Campbell Scientific CR3000 Micrologger - Manual (Page 361)

Section 8. Operation
361
Hence, the size of the responses to the file-receive commands that the CR3000
sends is governed by the Max Packet Size setting for the datalogger as well as
that of any of its parents in the LoggerNet network map. Note that this calculation
also takes into account the error rate for devices in the link.
BMP5 data-collection transaction does not provide any way for the client to
specify a cap on the size of the response message. This is the main reason why the
Max Packet Size setting exists. The CR3000 can look at this setting at the point
where it is forming a response message and cut short the amount of data that it
would normally send if the setting limits the message size.
8.5.4.2 Ping
Link integrity can be verified with the following procedure by using
PakBusGraph Ping Node. Nodes can be pinged with packets of 50, 100, 200, or
500 bytes.
Note Do not use packet sizes greater than 90 when pinging with 100 mW radio
modems and radio enabled dataloggers (see the appendix Telecommunications
Hardware
).
Pinging with ten repetitions of each packet size will characterize the link. Before
pinging, all other network traffic (scheduled data collections, clock checks, etc.)
should be temporarily disabled. Begin by pinging the first layer of links
(neighbors) from the PC / LoggerNet router, then proceed to nodes that are more
than one hop away. Table PakBus Link-Performance Gage
(p. 361)
provides a link-
performance gage.
Table 88. PakBus Link-Performance Gage
500 byte
Pings Sent Successes Link Status
10 10 excellent
10 9 good
10 7-8 adequate
10 <7 marginal
8.5.4.3 Traffic Flow
Keep beacon intervals as long as possible with higher traffic (large numbers of
nodes and / or frequent data collection). Long beacon intervals minimize
collisions with other packets and resulting retries. The minimum recommended
Beacon Interval setting is 60 seconds. If communications traffic is high, consider
setting beacon intervals of several minutes. If data throughput needs are great,
maximize data bandwidth by creating some branch routers, or by eliminating
beacons altogether and setting up neighbor filters.
8.5.5 LoggerNet Network-Map Configuration
As shown in figure Flat Map
(p. 362)
and figure Tree Map
(p. 362)
, the essential
element of a PakBus ® network device map in LoggerNet is the PakBusPort. After
adding the root port (COM, IP, etc), add a PakBusPort and the dataloggers.