diff --git a/srsepc/hdr/mme/s1ap.h b/srsepc/hdr/mme/s1ap.h
index ba4a982eb..509a887ee 100644
--- a/srsepc/hdr/mme/s1ap.h
+++ b/srsepc/hdr/mme/s1ap.h
@@ -71,10 +71,6 @@ public:
   bool handle_initiating_message(LIBLTE_S1AP_INITIATINGMESSAGE_STRUCT *msg, struct sctp_sndrcvinfo *enb_sri);
   bool handle_successful_outcome(LIBLTE_S1AP_SUCCESSFULOUTCOME_STRUCT *msg);
 
-  //bool handle_ue_context_release_request(LIBLTE_S1AP_MESSAGE_UECONTEXTRELEASEREQUEST_STRUCT *ue_rel, struct sctp_sndrcvinfo *enb_sri);
-  //bool send_initial_context_setup_request(uint32_t mme_ue_s1ap_id, struct srslte::gtpc_create_session_response *cs_resp, struct srslte::gtpc_f_teid_ie sgw_ctrl_fteid);
-  //bool handle_initial_context_setup_response(LIBLTE_S1AP_MESSAGE_INITIALCONTEXTSETUPRESPONSE_STRUCT *in_ctxt_resp);
-
   void activate_eps_bearer(uint32_t mme_s1ap_id, uint8_t ebi);
 
   void print_enb_ctx_info(const std::string &prefix, const enb_ctx_t &enb_ctx);
@@ -87,6 +83,8 @@ public:
   void add_new_ue_ctx(const ue_ctx_t &ue_ctx);
   bool delete_ue_ctx(ue_ctx_t *ue_ctx);
 
+  uint32_t allocate_m_tmsi();
+
   s1ap_args_t                    m_s1ap_args;
   srslte::log_filter            *m_s1ap_log;
 
@@ -94,6 +92,8 @@ public:
   s1ap_nas_transport*             m_s1ap_nas_transport;
   s1ap_ctx_mngmt_proc*             m_s1ap_ctx_mngmt_proc;
 
+  std::map<uint32_t, uint32_t>                      m_tmsi_to_s1ap_id;
+
 private:
   s1ap();
   virtual ~s1ap();
@@ -110,8 +110,8 @@ private:
   std::map<uint32_t, ue_ctx_t*>                     m_active_ues;
   std::map<uint16_t,std::set<uint32_t> >            m_enb_id_to_ue_ids;
   uint32_t                                          m_next_mme_ue_s1ap_id;
+  uint32_t                                          m_next_m_tmsi;
 
-  
   //FIXME the GTP-C should be moved to the MME class, the the packaging of GTP-C messages is done.
   mme_gtpc *m_mme_gtpc;
 };
diff --git a/srsepc/src/mme/s1ap.cc b/srsepc/src/mme/s1ap.cc
index e0887c44d..03eaadd35 100644
--- a/srsepc/src/mme/s1ap.cc
+++ b/srsepc/src/mme/s1ap.cc
@@ -73,7 +73,7 @@ s1ap::init(s1ap_args_t s1ap_args, srslte::log_filter *s1ap_log)
 
   m_s1ap_args = s1ap_args;
   srslte::s1ap_mccmnc_to_plmn(s1ap_args.mcc, s1ap_args.mnc, &m_plmn);
-
+  m_next_m_tmsi = rand();
   //Init log
   m_s1ap_log = s1ap_log;
 
@@ -307,243 +307,7 @@ s1ap::handle_successful_outcome(LIBLTE_S1AP_SUCCESSFULOUTCOME_STRUCT *msg)
   return true;
 }
 
