[tor-bugs] #21253 [Core Tor/Tor]: Add link handshakes to benchmark program

Tor Bug Tracker & Wiki blackhole at torproject.org
Fri Jan 20 16:41:28 UTC 2017


#21253: Add link handshakes to benchmark program
--------------------------+------------------------------------
 Reporter:  nickm         |          Owner:  nickm
     Type:  task          |         Status:  accepted
 Priority:  High          |      Milestone:  Tor: 0.3.0.x-final
Component:  Core Tor/Tor  |        Version:
 Severity:  Normal        |     Resolution:
 Keywords:                |  Actual Points:
Parent ID:                |         Points:
 Reviewer:                |        Sponsor:  SponsorU-must
--------------------------+------------------------------------

Comment (by nickm):

 work-in-progress branch in `linkbench`: done by kludging the unit test
 code, for fast results.

 TLS link handshake:

   - The biggest slowdown here comes from moving from 1024-bit RSA keys to
 2048-bit RSA keys on our TLS connections: this represents a 7x slowdown on
 the server side.  We should consider moving to ECDSA link certificates if
 they're used enough to make us not stand out.  This is the biggest
 additional cost in our new handshake.

 In-tor link handshake:

   - There appear to be no significant server-side slowdowns on the
 client->server link authentication stage.
   - The client side of the client->server link authentication stage is
 about 2x slower, but shouldn't matter for actual performance;
   - The server->server link authentication is slower than before by about
 the cost of a two ntor handshakes.  Caching certificate validity info
 could help here.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21253#comment:2>
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