# Old notes ## Do we actually do this? ```text How to deal with network down. - While all helpers are down/unreachable and there are no established or on-the-way testing circuits, launch a testing circuit. (Do this periodically in the same way we try to establish normal circuits when things are working normally.) (Testing circuits are a special type of circuit, that streams won't attach to by accident.) - When a testing circuit succeeds, mark all helpers up and hold the testing circuit open. - If a connection to a helper succeeds, close all testing circuits. Else mark that helper down and try another. - If the last helper is marked down and we already have a testing circuit established, then add the first hop of that testing circuit to the end of our helper node list, close that testing circuit, and go back to square one. (Actually, rather than closing the testing circuit, can we get away with converting it to a normal circuit and beginning to use it immediately?) ``` [Do we actually do any of the above? If so, let's spec it. If not, let's remove it. -NM] ## A thing we could do to deal with reachability And as a bonus, it leads to an answer to Nick's attack ("If I pick my helper nodes all on 18.0.0.0:*, then I move, you'll know where I bootstrapped") -- the answer is to pick your original three helper nodes without regard for reachability. Then the above algorithm will add some more that are reachable for you, and if you move somewhere, it's more likely (though not certain) that some of the originals will become useful. Is that smart or just complex? ## Some stuff that worries me about entry guards. 2006 Jun, Nickm It is unlikely for two users to have the same set of entry guards. Observing a user is sufficient to learn its entry guards. So, as we move around, entry guards make us linkable. If we want to change guards when our location (IP? subnet?) changes, we have two bad options. We could ```text - Drop the old guards. But if we go back to our old location, we'll not use our old guards. For a laptop that sometimes gets used from work and sometimes from home, this is pretty fatal. - Remember the old guards as associated with the old location, and use them again if we ever go back to the old location. This would be nasty, since it would force us to record where we've been. ``` [Do we do any of this now? If not, this should move into 099-misc or 098-todo. -NM]