[tor-bugs] #8494 [Tor]: Relay bandwidth in consensus should not exceed MaxAdvertisedBandwidth

Tor Bug Tracker & Wiki blackhole at torproject.org
Tue Mar 19 19:29:17 UTC 2013


#8494: Relay bandwidth in consensus should not exceed MaxAdvertisedBandwidth
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 Reporter:  alphawolf                                      |          Owner:                     
     Type:  defect                                         |         Status:  new                
 Priority:  normal                                         |      Milestone:  Tor: unspecified   
Component:  Tor                                            |        Version:  Tor: 0.2.4.11-alpha
 Keywords:  consesnsus, bandwidth, MaxAdvertisedBandwidth  |         Parent:                     
   Points:                                                 |   Actualpoints:                     
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Comment(by alphawolf):

 That could be... but then is there a point to having
 MaxAdvertisedBandwidth?  If I dropped my MaxAdvertisedBandwidth to 20KB,
 but left !RelayBandwidthRate at 128 KB, wouldn't the directory authorities
 decide that I provide waaay more bandwidth than others reporting 20 KB,
 causing more circuits to choose my relay and negating the purpose of
 setting this variable?  This bandwidth weighting stuff is confusing :-)

 Perhaps I should explain what I'm *trying* to accomplish, and what I've
 observed, and we can go from there...

 I've noticed that both the traffic I receive and the "bandwidth" in the
 consensus are rather volatile.  For example, when my consensus bandwidth
 is around my actual bandwidth, I receive lots of traffic... to the point
 of consistently saturating the !RelayBandwidthRate I've set, with frequent
 spikes up to RelayBandwidthBurst.  This tends to be followed by a sharp
 decrease in my bandwidth as reported in the consensus... which shortly
 after leads to a dramatic drop in traffic.  Then the consensus increases
 again and we repeat this cycle.  I'm trying level out this cycle.

 My theory was that if I reported less bandwidth than I actually had (plus
 had some "reserve" via RelayBandwidthBurst), then there would usually be
 enough bandwidth available when the "bandwidth scanners" came knocking
 that they would say "Yep, he's got as much bandwidth as he claims he has".
 This would, in theory, keep my consensus bandwidth level, and in theory,
 prevent the surge/drought cycle of traffic.  It hasn't actually worked out
 that way :-)  As of right now, the consensus bandwidth for my relay has
 dropped to "52" (down from "108" when this bug report was created), and my
 traffic is now but a trickle.

 So I guess... does MaxAdvertisedBandwidth actually *do* anything (or at
 least a *predictable* anything)... and if not, perhaps this bug report
 should be re-named "Deprecate MaxAdvertisedBandwidth".

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/8494#comment:2>
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