Use 1500 Bytes as the MTU for all FreeRTOS+TCP demos (#1105)

Co-authored-by: Joseph Julicher <jjulicher@mac.com>

FreeRTOS-Plus/Demo/FreeRTOS_Plus_TCP_Echo_Qemu_mps2/FreeRTOSIPConfig.h

@@ -248,11 +248,10 @@ extern UBaseType_t uxRand();
 #define ipconfigUSE_TCP_WIN                            ( 1 )
 
 /* The MTU is the maximum number of bytes the payload of a network frame can
- * contain.  For normal Ethernet V2 frames the maximum MTU is 1500.  Setting a
- * lower value can save RAM, depending on the buffer management scheme used.  If
- * ipconfigCAN_FRAGMENT_OUTGOING_PACKETS is 1 then (ipconfigNETWORK_MTU - 28) must
- * be divisible by 8. */
-#define ipconfigNETWORK_MTU                            1200U
+ * contain. Setting this to a number lower than that of the network you are
+ * connecting to is likely to cause dropped packets. Do not set this parameter
+ * lower than 1500 unless you fully understand the consequences. */
+#define ipconfigNETWORK_MTU                            1500U
 
 /* Set ipconfigUSE_DNS to 1 to include a basic DNS client/resolver.  DNS is used
  * through the FreeRTOS_gethostbyname() API function. */

FreeRTOS-Plus/Demo/FreeRTOS_Plus_TCP_IPv6_Demo/IPv6_Multi_WinSim_demo/FreeRTOSIPConfig.h

@@ -232,11 +232,10 @@ extern UBaseType_t uxRand();
 #define ipconfigUSE_TCP_WIN                            ( 1 )
 
 /* The MTU is the maximum number of bytes the payload of a network frame can
- * contain.  For normal Ethernet V2 frames the maximum MTU is 1500.  Setting a
- * lower value can save RAM, depending on the buffer management scheme used.  If
- * ipconfigCAN_FRAGMENT_OUTGOING_PACKETS is 1 then (ipconfigNETWORK_MTU - 28) must
- * be divisible by 8. */
-#define ipconfigNETWORK_MTU                            1200U
+ * contain. Setting this to a number lower than that of the network you are
+ * connecting to is likely to cause dropped packets. Do not set this parameter
+ * lower than 1500 unless you fully understand the consequences. */
+#define ipconfigNETWORK_MTU                            1500U
 
 /* Set ipconfigUSE_DNS to 1 to include a basic DNS client/resolver.  DNS is used
  * through the FreeRTOS_gethostbyname() API function. */

FreeRTOS-Plus/Test/FreeRTOS-Plus-TCP/Integration/Full-TCP-Networkless/Config/FreeRTOSIPConfig.h

@@ -232,11 +232,10 @@ extern void vLoggingPrintf( const char * pcFormatString,
 #define ipconfigUSE_TCP_WIN                            ( 1 )
 
 /* The MTU is the maximum number of bytes the payload of a network frame can
- * contain.  For normal Ethernet V2 frames the maximum MTU is 1500.  Setting a
- * lower value can save RAM, depending on the buffer management scheme used.  If
- * ipconfigCAN_FRAGMENT_OUTGOING_PACKETS is 1 then (ipconfigNETWORK_MTU - 28) must
- * be divisible by 8. */
-#define ipconfigNETWORK_MTU                            1200U
+ * contain. Setting this to a number lower than that of the network you are
+ * connecting to is likely to cause dropped packets. Do not set this parameter
+ * lower than 1500 unless you fully understand the consequences. */
+#define ipconfigNETWORK_MTU                            1500U
 
 /* Set ipconfigUSE_DNS to 1 to include a basic DNS client/resolver.  DNS is used
  * through the FreeRTOS_gethostbyname() API function. */

FreeRTOS-Plus/Test/FreeRTOS-Plus-TCP/Integration/Full-TCP-Suite/Config/FreeRTOSIPConfig.h

@@ -226,11 +226,10 @@ extern uint32_t ulRand();
 #define ipconfigUSE_TCP_WIN                            ( 1 )
 
 /* The MTU is the maximum number of bytes the payload of a network frame can
- * contain.  For normal Ethernet V2 frames the maximum MTU is 1500.  Setting a
- * lower value can save RAM, depending on the buffer management scheme used.  If
- * ipconfigCAN_FRAGMENT_OUTGOING_PACKETS is 1 then (ipconfigNETWORK_MTU - 28) must
- * be divisible by 8. */
-#define ipconfigNETWORK_MTU                            1200U
+ * contain. Setting this to a number lower than that of the network you are
+ * connecting to is likely to cause dropped packets. Do not set this parameter
+ * lower than 1500 unless you fully understand the consequences. */
+#define ipconfigNETWORK_MTU                            1500U
 
 /* Set ipconfigUSE_DNS to 1 to include a basic DNS client/resolver.  DNS is used
  * through the FreeRTOS_gethostbyname() API function. */