diff --git a/lib/core/include/core_network.h b/lib/core/include/core_network.h
index 9634e9774..6d9850922 100644
--- a/lib/core/include/core_network.h
+++ b/lib/core/include/core_network.h
@@ -5,6 +5,8 @@
 #include "core_time.h"
 #include "core_list.h"
 
+#define NO_FD_LOCK              1  /* New experimental method */
+
 #if HAVE_ARPA_INET_H
 #include <arpa/inet.h>
 #endif
diff --git a/lib/core/src/unix/socket.c b/lib/core/src/unix/socket.c
index a1fb64717..7bef31aca 100644
--- a/lib/core/src/unix/socket.c
+++ b/lib/core/src/unix/socket.c
@@ -9,6 +9,14 @@
 #define MAX_SOCK_POOL_SIZE              512
 #define MAX_SOCK_NODE_POOL_SIZE         512
 
+#if NO_FD_LOCK
+#define FD_LOCK
+#define FD_UNLOCK
+#else
+#define FD_LOCK mutex_lock(mutex);
+#define FD_UNLOCK mutex_unlock(mutex);
+#endif
+
 static int max_fd;
 static list_t fd_list;
 static fd_set read_fds;
@@ -659,7 +667,7 @@ status_t sock_register(sock_id id, sock_handler handler, void *data)
         return CORE_ERROR;
     }
 
-    mutex_lock(mutex);
+    FD_LOCK
 
     if (sock->fd > max_fd)
     {
@@ -670,7 +678,7 @@ status_t sock_register(sock_id id, sock_handler handler, void *data)
 
     list_append(&fd_list, sock);
 
-    mutex_unlock(mutex);
+    FD_UNLOCK
 
     return CORE_OK;
 }
@@ -679,11 +687,11 @@ status_t sock_unregister(sock_id id)
 {
     d_assert(id, return CORE_ERROR,);
 
-    mutex_lock(mutex);
+    FD_LOCK
 
     list_remove(&fd_list, id);
 
-    mutex_unlock(mutex);
+    FD_UNLOCK
 
     return CORE_OK;
 }
@@ -693,19 +701,19 @@ int sock_is_registered(sock_id id)
     sock_t *sock = (sock_t *)id;
     sock_t *iter = NULL;
 
-    mutex_lock(mutex);
+    FD_LOCK
 
     d_assert(id, return CORE_ERROR,);
     for (iter = list_first(&fd_list); iter != NULL; iter = list_next(iter))
     {
         if (iter == sock)
         {
-            mutex_unlock(mutex);
+            FD_UNLOCK
             return 1;
         }
     }
 
-    mutex_unlock(mutex);
+    FD_UNLOCK
     return 0;
 }
 
@@ -811,7 +819,7 @@ static void set_fds(fd_set *fds)
 {
     sock_t *sock = NULL;
 
-    mutex_lock(mutex);
+    FD_LOCK
 
     FD_ZERO(fds);
     for (sock = list_first(&fd_list); sock != NULL; sock = list_next(sock))
@@ -819,14 +827,14 @@ static void set_fds(fd_set *fds)
         FD_SET(sock->fd, fds);
     }
 
-    mutex_unlock(mutex);
+    FD_UNLOCK
 }
 
 static void fd_dispatch(fd_set *fds)
 {
     sock_t *sock = NULL;
 
-    mutex_lock(mutex);
+    FD_LOCK
 
     for (sock = list_first(&fd_list); sock != NULL; sock = list_next(sock))
     {
@@ -839,5 +847,5 @@ static void fd_dispatch(fd_set *fds)
         }
     }
 
-    mutex_unlock(mutex);
+    FD_UNLOCK
 }
diff --git a/src/mme/mme_context.c b/src/mme/mme_context.c
index e3a8214d4..895eda138 100644
--- a/src/mme/mme_context.c
+++ b/src/mme/mme_context.c
@@ -5,6 +5,7 @@
 #include "core_lib.h"
 #include "core_msgq.h"
 #include "core_fsm.h"
+#include "core_network.h"
 
 #include <mongoc.h>
 #include <yaml.h>
@@ -1402,8 +1403,12 @@ status_t mme_enb_remove(mme_enb_t *enb)
 
     enb_ue_remove_in_enb(enb);
 
+#ifdef NO_FD_LOCK
+#else
+#error do not use lock in socket fd
     if (enb->sock_type == SOCK_STREAM)
         s1ap_delete(enb->sock);
+#endif
     core_free(enb->addr);
 
     index_free(&mme_enb_pool, enb);
diff --git a/src/mme/mme_sm.c b/src/mme/mme_sm.c
index 70bb32555..3c78423f3 100644
--- a/src/mme/mme_sm.c
+++ b/src/mme/mme_sm.c
@@ -122,6 +122,10 @@ void mme_state_operational(fsm_t *s, event_t *e)
             addr = (c_sockaddr_t *)event_get_param2(e);
             d_assert(addr, break, "Null param");
 
+#ifdef NO_FD_LOCK
+            enb = mme_enb_find_by_addr(addr);
+#else
+#error do not use lock in socket fd
             /* 
              * <Connection Refused>
              * if socket type is SOCK_STREAM,
@@ -132,6 +136,7 @@ void mme_state_operational(fsm_t *s, event_t *e)
                 enb = mme_enb_find_by_sock(sock);
             else
                 enb = mme_enb_find_by_addr(addr);
+#endif
             core_free(addr);
 
             if (enb)
diff --git a/src/mme/s1ap_sctp.c b/src/mme/s1ap_sctp.c
index 50b5e6a18..492b78637 100644
--- a/src/mme/s1ap_sctp.c
+++ b/src/mme/s1ap_sctp.c
@@ -161,8 +161,14 @@ int s1ap_recv_handler(sock_id sock, void *data)
             event_set(&e, MME_EVT_S1AP_LO_CONNREFUSED);
             event_set_param1(&e, (c_uintptr_t)sock);
             event_set_param2(&e, (c_uintptr_t)addr);
+#ifdef NO_FD_LOCK
+            sock_delete(sock);
+#else
+#error do not use lock in socket fd
+#endif
             if (mme_event_send(&e) != CORE_OK)
             {
+                d_error("Event MME_EVT_S1AP_LO_CONNREFUSED failed");
                 core_free(addr);
             }