			sizeof(initiating_msg));
+
+	buffer_copy(&g_acpt_buffer, &s1apPDU.procedurecode,
+			sizeof(s1apPDU.procedurecode));
+
+	buffer_copy(&g_acpt_buffer, &s1apPDU.criticality,
+				sizeof(s1apPDU.criticality));
+
+	s1ap_len_pos = g_acpt_buffer.pos;
+
+	/* length of Detach Accept */
+	u8value = 0;
+	buffer_copy(&g_acpt_buffer, &u8value, sizeof(u8value));
+
+	/* TODO remove hardcoded values */
+	uint8_t chProtoIENo[3] = {0,0,3};
+	buffer_copy(&g_acpt_buffer, chProtoIENo, 3);
+
+	/* id-MME-UE-S1AP-ID */
+	protocolIe_Id = id_MME_UE_S1AP_ID;
+	copyU16(tmpStr, protocolIe_Id);
+	buffer_copy(&g_acpt_buffer, tmpStr, sizeof(protocolIe_Id));
+	buffer_copy(&g_acpt_buffer, &protocolIe_criticality,
+					sizeof(protocolIe_criticality));
+	datalen = 2;
+	/* TODO need to add proper handling*/
+	unsigned char mme_ue_id[3];
+	datalen = copyU16(mme_ue_id, s1apPDU.value.data[0].val.mme_ue_s1ap_id);
+	buffer_copy(&g_acpt_buffer, &datalen, sizeof(datalen));
+	buffer_copy(&g_acpt_buffer, mme_ue_id, datalen);
+
+	/* id-eNB-UE-S1AP-ID */
+	protocolIe_Id = id_eNB_UE_S1AP_ID;
+	copyU16(tmpStr, protocolIe_Id);
+	buffer_copy(&g_acpt_buffer, tmpStr, sizeof(protocolIe_Id));
+	buffer_copy(&g_acpt_buffer, &protocolIe_criticality,
+					sizeof(protocolIe_criticality));
+	/* TODO needs proper handling*/
+	unsigned char enb_ue_id[3];
+	datalen = copyU16(enb_ue_id, s1apPDU.value.data[1].val.enb_ue_s1ap_id);
+	buffer_copy(&g_acpt_buffer, &datalen, sizeof(datalen));
+	buffer_copy(&g_acpt_buffer, enb_ue_id, datalen);
+
+	/* NAS PDU start */
+	protocolIe_Id = id_NAS_PDU;
+	copyU16(tmpStr, protocolIe_Id);
+	buffer_copy(&g_acpt_buffer, tmpStr, sizeof(protocolIe_Id));
+	buffer_copy(&g_acpt_buffer, &protocolIe_criticality,
+					sizeof(protocolIe_criticality));
+
+	nas_len_pos = g_acpt_buffer.pos;
+
+	datalen = 0;
+	buffer_copy(&g_acpt_buffer, &datalen, sizeof(datalen));
+
+	buffer_copy(&g_acpt_buffer, &datalen, sizeof(datalen));
+
+	nas_pdu_header *nas_hdr = &(s1apPDU.value.data[2].val.nas.header);
+
+	/* security header and protocol discriminator */
+	u8value = (nas_hdr->security_header_type << 4 |
+			nas_hdr->proto_discriminator);
+	buffer_copy(&g_acpt_buffer, &u8value, sizeof(u8value));
+
+	/* mac */
+	/* placeholder for mac. mac value will be calculated later */
+	buffer_copy(&g_acpt_buffer, nas_hdr->mac, MAC_SIZE);
+	mac_data_pos = g_acpt_buffer.pos;
+
+	/* sequence number */
+	buffer_copy(&g_acpt_buffer, &(nas_hdr->seq_no),
+			sizeof(nas_hdr->seq_no));
+
+	/* security header and protocol discriminator */
+	nas_hdr->security_header_type = Plain;
+	u8value = (nas_hdr->security_header_type << 4 |
+			nas_hdr->proto_discriminator);
+	buffer_copy(&g_acpt_buffer, &u8value, sizeof(u8value));
+
+	/* message type */
+	buffer_copy(&g_acpt_buffer, &(nas_hdr->message_type),
+			sizeof(nas_hdr->message_type));
+
+	/* NAS PDU end */
+
+	/* Calculate mac */
+	uint8_t direction = 1;
+	uint8_t bearer = 0;
+
+	calculate_mac(g_acptReqInfo->int_key, nas_hdr->seq_no,
+			direction, bearer, &g_acpt_buffer.buf[mac_data_pos],
+			g_acpt_buffer.pos - mac_data_pos,
+			&g_acpt_buffer.buf[mac_data_pos - MAC_SIZE]);
+
+	/* Copy nas length to nas length field */
+	datalen = g_acpt_buffer.pos - nas_len_pos -1;
+	memcpy(&(g_acpt_buffer.buf[nas_len_pos]), &datalen, sizeof(datalen));
+
+	/* Copy nas length to nas length field */
+	datalen = g_acpt_buffer.pos - nas_len_pos - 2;
+	memcpy(&(g_acpt_buffer.buf[nas_len_pos + 1]), &datalen, sizeof(datalen));
+
+	/* Copy length to s1ap length field */
+	datalen = g_acpt_buffer.pos - s1ap_len_pos - 1;
+	memcpy(g_acpt_buffer.buf + s1ap_len_pos, &datalen, sizeof(datalen));
+
+	/* TODO: temp fix */
+	//g_ics_buffer.buf[1] = 0x09;
+	send_sctp_msg(g_acptReqInfo->enb_fd, g_acpt_buffer.buf, g_acpt_buffer.pos,1);
+
