1 Filename: 138-remove-down-routers-from-consensus.txt
2 Title: Remove routers that are not Running from consensus documents
5 Author: Peter Palfrader
8 Implemented-In: 0.2.1.2-alpha
12 Tor directory authorities hourly vote and agree on a consensus document
13 which lists all the routers on the network together with some of their
14 basic properties, like if a router is an exit node, whether it is
15 stable or whether it is a version 2 directory mirror.
17 One of the properties given with each router is the 'Running' flag.
18 Clients do not use routers that are not listed as running.
20 This proposal suggests that routers without the Running flag are not
25 At a typical bootstrap a client downloads a 140KB consensus, about
26 10KB of certificates to verify that consensus, and about 1.6MB of
27 server descriptors, about 1/4 of which it requires before it will
28 start building circuits.
30 Another proposal deals with how to get that huge 1.6MB fraction to
31 effectively zero (by downloading only individual descriptors, on
32 demand). Should that get successfully implemented that will leave the
33 140KB compressed consensus as a large fraction of what a client needs
34 to get in order to work.
36 About one third of the routers listed in a consensus are not running
37 and will therefore never be used by clients who use this consensus.
38 Not listing those routers will save about 30% to 40% in size.
42 Authority directory servers produce vote documents that include all
43 the servers they know about, running or not, like they currently
44 do. In addition these vote documents also state that the authority
45 supports a new consensus forming method (method number 4).
47 If more than two thirds of votes that an authority has received claim
48 they support method 4 then this new method will be used: The
49 consensus document is formed like before but a new last step removes
50 all routers from the listing that are not marked as Running.