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61 lines
2.4 KiB
Plaintext
61 lines
2.4 KiB
Plaintext
Filename: 147-prevoting-opinions.txt
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Title: Eliminate the need for v2 directories in generating v3 directories
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Version: $Revision$
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Last-Modified: $Date$
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Author: Nick Mathewson
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Created: 2-Jul-2008
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Status: Accepted
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Target: 0.2.1.x
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Overview
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We propose a new v3 vote document type to replace the role of v2
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networkstatus information in generating v3 consensuses.
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Motivation
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When authorities vote on which descriptors are to be listed in the
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next consensus, it helps if they all know about the same descriptors
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as one another. But a hostile, confused, or out-of-date server may
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upload a descriptor to only some authorities. In the current v3
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directory design, the authorities don't have a good way to tell one
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another about the new descriptor until they exchange votes... but by
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the time this happens, they are already committed to their votes,
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and they can't add anybody they learn about from other authorities
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until the next voting cycle. That's no good!
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The current Tor implementation avoids this problem by having
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authorities also look at v2 networkstatus documents, but we'd like
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in the long term to eliminate these, once 0.1.2.x is obsolete.
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Design:
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We add a new value for vote-status in v3 consensus documents in
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addition to "consensus" and "vote": "opinion". Authorities generate
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and sign an opinion document as if they were generating a vote,
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except that they generate opinions earlier than they generate votes.
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Authorities don't need to generate more than one opinion document
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per voting interval, but may. They should send it to the other
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authorities they know about, at the regular vote upload URL, before
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the authorities begin voting, so that enough time remains for the
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authorities to fetch new descriptors.
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Additionally, authories make their opinions available at
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http://<hostname>/tor/status-vote/next/opinion.z
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and download opinions from authorities they haven't heard from in a
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while.
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Authorities MAY generate opinions on demand.
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Upon receiving an opinion document, authorities scan it for any
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descriptors that:
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- They might accept.
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- Are for routers they don't know about, or are published more
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recently than any descriptor they have for that router.
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Authorities then begin downloading such descriptors from authorities
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that claim to have them.
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Authorities MAY cache opinion documents, but don't need to.
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