diff --git a/src/transport_layer/etcp_connections.c b/src/transport_layer/etcp_connections.c
index d2223564..49ce37d8 100644
--- a/src/transport_layer/etcp_connections.c
+++ b/src/transport_layer/etcp_connections.c
@@ -1255,7 +1255,7 @@ int etcp_encrypt_send(struct ETCP_DGRAM* dgram) {
     int udp_ov = (dgram->link->remote_addr.ss_family == AF_INET6) ? IP_UDP_OVERHEAD_V6 : IP_UDP_OVERHEAD_V4;
     int wire_ov = udp_ov + SC_ENCRYPT_OVERHEAD;
     if (len<0 || len + (int)dgram->noencrypt_len > (int)(dgram->link->mtu - wire_ov)) { dgram->link->send_errors++; errcode=1; goto es_err; }
-    uint8_t enc_buf[PACKET_DATA_MAX_MTU];// должно вмещать mtu - udp_ov (до 2020 байт)
+    uint8_t enc_buf[PACKET_DATA_MAX_MTU];// макс запись = data_len + 32 <= mtu - wire_ov + 32 = 1468
     size_t enc_buf_len=0;
     dgram->timestamp=get_current_timestamp();
     
diff --git a/src/transport_layer/etcp_connections.h b/src/transport_layer/etcp_connections.h
index a860af19..cbcbbaba 100644
--- a/src/transport_layer/etcp_connections.h
+++ b/src/transport_layer/etcp_connections.h
@@ -28,7 +28,9 @@ extern "C" {
 #define INFLIGHT_LIM_MAX  1048576   // 1M
 
 #define PACKET_DATA_SIZE        2048
-#define PACKET_DATA_MAX_MTU     2048
+// Wire-MTU кап: пакет на проводе не должен превышать 1500 (согласовано с TUN_MAX_PACKET_SIZE).
+// PACKET_DATA_SIZE (2048) — это внутренний буфер аллокации/приёма, а не wire-MTU.
+#define PACKET_DATA_MAX_MTU     1500
 #define ETCP_MAX_PAYLOAD_SIZE   (PACKET_DATA_SIZE - ETCP_ACK_BASE_SIZE - 5) /* 2035 */
 #define ETCP_RFC791_MIN_MTU     576
 
diff --git a/tests/test_etcp_link_stress.c b/tests/test_etcp_link_stress.c
index 3e00e6c5..6f6934ff 100644
--- a/tests/test_etcp_link_stress.c
+++ b/tests/test_etcp_link_stress.c
@@ -256,6 +256,20 @@ static int run_traffic(int n, uint64_t timeout_ms) {
     }
 }
 
+// Проверяет, что конкретный линк (по серверному порту) реально перенёс данные.
+// Линк может пропустить короткий burst из-за keepalive-стабилизации link_status,
+// поэтому повторяем до нескольких keepalive-тиков. Возвращает 0 если линк нёс трафик.
+static int check_link_traffic(uint16_t srv_port, const char* label) {
+    for (int attempt = 0; attempt < 6; attempt++) {
+        uint64_t before = client_link_acked(srv_port);
+        if (run_traffic(TRAFFIC_PACKETS, TRAFFIC_TIMEOUT_MS) != 0) return -1;
+        if (client_link_acked(srv_port) > before) return 0;
+        uasync_poll(ua, 50);
+    }
+    printf("    [%s] link never carried traffic\n", label);
+    return -1;
+}
+
 // ===== instance lifecycle =====
 
 static int start_instances(void) {
@@ -306,9 +320,7 @@ static int session_a(void) {
 
     // -- per-link трафик на исходном линке --
     printf("[A] traffic on initial link...\n");
-    uint64_t ack0 = client_link_acked(server_port);
-    CHECK(run_traffic(TRAFFIC_PACKETS, TRAFFIC_TIMEOUT_MS) == 0, "initial traffic failed");
-    CHECK(client_link_acked(server_port) > ack0, "initial link carried no traffic");
+    CHECK(check_link_traffic(server_port, "initial") == 0, "initial link carried no traffic");
     CHECK(sc->reinit_count == srv_reinit0 && cc->reinit_count == cli_reinit0, "reinit during initial traffic");
 
     // -- V1: клиент дозванивается до нового серверного сокета S1 --
@@ -324,9 +336,7 @@ static int session_a(void) {
     g_sock = s1;
     CHECK(poll_until(c_socket_link_up, LINK_UP_TIMEOUT_MS, "V1 link up (server)") == 0, "V1 server link did not come up");
     CHECK(sc->reinit_count == srv_reinit0 && cc->reinit_count == cli_reinit0, "reinit during V1");
-    ack0 = client_link_acked(sp1);
-    CHECK(run_traffic(TRAFFIC_PACKETS, TRAFFIC_TIMEOUT_MS) == 0, "V1 traffic failed");
-    CHECK(client_link_acked(sp1) > ack0, "V1 link carried no traffic");
+    CHECK(check_link_traffic(sp1, "V1") == 0, "V1 link carried no traffic");
 
     // -- V2: сервер дозванивается до клиента --
     int sp2 = alloc_port();
@@ -341,9 +351,7 @@ static int session_a(void) {
     g_conn = cc; g_port = sp2;
     CHECK(poll_until(c_link_on_port_up, LINK_UP_TIMEOUT_MS, "V2 link up (client)") == 0, "V2 client link did not come up");
     CHECK(sc->reinit_count == srv_reinit0 && cc->reinit_count == cli_reinit0, "reinit during V2");
-    ack0 = client_link_acked(sp2);
-    CHECK(run_traffic(TRAFFIC_PACKETS, TRAFFIC_TIMEOUT_MS) == 0, "V2 traffic failed");
-    CHECK(client_link_acked(sp2) > ack0, "V2 link carried no traffic");
+    CHECK(check_link_traffic(sp2, "V2") == 0, "V2 link carried no traffic");
 
     printf("[A] after adds: server links_up=%d/%d client links_up=%d/%d\n",
            count_links_up(sc), count_links(sc), count_links_up(cc), count_links(cc));