--- a/src/event/quic/ngx_event_quic_output.c
+++ b/src/event/quic/ngx_event_quic_output.c
@@ -844,7 +844,7 @@ ngx_quic_send_stateless_reset(ngx_connec
 ngx_int_t
 ngx_quic_send_cc(ngx_connection_t *c)
 {
-    ngx_quic_frame_t        frame;
+    ngx_quic_frame_t       *frame;
     ngx_quic_connection_t  *qc;
 
     qc = ngx_quic_get_connection(c);
@@ -860,22 +860,27 @@ ngx_quic_send_cc(ngx_connection_t *c)
         return NGX_OK;
     }
 
-    ngx_memzero(&frame, sizeof(ngx_quic_frame_t));
+    frame = ngx_quic_alloc_frame(c);
+    if (frame == NULL) {
+        return NGX_ERROR;
+    }
 
-    frame.level = qc->error_level;
-    frame.type = qc->error_app ? NGX_QUIC_FT_CONNECTION_CLOSE_APP
-                               : NGX_QUIC_FT_CONNECTION_CLOSE;
-    frame.u.close.error_code = qc->error;
-    frame.u.close.frame_type = qc->error_ftype;
+    frame->level = qc->error_level;
+    frame->type = qc->error_app ? NGX_QUIC_FT_CONNECTION_CLOSE_APP
+                                : NGX_QUIC_FT_CONNECTION_CLOSE;
+    frame->u.close.error_code = qc->error;
+    frame->u.close.frame_type = qc->error_ftype;
 
     if (qc->error_reason) {
-        frame.u.close.reason.len = ngx_strlen(qc->error_reason);
-        frame.u.close.reason.data = (u_char *) qc->error_reason;
+        frame->u.close.reason.len = ngx_strlen(qc->error_reason);
+        frame->u.close.reason.data = (u_char *) qc->error_reason;
     }
 
+    frame->ignore_congestion = 1;
+
     qc->last_cc = ngx_current_msec;
 
-    return ngx_quic_frame_sendto(c, &frame, 0, qc->path);
+    return ngx_quic_frame_sendto(c, frame, 0, qc->path);
 }
 
 
@@ -1184,22 +1189,32 @@ ngx_quic_frame_sendto(ngx_connection_t *
     size_t                  max, max_payload, min_payload, pad;
     ssize_t                 len, sent;
     ngx_str_t               res;
+    ngx_msec_t              now;
     ngx_quic_header_t       pkt;
     ngx_quic_send_ctx_t    *ctx;
+    ngx_quic_congestion_t  *cg;
     ngx_quic_connection_t  *qc;
 
     static u_char           src[NGX_QUIC_MAX_UDP_PAYLOAD_SIZE];
     static u_char           dst[NGX_QUIC_MAX_UDP_PAYLOAD_SIZE];
 
     qc = ngx_quic_get_connection(c);
+    cg = &qc->congestion;
     ctx = ngx_quic_get_send_ctx(qc, frame->level);
 
+    now = ngx_current_msec;
+
     max = ngx_quic_path_limit(c, path, path->mtu);
 
     ngx_log_debug3(NGX_LOG_DEBUG_EVENT, c->log, 0,
                    "quic sendto %s packet max:%uz min:%uz",
                    ngx_quic_level_name(ctx->level), max, min);
 
+    if (cg->in_flight >= cg->window && !frame->ignore_congestion) {
+        ngx_quic_free_frame(c, frame);
+        return NGX_AGAIN;
+    }
+
     ngx_quic_init_packet(c, ctx, &pkt, path);
 
     min_payload = ngx_quic_payload_size(&pkt, min);
@@ -1210,6 +1225,7 @@ ngx_quic_frame_sendto(ngx_connection_t *
     min_payload = ngx_max(min_payload, pad);
 
     if (min_payload > max_payload) {
+        ngx_quic_free_frame(c, frame);
         return NGX_AGAIN;
     }
 
@@ -1221,11 +1237,13 @@ ngx_quic_frame_sendto(ngx_connection_t *
 
     len = ngx_quic_create_frame(NULL, frame);
     if ((size_t) len > max_payload) {
+        ngx_quic_free_frame(c, frame);
         return NGX_AGAIN;
     }
 
     len = ngx_quic_create_frame(src, frame);
     if (len == -1) {
+        ngx_quic_free_frame(c, frame);
         return NGX_ERROR;
     }
 
@@ -1242,18 +1260,45 @@ ngx_quic_frame_sendto(ngx_connection_t *
     ngx_quic_log_packet(c->log, &pkt);
 
     if (ngx_quic_encrypt(&pkt, &res) != NGX_OK) {
+        ngx_quic_free_frame(c, frame);
         return NGX_ERROR;
     }
 
+    frame->pnum = ctx->pnum;
+    frame->first = now;
+    frame->last = now;
+    frame->plen = res.len;
+
     ctx->pnum++;
 
     sent = ngx_quic_send(c, res.data, res.len, path->sockaddr, path->socklen);
     if (sent < 0) {
+        ngx_quic_free_frame(c, frame);
         return sent;
     }
 
     path->sent += sent;
 
+    if (frame->need_ack && !qc->closing) {
+        ngx_queue_insert_tail(&ctx->sent, &frame->queue);
+
+        cg->in_flight += frame->plen;
+
+    } else {
+        ngx_quic_free_frame(c, frame);
+        return NGX_OK;
+    }
+
+    ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0,
+                   "quic congestion send if:%uz", cg->in_flight);
+
+    if (!qc->send_timer_set) {
+        qc->send_timer_set = 1;
+        ngx_add_timer(c->read, qc->tp.max_idle_timeout);
+    }
+
+    ngx_quic_set_lost_timer(c);
+
     return NGX_OK;
 }