+	log_msg(LOG_INFO, "Detach Accept sent to UE.");
+
+	return SUCCESS;
+}
+
+/**
+* essage processing for ue context release
+*/
+static int
+ue_ctx_release_processing(struct detach_accept_Q_msg *g_acptReqInfo)
+{
+	Buffer g_ctxrel_buffer;
+	unsigned char tmpStr[4];
+	struct s1ap_PDU s1apPDU;
+	uint16_t protocolIe_Id;
+	uint8_t protocolIe_criticality = CRITICALITY_REJECT;
+	uint8_t initiating_msg = 0;
+	uint8_t datalen = 0;
+	uint8_t s1ap_len_pos;
+	uint8_t u8value = 0;
+
+	s1apPDU.procedurecode = id_UEContexRelease;
+	s1apPDU.criticality = CRITICALITY_IGNORE;
+
+	g_ctxrel_buffer.pos = 0;
+
+	buffer_copy(&g_ctxrel_buffer, &initiating_msg,
+			sizeof(initiating_msg));
+
+	buffer_copy(&g_ctxrel_buffer, &s1apPDU.procedurecode,
+			sizeof(s1apPDU.procedurecode));
+
+	buffer_copy(&g_ctxrel_buffer, &s1apPDU.criticality,
+				sizeof(s1apPDU.criticality));
+
+	s1ap_len_pos = g_ctxrel_buffer.pos;
+
+	/* length of UE Context Release */
+	u8value = 0;
+	buffer_copy(&g_ctxrel_buffer, &u8value, sizeof(u8value));
+
+	/* TODO remove hardcoded values */
+	uint8_t chProtoIENo[3] = {0,0,2};
+	buffer_copy(&g_ctxrel_buffer, chProtoIENo, 3);
+
+	/* id-UE-S1AP-IDs */
+	protocolIe_Id = id_UE_S1AP_IDs;
+	copyU16(tmpStr, protocolIe_Id);
+	buffer_copy(&g_ctxrel_buffer, tmpStr, sizeof(protocolIe_Id));
+	buffer_copy(&g_ctxrel_buffer, &protocolIe_criticality,
+					sizeof(protocolIe_criticality));
+
+	uint8_t mme_ue_id[4];
+	uint8_t mme_ue_id_len = copyU16(mme_ue_id,
+				s1apPDU.value.data[0].val.mme_ue_s1ap_id);
+
+	if (mme_ue_id[0] == 0x40 || mme_ue_id[0] == 0x80)
+		mme_ue_id[0] = ((mme_ue_id[0] & 0x0F)<<4 |
+				(mme_ue_id[0] & 0xF0)>>4);
+
+	uint8_t enb_ue_id[4];
+	uint8_t enb_ue_id_len = copyU16(enb_ue_id,
+				s1apPDU.value.data[1].val.enb_ue_s1ap_id);
+
+	datalen = mme_ue_id_len + enb_ue_id_len;
+	buffer_copy(&g_ctxrel_buffer, &datalen, sizeof(datalen));
+	buffer_copy(&g_ctxrel_buffer, mme_ue_id, mme_ue_id_len);
+	buffer_copy(&g_ctxrel_buffer, enb_ue_id, enb_ue_id_len);
+
+#if 0
+	/* id-MME-UE-S1AP-ID */
+	protocolIe_Id = id_MME_UE_S1AP_ID;
+	copyU16(tmpStr, protocolIe_Id);
+	buffer_copy(&g_ctxrel_buffer, tmpStr,
+	                                sizeof(protocolIe_Id));
+
+	protocolIe_criticality = CRITICALITY_REJECT;
+	buffer_copy(&g_ctxrel_buffer, &protocolIe_criticality,
+	                                sizeof(protocolIe_criticality));
+
+	datalen = 2;
+
+	/* TODO needs proper handling*/
+	unsigned char mme_ue_id[4];
+	datalen = copyU16(mme_ue_id, s1apPDU.value.data[0].val.mme_ue_s1ap_id);
+	buffer_copy(&g_ctxrel_buffer, &datalen, sizeof(datalen));
+	buffer_copy(&g_ctxrel_buffer, mme_ue_id, datalen);
+#endif
+
+	/* id-Cause */
+	protocolIe_Id = id_Cause;
+	protocolIe_criticality = CRITICALITY_IGNORE;
+	copyU16(tmpStr, protocolIe_Id);
+	buffer_copy(&g_ctxrel_buffer, tmpStr, sizeof(protocolIe_Id));
+	buffer_copy(&g_ctxrel_buffer, &protocolIe_criticality,
+					sizeof(protocolIe_criticality));
+	datalen = 1;
+	buffer_copy(&g_ctxrel_buffer, &datalen, sizeof(datalen));
+	/* TODO : Revisit. cause : nas(2) and value : detach (2), why 0x24 ? */
+	u8value = 0x24;
+	buffer_copy(&g_ctxrel_buffer, &u8value, sizeof(u8value));
+
+	/* Copy length to s1ap length field */
+	datalen = g_ctxrel_buffer.pos - s1ap_len_pos - 1;
+	memcpy(g_ctxrel_buffer.buf + s1ap_len_pos, &datalen, sizeof(datalen));
+	send_sctp_msg(g_acptReqInfo->enb_fd, g_ctxrel_buffer.buf, g_ctxrel_buffer.pos,1);
+
+	log_msg(LOG_INFO,"S1 Release sent to UE");
+
+	return SUCCESS;
+}
+
+/**
+* Thread function for stage.
+*/
+void*
+detach_accept_handler(void *data)
+{
+   log_msg(LOG_INFO, "detach accept handler ready.\n");
+   struct detach_accept_Q_msg *msg = (struct detach_accept_Q_msg *)data;
+
+   detach_accept_processing(msg);
+   ue_ctx_release_processing(msg);
+
+   return NULL;
+}