diff --git a/srsepc/hdr/spgw/spgw.h b/srsepc/hdr/spgw/spgw.h
index 12ec01d51..a9c1b9ba3 100644
--- a/srsepc/hdr/spgw/spgw.h
+++ b/srsepc/hdr/spgw/spgw.h
@@ -56,11 +56,11 @@ typedef struct {
 typedef struct {
   uint64_t imsi;
   in_addr_t ue_ipv4;
-  struct srslte::gtpc_f_teid_ie uplink_ctrl;
-  struct srslte::gtpc_f_teid_ie uplink_user;
-  struct srslte::gtpc_f_teid_ie downlink_ctrl;
-  struct srslte::gtpc_f_teid_ie downlink_user;
-} spgw_ue_ctxr;
+  struct srslte::gtpc_f_teid_ie up_ctrl_fteid;
+  struct srslte::gtpc_f_teid_ie up_user_fteid;
+  struct srslte::gtpc_f_teid_ie dw_ctrl_fteid;
+  struct srslte::gtpc_f_teid_ie dw_user_fteid;
+} spgw_ue_ctx;
 
 class spgw:
   public thread
@@ -101,6 +101,9 @@ private:
   uint64_t m_next_ctrl_teid;
   uint64_t m_next_user_teid;
 
+  std::map<uint32_t,spgw_ue_ctx*> m_teid_to_ue_ctx;      //Map control TEID to ue_ctx. Usefull to get reply ctrl TEID
+  std::map<in_addr_t,gtpc_f_teid_ie> m_ip_to_teid;          //Map IP to User-plane TEID for downlink traffic
+
   /*Logs*/
   srslte::log_filter  *m_spgw_log;
 
diff --git a/srsepc/src/mme/mme_gtpc.cc b/srsepc/src/mme/mme_gtpc.cc
index 7c314a9a7..75b811835 100644
--- a/srsepc/src/mme/mme_gtpc.cc
+++ b/srsepc/src/mme/mme_gtpc.cc
@@ -167,7 +167,7 @@ void
 mme_gtpc::send_modify_bearer_request(erab_ctx_t *erab_ctx)
 {
   m_mme_gtpc_log->info("Sending GTP-C Modify bearer request\n");
-  srslte::gtpc_pdu pdu;
+  srslte::gtpc_pdu mb_req_pdu;
   srslte::gtpc_f_teid_ie *enb_fteid = &erab_ctx->enb_fteid; 
   srslte::gtpc_f_teid_ie *sgw_ctrl_fteid = &erab_ctx->sgw_ctrl_fteid; 
 
@@ -176,14 +176,16 @@ mme_gtpc::send_modify_bearer_request(erab_ctx_t *erab_ctx)
   header->teid = sgw_ctrl_fteid->teid;
   header->type = srslte::GTPC_MSG_TYPE_MODIFY_BEARER_REQUEST;
 
-  srslte::gtpc_modify_bearer_request mb_req;
-  mb_req.eps_bearer_context_to_modify.ebi = erab_ctx->erab_id;
-  mb_req.eps_bearer_context_to_modify.s1_u_enb_f_teid.ipv4 = enb_fteid->ipv4;
-  mb_req.eps_bearer_context_to_modify.s1_u_enb_f_teid.teid = enb_fteid->teid;
+  srslte::gtpc_modify_bearer_request *mb_req = &mb_req_pdu.modify_bearer_request;
+  mb_req->eps_bearer_context_to_modify.ebi = erab_ctx->erab_id;
+  mb_req->eps_bearer_context_to_modify.s1_u_enb_f_teid.ipv4 = enb_fteid->ipv4;
+  mb_req->eps_bearer_context_to_modify.s1_u_enb_f_teid.teid = enb_fteid->teid;
 
   m_mme_gtpc_log->info("GTP-C Modify bearer request -- S-GW Control TEID %d\n", sgw_ctrl_fteid->teid );
   m_mme_gtpc_log->info("GTP-C Modify bearer request -- S1-U TEID 0x%x\n", enb_fteid->teid );
 
-  
+  //
+  srslte::gtpc_pdu mb_resp_pdu;
+  m_spgw->handle_modify_bearer_request(&mb_req_pdu,&mb_resp_pdu); 
 }
 } //namespace srsepc
diff --git a/srsepc/src/spgw/spgw.cc b/srsepc/src/spgw/spgw.cc
index b5f5773cb..2f47de745 100644
--- a/srsepc/src/spgw/spgw.cc
+++ b/srsepc/src/spgw/spgw.cc
@@ -315,13 +315,7 @@ spgw::handle_create_session_request(struct srslte::gtpc_create_session_request *
 
 
   m_spgw_log->info("Received Create Session Request\n");
-  //Setup GTP-C header
-  header->piggyback = false;
-  header->teid_present = true;
-  header->teid = cs_req->sender_f_teid.teid;  //Send create session requesponse to the CS Request TEID
-  header->type = srslte::GTPC_MSG_TYPE_CREATE_SESSION_RESPONSE;
-
-  //Setup uplink control TEID
+    //Setup uplink control TEID
   uint64_t spgw_uplink_ctrl_teid = get_new_ctrl_teid();
   //Setup uplink user TEID
   uint64_t spgw_uplink_user_teid = get_new_user_teid();
@@ -329,9 +323,19 @@ spgw::handle_create_session_request(struct srslte::gtpc_create_session_request *
   in_addr_t ue_ip = get_new_ue_ipv4();
 
   //Save the UE IP to User TEID map //TODO!!!
+  struct sgw_ue_ctx *ue_ctx = new sgw_ue_ctx;
+  sgw_ue_ctx->imsi = cs_req->imsi;
+  sgw_ue_ctx->ul_user_fteid.teid = spgw_uplink_user_teid;
+  sgw_ue_ctx->ul_ctrl_fteid = spgw_uplink_ctrl_teid;
+  sgw_ue_ctx->ue_ipv4 = ue_ip; 
 
   //Create session response message
-  //Initialize to zero\\
+  //Setup GTP-C header
+  header->piggyback = false;
+  header->teid_present = true;
+  header->teid = cs_req->sender_f_teid.teid;  //Send create session requesponse to the CS Request TEID
+  header->type = srslte::GTPC_MSG_TYPE_CREATE_SESSION_RESPONSE;
+  //Initialize to zero
   bzero(cs_resp,sizeof(struct srslte::gtpc_create_session_response));
   //Setup Cause
   cs_resp->cause.cause_value = srslte::GTPC_CAUSE_VALUE_REQUEST_ACCEPTED;
@@ -354,6 +358,21 @@ spgw::handle_create_session_request(struct srslte::gtpc_create_session_request *
   return;
 }
 
+void
+spgw::handle_modify_bearer_request(struct srslte::gtpc_pdu *mb_req_pdu, struct srslte::gtpc_pdu *mb_resp_pdu)
+{
+  m_spgw_log->info("Received Modified Bearer Request\n");
 
+  //Get control tunnel info from  
+  //Setting up Modify bearer request PDU
+  //Header
+  srslte::gtpc_header *header = &mb_req_pdu->header;
+  header->piggyback = false;
+  header->teid_present = true;
+  header->teid = ;  //
+  header->type = srslte::GTPC_MSG_TYPE_MODIFY_BEARER_RESPONSE;
 
+  //PDU
+  srslte::gtpc_modify_bearer_response *mb_resp = mb_req_pdu.choice.modify_bearer_response;
+}
 } //namespace srsepc