[tor-bugs] #15482 [Tor]: Don't surprise users with new circuits in the middle of browsing

[Tor Bug Tracker & Wiki]

#15482: Don't surprise users with new circuits in the middle of browsing
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     Reporter:           |      Owner:  mikeperry
  mikeperry              |     Status:  needs_information
         Type:           |  Milestone:  Tor: 0.2.7.x-final
  enhancement            |    Version:
     Priority:  normal   |   Keywords:  tbb-usability, MikePerry201503,
    Component:  Tor      |  tbb-wants, TorBrowserTeam201507R
   Resolution:           |  Parent ID:
Actual Points:           |
       Points:           |
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Comment (by yawning):

 From an IRC discussion with arma today...

 This is probably contributing to things like:
 https://tor.stackexchange.com/questions/7164/why-do-relays-not-end-idle-
 tcp-sessions

 (TLDR: Someone is running a relay on a gigabit residential line behind an
 ISP supplied awful router, and it ends up being underutilized because the
 NAT table fills up.)

 Since channels are torn down after the last circuit is destroyed,
 extending circuit lifespan will increase the number of open channels at a
 given time, this new behavior probably is increasing the damage done by
 relays on residential lines to network health.

 IMO it's not a reason to kill this feature since this problem will crop up
 as the network and our userbase grows (As the number of users tends
 towards infinity, the number of channels required at any given time gets
 closer and closer to the total number of relays in the network for a
 middle relay).

 Metrics on the number of open circuits/channels on a given relay may be
 useful to get an idea about what we should ask of relay operators.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/15482#comment:26>
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