-  /*
-bool
-s1ap::send_initial_context_setup_request(uint32_t mme_ue_s1ap_id, struct srslte::gtpc_create_session_response *cs_resp, struct srslte::gtpc_f_teid_ie sgw_ctrl_fteid)
-{
-  ue_ctx_t *ue_ctx;
-
-  //Prepare reply PDU
-  LIBLTE_S1AP_S1AP_PDU_STRUCT pdu;
-  bzero(&pdu, sizeof(LIBLTE_S1AP_S1AP_PDU_STRUCT));
-  pdu.choice_type = LIBLTE_S1AP_S1AP_PDU_CHOICE_INITIATINGMESSAGE;
-
-  LIBLTE_S1AP_INITIATINGMESSAGE_STRUCT *init = &pdu.choice.initiatingMessage;
-  init->procedureCode = LIBLTE_S1AP_PROC_ID_INITIALCONTEXTSETUP;
-  init->choice_type   = LIBLTE_S1AP_INITIATINGMESSAGE_CHOICE_INITIALCONTEXTSETUPREQUEST;
-
-  LIBLTE_S1AP_MESSAGE_INITIALCONTEXTSETUPREQUEST_STRUCT *in_ctxt_req = &init->choice.InitialContextSetupRequest;
-  
-  LIBLTE_S1AP_E_RABTOBESETUPITEMCTXTSUREQ_STRUCT *erab_ctxt = &in_ctxt_req->E_RABToBeSetupListCtxtSUReq.buffer[0]; //FIXME support more than one erab
-  srslte::byte_buffer_t *reply_buffer = m_pool->allocate(); 
-
-  m_s1ap_log->info("Preparing to send Initial Context Setup request\n");
-
-  //Find UE Context
-  std::map<uint32_t, ue_ctx_t*>::iterator ue_ctx_it = m_active_ues.find(mme_ue_s1ap_id);
-  if(ue_ctx_it == m_active_ues.end())
-  {
-    m_s1ap_log->error("Could not find UE to send Setup Context Request. MME S1AP Id: %d", mme_ue_s1ap_id);
-    return false;
-  }
-  ue_ctx = ue_ctx_it->second;
-
-  //Add MME and eNB S1AP Ids
-  in_ctxt_req->MME_UE_S1AP_ID.MME_UE_S1AP_ID = ue_ctx->mme_ue_s1ap_id;
-  in_ctxt_req->eNB_UE_S1AP_ID.ENB_UE_S1AP_ID = ue_ctx->enb_ue_s1ap_id;
-
-  //Set UE-AMBR
-  in_ctxt_req->uEaggregateMaximumBitrate.uEaggregateMaximumBitRateDL.BitRate=1000000000;//2^32-1
-  in_ctxt_req->uEaggregateMaximumBitrate.uEaggregateMaximumBitRateUL.BitRate=1000000000;//FIXME Get UE-AMBR from HSS
-
-  //Setup eRAB context
-  in_ctxt_req->E_RABToBeSetupListCtxtSUReq.len = 1;
-  erab_ctxt->e_RAB_ID.E_RAB_ID = cs_resp->eps_bearer_context_created.ebi;
-  //Setup E-RAB QoS parameters
-  erab_ctxt->e_RABlevelQoSParameters.qCI.QCI = 9;
-  erab_ctxt->e_RABlevelQoSParameters.allocationRetentionPriority.priorityLevel.PriorityLevel = 15 ;//Lowest
-  erab_ctxt->e_RABlevelQoSParameters.allocationRetentionPriority.pre_emptionCapability = LIBLTE_S1AP_PRE_EMPTIONCAPABILITY_SHALL_NOT_TRIGGER_PRE_EMPTION;
-  erab_ctxt->e_RABlevelQoSParameters.allocationRetentionPriority.pre_emptionVulnerability = LIBLTE_S1AP_PRE_EMPTIONVULNERABILITY_PRE_EMPTABLE;
-
-  erab_ctxt->e_RABlevelQoSParameters.gbrQosInformation_present=false;
-  
-  //Set E-RAB S-GW F-TEID
-  if (cs_resp->eps_bearer_context_created.s1_u_sgw_f_teid_present == false){
-    m_s1ap_log->error("Did not receive S1-U TEID in create session response\n");
-    return false;
-  } 
-  erab_ctxt->transportLayerAddress.n_bits = 32; //IPv4
-  uint32_t sgw_s1u_ip = htonl(cs_resp->eps_bearer_context_created.s1_u_sgw_f_teid.ipv4);
-  //uint32_t sgw_s1u_ip = cs_resp->eps_bearer_context_created.s1_u_sgw_f_teid.ipv4;
-  uint8_t *tmp_ptr =  erab_ctxt->transportLayerAddress.buffer;
-  liblte_value_2_bits(sgw_s1u_ip, &tmp_ptr, 32);//FIXME consider ipv6
-
-  uint32_t tmp_teid = cs_resp->eps_bearer_context_created.s1_u_sgw_f_teid.teid; 
-  memcpy(erab_ctxt->gTP_TEID.buffer, &tmp_teid, sizeof(uint32_t));
-
-  //Set UE security capabilities and k_enb
-  bzero(in_ctxt_req->UESecurityCapabilities.encryptionAlgorithms.buffer,sizeof(uint8_t)*16); 
-  bzero(in_ctxt_req->UESecurityCapabilities.integrityProtectionAlgorithms.buffer,sizeof(uint8_t)*16); 
-  for(int i = 0; i<3; i++)
-  {
-    if(ue_ctx->ue_network_cap.eea[i+1] == true)
-    {
-      in_ctxt_req->UESecurityCapabilities.encryptionAlgorithms.buffer[i] = 1;          //EEA supported
-    }
-    else
-    {
-      in_ctxt_req->UESecurityCapabilities.encryptionAlgorithms.buffer[i] = 0;          //EEA not supported
-    }
-    if(ue_ctx->ue_network_cap.eia[i+1] == true)
-    {
-      in_ctxt_req->UESecurityCapabilities.integrityProtectionAlgorithms.buffer[i] = 1;          //EEA supported
-    }
-    else
-    {
-      in_ctxt_req->UESecurityCapabilities.integrityProtectionAlgorithms.buffer[i] = 0;          //EEA not supported
-    }
-    // in_ctxt_req->UESecurityCapabilities.integrityProtectionAlgorithms.buffer[0] = 1; //EIA1
-  }
-  uint8_t key_enb[32];
-  liblte_security_generate_k_enb(ue_ctx->security_ctxt.k_asme, ue_ctx->security_ctxt.ul_nas_count, key_enb);
