Gaba Rodriguez

The State of IPv6 Support on the Tor Network

Gaba Rodriguez
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The team behind the Tor Project has been making good on its goal to provide improved IPv6 support on the Tor network. Here's an update!

In our last article on RIPE Labs we talked about work that took place in 2020 that was related to giving IPv6 support to the Tor network. Tor is the first release that includes all the work we described there. Relays running are the first to report IPv6 bandwidth statistics.

Tor Versions

As of 2 December 2020, 54% of the relays on the network run a version of Tor that supports IPv6. Of the 6,852 relays in the network, 3,587 are running version 0.4.4 and 8 relays are running the latest Tor version 0.4.5. From all those, 1,588 are announcing an IPv6 address and port for the OR protocol. 1,587 relays are reachable on IPv6 by the directory authorities. 626 permit exiting to IPv6 targets.


Graph of Relays by IP Version

 The latest consensus published in November contains:

  • 6,538 relays:
    • 1,562 of these (36.39% TCW) have an IPv6 ORPort
    • 1,067 of these (24.86% TCW) support at least partial IPv6 reachability checks
    •  55 of these (1.90% TCW) support full IPv6 reachability checks
  • 2,527 "usable guards" and Wgd=0.
    • 641 of these (29.73% UGCW) support IPv6 clients.
    • 446 of these (21.33% UGCW) support at least partial IPv6 reachability checks.
    • 36 of these (2.92% UGCW) support full IPv6 reachability checks.


Fraction of reported bytes for which IP version is known


The IPv6 stats that we are collecting are:

  • The number of Tor relays that support IPv6 reachability checks (full versus partial)
  • The number of Tor relays that have an IPv6 ORPort
  • The number of connections, and consumed bandwidth, using IPv4 and IPv6
  • IPv6 bandwidth statistics

Remember that for relays to report IPv6 bandwidth statistics, they would have to set the option ConnDirectionStatistics to 1 and leave the ExtraInfoStatistics option enabled (it is on by default) to be able to report IPv6 bandwidth statistics. This is the relay operators’ decision, since relays are operated by volunteers. We will keep the statistics code in the codebase for when 0.4.5 is released and relays start reporting it.

The Tor Project was a funding recipient of the RIPE NCC Community Projects Fund 2019.

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About the author

Gabriela Rodriguez is responsible for supporting all engineering projects at Tor. She coordinates roadmaps, tracks priorities, and ensures that Tor is always thinking “user first.” Gabriela has been developing software for over 20 years working for companies and nonprofits in Uruguay, California, and internationally. Prior to joining Tor, Gabriela coordinated a program on gender and technology at Tactical Tech Collective in Latin America and before that, she was a Software Engineer at Mozilla Foundation.

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