torspec/proposals/145-newguard-flag.txt
2015-02-13 15:30:35 -05:00

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Filename: 145-newguard-flag.txt
Title: Separate "suitable as a guard" from "suitable as a new guard"
Author: Nick Mathewson
Created: 1-Jul-2008
Status: Superseded
[This could be obsoleted by proposal 141, which could replace NewGuard
with a Guard weight.]
[This _is_ superseded by 236, which adds guard weights for real.]
Overview
Right now, Tor has one flag that clients use both to tell which
nodes should be kept as guards, and which nodes should be picked
when choosing new guards. This proposal separates this flag into
two.
Motivation
Balancing clients amoung guards is not done well by our current
algorithm. When a new guard appears, it is chosen by clients
looking for a new guard with the same probability as all existing
guards... but new guards are likelier to be under capacity, whereas
old guards are likelier to be under more use.
Implementation
We add a new flag, NewGuard. Clients will change so that when they
are choosing new guards, they only consider nodes with the NewGuard
flag set.
For now, authorities will always set NewGuard if they are setting
the Guard flag. Later, it will be easy to migrate authorities to
set NewGuard for underused guards.
Alternatives
We might instead have authorities list weights with which nodes
should be picked as guards.