diff --git a/src/mms/inc_private/cotp.h b/src/mms/inc_private/cotp.h
index cba02c19..b7877cc8 100644
--- a/src/mms/inc_private/cotp.h
+++ b/src/mms/inc_private/cotp.h
@@ -84,7 +84,8 @@ CotpConnection_setTpduSize(CotpConnection* self, int tpduSize /* in byte */);
 
 LIB61850_INTERNAL void
 CotpConnection_init(CotpConnection* self, Socket socket,
-        ByteBuffer* payloadBuffer, ByteBuffer* readBuffer, ByteBuffer* writeBuffer);
+        ByteBuffer* payloadBuffer, ByteBuffer* readBuffer, ByteBuffer* writeBuffer,
+        uint8_t* socketExtensionBuffer, int socketExtensionBufferSize);
 
 LIB61850_INTERNAL CotpIndication
 CotpConnection_parseIncomingMessage(CotpConnection* self);
diff --git a/src/mms/iso_client/iso_client_connection.c b/src/mms/iso_client/iso_client_connection.c
index 6e71263a..435ab9bc 100644
--- a/src/mms/iso_client/iso_client_connection.c
+++ b/src/mms/iso_client/iso_client_connection.c
@@ -200,8 +200,12 @@ sendConnectionRequestMessage(IsoClientConnection self)
         self->cotpConnection->handleSet = NULL;
     }
 
+    int socketExtensionBufferSize = CONFIG_MMS_MAXIMUM_PDU_SIZE + 1000;
+    uint8_t* socketExtensionBuffer = GLOBAL_MALLOC(socketExtensionBufferSize);
+
     /* COTP (ISO transport) handshake */
-    CotpConnection_init(self->cotpConnection, self->socket, self->receiveBuffer, self->cotpReadBuffer, self->cotpWriteBuffer);
+    CotpConnection_init(self->cotpConnection, self->socket, self->receiveBuffer, self->cotpReadBuffer, self->cotpWriteBuffer,
+            socketExtensionBuffer, socketExtensionBufferSize);
 
 #if (CONFIG_MMS_SUPPORT_TLS == 1)
     if (self->parameters->tlsConfiguration) {
@@ -774,9 +778,13 @@ IsoClientConnection_destroy(IsoClientConnection self)
         GLOBAL_FREEMEM(self->receiveBuf);
     if (self->receiveBuffer != NULL)
         GLOBAL_FREEMEM(self->receiveBuffer);
+
     if (self->cotpConnection != NULL) {
         if (self->cotpConnection->handleSet != NULL)
             Handleset_destroy(self->cotpConnection->handleSet);
+
+        GLOBAL_FREEMEM(self->cotpConnection->socketExtensionBuffer);
+
         GLOBAL_FREEMEM(self->cotpConnection);
     }
 
diff --git a/src/mms/iso_cotp/cotp.c b/src/mms/iso_cotp/cotp.c
index 80df4ce1..70f3dc62 100644
--- a/src/mms/iso_cotp/cotp.c
+++ b/src/mms/iso_cotp/cotp.c
@@ -503,7 +503,8 @@ cpo_error:
 
 void
 CotpConnection_init(CotpConnection* self, Socket socket,
-        ByteBuffer* payloadBuffer, ByteBuffer* readBuffer, ByteBuffer* writeBuffer)
+        ByteBuffer* payloadBuffer, ByteBuffer* readBuffer, ByteBuffer* writeBuffer,
+        uint8_t* socketExtensionBuffer, int socketExtensionBufferSize)
 {
     self->state = 0;
     self->socket = socket;
@@ -536,8 +537,8 @@ CotpConnection_init(CotpConnection* self, Socket socket,
     self->readBuffer = readBuffer;
     self->packetSize = 0;
 
-    self->socketExtensionBuffer = GLOBAL_MALLOC(CONFIG_MMS_MAXIMUM_PDU_SIZE + 120);
-    self->socketExtensionBufferSize = CONFIG_MMS_MAXIMUM_PDU_SIZE + 120;
+    self->socketExtensionBuffer = socketExtensionBuffer;
+    self->socketExtensionBufferSize = socketExtensionBufferSize;
     self->socketExtensionBufferFill = 0;
 }
 
diff --git a/src/mms/iso_server/iso_connection.c b/src/mms/iso_server/iso_connection.c
index caf4331e..653379e4 100644
--- a/src/mms/iso_server/iso_connection.c
+++ b/src/mms/iso_server/iso_connection.c
@@ -122,6 +122,8 @@ finalizeIsoConnection(IsoConnection self)
     if (self->cotpConnection) {
         if (self->cotpConnection->handleSet)
             Handleset_destroy(self->cotpConnection->handleSet);
+
+        GLOBAL_FREEMEM(self->cotpConnection->socketExtensionBuffer);
     }
 
     GLOBAL_FREEMEM(self->cotpConnection);
@@ -527,7 +529,10 @@ IsoConnection_create(Socket socket, IsoServer isoServer, bool isSingleThread)
         ByteBuffer_wrap(&(self->cotpWriteBuffer), self->cotpWriteBuf, 0, CONFIG_COTP_MAX_TPDU_SIZE + TPKT_RFC1006_HEADER_SIZE);
 
         self->cotpConnection = (CotpConnection*) GLOBAL_CALLOC(1, sizeof(CotpConnection));
-        CotpConnection_init(self->cotpConnection, self->socket, &(self->rcvBuffer), &(self->cotpReadBuffer), &(self->cotpWriteBuffer));
+        int socketExtensionBufferSize = CONFIG_MMS_MAXIMUM_PDU_SIZE + 1000;
+        uint8_t* socketExtensionBuffer = GLOBAL_MALLOC(socketExtensionBufferSize);
+        CotpConnection_init(self->cotpConnection, self->socket, &(self->rcvBuffer), &(self->cotpReadBuffer), &(self->cotpWriteBuffer),
+                socketExtensionBuffer, socketExtensionBufferSize);
 
 #if (CONFIG_MMS_SUPPORT_TLS == 1)
         if (self->tlsSocket)
@@ -602,6 +607,8 @@ IsoConnection_destroy(IsoConnection self)
     if (self->cotpConnection) {
         if (self->cotpConnection->handleSet)
             Handleset_destroy(self->cotpConnection->handleSet);
+
+        GLOBAL_FREEMEM(self->cotpConnection->socketExtensionBuffer);
     }
 
     GLOBAL_FREEMEM(self);