Library /sys$common/syshlp/ncphelp.hlb SET, LINE, BUFFER SIZE number  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Specifies in bytes the size of receive buffers for the specified line,
 thereby controlling the maximum size of NSP message segments that can
 be received from or forwarded to an adjacent node which has accepted
 the line buffer size.  Use a value up to 65,535 for non-broadcast
 lines.   For broadcast lines, BUFFER SIZE should not be raised to a
 value higher  than 1498 bytes.  For Ethernet and FDDI lines, the value
 of 1498 bytes is provided as the default.  For all other types of
 lines, the default is the  executor BUFFER SIZE value (as specified in
 the SET EXECUTOR command).

 This parameter does not apply to X.25 lines.

 You can use BUFFER SIZE to increase the size of NSP messages for
 logical links over this line.