-  liblte_unpack(key_enb, 32, in_ctxt_req->SecurityKey.buffer);
-  m_s1ap_log->info("Generating KeNB with UL NAS COUNT: %d\n",ue_ctx->security_ctxt.ul_nas_count);
-  //Set Attach accepted and activat default bearer NAS messages
-  if(cs_resp->paa_present != true)
-  {
-    m_s1ap_log->error("PAA not present\n");
-    return false;
-  }
-  if(cs_resp->paa.pdn_type != srslte::GTPC_PDN_TYPE_IPV4)
-  {
-    m_s1ap_log->error("IPv6 not supported yet\n");
-    return false;
-  }
-  srslte::byte_buffer_t *nas_buffer = m_pool->allocate();
-  m_s1ap_nas_transport->pack_attach_accept(ue_ctx, erab_ctxt, &cs_resp->paa, nas_buffer); 
-
-  
-  LIBLTE_ERROR_ENUM err = liblte_s1ap_pack_s1ap_pdu(&pdu, (LIBLTE_BYTE_MSG_STRUCT*)reply_buffer);
-  if(err != LIBLTE_SUCCESS)
-  {
-    m_s1ap_log->error("Could not pack Initial Context Setup Request Message\n");
-    return false;
-  }
-  //Send Reply to eNB 
-  ssize_t n_sent = sctp_send(m_s1mme,reply_buffer->msg, reply_buffer->N_bytes, &ue_ctx->enb_sri, 0);
-  if(n_sent == -1)
-  {
-      m_s1ap_log->error("Failed to send Initial Context Setup Request\n");
-      return false;
-  }
-
-  //Change E-RAB state to Context Setup Requested and save S-GW control F-TEID
-  ue_ctx->erabs_ctx[erab_ctxt->e_RAB_ID.E_RAB_ID].state = ERAB_CTX_REQUESTED;
-  ue_ctx->erabs_ctx[erab_ctxt->e_RAB_ID.E_RAB_ID].sgw_ctrl_fteid.teid = sgw_ctrl_fteid.teid;
-  ue_ctx->erabs_ctx[erab_ctxt->e_RAB_ID.E_RAB_ID].sgw_ctrl_fteid.ipv4 = sgw_ctrl_fteid.ipv4;
-
-  struct in_addr addr;
-  addr.s_addr = sgw_s1u_ip;
-  m_s1ap_log->info("Sent Intial Context Setup Request. E-RAB id %d \n",erab_ctxt->e_RAB_ID.E_RAB_ID);
-  m_s1ap_log->info("Initial Context -- S1-U TEID 0x%x. IP %s \n", tmp_teid,inet_ntoa(addr));
-  m_s1ap_log->console("Sent Intial Context Setup Request, E-RAB id %d\n",erab_ctxt->e_RAB_ID.E_RAB_ID);
-  m_s1ap_log->console("Initial Context -- S1-U TEID 0x%x. IP %s \n", tmp_teid,inet_ntoa(addr));
-
-  m_pool->deallocate(reply_buffer);
-  m_pool->deallocate(nas_buffer);
-  return true;
-}
-
-
-bool
-s1ap::handle_initial_context_setup_response(LIBLTE_S1AP_MESSAGE_INITIALCONTEXTSETUPRESPONSE_STRUCT *in_ctxt_resp)
-{
-
-  uint32_t mme_ue_s1ap_id = in_ctxt_resp->MME_UE_S1AP_ID.MME_UE_S1AP_ID;
-  std::map<uint32_t,ue_ctx_t*>::iterator ue_ctx_it = m_active_ues.find(mme_ue_s1ap_id);
-  if (ue_ctx_it == m_active_ues.end())
-  {
-    m_s1ap_log->error("Could not find UE's context in active UE's map\n");
-    return false;
-  }
-  for(uint32_t i=0; i<in_ctxt_resp->E_RABSetupListCtxtSURes.len;i++)
-  {
-    uint8_t erab_id = in_ctxt_resp->E_RABSetupListCtxtSURes.buffer[i].e_RAB_ID.E_RAB_ID;
-    erab_ctx_t *erab_ctx = &ue_ctx_it->second->erabs_ctx[erab_id];
-    if (erab_ctx->state != ERAB_CTX_REQUESTED)
-    {
-      m_s1ap_log->error("E-RAB requested was not active %d\n",erab_id);
-      return false;
-    }
-    //Mark E-RAB with context setup
-    erab_ctx->state = ERAB_CTX_SETUP;
-
-    //Set the GTP information
-    uint8_t *bit_ptr = in_ctxt_resp->E_RABSetupListCtxtSURes.buffer[i].transportLayerAddress.buffer;
-    erab_ctx->enb_fteid.ipv4 = htonl(liblte_bits_2_value(&bit_ptr,32));
-    memcpy(&erab_ctx->enb_fteid.teid, in_ctxt_resp->E_RABSetupListCtxtSURes.buffer[i].gTP_TEID.buffer, 4);
-    erab_ctx->enb_fteid.teid = ntohl(erab_ctx->enb_fteid.teid);
-
-    char enb_addr_str[INET_ADDRSTRLEN+1];
-    const char *err = inet_ntop(AF_INET, &erab_ctx->enb_fteid.ipv4,enb_addr_str,sizeof(enb_addr_str));
-    if(err == NULL)
-    {
-      m_s1ap_log->error("Error converting IP to string\n");
-    }
-
-    m_s1ap_log->info("E-RAB Context Setup. E-RAB id %d\n",erab_ctx->erab_id);
-    m_s1ap_log->info("E-RAB Context -- eNB TEID 0x%x, eNB Address %s\n", erab_ctx->enb_fteid.teid, enb_addr_str);
-    m_s1ap_log->console("E-RAB Context Setup. E-RAB id %d\n",erab_ctx->erab_id);
-    m_s1ap_log->console("E-RAB Context -- eNB TEID 0x%x; eNB GTP-U Address %s\n", erab_ctx->enb_fteid.teid, enb_addr_str);
-
-  }
-  return true;
-}
-
-bool
-s1ap::handle_ue_context_release_request(LIBLTE_S1AP_MESSAGE_UECONTEXTRELEASEREQUEST_STRUCT *ue_rel, struct sctp_sndrcvinfo *enb_sri)
-{
-
-  uint32_t mme_ue_s1ap_id = ue_rel->MME_UE_S1AP_ID.MME_UE_S1AP_ID;
-  m_s1ap_log->info("Received UE Context Release Request. MME-UE S1AP Id: %d\n", mme_ue_s1ap_id);
-  m_s1ap_log->console("Received UE Context Release Request. MME-UE S1AP Id %d\n", mme_ue_s1ap_id);
 
