diff --git a/include/patty/ax25/sock.h b/include/patty/ax25/sock.h
index 0caf556..75f41c8 100644
--- a/include/patty/ax25/sock.h
+++ b/include/patty/ax25/sock.h
@@ -234,7 +234,9 @@ ssize_t patty_ax25_sock_recv_pending(patty_ax25_sock *sock);
 
 ssize_t patty_ax25_sock_resend(patty_ax25_sock *sock, int seq);
 
-void patty_ax25_sock_ack(patty_ax25_sock *sock, int seq);
+int patty_ax25_sock_ack(patty_ax25_sock *sock, int seq);
+
+int patty_ax25_sock_ack_pending(patty_ax25_sock *sock);
 
 ssize_t patty_ax25_sock_send_rr(patty_ax25_sock *sock,
                                 enum patty_ax25_frame_cr cr,
diff --git a/src/server.c b/src/server.c
index 8b858df..9b3b55a 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1503,6 +1503,17 @@ static int handle_i(patty_ax25_server *server,
 
     patty_ax25_sock_ack(sock, frame->nr - 1);
 
+    if (patty_ax25_sock_ack_pending(sock) == 0) {
+        patty_timer_stop(&sock->timer_t1);
+    } else {
+        sock->retries = sock->n_retry;
+        sock->flow    = PATTY_AX25_SOCK_WAIT;
+
+        fd_clear(server, sock->fd);
+
+        patty_timer_start(&sock->timer_t1, sock->n_ack);
+    }
+
     if (frame->ns == sock->vr) {
         patty_ax25_sock_vr_incr(sock);
     } else if (frame->ns == sock->vr + 1) {
@@ -1588,6 +1599,22 @@ reply_dm:
     return reply_dm(iface, frame, PATTY_AX25_FRAME_FINAL);
 }
 
+static int frame_ack(patty_ax25_server *server,
+                     patty_ax25_sock *sock,
+                     patty_ax25_frame *frame) {
+    if (sock == NULL) {
+        return 0;
+    }
+
+    if (patty_ax25_sock_ack(sock, frame->nr - 1) > 0) {
+        patty_timer_stop(&sock->timer_t1);
+    }
+
+    if (patty_ax25_sock_ack_pending(sock) > 0) {
+        patty_timer_start(&sock->timer_t1, sock->n_ack);
+    }
+}
+
 static int handle_rr(patty_ax25_server *server,
                      patty_ax25_sock *sock,
                      patty_ax25_frame *frame) {
@@ -1595,9 +1622,13 @@ static int handle_rr(patty_ax25_server *server,
         return 0;
     }
 
-    patty_ax25_sock_ack(sock, frame->nr - 1);
+    if (patty_ax25_sock_ack(sock, frame->nr - 1) > 0) {
 
-    patty_timer_stop(&sock->timer_t1);
+    }
+
+    if (patty_ax25_sock_ack_pending(sock) == 0) {
+        patty_timer_stop(&sock->timer_t1);
+    }
 
     switch (frame->cr) {
         case PATTY_AX25_FRAME_COMMAND:
@@ -1610,11 +1641,20 @@ static int handle_rr(patty_ax25_server *server,
                 patty_ax25_sock_send_rnr(sock, PATTY_AX25_FRAME_RESPONSE, 1);
 
         case PATTY_AX25_FRAME_RESPONSE:
-            sock->retries = sock->n_retry;
+            if (patty_ax25_sock_ack_pending(sock) == 0) {
+                sock->retries = sock->n_retry;
 
-            fd_watch(server, sock->fd);
+                fd_watch(server, sock->fd);
 
-            patty_timer_start(&sock->timer_t3, PATTY_AX25_SOCK_DEFAULT_KEEPALIVE);
+                patty_timer_start(&sock->timer_t3, PATTY_AX25_SOCK_DEFAULT_KEEPALIVE);
+            } else {
+                sock->retries = sock->n_retry;
+                sock->flow    = PATTY_AX25_SOCK_WAIT;
+
+                fd_clear(server, sock->fd);
+
+                patty_timer_start(&sock->timer_t1, sock->n_ack);
+            }
 
         default:
             break;
@@ -1630,17 +1670,19 @@ static int handle_rnr(patty_ax25_server *server,
         return 0;
     }
 
