Commit abd1ca18 authored by Nick Mathewson's avatar Nick Mathewson 🐘
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r12522@Kushana: nickm | 2007-03-10 02:38:33 -0500 

 Mark 107 closed (since it was implemented and merged into the spec). Put MTBF proposal in 108.


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doc/spec/proposals/000-index.txt

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@@ -25,4 +25,5 @@ Proposals by number: 
104  Long and Short Router Descriptors [OPEN]

105  Version negotiation for the Tor protocol [OPEN]

106  Checking fewer things during TLS handshakes [CLOSED]

107  Uptime Sanity Checking [OPEN]
 
107  Uptime Sanity Checking [CLOSED]

108  Base "Stable" Flag on Mean Time Between Failures [OPEN]

doc/spec/proposals/107-uptime-sanity-checking.txt

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   limit and spec wording was suggested by Roger in an or-dev post on 9 March

   2007.



   This proposal also led to 108-mtbf-based-uptime.txt
 
   This proposal also led to 108-mtbf-based-stability.txt

doc/spec/proposals/108-mtbf-based-uptime.txt

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Filename: 108-mtbf-based-stability.txt

Title: Base "Stable" Flag on Mean Time Between Failures

Version: $Revision: 12105 $

Last-Modified: $Date: 2007-01-30T07:50:01.643717Z $

Author: Nick Mathewson

Created:

Status: Open



Overview:



   This document proposes that we change how directory authorities set the

   stability flag from inspection of routers declared Uptime to the

   authorities' perceived mean time between failure for the router.



Motivation:



   Clients prefer nodes that the authorities call Stable.  This flags are (as

   of 0.2.0.0-alpha-dev) set entirely based on the nodes' declared values for

   uptime.  This creates an opportunity for malicious nodes to declare

   falsely high uptimes in order to get more traffic.



Spec changes:



   Instead of setting the current rule for setting the Stable flag:



   "An authority should call a server Stable if its observed MTBF for

   the past month is at or above the median MTBF for Valid servers.



   MTBF shall be defined as the mean length of the runs observed by a

   given directory authority.  A run begins when an authority decides

   that the server is Running, and ends when the authority decides that

   the server is not Running.  In-progress runs are counted when

   measuring MTBF."



Issues:



   How do you define a clipped MTBF?  If the current month begins with one

   day at the end of a one-year uptime, and then has 29 days of uptime, do we

   average one day and 29 days?  Or do we average one year and 29 days?  Or

   take 29 days on its own and discard the year?



   Surely somebody has done this kinds of thing before.