Campbell Scientific CR6 CR6 Measurement and Control System - Page 398

Hello-Message, 5.3.2 Beacon, 5.3.3 Hello-Request, 5.3.4 Neighbor Lists, 5.3.5 Adjusting Links

Page 398 highlights

Section 8. Operation 8.5.3.1 Hello-Message A hello-message is a two-way exchange between nodes to negotiate a neighbor link. A hello-message is sent out in response to one or both of either a beacon or a hello-request. 8.5.3.2 Beacon A beacon is a one-way broadcast sent by a node at a specified interval telling all nodes within hearing that a hello-message can be sent. If a node wishes to establish itself as a neighbor to the beaconing node, it will then send a hellomessage to the beaconing node. Nodes already established as neighbors will not respond to a beacon. 8.5.3.3 Hello-Request A hello-request is a one-way broadcast. All nodes hearing a hello-request (existing and potential neighbors) will issue a hello-message to negotiate or renegotiate a neighbor relationship with the broadcasting node. 8.5.3.4 Neighbor Lists PakBus devices in a network can be configured with a neighbor list. The CR6 sends out a hello-message to each node in the list whose CVI has expired at a random interval1. If a node responds, a hello-message is exchanged and the node becomes a neighbor. Neighbor filters dictate which nodes are neighbors and force packets to take routes specified by the network administrator. LoggerNet, which is a PakBus® node, derives its neighbor filter from link information in the LoggerNet Setup device map. 1Interval is a random number of seconds between the interval and two times the interval, where the interval is the CVI (if non-zero) or 300 seconds if the CVI setting is set to zero. 8.5.3.5 Adjusting Links PakBusGraph, a client of LoggerNet, is particularly useful when testing and adjusting PakBus routes. Paths established by way of beaconing may be redundant and vary in reliability. Redundant paths can provide backup links in the event the primary path fails. Redundant and unreliable paths can be eliminated by activating neighbor-filters in the various nodes and by disabling some beacons. 8.5.3.6 Maintaining Links Links are maintained by means of the CVI (communication verification interval). The CVI can be specified in each node with the Verify Interval setting in DevConfig (ComPorts Settings). The following rules apply: Note During the hello-message, a CVI must be negotiated between two neighbors. The negotiated CVI is the lesser of the first node's CVI and 6/5ths of the neighbor's CVI. • If Verify Interval = 0, then CVI = 2.5 x Beacon Interval* • If Verify Interval = 60, then CVI = 60 seconds* 398

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Section 8.
Operation
8.5.3.1 Hello-Message
A hello-message is a two-way exchange between nodes to negotiate a neighbor
link.
A hello-message is sent out in response to one or both of either a beacon or
a hello-request.
8.5.3.2 Beacon
A beacon is a one-way broadcast sent by a node at a specified interval telling all
nodes within hearing that a hello-message can be sent. If a node wishes to
establish itself as a neighbor to the beaconing node, it will then send a hello-
message to the beaconing node. Nodes already established as neighbors will not
respond to a beacon.
8.5.3.3 Hello-Request
A hello-request is a one-way broadcast.
All nodes hearing a hello-request
(existing and potential neighbors) will issue a hello-message to negotiate or re-
negotiate a neighbor relationship with the broadcasting node.
8.5.3.4 Neighbor Lists
PakBus devices in a network can be configured with a neighbor list. The CR6
sends out a hello-message to each node in the list whose CVI has expired at a
random interval
1
. If a node responds, a hello-message is exchanged and the node
becomes a neighbor.
Neighbor filters dictate which nodes are neighbors and force packets to take
routes specified by the network administrator.
LoggerNet,
which is a PakBus
®
node, derives its neighbor filter from link information in the
LoggerNet
Setup
device map.
1
Interval is a random number of seconds between the interval and two times the interval, where the
interval is the CVI (if non-zero) or 300 seconds if the CVI setting is set to zero.
8.5.3.5 Adjusting Links
PakBusGraph
, a client of
LoggerNet
, is particularly useful when testing and
adjusting PakBus routes. Paths established by way of beaconing may be
redundant and vary in reliability. Redundant paths can provide backup links in the
event the primary path fails. Redundant and unreliable paths can be eliminated by
activating neighbor-filters in the various nodes and by disabling some beacons.
8.5.3.6 Maintaining Links
Links are maintained by means of the CVI (communication verification interval).
The CVI can be specified in each node with the
Verify Interval
setting in
DevConfig
(
ComPorts Settings
). The following rules apply:
Note
During the hello-message, a CVI must be negotiated between two
neighbors. The negotiated CVI is the lesser of the first node's CVI and 6/5ths of
the neighbor's CVI.
If
Verify Interval
=
0
, then CVI = 2.5 x
Beacon Interval
*
If
Verify Interval
=
60
, then CVI = 60 seconds*
398