[tor-dev] [RFC] Proposal draft: The move to a single guard node

Nicholas Hopper hopper at cs.umn.edu
Fri Apr 11 20:46:49 UTC 2014

On Fri, Apr 11, 2014 at 7:45 AM, George Kadianakis <desnacked at riseup.net> wrote:
> I see. That makes sense, I think.


> I will ponder on this a bit more, and then edit the proposal.

When/if you become convinced, let me know if you want me to draft a patch.

> (I would like to think a bit more about how accurate the assumption
> "relay has been a guard for 0.25 of the rotation period =>
> relay has 0.25 of its bandwidth occupied for guard purposes")

Here's another way to think of it: purely from a load balancing
perspective, we would like clients that rotated guards when R had its
guard flag to treat R like a guard, and clients that haven't to treat
R like it's not a guard.

Using the approximation ("fraction of periods R had the guard flag" =
"fraction of nodes that rotated when R had the guard flag") this means
that "relay has been a guard for 0.25 of the rotation period => 0.25
of the clients weight the relay as a guard."  Since we don't actually
want to partition the network this way, the (weighted) average of the
two weights will produce the same behavior.

Nicholas Hopper
Associate Professor, Computer Science & Engineering, University of Minnesota
Visiting Research Director, The Tor Project

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