clearId

A unique ID for this packet.
Always 0 for no-ack packets or non broadcast packets (and therefore take zero bytes of space).
Otherwise a unique ID for this packet, useful for flooding algorithms.
ID only needs to be unique on a _per sender_ basis, and it only
needs to be unique for a few minutes (long enough to last for the length of
any ACK or the completion of a mesh broadcast flood).
Note: Our crypto implementation uses this id as well.
See [crypto](/docs/overview/encryption) for details.