Digi XBee 3 ZigBee User Manual page 113

Transmission, addressing, and routing
The maximum payload is calculated to estimate for aggregator source-routing. To reduce the
maximum payload, when an aggregator sends a source-routed message it embeds the route into the
message as overhead, or into each fragment of the message, if fragmentation is necessary. If you use
APS encryption (EE1, Tx Option 0x20), it reduces the number further.
The route overhead is 2 bytes plus 2 bytes per hop. The bytes are:
One byte is the number of hops
n
One byte is an index into the route list that increments in value at each hop
n
Other data is a list of the 16-bit network addresses of the routing radios
n
Aggregator source-routed payload maximums do not apply to messages that are sourced by non-
aggregator nodes, which send route records ahead of their messages to aggregators. Aggregators
are either Coordinators or Routers which have the following:
Source routing enabled or
n
AR setting which is not 0xFF
n
The following table shows the aggregator source-routed payload maximums as a function of hops and
APS encryption:
Hops Maximum encrypted payload
1 255
2 255
3 255
4 255
5 255
6 215
7 205
8 195
9 185
10 175
11 165
12 155
13 145
14 135
15 125
16 115
17 105
18 95
Digi XBee® 3 Zigbee® RF Module
Maximum RF payload size
Maximum unencrypted payload
255
255
255
255
255
255
250
240
230
220
210
200
190
180
170
160
150
140
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