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Topic: BLE hop limit field (Read 169 times) previous topic - next topic


Apr 21, 2019, 03:48 am Last Edit: Apr 21, 2019, 03:51 am by kengel
I was reading about Bluetooth mesh networking on Wikipedia and came across this:

Bluetooth Mesh is a flood network. It's based on the nodes relaying the messages: every relay node that receives a network packet that authenticates against a known network key that is not in message cache, that has a TTL ≥ 2 can be re-transmitted with TTL = TTL - 1.
This seems to imply that the the packet won't be re-transmitted once TTL <= 1. Is this correct? I expected the last part to read "that has a TTL ≥ 1 can be re-transmitted with TTL = TTL - 1."


Apr 22, 2019, 01:56 am Last Edit: Apr 22, 2019, 01:59 am by kengel
Apparently this refers to the TTL field of an incoming packet before the receiving node has decremented the field. Since the TTL field is checked after the field is decremented, a node that receives a packet with a TTL of 1 would decrement the field to 0, check the field, then discard the packet.

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