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+Filename: 138-remove-down-routers-from-consensus
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+Title: Remove routers that are not Running from consensus documents
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+Version: $Revision$
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+Last-Modified: $Date$
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+Author: Peter Palfrader
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+Created: 11-Jun-2008
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+Status: Open
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+
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+1. Overview.
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+
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+ Tor directory authorities hourly vote and agree on a consensus document
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+ which lists all the routers on the network together with some of their
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+ basic properties, like if a router is an exit node, whether it is
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+ stable or whether it is a version 2 directory mirror.
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+
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+ One of the properties given with each router is the 'Running' flag.
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+ Clients do not use routers that are not listed as running.
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+
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+ This proposal suggests that routers without the Running flag are not
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+ listed at all.
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+
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+2. Current status
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+
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+ At a typical bootstrap a client downloads a 140KB consensus, about
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+ 10KB of certificates to verify that consensus, and about 1.6MB of
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+ server descriptors, about half of which it requires before it will
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+ start building circuits.
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+
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+ Another proposal deals with how to get that huge 1.6MB fraction to
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+ effectively zero (by downloading only individual descriptors, on
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+ demand). Should that get successfully implemented that will leave the
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+ 140KB compressed consensus as a large fraction of what a client needs
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+ to get in order to work.
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+
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+ About one third of the routers listed in a consensus are not running
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+ and will therefor never be used by clients who use this consensus.
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+ Not listing those routers will safe about 30% to 40% in size.
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+
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+3. Proposed change
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+
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+ Authority directory servers produce vote documents that include all
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+ the servers they know about, running or not, like they currently
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+ do. In addition these vote documents also state that the authority
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+ supports a new consensus forming method (method number 4).
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+
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+ If more than two thirds of votes that an authority has received claim
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+ they support method 4 then this new method will be used: The
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+ consensus document is formed like before but a new last step removes
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+ all routers from the listing that are not marked as Running.
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Nick Mathewson