diff --git a/lib/include/srslte/asn1/gtpc.h b/lib/include/srslte/asn1/gtpc.h
index e670333bf..e216bcf12 100644
--- a/lib/include/srslte/asn1/gtpc.h
+++ b/lib/include/srslte/asn1/gtpc.h
@@ -74,6 +74,8 @@ typedef union gtpc_msg_choice
 {
   struct gtpc_create_session_request create_session_request;
   struct gtpc_create_session_response create_session_response;
+  struct gtpc_modify_bearer_request modify_bearer_request;
+  //struct gtpc_modify_bearer_response modify_bearer_response;
 } gtpc_msg_choice_t;
 
 /****************************************************************************
diff --git a/srsepc/hdr/spgw/spgw.h b/srsepc/hdr/spgw/spgw.h
index a9c1b9ba3..2ea2278c8 100644
--- a/srsepc/hdr/spgw/spgw.h
+++ b/srsepc/hdr/spgw/spgw.h
@@ -53,14 +53,14 @@ typedef struct {
 } spgw_args_t;
 
 
-typedef struct {
+typedef struct spgw_tunnel_ctx {
   uint64_t imsi;
   in_addr_t ue_ipv4;
   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;
+} spgw_tunnel_ctx_t;
 
 class spgw:
   public thread
@@ -73,6 +73,7 @@ public:
   void run_thread();
 
   void handle_create_session_request(struct srslte::gtpc_create_session_request *cs_req, struct srslte::gtpc_pdu *cs_resp_pdu);
+  void handle_modify_bearer_request(struct srslte::gtpc_pdu *mb_req_pdu, struct srslte::gtpc_pdu *mb_resp_pdu);
 
 private:
 
@@ -101,8 +102,8 @@ 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
+  std::map<uint32_t,spgw_tunnel_ctx*> m_teid_to_tunnel_ctx;         //Map control TEID to tunnel ctx. Usefull to get reply ctrl TEID, UE IP, etc.
+  std::map<in_addr_t,srslte::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 75b811835..8da689f32 100644
--- a/srsepc/src/mme/mme_gtpc.cc
+++ b/srsepc/src/mme/mme_gtpc.cc
@@ -176,7 +176,7 @@ 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_pdu.modify_bearer_request;
+  srslte::gtpc_modify_bearer_request *mb_req = &mb_req_pdu.choice.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;
diff --git a/srsepc/src/spgw/spgw.cc b/srsepc/src/spgw/spgw.cc
index 2f47de745..5a9b7f6c6 100644
--- a/srsepc/src/spgw/spgw.cc
+++ b/srsepc/src/spgw/spgw.cc
@@ -323,11 +323,11 @@ 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; 
+  spgw_tunnel_ctx_t *tunnel_ctx = new spgw_tunnel_ctx_t;
+  tunnel_ctx->imsi = cs_req->imsi;
+  tunnel_ctx->up_user_fteid.teid = spgw_uplink_user_teid;
+  tunnel_ctx->up_ctrl_fteid.teid = spgw_uplink_ctrl_teid;
+  tunnel_ctx->ue_ipv4 = ue_ip;
 
   //Create session response message
   //Setup GTP-C header
@@ -363,13 +363,28 @@ spgw::handle_modify_bearer_request(struct srslte::gtpc_pdu *mb_req_pdu, struct s
 {
   m_spgw_log->info("Received Modified Bearer Request\n");
 
-  //Get control tunnel info from  
-  //Setting up Modify bearer request PDU
+  //Get control tunnel info from mb_req PDU
+  uint32_t ctrl_teid = mb_req_pdu->header.teid;
+  std::map<uint32_t,spgw_tunnel_ctx_t*>::iterator tunnel_it = m_teid_to_tunnel_ctx.find(ctrl_teid);
+  if(tunnel_it == m_teid_to_tunnel_ctx.end())
+  {
+    m_spgw_log->warning("Could not find TEID %d to modify",ctrl_teid);
+    return;
+  }
+  spgw_tunnel_ctx_t *tunnel_ctx = tunnel_it->second;
+
+  //Store user DW link TEID
+  srslte::gtpc_modify_bearer_request *mb_req = &mb_req_pdu->choice.modify_bearer_request;
+  tunnel_ctx->dw_user_fteid = mb_req->eps_bearer_context_to_modify.s1_u_enb_f_teid;
+  //Set up actual tunnel
+  //TODO!!!
+
+  //Setting up Modify bearer response PDU
   //Header
   srslte::gtpc_header *header = &mb_req_pdu->header;
   header->piggyback = false;
   header->teid_present = true;
-  header->teid = ;  //
+  header->teid = tunnel_ctx->dw_ctrl_fteid.teid;  //
   header->type = srslte::GTPC_MSG_TYPE_MODIFY_BEARER_RESPONSE;
 
   //PDU