diff --git a/conev.h b/conev.h
index 8e99c65..31c6fd1 100644
--- a/conev.h
+++ b/conev.h
@@ -77,6 +77,7 @@ struct eval {
     ssize_t round_sent;
     unsigned int round_count;
     int attempt;
+    unsigned int part_sent;
     bool cache;
     bool mark; //
 };
diff --git a/desync.c b/desync.c
index 7bc4140..f2b32e2 100644
--- a/desync.c
+++ b/desync.c
@@ -521,7 +521,7 @@ static void tamp(char *buffer, size_t bfsize, ssize_t *n,
 
 
 ssize_t desync(struct poolhd *pool, 
-        struct eval *val, struct buffer *buff, ssize_t *np)
+        struct eval *val, struct buffer *buff, ssize_t *np, bool *wait)
 {
     struct desync_params dp = params.dp[val->pair->attempt];
     struct proto_info info = { 0 };
@@ -531,6 +531,7 @@ ssize_t desync(struct poolhd *pool,
     size_t bfsize = buff->size;
     ssize_t offset = buff->offset;
     ssize_t skip = val->pair->round_sent;
+    unsigned int part_skip = val->pair->part_sent;
     
     if (!skip && params.debug) {
         init_proto_info(buffer, *np, &info);
@@ -551,25 +552,37 @@ ssize_t desync(struct poolhd *pool,
     long lp = offset;
     struct part part;
     int i = 0, r = 0;
+    unsigned int curr_part = 0;
+    bool need_wait = false;
     
     for (; r > 0 || i < dp.parts_n; r--) {
         if (r <= 0) {
             part = dp.parts[i];
             r = part.r; i++;
         }
+        curr_part++;
+
         long pos = gen_offset(part.pos, part.flag, buffer, n, lp, &info);
         pos += (long )part.s * (part.r - r);
         
-        if (skip && pos <= skip && !(part.flag & OFFSET_START)) {
+        if ((skip && pos <= skip) 
+                && curr_part <= part_skip && !(part.flag & OFFSET_START)) {
             continue;
         }
-        if (offset && pos <= offset) {
+        if (offset && pos < offset) {
             continue;
         }
         if (pos < 0 || pos > n || pos < lp) {
             LOG(LOG_E, "split cancel: pos=%ld-%ld, n=%zd\n", lp, pos, n);
             break;
         }
+	
+        if (need_wait) {
+            set_timer(pool, val, params.await_int);
+            *wait = true;
+            return lp - offset;
+        }
+        
         ssize_t s = 0;
         
         if (sock_has_notsent(sfd)) {
@@ -605,9 +618,11 @@ ssize_t desync(struct poolhd *pool,
                 break;
         }
         LOG(LOG_S, "split: pos=%ld-%ld (%zd), m: %s\n", lp, pos, s, demode_str[part.m]);
-        
+        val->pair->part_sent = curr_part;
+
         if (s == ERR_WAIT) {
             set_timer(pool, val, params.await_int);
+            *wait = true;
             return lp - offset;
         }
         if (s < 0) {
@@ -615,12 +630,23 @@ ssize_t desync(struct poolhd *pool,
                 return lp - offset;
             }
             return -1;
-        } 
+        }
         else if (s != (pos - lp)) {
             LOG(LOG_E, "%zd != %ld\n", s, pos - lp);
             return lp + s - offset;
         }
         lp = pos;
+	
+        if (params.wait_send) {
+            if (lp < n) {
+                set_timer(pool, val, params.await_int);
+                *wait = true;
+                return lp - offset;
+            }
+            else {
+                need_wait = true;
+            }
+        }
     }
     // send all/rest
     if (lp < n) {
diff --git a/desync.h b/desync.h
index f6060ae..8917e83 100644
--- a/desync.h
+++ b/desync.h
@@ -12,7 +12,7 @@
     #include <sys/socket.h>
 #endif
 
-ssize_t desync(struct poolhd *pool, struct eval *val, struct buffer *buff, ssize_t *n);
+ssize_t desync(struct poolhd *pool, struct eval *val, struct buffer *buff, ssize_t *n, bool *wait);
 
 ssize_t desync_udp(int sfd, char *buffer, ssize_t n, const struct sockaddr *dst, int dp_c);
 
diff --git a/extend.c b/extend.c
index 24b18af..8f3c58d 100644
--- a/extend.c
+++ b/extend.c
@@ -173,6 +173,7 @@ static int reconnect(struct poolhd *pool, struct eval *val, int m)
     
     client->buff->offset = 0;
     client->round_sent = 0;
+    client->part_sent = 0;
     return 0;
 }
 