-  std::map<uint32_t, ue_ctx_t*>::iterator ue_ctx = m_active_ues.find(mme_ue_s1ap_id);
-  if(ue_ctx == m_active_ues.end() )
-  {
-    m_s1ap_log->info("UE not found. MME-UE S1AP Id: %d\n", mme_ue_s1ap_id);
-    return false;
-  }
-  
-  //Delete UE within eNB UE set
-  std::map<int32_t,uint16_t>::iterator it = m_sctp_to_enb_id.find(enb_sri->sinfo_assoc_id);
-  if(it == m_sctp_to_enb_id.end() )
-  {
-    m_s1ap_log->error("Could not find eNB for this request.\n");
-    return false;
-  } 
-  uint16_t enb_id = it->second; 
-  std::map<uint16_t,std::set<uint32_t> >::iterator ue_set = m_enb_id_to_ue_ids.find(enb_id);
-  if(ue_set == m_enb_id_to_ue_ids.end())
-  {
-    m_s1ap_log->error("Could not find the eNB's UEs.\n");
-    return false;
-  }
-  ue_set->second.erase(mme_ue_s1ap_id);
-
-  //Delete any context at the SPGW
-  bool active = false;
-  for(int i=0;i<MAX_ERABS_PER_UE;i++)
-  {
-    if(ue_ctx->second->erabs_ctx[i].state != ERAB_DEACTIVATED)
-    {
-      active = true;
-      break;
-    }
-  }
-  if(active == true)
-  {
-    //There are active E-RABs, send delete session request
-    m_mme_gtpc->send_delete_session_request(ue_ctx->second);
-  }
-
-  //Delete UE context
-  delete ue_ctx->second;
-  m_active_ues.erase(ue_ctx);
-  m_s1ap_log->info("Deleted UE Context.\n");
-  return true;
-}
-  */
 bool
 s1ap::delete_ue_ctx(ue_ctx_t *ue_ctx)
 {
@@ -668,6 +432,12 @@ s1ap::activate_eps_bearer(uint32_t mme_s1ap_id, uint8_t ebi)
   return;
 }
 
