Filename: 138-remove-down-routers-from-consensus.txt Title: Remove routers that are not Running from consensus documents Author: Peter Palfrader Created: 11-Jun-2008 Status: Closed Implemented-In: 0.2.1.2-alpha 1. Overview. Tor directory authorities hourly vote and agree on a consensus document which lists all the routers on the network together with some of their basic properties, like if a router is an exit node, whether it is stable or whether it is a version 2 directory mirror. One of the properties given with each router is the 'Running' flag. Clients do not use routers that are not listed as running. This proposal suggests that routers without the Running flag are not listed at all. 2. Current status At a typical bootstrap a client downloads a 140KB consensus, about 10KB of certificates to verify that consensus, and about 1.6MB of server descriptors, about 1/4 of which it requires before it will start building circuits. Another proposal deals with how to get that huge 1.6MB fraction to effectively zero (by downloading only individual descriptors, on demand). Should that get successfully implemented that will leave the 140KB compressed consensus as a large fraction of what a client needs to get in order to work. About one third of the routers listed in a consensus are not running and will therefore never be used by clients who use this consensus. Not listing those routers will save about 30% to 40% in size. 3. Proposed change Authority directory servers produce vote documents that include all the servers they know about, running or not, like they currently do. In addition these vote documents also state that the authority supports a new consensus forming method (method number 4). If more than two thirds of votes that an authority has received claim they support method 4 then this new method will be used: The consensus document is formed like before but a new last step removes all routers from the listing that are not marked as Running.