-    patty_timer_stop(&sock->timer_t1);
-
     patty_ax25_sock_ack(sock, frame->nr - 1);
 
+    if (patty_ax25_sock_ack_pending(sock) == 0) {
+        patty_timer_stop(&sock->timer_t1);
+    }
+
     switch (frame->cr) {
         case PATTY_AX25_FRAME_COMMAND:
             if (frame->pf == 0) {
                 break;
             }
 
-            return FD_ISSET(sock->fd, &server->fds_watch)?
+            return sock->flow == PATTY_AX25_SOCK_READY?
                 patty_ax25_sock_send_rr(sock, PATTY_AX25_FRAME_RESPONSE, 1):
                 patty_ax25_sock_send_rnr(sock, PATTY_AX25_FRAME_RESPONSE, 1);
 
@@ -1650,7 +1692,11 @@ static int handle_rnr(patty_ax25_server *server,
 
             fd_clear(server, sock->fd);
 
-            patty_timer_start(&sock->timer_t3, PATTY_AX25_SOCK_DEFAULT_KEEPALIVE);
+            if (patty_ax25_sock_ack_pending(sock) == 0) {
+                patty_timer_start(&sock->timer_t3, PATTY_AX25_SOCK_DEFAULT_KEEPALIVE);
+            } else {
+                patty_timer_start(&sock->timer_t1, sock->n_ack);
+            }
 
         default:
             break;
diff --git a/src/sock.c b/src/sock.c
index e8a8579..666d014 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -71,8 +71,7 @@ static inline int tx_seq(patty_ax25_sock *sock, int seq) {
 }
 
 static inline struct slot *tx_slot(patty_ax25_sock *sock, int seq) {
-    size_t win = sock->n_window_tx,
-             i = tx_seq(sock, seq) % win;
+    int i = tx_seq(sock, seq) % sock->n_window_tx;
 
     return (struct slot *)
         ((uint8_t *)sock->tx_slots + (i * tx_slot_size(sock)));
@@ -653,17 +652,19 @@ static ssize_t frame_send(patty_ax25_sock *sock,
 
     if (info && infolen) {
         if (PATTY_AX25_FRAME_CONTROL_I(control)) {
-            struct slot *slot = tx_slot(sock, sock->vs);
-
             buf[offset++] = proto;
-
-            slot->len = offset;
-            slot->ack = 0;
         }
 
         memcpy(buf + offset, info, infolen);
 
         offset += infolen;
+
+        if (PATTY_AX25_FRAME_CONTROL_I(control)) {
+            struct slot *slot = tx_slot(sock, sock->vs);
+
+            slot->len = offset;
+            slot->ack = 0;
+        }
     }
 
     return patty_ax25_if_send(sock->iface, buf, offset);
@@ -682,18 +683,37 @@ ssize_t patty_ax25_sock_resend(patty_ax25_sock *sock, int seq) {
     return slot->len > 0? patty_ax25_if_send(sock->iface, buf, slot->len): 0;
 }
 
-void patty_ax25_sock_ack(patty_ax25_sock *sock, int seq) {
-    int i;
+int patty_ax25_sock_ack(patty_ax25_sock *sock, int seq) {
+    int ret = 0,
+        i;
 
     for (i=0; i<sock->n_window_tx; i++) {
         struct slot *slot = tx_slot(sock, seq - i);
 
         if (slot->len > 0) {
             slot->ack = 1;
+            ret++;
         }
     }
 
     sock->va = seq;
+
+    return ret;
+}
+
+int patty_ax25_sock_ack_pending(patty_ax25_sock *sock) {
+    int ret = 0,
+        i;
+
+    for (i=0; i<sock->n_window_tx; i++) {
+        struct slot *slot = tx_slot(sock, i);
+
+        if (slot->len > 0 && slot->ack == 0) {
+            ret++;
+        }
+    }
+
+    return ret;
 }
 
 static uint16_t control_i(patty_ax25_sock *sock, int flag) {