Route Discovery; Throughput; Xbee Digimesh 2.4 Transmission Timeouts - Digi XBee User Manual

®
XBee/XBee-PRO DigiMesh 2.4 User Manual

Route Discovery

If the source node doesn't have a route to the requested destination, the packet is queued to
await a route discovery (RD) process. This process is also used when a route fails. A route fails
when the source node uses up its network retries without ever receiving an ACK. This results in
the source node initiating RD.
RD begins by the source node broadcasting a route request (RREQ). Any router that receives the
RREQ that is not the ultimate destination is called 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, information from the RREQ is saved and the
RREQ is updated and broadcast. When the ultimate destination receives the RREQ, it unicasts a
route reply (RREP) back to the source node along the path of the RREQ. This is done regardless
of route quality and regardless of how many times an RREQ has been seen 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 will use for the queued packet and for subsequent
packets with the same destination address.

Throughput

Throughput in a DigiMesh network varies by a number of variables, including: number of hops,
encryption enabled/disabled, sleeping end devices, failures/route discoveries. Our empirical
testing showed the following throughput performance in a robust operating environment (low
interference).
Configuration
1 hop, Encryption Disabled
3 hop, Encryption Disabled
6 hop, Encryption Disabled
1 hop, Encryption Enabled
3 hop, Encryption Enabled
6 hop, Encryption Enabled
Note: Data throughput measurements were made setting the serial interface rate to 115200
bps, and measuring the time to send 100,000 bytes from source to destination. During the
test, no route discoveries or failures occurred.

XBee DigiMesh 2.4 Transmission Timeouts

When a node receives an API TX Request (API configured modules) or an RO timeout occurs
(modules configured for Transparent Mode) the time required to route the data to its destination
depends on a number of configured parameters, whether the transmission is a unicast or a
broadcast, and if the route to the destination address is known. Timeouts or timing information is
provided for the following transmission types:
• Transmitting a broadcast
• Transmitting a unicast with a known route
• Transmitting a unicast with an unknown route
© 2014 Digi International Inc.
Data Throughput
27.0 kbps
10.9 kbps
5.78 kbps
20.5 kbps
9.81 kbps
4.7 kbps
43