[tor-relays] two relays serving same hidden service

[Roger Dingledine]

On Sat, Apr 09, 2011 at 04:23:21PM -0400, cmeclax-sazri wrote:
> Suppose I have this setup: Dhole, Dingo, and Fennec are three computers on a 
> LAN. Dhole and Dingo both have external IP addresses and both run Tor relays. 
> Fennec runs a hidden service. Both Dhole and Dingo have the same hidden 
> service address, paxamifrabolerfu.onion, pointing to Fennec's LAN address. 
> Alice tries to connect to paxamifrabolerfu.onion. What happens?

First, it doesn't matter if they're relays or clients. Hidden services
don't need to be on a relay.

The answer if two different Tors have the same hidden service private
key is that they will each publish a hidden service descriptor. Whichever
one published more recently is the one that a user accessing the hidden
service will probably find and use.

This approach can provide a very crude load balancing. More interesting,
it can also provide a very crude failover, where if one of them
disappears, an hour or so later the other will publish and the hidden
service will become reachable again.

--Roger