[erlang-questions] IP search optimization

[Sid Muller]

Hi,

I was wondering if someone knowledgeable in IP/CIDR and bitstrings could give me some advice on how to proceed?

I'm storing network address in an ets table, for example:
77.242.16.0/20
31.24.168.0/21

And then I want to check if an IP (31.24.171.44) belongs to any network address in the ets table (the table can get pretty large).
The crux of the matter is that I am not sure which of the following routes to pursue because I only get the IP but CIDR is stored in ets with each network:

1. Should I store the network/CIDR in ets as tuples:
{{77, 42, 6, 0}, 20}
{{31, 24, 168, 0}, 21}
and search for the IP as a tuple ({31, 24, 171, 44}) byte by byte?

2. Should I store the Network as a bitstring:
<<77,242,1:4>>
<<31,24,21:5>>
And then search for the IP as a bitstring match?

3. Should I store the network/CIDR as binary:
<<"77.242.16.0/20">>
<<"31.24.168.0/21">>

I think the best solution would be the #2 but this one, just like the others I don't know the CIDR ahead of time to be able to trim the CIDR off the IP and then do a simple key based match from ets.

Any thoughts?

Thank you