Campbell Scientific PakBus Networking Guide - Manual (Page 10)

PakBus Networking Guide
3.3 Routers
A router is a PakBus device that can accept a packet and forward it toward its
ultimate network destination. Routing is fundamentally driven by the router’s
ability to learn about neighbors and the sharing of that information with other
routers in the network. When a change occurs in a router on the network, that
router will exchange the new neighbor information with other known routers.
Routers ultimately determine the best complete route to a destination by using
the known routes information they maintain from all other routers. This
information gives routers knowledge of every known link in the network and
the ability to calculate the best complete route based on the hop metric of each
link.
3.4 Discovering Devices
PakBus devices on a network may initially be unaware of each other. One
benefit of using a PakBus network is that PakBus devices can automatically
discover other PakBus devices on the network. There are three ways that
devices can initiate a hello exchange and discover each other as neighbors:
1. Using a beacon
2. Using an allowed neighbor list
3. Using instructions in the datalogger program
3.4.1 Beacons
Beacons are a simple way for devices to discover neighbors. When devices are
configured to beacon, a beacon broadcast packet is sent over the network at a
regular specified interval. A PakBus device on the network that receives the
beacon will respond with a hello message to the device that sent the beacon.
The hello message includes the device’s PakBus address. When the device that
sent the beacon receives a hello message, it will answer with a hello response
packet and complete the hello exchange process.
Beacons will use network resources since they broadcast over the network each
time the specified beacon interval occurs. If using a metered connection or a
network that needs limited traffic, carefully consider the consequences before
implementing beacons as a method of discovering neighbors.
3.4.2 Allowed Neighbor List
Allowed neighbor lists can be used as another method of introducing devices to
each other. Entering the address of a device in the allowed neighbor list of a
datalogger will initiate discovery of the device.
Allowed neighbor lists also act as communication filters. A datalogger with a
declared allowed neighbor list will only communicate with node that has an
address of 4000 or greater or that has an address in the list. The receiving
device will ignore communication packets from other nodes.
Allowed neighbor lists can be used to declare specific communication paths
between nodes rather than having the devices discover alternate undesirable
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