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Networking methods
If a message has a broadcast address, it is broadcast to all neighbors, then all routers that receive the
message rebroadcast the message MT+1 times. Eventually, the message reaches the entire network.
Packet tracking prevents a node from resending a broadcast message more than MT+1 times. This
means that a node that relays a broadcast will only relay it after it receives it the first time and it will
discard repeated instances of the same packet.
Route discovery
Route discovery is a process that occurs when:
1. The source node does not have a route to the requested destination.
2. A route fails. This happens when the source node uses up its network retries without receiving
an ACK.
Route discovery begins by the source node broadcasting a route request (RREQ). We call any router
that receives the RREQ and is not the ultimate destination, an intermediate node.
Intermediate nodes may either drop or forward a RREQ, depending on whether the new RREQ has a
better route back to the source node. If so, the node saves, updates and broadcasts the RREQ.
When the ultimate destination receives the RREQ, it unicasts a route reply (RREP) back to the source
node along the path of the RREQ. It does this regardless of route quality and regardless of how many
times it has seen an RREQ before.
This allows the source node to receive multiple route replies. The source node selects the route with
the best round trip route quality, which it uses for the queued packet and for subsequent packets with
the same destination address.
Transmission timeouts
When a device in API operating mode receives a Transmit Request (0x10, 0x11) frame, or a device in
Transparent operating mode meets the packetization requirements (RO, RB), the time required to
route the data to its destination depends on:
A number of configured parameters.
n
Whether the transmission is a unicast or a broadcast.
n
If the route to the destination address is known.
n
Timeouts or timing information is provided for the following transmission types:
Broadcast transmission
n
Unicast transmission on a known route
n
Unicast transmission on an unknown route
n
Unicast transmission on a broken route
n
Note
The timeouts in this documentation are theoretical timeouts and are not precisely accurate.
Your application should pad the calculated maximum timeouts by a few hundred milliseconds. When
you use API operating mode, use
a transmission is complete.
Unicast one hop time
unicastOneHopTime is a building block of many of the following calculations. It represents the amount
of time it takes to send a unicast transmission between two adjacent nodes. The amount of time
depends on the %H parameter.
XBee®/XBee-PRO XTend Compatible (XTC) DigiMesh RF Module User Guide
Transmit Status frame - 0x8B
Delivery methods
as the primary method to determine if
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