+uint32_t
+s1ap::allocate_m_tmsi()
+{
+  return m_next_m_tmsi++;
+}
+
 void
 s1ap::print_enb_ctx_info(const std::string &prefix, const enb_ctx_t &enb_ctx)
 {
diff --git a/srsepc/src/mme/s1ap_nas_transport.cc b/srsepc/src/mme/s1ap_nas_transport.cc
index 3a8425f91..6746b7e00 100644
--- a/srsepc/src/mme/s1ap_nas_transport.cc
+++ b/srsepc/src/mme/s1ap_nas_transport.cc
@@ -81,7 +81,7 @@ s1ap_nas_transport::handle_initial_ue_message(LIBLTE_S1AP_MESSAGE_INITIALUEMESSA
   LIBLTE_MME_ATTACH_REQUEST_MSG_STRUCT attach_req;
   LIBLTE_MME_PDN_CONNECTIVITY_REQUEST_MSG_STRUCT pdn_con_req;
 
-  uint64_t    imsi;
+  uint64_t    imsi = 0;
   uint8_t     k_asme[32];
   uint8_t     autn[16]; 
   uint8_t     rand[6];
@@ -106,13 +106,31 @@ s1ap_nas_transport::handle_initial_ue_message(LIBLTE_S1AP_MESSAGE_INITIALUEMESSA
     return false;
   }
 
