Library /sys$common/syshlp/nclhelp.hlb set, routing, segment_buffer_size  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Support: All
    Default: 570           Value: 0-65535

    Maximum segment size, in octets, to be used by the Transport
    layer. A value of zero means that the segment size is unlimited.