The address bits not used by the transport plugin for its internal addressing constitute its network address bits.
In order for Connext DDS to properly route the messages, each unicast interface in the DDS domain must have a unique address.
You specify the network address when installing a transport plugin via the register_transport() operation (Installing Additional Builtin Transport Plugins with register_transport()). Choose the network address for a transport plugin so that the resulting fully qualified 128-bit address will be unique in the DDS domain.
If two instances of a transport plugin are registered with a DomainParticipant, they need different network addresses so that their unicast interfaces will have unique, fully qualified 128-bit addresses.
While it is possible to create multiple transports with the same network address (this can be useful for certain situations), this requires special entity configuration for most transports to avoid clashes in resource use (e.g., sockets for UDPv4 transport).
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