mirror of
https://gitlab.torproject.org/tpo/core/tor.git
synced 2024-11-28 06:13:31 +01:00
47 lines
1.7 KiB
Plaintext
47 lines
1.7 KiB
Plaintext
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: 10-Mar-2007
|
|
Status: Open
|
|
|
|
Overview:
|
|
|
|
This document proposes that we change how directory authorities set the
|
|
stability flag from inspection of a router's declared Uptime to the
|
|
authorities' perceived mean time between failure for the router.
|
|
|
|
Motivation:
|
|
|
|
Clients prefer nodes that the authorities call Stable. This flag is (as
|
|
of 0.2.0.0-alpha-dev) set entirely based on the node's declared value for
|
|
uptime. This creates an opportunity for malicious nodes to declare
|
|
falsely high uptimes in order to get more traffic.
|
|
|
|
Spec changes:
|
|
|
|
Replace the current rule for setting the Stable flag with:
|
|
|
|
"Stable" -- A router is 'Stable' if it is active and its observed MTBF
|
|
for the past month is at or above the median MTBF for active routers.
|
|
Routers are never called stable if they are running a version of Tor
|
|
known to drop circuits stupidly. (0.1.1.10-alpha through 0.1.1.16-rc
|
|
are stupid this way.)
|
|
|
|
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.
|
|
|