The transport plugin sets the value for this field.

A transport plugin should define the range of addresses (starting from 0x0) that are meaningful to the plugin. It does this by setting the number of bits of an IPv6 address that will be used to designate an address in the network to which the transport plugin is connected.

For example, for an address range of 0-255, the address_bit_count should be set to 8. For the range of addresses used by IPv4 (4 bytes), it should be set to 32.