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  But a hostile, confused, or out-of-date server may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+  in the long term to eliminate these, once 0.1.2.x is obsolete.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