diff --git a/src/Dispatcher.cpp b/src/Dispatcher.cpp
index ae225d36..cd7090d1 100644
--- a/src/Dispatcher.cpp
+++ b/src/Dispatcher.cpp
@@ -101,6 +101,12 @@ void Dispatcher::checkRecv() {
 #endif
 
         pkt->header = raw[i++];
+        if (pkt->hasTransCodes()) {
+          memcpy(&pkt->trans_codes[0], &raw[i], 2); i += 2;
+          memcpy(&pkt->trans_codes[1], &raw[i], 2); i += 2;
+        } else {
+          pkt->trans_codes[0] = pkt->trans_codes[1] = 0;
+        }
         pkt->path_len = raw[i++];
 
         if (pkt->path_len > MAX_PATH_SIZE || i + pkt->path_len > len) {
@@ -132,7 +138,7 @@ void Dispatcher::checkRecv() {
     #if MESH_PACKET_LOGGING
     Serial.print(getLogDateTime());
     Serial.printf(": RX, len=%d (type=%d, route=%s, payload_len=%d) SNR=%d RSSI=%d score=%d", 
-            2 + pkt->path_len + pkt->payload_len, pkt->getPayloadType(), pkt->isRouteDirect() ? "D" : "F", pkt->payload_len,
+            pkt->getRawLength(), pkt->getPayloadType(), pkt->isRouteDirect() ? "D" : "F", pkt->payload_len,
             (int)pkt->getSNR(), (int)_radio->getLastRSSI(), (int)(score*1000));
 
     static uint8_t packet_hash[MAX_HASH_SIZE];
@@ -147,7 +153,7 @@ void Dispatcher::checkRecv() {
       Serial.printf("\n");
     }
     #endif
-    logRx(pkt, 2 + pkt->path_len + pkt->payload_len, score);   // hook for custom logging
+    logRx(pkt, pkt->getRawLength(), score);   // hook for custom logging
 
     if (pkt->isRouteFlood()) {
       n_recv_flood++;
@@ -212,6 +218,10 @@ void Dispatcher::checkSend() {
     raw[len++] = NODE_ID;
 #endif
     raw[len++] = outbound->header;
+    if (outbound->hasTransCodes()) {
+      memcpy(&raw[len], &outbound->trans_codes[0], 2); len += 2;
+      memcpy(&raw[len], &outbound->trans_codes[1], 2); len += 2;
+    }
     raw[len++] = outbound->path_len;
     memcpy(&raw[len], outbound->path, outbound->path_len); len += outbound->path_len;
 
diff --git a/src/Mesh.cpp b/src/Mesh.cpp
index 0a0fd769..fe3b2473 100644
--- a/src/Mesh.cpp
+++ b/src/Mesh.cpp
@@ -15,7 +15,7 @@ bool Mesh::allowPacketForward(const mesh::Packet* packet) {
   return false;  // by default, Transport NOT enabled
 }
 uint32_t Mesh::getRetransmitDelay(const mesh::Packet* packet) { 
-  uint32_t t = (_radio->getEstAirtimeFor(packet->path_len + packet->payload_len + 2) * 52 / 50) / 2;
+  uint32_t t = (_radio->getEstAirtimeFor(packet->getRawLength()) * 52 / 50) / 2;
 
   return _rng->nextInt(0, 5)*t;
 }
diff --git a/src/Packet.cpp b/src/Packet.cpp
index e338b60d..386585fc 100644
--- a/src/Packet.cpp
+++ b/src/Packet.cpp
@@ -10,6 +10,10 @@ Packet::Packet() {
   payload_len = 0;
 }
 
+int Packet::getRawLength() const {
+  return 2 + path_len + payload_len + (hasTransCodes() ? 4 : 0);
+}
+
 void Packet::calculatePacketHash(uint8_t* hash) const {
   SHA256 sha;
   uint8_t t = getPayloadType();
@@ -24,6 +28,10 @@ void Packet::calculatePacketHash(uint8_t* hash) const {
 uint8_t Packet::writeTo(uint8_t dest[]) const {
   uint8_t i = 0;
   dest[i++] = header;
+  if (hasTransCodes()) {
+    memcpy(&dest[i], &trans_codes[0], 2); i += 2;
+    memcpy(&dest[i], &trans_codes[1], 2); i += 2;
+  }
   dest[i++] = path_len;
   memcpy(&dest[i], path, path_len); i += path_len;
   memcpy(&dest[i], payload, payload_len); i += payload_len;
@@ -33,6 +41,12 @@ uint8_t Packet::writeTo(uint8_t dest[]) const {
 bool Packet::readFrom(const uint8_t src[], uint8_t len) {
   uint8_t i = 0;
   header = src[i++];
+  if (hasTransCodes()) {
+    memcpy(&trans_codes[0], &src[i], 2); i += 2;
+    memcpy(&trans_codes[1], &src[i], 2); i += 2;
+  } else {
+    trans_codes[0] = trans_codes[1] = 0;
+  }
   path_len = src[i++];
   if (path_len > sizeof(path)) return false;   // bad encoding
   memcpy(path, &src[i], path_len); i += path_len;
diff --git a/src/Packet.h b/src/Packet.h
index e20b3a49..dfd61da8 100644
--- a/src/Packet.h
+++ b/src/Packet.h
@@ -11,10 +11,10 @@ namespace mesh {
 #define PH_VER_SHIFT         6
 #define PH_VER_MASK       0x03   // 2-bits
 
