148 | Managing the Radio
Aprisa SR+ User Manual 1.11.1
Radio > Advanced Setup
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ADVANCED CHANNEL SETTINGS
Default Packet Time to Live (ms)
This parameter sets the time packets that are neither Serial nor Ethernet (such as registration, inter-unit
messaging, firmware distribution etc). The default setting is 1500 ms. The default parameter should work
for most situations.
Serial Packet Time to Live (ms)
This parameter sets the time a serial packet is allowed to live in the system before being dropped if it
cannot be transmitted over the air. The default setting is 2500 ms.
In the case of serial poll SCADA networks such as MODBUS and IEC 60870.50.101, it is important to ensure
the replies from the RTU are in the correct sequence and are not timed out replies from Master requests. If
the TTL value is too long, the SCADA master will detect sequence errors.
It is recommended to use a TTL which is half the serial SCADA timeou
t. This is commonly called the ‘scan
timeout’ or ‘link layer time out’ or ‘retry timeout’.
Ethernet Packet Time to Live (ms)
This parameter sets the time an Ethernet packet is allowed to live in the system before being dropped if it
cannot be transmitted over the air. The default setting is 2500 ms.
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