Maximum transmission unit on PPP/SLIP connections RRS feed

  • Question

  • Hi,


    We use the WINCE 4.20 platform based on ARMV4I and the associated PPP, ASYNCMAC and UNIMODEM  components.

    We need to connect our platform to a slip server which works with a MTU of 256 bytes via a null-modem  connection.

    We did the following configurations:

    -          add the registry sub key name “PPPMTU”  associated to the hexdecimal value of 0x100H to the “UNIMODEM” key associated to the serial component we use to define the null modem connection,

    -          add the registry subkey name “MaxFrameSize” (and MaxSendFrameSize )  associated to the value of 0x100H to the “HKEY_LOCAL_MACHINE\Comm\AsyncMac1\Parms” key.

    -          Initialise the field dwFrameSize of the RAS phonebook entry corresponding to the SLIP server to the value 0x100


    After the function “RasDial” succeeded, the connection is established with SLIP server but if we use the “netstat /e“ function , we notice the MTU is initialised to the value 1006; it is also confirmed by the function “ping “Address IP” –l 1000 –n 1” which failed as soon as the parameter of the option L is superior of 228.

    If we tried the same operation on a PPP server with another phonebook entry ( without initialising the field . dwFrameSize) , it is OK , the MTU is valid at 256 bytes.


    Thanks for your help.

    Monday, November 22, 2010 1:51 PM