Specifies the X.25 default Windowsize used in ISO8208 (X.25 DTE <-> DTE) Filetransferprotocol. Applications such as OFTP normally uses 7 but some Applications did not use X.25 negotiation, so the CAPI uses here a default from 2 and the connection is closed by a X.25 Reset. Setting this value to 7 is not standard but useful for the customer to avoid this error.