diff --git a/scapy/layers/ipsec.py b/scapy/layers/ipsec.py
index f8c601fa..f566d288 100644
--- a/scapy/layers/ipsec.py
+++ b/scapy/layers/ipsec.py
@@ -138,6 +138,7 @@ bind_layers(IP, ESP, proto=socket.IPPROTO_ESP)
 bind_layers(IPv6, ESP, nh=socket.IPPROTO_ESP)
 bind_layers(UDP, ESP, dport=4500)  # NAT-Traversal encapsulation
 bind_layers(UDP, ESP, sport=4500)  # NAT-Traversal encapsulation
+bind_layers(UDP, ESP, dport=4545)  # NAT-Traversal encapsulation - random port
 
 ###############################################################################

@@ -359,11 +359,8 @@ class CryptAlgo(object):
             encryptor = cipher.encryptor()
 
             if self.is_aead:
-                if esn_en:
-                    aad = struct.pack('!LLL', esp.spi, esn, esp.seq)
-                else:
-                    aad = struct.pack('!LL', esp.spi, esp.seq)
-                encryptor.authenticate_additional_data(aad)
+                encryptor.authenticate_additional_data(sa.build_aead(esp))
+
                 data = encryptor.update(data) + encryptor.finalize()
                 data += encryptor.tag[:self.icv_size]
             else:
@@ -401,12 +398,7 @@ class CryptAlgo(object):
 
             if self.is_aead:
                 # Tag value check is done during the finalize method
-                if esn_en:
-                    decryptor.authenticate_additional_data(
-                        struct.pack('!LLL', esp.spi, esn, esp.seq))
-                else:
-                    decryptor.authenticate_additional_data(
-                        struct.pack('!LL', esp.spi, esp.seq))
+                decryptor.authenticate_additional_data(sa.build_aead(esp))
             try:
                 data = decryptor.update(data) + decryptor.finalize()
             except InvalidTag as err:
@@ -545,7 +537,7 @@ class AuthAlgo(object):
         else:
             return self.mac(key, self.digestmod(), default_backend())
 
-    def sign(self, pkt, key):
+    def sign(self, pkt, key, trailer=None):
         """
         Sign an IPsec (ESP or AH) packet with this algo.
 
@@ -561,16 +553,20 @@ class AuthAlgo(object):
 
         if pkt.haslayer(ESP):
             mac.update(raw(pkt[ESP]))
+            if trailer:
+                mac.update(trailer)
             pkt[ESP].data += mac.finalize()[:self.icv_size]
 
         elif pkt.haslayer(AH):
             clone = zero_mutable_fields(pkt.copy(), sending=True)
             mac.update(raw(clone))
+            if trailer:
+                mac.update(trailer)
             pkt[AH].icv = mac.finalize()[:self.icv_size]
 
         return pkt
 
-    def verify(self, pkt, key):
+    def verify(self, pkt, key, trailer):
         """
         Check that the integrity check value (icv) of a packet is valid.
 
@@ -602,6 +598,8 @@ class AuthAlgo(object):
             clone = zero_mutable_fields(pkt.copy(), sending=False)
 
         mac.update(raw(clone))
+        if trailer:
+            mac.update(trailer) # bytearray(4)) #raw(trailer))
         computed_icv = mac.finalize()[:self.icv_size]
 
         # XXX: Cannot use mac.verify because the ICV can be truncated
@@ -864,6 +862,23 @@ class SecurityAssociation(object):
                 raise TypeError('nat_t_header must be %s' % UDP.name)
         self.nat_t_header = nat_t_header
 
+    def build_aead(self, esp):
+        if self.esn_en:
+            return (struct.pack('!LLL', esp.spi, self.seq_num >> 32, esp.seq))
+        else:
+            return (struct.pack('!LL', esp.spi, esp.seq))
+
+    def build_seq_num(self, num):
+        # only lower order bits are  transmitted
+        # higher order bits are used in the ICV
+        lower = num & 0xffffffff
+        upper = num >> 32
+
+        if self.esn_en:
+            return lower, struct.pack("!I", upper)
+        else:
+            return lower, None
+
     def check_spi(self, pkt):
         if pkt.spi != self.spi:
             raise TypeError('packet spi=0x%x does not match the SA spi=0x%x' %
@@ -877,7 +892,8 @@ class SecurityAssociation(object):
             if len(iv) != self.crypt_algo.iv_size:
                 raise TypeError('iv length must be %s' % self.crypt_algo.iv_size)  # noqa: E501
 
-        esp = _ESPPlain(spi=self.spi, seq=seq_num or self.seq_num, iv=iv)
+        low_seq_num, high_seq_num = self.build_seq_num(seq_num or self.seq_num)
+        esp = _ESPPlain(spi=self.spi, seq=low_seq_num, iv=iv)
 
         if self.tunnel_header:
             tunnel = self.tunnel_header.copy()
@@ -901,7 +917,7 @@ class SecurityAssociation(object):
                                       esn_en=esn_en or self.esn_en,
                                       esn=esn or self.esn)
 
-        self.auth_algo.sign(esp, self.auth_key)
+        self.auth_algo.sign(esp, self.auth_key, high_seq_num)
 
         if self.nat_t_header:
             nat_t_header = self.nat_t_header.copy()
@@ -928,7 +944,8 @@ class SecurityAssociation(object):
 
     def _encrypt_ah(self, pkt, seq_num=None):
 
-        ah = AH(spi=self.spi, seq=seq_num or self.seq_num,
+        low_seq_num, high_seq_num = self.build_seq_num(seq_num or self.seq_num)
+        ah = AH(spi=self.spi, seq=low_seq_num,
                 icv=b"\x00" * self.auth_algo.icv_size)
 
         if self.tunnel_header:
@@ -968,7 +985,8 @@ class SecurityAssociation(object):
         else:
             ip_header.plen = len(ip_header.payload) + len(ah) + len(payload)
 
-        signed_pkt = self.auth_algo.sign(ip_header / ah / payload, self.auth_key)  # noqa: E501
+        signed_pkt = self.auth_algo.sign(ip_header / ah / payload,
+                                         self.auth_key, high_seq_num)  # noqa: E501
 
         # sequence number must always change, unless specified by the user
         if seq_num is None:
@@ -1005,11 +1023,12 @@ class SecurityAssociation(object):
 
     def _decrypt_esp(self, pkt, verify=True, esn_en=None, esn=None):
 
+        low_seq_num, high_seq_num = self.build_seq_num(self.seq_num)
         encrypted = pkt[ESP]
 
         if verify:
             self.check_spi(pkt)
-            self.auth_algo.verify(encrypted, self.auth_key)
+            self.auth_algo.verify(encrypted, self.auth_key, high_seq_num)
 
         esp = self.crypt_algo.decrypt(self, encrypted, self.crypt_key,
                                       self.crypt_algo.icv_size or
@@ -1050,11 +1069,12 @@ class SecurityAssociation(object):
 
     def _decrypt_ah(self, pkt, verify=True):
 
+        low_seq_num, high_seq_num = self.build_seq_num(self.seq_num)
         if verify:
             self.check_spi(pkt)
-            self.auth_algo.verify(pkt, self.auth_key)
+            self.auth_algo.verify(pkt, self.auth_key, high_seq_num)
 
         ah = pkt[AH]
         payload = ah.payload