@@ -404,7 +405,7 @@ static int cancel_setup(struct eval *remote)
 
 
 ssize_t tcp_send_hook(struct poolhd *pool, 
-        struct eval *remote, struct buffer *buff, ssize_t *n)
+        struct eval *remote, struct buffer *buff, ssize_t *n, bool *wait)
 {
     ssize_t sn = -1;
     int skip = remote->flag != FLAG_CONN; 
@@ -423,7 +424,7 @@ ssize_t tcp_send_hook(struct poolhd *pool,
         }
         else {
             LOG(LOG_S, "desync TCP: group=%d, round=%d, fd=%d\n", m, r, remote->fd);
-            sn = desync(pool, remote, buff, n);
+            sn = desync(pool, remote, buff, n, wait);
         }
     }
     if (skip) {
@@ -467,6 +468,7 @@ ssize_t tcp_recv_hook(struct poolhd *pool,
     if (val->round_sent == 0) {
         val->round_count++;
         val->pair->round_sent = 0;
+        val->pair->part_sent = 0;
     }
     if (val->flag == FLAG_CONN && !val->round_sent) {
         int *nr = params.dp[val->pair->attempt].rounds;
diff --git a/extend.h b/extend.h
index ed8a0e8..8e9fecb 100644
--- a/extend.h
+++ b/extend.h
@@ -11,7 +11,7 @@ int connect_hook(struct poolhd *pool, struct eval *val,
         const union sockaddr_u *dst, evcb_t next);
         
 ssize_t tcp_send_hook(struct poolhd *pool, 
-        struct eval *remote, struct buffer *buff, ssize_t *n);
+        struct eval *remote, struct buffer *buff, ssize_t *n, bool *wait);
         
 ssize_t tcp_recv_hook(struct poolhd *pool, 
         struct eval *val, struct buffer *buff);
diff --git a/main.c b/main.c
index 5d97f80..bdc357a 100644
--- a/main.c
+++ b/main.c
@@ -178,6 +178,7 @@ const struct option options[] = {
     {"tlsrec",        1, 0, 'r'},
     {"udp-fake",      1, 0, 'a'},
     {"def-ttl",       1, 0, 'g'},
+    {"wait-send",     0, 0, 'Z'}, //
     {"await-int",     1, 0, 'W'}, //
     #ifdef __linux__
     {"drop-sack",     0, 0, 'Y'},
@@ -1067,6 +1068,10 @@ int main(int argc, char **argv)
             dp->drop_sack = 1;
             break;
         
+        case 'Z':
+            params.wait_send = 1;
+            break;
+        
         case 'W':
             params.await_int = atoi(optarg);
             break;
diff --git a/params.h b/params.h
index 088f5b3..23fba1e 100644
--- a/params.h
+++ b/params.h
@@ -102,6 +102,7 @@ struct params {
     int dp_count;
     struct desync_params *dp;
     int await_int;
+    bool wait_send;
     int def_ttl;
     bool custom_ttl;
     
diff --git a/proxy.c b/proxy.c
index 68512ce..421f1c4 100644
--- a/proxy.c
+++ b/proxy.c
@@ -662,12 +662,13 @@ int on_tunnel(struct poolhd *pool, struct eval *val, int etype)
         }
         n = val->buff->lock - val->buff->offset;
         
-        ssize_t sn = tcp_send_hook(pool, pair, val->buff, &val->buff->lock);
+        bool wait = false;
+        ssize_t sn = tcp_send_hook(pool, pair, val->buff, &val->buff->lock, &wait);
         if (sn < 0) {
             uniperror("send");
             return -1;
         }
-        if (sn < n) {
+        if (sn < n || wait) {
             val->buff->offset += sn;
             return 0;
         }
@@ -694,19 +695,26 @@ int on_tunnel(struct poolhd *pool, struct eval *val, int etype)
         if (n < 0) {
             return -1;
         }
-        ssize_t sn = tcp_send_hook(pool, pair, buff, &n);
+        
+        bool wait = false;
+        ssize_t sn = tcp_send_hook(pool, pair, buff, &n, &wait);
         if (sn < 0) {
             uniperror("send");
             return -1;
         }
-        if (sn < n) {
-            LOG(LOG_S, "send: %zd != %zd (fd=%d)\n", sn, n, pair->fd);
+        if (sn < n || wait) {
+            if (sn < n) {
+                LOG(LOG_S, "send: %zd != %zd (fd=%d)\n", sn, n, pair->fd);
+            }
+            else {
+                LOG(LOG_S, "send: %zd, but not done yet (fd=%d)\n", sn, pair->fd);
+            }
             
             buff->lock = n;
             buff->offset = sn;
             
             if (mod_etype(pool, val, 0) ||
-                    mod_etype(pool, pair, !pair->tv_ms ? POLLOUT : 0)) {
+                    mod_etype(pool, pair, !wait ? POLLOUT : 0)) {
                 uniperror("mod_etype");
                 return -1;
             }