138-remove-down-routers-from-consensus.txt 2.0 KB

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  1. Filename: 138-remove-down-routers-from-consensus.txt
  2. Title: Remove routers that are not Running from consensus documents
  3. Author: Peter Palfrader
  4. Created: 11-Jun-2008
  5. Status: Closed
  6. Implemented-In: 0.2.1.2-alpha
  7. 1. Overview.
  8. Tor directory authorities hourly vote and agree on a consensus document
  9. which lists all the routers on the network together with some of their
  10. basic properties, like if a router is an exit node, whether it is
  11. stable or whether it is a version 2 directory mirror.
  12. One of the properties given with each router is the 'Running' flag.
  13. Clients do not use routers that are not listed as running.
  14. This proposal suggests that routers without the Running flag are not
  15. listed at all.
  16. 2. Current status
  17. At a typical bootstrap a client downloads a 140KB consensus, about
  18. 10KB of certificates to verify that consensus, and about 1.6MB of
  19. server descriptors, about 1/4 of which it requires before it will
  20. start building circuits.
  21. Another proposal deals with how to get that huge 1.6MB fraction to
  22. effectively zero (by downloading only individual descriptors, on
  23. demand). Should that get successfully implemented that will leave the
  24. 140KB compressed consensus as a large fraction of what a client needs
  25. to get in order to work.
  26. About one third of the routers listed in a consensus are not running
  27. and will therefore never be used by clients who use this consensus.
  28. Not listing those routers will save about 30% to 40% in size.
  29. 3. Proposed change
  30. Authority directory servers produce vote documents that include all
  31. the servers they know about, running or not, like they currently
  32. do. In addition these vote documents also state that the authority
  33. supports a new consensus forming method (method number 4).
  34. If more than two thirds of votes that an authority has received claim
  35. they support method 4 then this new method will be used: The
  36. consensus document is formed like before but a new last step removes
  37. all routers from the listing that are not marked as Running.