Identifying an NDIS Port
An NDIS port is identified by its port number. When a miniport driver calls the NdisMAllocatePort function to allocate a port, NDIS allocates and assigns the lowest available port number to the port. When a miniport driver calls the NdisMFreePort function to free a port, NDIS also frees the port number that is assigned to the freed port so that NDIS can reuse the port number.
If a driver maintains separate context areas for each port, the driver must provide an efficient algorithm for translating the port number to the corresponding context area.