NetIPC 3000/XL Programmer's Reference Manual (5958-8600)

108 Chapter3
NetIPC Intrinsics
IPCRECVCN
Checksum enabled by either IPCCONNECT or TCP
(remote or local) configuration overrides a 0 setting
(checksum disabled) for this flag. Checksum error
checking is handled at the link level and is not
normally required at the user level.
In fact, checksumming is only used for connections
between nodes and is not used for connections
within the same node. Enabling checksum may
reduce network performance. Recommended
value: 0.
• flags [25] — discarded (output). For X.25 protocol
access. Indicates that the call user data (CUD) or the
facility field was present, but that the data had to be
discarded or truncated. If the call user data option
(code=5) is not specified the call user data is
discarded. If the CUD or the facility field buffer is
not long enough to contain the data, this flag is set
and the data is truncated.
opt (input)
Record or byte array, by reference. A list of options,
with associated information. The following options are
defined:
• maximum send size (code=3, length=2; 2-byte
integer) (input). (TCP only). This option, which must
be in the range from 1 to 30,000, specifies the length
of the longest message that the user expects to send
on this connection. The information is passed to the
protocol module. If this option is not specified, then
the protocol module will be able to handle messages
at least 1,024 bytes long. If the specified value is
smaller than a previously specified maximum send
size, then the new value is ignored.
• maximum receive size (code=4, length=2; 2-byte
integer) (input). (TCP only.) This option, which must
be in the range from 1 to 30,000, specifies the length
of the longest message that the user expects to
receive on this connection. The information is passed
to the protocol module. If this option is not specified,
then the protocol module will be able to handle
messages at least 1,024 bytes long. If the specified
value is smaller than a previously specified
maximum receive size, then the new value is
ignored.
• call user data (code=5, length=n, n bytes) (output),
(X.25 only.) This option provides a buffer for the