Specifications

Section 14. PakBus Overview
14-4
14.4.6 Maintaining Links
Links are maintained by means of the CVI (communications verification
interval). The CVI can be specified in each node with DevConfig. The
following rules* apply:
If Verify Interval = 0, then CVI = 2.5 x beacon interval*
If Verify Interval = 60, then CVI = 60 seconds*
If Beacon Interval = 0 and Verify Interval = 0, then CVI = 300 seconds*
*During the hello-message, a CVI must be negotiated between two neighbors.
The negotiated CVI will be the lesser of the first nodes CVI and 6/5ths of the
neighbors CVI.
If the CR1000 does not hear from a neighbor for one CVI, it begins again to
send a Hello message to that node at the random interval.
Users should base verification intervals on the timing of normal
communications such as scheduled LoggerNet collections or datalogger to
dataloggers communications. The idea is to not allow the verification interval
to expire before normal communications. If the verification interval expires
the devices will initiate hello exchanges in an attempt to regain neighbor status,
increasing traffic in the network.
14.5 Troubleshooting
Various tools and methods have been developed to assist in troubleshooting
PakBus networks.
14.5.1 Link Integrity
With beaconing or neighbor filter discovery, links are established and verified
using relatively small data packets (Hello messages). When links are used for
regular telecommunications, however, longer messages are used.
Consequently, a link may be reliable enough for discovery but unreliable with
larger packets. This condition is most common in radio networks.
PakBus communications over marginal links can often be improved by
reducing the size of the PakBus packets. Best results are obtained when the
maximum packet sizes in both nodes are reduced.
Automatic Packet Size Adjustment
The BMP5 file receive transaction allows the BMP5 client (LoggerNet) to
specify the size of the next fragment of the file that the CR1000 sends.
The file receive transaction is used to get table definitions from
the datalogger.
Because LoggerNet must specify a size for the next fragment of the file, it uses
whatever size restrictions that apply to the link.
NOTE