Echelon Neuron C - Manual (Page 188)

168 Network Variable, Configuration Property, and Message Tag Declarations
ackd (the default) — acknowledged service; with retry; if
acknowledgments are not received from all receiving
devices before the layer 4 retransmission timer expires,
the message is sent again, up to the retry count.
An unacknowledged (unackd) network variable uses
minimal network resources to propagate its values to
other devices. As a result, propagation failures are more
likely to occur, and failures are not detected by the
sending device. This class might be used for variables
that are updated on a frequent, periodic basis, where loss
of an update is not critical, or in cases where the
probability of a collision or transmission error is
extremely low.
The repeated (unackd_rpt) service is typically used when
a message is propagated to many devices, and a reliable
delivery is required. This option reduces the network
traffic caused by a large number of devices sending
acknowledgements simultaneously and can provide the
same reliability as the acknowledged service by using a
repeat count equal to the retry count.
The config keyword, the default, indicates that this
service type can be changed by a network tool. This
option allows a network tool to change the service
specification at installation time.
The nonconfig keyword indicates that this service cannot
be changed by a network tool.
authenticated | nonauthenticated [(config | nonconfig)]
Specifies whether a network variable update requires
authentication. With authentication, the identity of the
sending device is verified by all receiving devices.
Abbreviations for authentication are auth and nonauth.
The config and nonconfig keywords specify whether the
authentication designation can be changed by a network
tool.
A network variable connection is authenticated only if the
readers
and writers have the authenticated keywords
specified. However, if only the originator of a network
variable update or poll has used the keyword, the
connection is not authenticated (although the update does
take place). See also the Authentication section in
Chapter 3, How Devices Communicate Using Network
Variables, of the Neuron C Programmer's Guide .
The default is nonauth (config).
Note: Use only the acknowledged service with
authenticated updates. Do not use the unacknowledged
or repeated services.