-  //Get IMSI
-  imsi = 0;
-  for(int i=0;i<=14;i++){
-    imsi  += attach_req.eps_mobile_id.imsi[i]*std::pow(10,14-i);
+  //Get Mobile ID
+  if(attach_req.eps_mobile_id.type_of_id == LIBLTE_MME_EPS_MOBILE_ID_TYPE_IMSI)
+  {
+    //IMSI style attach
+    imsi = 0;
+    for(int i=0;i<=14;i++){
+      imsi  += attach_req.eps_mobile_id.imsi[i]*std::pow(10,14-i);
+    }
+  }
+  else if(attach_req.eps_mobile_id.type_of_id == LIBLTE_MME_EPS_MOBILE_ID_TYPE_GUTI)
+  {
+    //GUTI style attach
+    uint32_t m_tmsi = attach_req.eps_mobile_id.guti.m_tmsi;
+    std::map<uint32_t,uint32_t>::iterator it = m_s1ap->m_tmsi_to_s1ap_id.find(m_tmsi);
+    if(it == m_s1ap->m_tmsi_to_s1ap_id.end())
+    {
+      //FIXME Send Id request
+      m_s1ap_log->info("Could not find M-TMSI in attach request\n");
+      return false;
+    }
+    ue_ctx_t *tmp = m_s1ap->find_ue_ctx(it->second);
+    imsi = tmp->imsi;
   }
   m_s1ap_log->console("Attach request from IMSI: %015lu\n", imsi);
-  m_s1ap_log->info("Attach request from IMSI: %015lu\n", imsi);  
+  m_s1ap_log->info("Attach request from IMSI: %015lu\n", imsi);
 
   //Get UE network capabilities
   memcpy(&ue_ctx.ue_network_cap, &attach_req.ue_network_cap, sizeof(LIBLTE_MME_UE_NETWORK_CAPABILITY_STRUCT));
@@ -745,18 +763,18 @@ s1ap_nas_transport::pack_attach_accept(ue_ctx_t *ue_ctx, LIBLTE_S1AP_E_RABTOBESE
   attach_accept.t3412.value = 30;                                    // 30 minute periodic timer
   //FIXME: Set tai_list from config
   attach_accept.tai_list.N_tais = 1;
-  attach_accept.tai_list.tai[0].mcc = 1;
-  attach_accept.tai_list.tai[0].mnc = 1;
-  attach_accept.tai_list.tai[0].tac = 7;
+  attach_accept.tai_list.tai[0].mcc = m_s1ap->m_s1ap_args.mcc;
+  attach_accept.tai_list.tai[0].mnc = m_s1ap->m_s1ap_args.mnc;
+  attach_accept.tai_list.tai[0].tac = m_s1ap->m_s1ap_args.tac;
 
   //Allocate a GUTI ot the UE
   attach_accept.guti_present=true;
   attach_accept.guti.type_of_id = 6; //110 -> GUTI
-  attach_accept.guti.guti.mcc = 1;
-  attach_accept.guti.guti.mnc = 1;
+  attach_accept.guti.guti.mcc = m_s1ap->m_s1ap_args.mcc;
+  attach_accept.guti.guti.mnc = m_s1ap->m_s1ap_args.mnc;
   attach_accept.guti.guti.mme_group_id = 0x0001;
   attach_accept.guti.guti.mme_code = 0x1a;
-  attach_accept.guti.guti.m_tmsi = 0x124ae;
+  attach_accept.guti.guti.m_tmsi = m_s1ap->allocate_m_tmsi();
   /*
   typedef struct{
     uint32 m_tmsi;