-#define ROUTE_TYPE_RESERVED1     0x00    // FUTURE
+#define ROUTE_TYPE_TRANS_FLOOD   0x00    // flood mode + transport codes
 #define ROUTE_TYPE_FLOOD         0x01    // flood mode, needs 'path' to be built up (max 64 bytes)
 #define ROUTE_TYPE_DIRECT        0x02    // direct route, 'path' is supplied
-#define ROUTE_TYPE_RESERVED2     0x03    // FUTURE
+#define ROUTE_TYPE_TRANS_DIRECT  0x03    // direct route + transport codes
 
 #define PAYLOAD_TYPE_REQ         0x00    // request (prefixed with dest/src hashes, MAC) (enc data: timestamp, blob)
 #define PAYLOAD_TYPE_RESPONSE    0x01    // response to REQ or ANON_REQ (prefixed with dest/src hashes, MAC) (enc data: timestamp, blob)
@@ -43,6 +43,7 @@ public:
 
   uint8_t header;
   uint16_t payload_len, path_len;
+  uint16_t trans_codes[2];
   uint8_t path[MAX_PATH_SIZE];
   uint8_t payload[MAX_PACKET_PAYLOAD];
   int8_t _snr;
@@ -58,8 +59,10 @@ public:
    */
   uint8_t getRouteType() const { return header & PH_ROUTE_MASK; }
 
-  bool isRouteFlood() const { return getRouteType() == ROUTE_TYPE_FLOOD; }
-  bool isRouteDirect() const { return getRouteType() == ROUTE_TYPE_DIRECT; }
+  bool isRouteFlood() const { return getRouteType() == ROUTE_TYPE_FLOOD || getRouteType() == ROUTE_TYPE_TRANS_FLOOD; }
+  bool isRouteDirect() const { return getRouteType() == ROUTE_TYPE_DIRECT || getRouteType() == ROUTE_TYPE_TRANS_DIRECT; }
+
+  bool hasTransCodes() const { return getRouteType() == ROUTE_TYPE_TRANS_FLOOD || getRouteType() == ROUTE_TYPE_TRANS_DIRECT; }
 
   /**
    * \returns  one of PAYLOAD_TYPE_ values
@@ -76,6 +79,11 @@ public:
 
   float getSNR() const { return ((float)_snr) / 4.0f; }
 
+  /**
+   * \returns  the encoded/wire format length of this packet
+   */
+  int getRawLength() const;
+
   /**
    * \brief  save entire packet as a blob
    * \param dest  (OUT) destination buffer (assumed to be MAX_MTU_SIZE)
diff --git a/src/helpers/BaseChatMesh.cpp b/src/helpers/BaseChatMesh.cpp
index 083a0629..989fcb2c 100644
--- a/src/helpers/BaseChatMesh.cpp
+++ b/src/helpers/BaseChatMesh.cpp
@@ -252,7 +252,7 @@ int  BaseChatMesh::sendMessage(const ContactInfo& recipient, uint32_t timestamp,
   mesh::Packet* pkt = composeMsgPacket(recipient, timestamp, attempt, text, expected_ack);
   if (pkt == NULL) return MSG_SEND_FAILED;
 
-  uint32_t t = _radio->getEstAirtimeFor(pkt->payload_len + pkt->path_len + 2);
+  uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
 
   int rc;
   if (recipient.out_path_len < 0) {
@@ -279,7 +279,7 @@ int  BaseChatMesh::sendCommandData(const ContactInfo& recipient, uint32_t timest
   auto pkt = createDatagram(PAYLOAD_TYPE_TXT_MSG, recipient.id, recipient.shared_secret, temp, 5 + text_len);
   if (pkt == NULL) return MSG_SEND_FAILED;
 
-  uint32_t t = _radio->getEstAirtimeFor(pkt->payload_len + pkt->path_len + 2);
+  uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
   int rc;
   if (recipient.out_path_len < 0) {
     sendFlood(pkt);
@@ -362,7 +362,7 @@ int BaseChatMesh::sendLogin(const ContactInfo& recipient, const char* password,
 
   auto pkt = createAnonDatagram(PAYLOAD_TYPE_ANON_REQ, self_id, recipient.id, recipient.shared_secret, temp, tlen);
   if (pkt) {
-    uint32_t t = _radio->getEstAirtimeFor(pkt->payload_len + pkt->path_len + 2);
+    uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
     if (recipient.out_path_len < 0) {
       sendFlood(pkt);
       est_timeout = calcFloodTimeoutMillisFor(t);
@@ -386,7 +386,7 @@ int  BaseChatMesh::sendStatusRequest(const ContactInfo& recipient, uint32_t& est
 
   auto pkt = createDatagram(PAYLOAD_TYPE_REQ, recipient.id, recipient.shared_secret, temp, sizeof(temp));
   if (pkt) {
-    uint32_t t = _radio->getEstAirtimeFor(pkt->payload_len + pkt->path_len + 2);
+    uint32_t t = _radio->getEstAirtimeFor(pkt->getRawLength());
     if (recipient.out_path_len < 0) {
       sendFlood(pkt);
       est_timeout = calcFloodTimeoutMillisFor(t);