Campbell RF410 Manuál s instrukcemi stáhnout pdf (Strana 57)

PakBus Networking Guide

7.2.4.2 Two Level Packet Addressing

Examination of a packet header reveals four PakBus Addresses. Referring to

the above BMP5 Example Packet (portrayed below) hex digits 2 – 4 (“001”)

represent the neighbor PakBus Address to which the packet is going. Digits 6 –

8 represent the neighbor PakBus Address from which the packet came (“ffe”).

12345678910111213141516

bd a 0 0 16f f e1 0 0 10f f e

17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

032e00000000d25ebd

Digits 10 – 12 represent the ultimate destination PakBus Address. Digits 14 – 16

represent the source PakBus Address. In this example, since there are no routers, both

address levels use the same PakBus Addresses. If there were routers in the path, you

would see the packet assume different to/from neighbor PakBus Addresses as it

traveled along but the source and destination would remain constant.

7.3 Neighbor

The term “Neighbor” has special meaning in PakBus networking. A neighbor to

a PakBus device is another PakBus device with which it has recently

communicated directly (without a router). In a *D17 routing table, neighbors

are indicated by a single address xxxx (see *D Setup for the CR10X, CR510

and CR23X). If a second address yyyy is present then a route exists to the

destination but at least one router is needed to get there. Before a PakBus

device can consider another device to be a neighbor, they must successfully

accomplish a hello exchange and periodically communicate in some fashion.

Discovery is always two-way.

PakBus devices can discover a neighbor by:

• Sending a hello message to a *D19 Neighbor Filter potential neighbor and

getting back a hello response

• Beaconing and doing a successful hello exchange

• Communicating via P190, P191, P192, P196, P198, P224 and doing a

hello exchange

• Static route in LoggerNet or P190 datalogger communicating with a device

followed by a hello exchange

Only a successful hello exchange can establish devices as neighbors.

For successful routing, network devices must maintain an accurate list of

currently viable links. If a device has not heard from a certain neighbor within a

period equal to the lesser of the two devices’ communications verification

intervals × 2.5, it will initiate a hello-exchange. If the attempt fails, the device

will try again. If unsuccessful after 4 such attempts, the neighbor will be

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Campbell RF410 Manuál s instrukcemi Strana 57