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Comment by AshleysBrain | Hacker News Reader

How could NAT work for an entire country of people behind one IP? My understanding was that NAT allows communication over separate ports, so for example a router with ip 123.45.67.89 can run three clients by sending their data over ports 50000, 50001 and 50002. How does this work when more than 65k people are trying to connect? There don't seem to be enough ports for that to be possible.

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This is a dramatic simplification, but TCP uses the quadruplet of source IP/source port/dest IP/dest port as a session identifier, so you can potentially get 2 billion people using one outgoing port to 2 billion different servers with different IPs in the absolute best case (which wouldn't happen, of course).

that limit only happens when 65k people try to use the same remote ip, otherwise the distinction can still be made for tcp streams.

Is there a minister of Port forwarding? What happens when I fire up chrome and Firefox with 80 pages each? Am I limited to a number out going connections? I assume the entire country is running off a Windows 95 box with two nics but that's just the way I imagine most cg-nat.

I've exhausted a SQL server for ports, for science. Yes you are limited to the number of outgoing to ~64000 outgoing ports. Chances are your network equipment (not enterprise grade) will run out of switching contexts before you run out of ports.

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