This parameter specifies an upper limit on the size, in bytes,
    of the user data area in the largest packet sent by NISCA on any
    local area network (LAN).

    NISCS_MAX_PKTSZ allows the system manager to change the packet
    size used for cluster communications on network communication
    paths. PEDRIVER automatically allocates memory to support
    the largest packet size that is usable by any virtual circuit
    connected to the system up to the limit set by this parameter. On
    Alpha and Integrity servers, to optimize performance, the default
    value is the largest packet size currently supported by OpenVMS.

    PEDRIVER uses NISCS_MAX_PKTSZ to compute the maximum amount of
    data to transmit in any LAN packet:

    LAN packet size <= LAN header (padded Ethernet format)
                       + NISCS_MAX_PKTSZ
                       + NISCS checksum (only if data checking
                                         is enabled)
                       + LAN CRC or FCS

    The actual packet size automatically used by PEDRIVER might be
    smaller than the NISCS_MAX_PKTSZ limit for any of the following
    reasons:

    o  On a per-LAN path basis, if PEdriver determines that the LAN
       path between two nodes, including the local and remote LAN
       adapters and intervening LAN equipment, can only convey a
       lesser size.

       In other words, only nodes with large-packet LAN adapters
       connected end-to-end by large-packet LAN equipment can use
       large packets. Nodes connected to large-packet LANs but having
       an end-to-end path that involves an Ethernet segment restrict
       packet size to that of an Ethernet packet (1498 bytes).

    o  For performance reasons, PEDRIVER might further limit
       the upper bound on packet size so that the packets can be
       allocated from a lookaside list in the nonpaged pool.

    The actual memory allocation includes the required data structure
    overhead used by PEDRIVER and the LAN drivers, in addition to the
    actual LAN packet size.

    The following table shows the minimum NISCS_MAX_PKTSZ value
    required to use the maximum packet size supported by specified
    LAN types:

    Type of LAN           Minimum Value for NISCS_MAX_PKTSZ

    Ethernet              1498

    FDDI                  4382 (before Version 7.3)
                          4396 (Version 7.3 and later)

    Gigabit Ethernet      8192

    ATM                   7606

    Note that the maximum packet size for some Gigabit Ethernet
    adapters is larger than the maximum value of NISCS_MAX_PKTSZ
    (8192 bytes). See the LAN_FLAGS parameter for a description of
    how to enable jumbo frames on Gigabit Ethernet-that is, packet
    sizes larger than those noted for Ethernet.

    On Alpha and Integrity servers, NISCS_MAX_PKTSZ is an AUTOGEN
    parameter.