Transmission, addressing, and routing RF packet routing
XBee/XBee-PRO ZigBee RF Modules User Guide 66
Then the Create Source Route API frame would be:
7E 0012 21 00 0013A200 404A1234 EEFF 00 02 CCDD AABB 5C
Where:
0x0012 - length
0x21 - API ID (create source route)
0x00 - frame ID (set to 0 always)
0x0013A200 404A1234 - 64-bit address of R3 (destination)
0xEEFF - 16-bit address of R3 (destination)
0x00 - Route options (set to 0)
0x02 - Number of intermediate devices in the source route
0xCCDD - Address of furthest device (1-hop from target)
0xAABB - Address of next-closer device
0x5C - Checksum (0xFF - SUM (all bytes after length))
Repairing source routes
It is possible in a network to have an existing source route fail (for example a device in the route moves or goes
down, and so forth). If a device goes down in a source routed network, all routes that used the device will be
broken.
As mentioned previously, source routing must be used with many-to-one routing. A device that uses source
routing must also send a periodic many-to-one broadcast in order to keep routes fresh. If a source route is
broken, remote devices must send in new route record transmissions to the data collector to provide it with a
new source route. This requires that remote devices periodically send data transmissions into the data collector.
See Acquiring source routes on page 65 for details.
Retries and acknowledgments
ZigBee includes acknowledgment packets at both the Mac and Application Support (APS) layers. When data is
transmitted to a remote device, it may traverse multiple hops to reach the destination. As data is transmitted
from one node to its neighbor, an Ack is transmitted in the opposite direction to indicate that the transmission
was successfully received. If the Ack is not received, the transmitting device will retransmit the data, up to four
times. This Ack is called the Mac layer acknowledgment.
In addition, the device that originated the transmission expects to receive an acknowledgment packet (Ack) from
the destination device. This Ack will traverse the same path that the data traversed, but in the opposite direction.
If the originator fails to receive this Ack, it will retransmit the data, up to two times until an Ack is received. This
Ack is called the ZigBee APS layer acknowledgment.
Note Refer to the ZigBee specification for more details.
Device 16-bit address
R1 0xAABB
R2 0xCCDD
R3 0xEEFF
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