Changes between Initial Version and Version 7 of Ticket #29084

May 14, 2019, 12:17:50 AM (18 months ago)


  • Ticket #29084

    • Property Parent ID changed from #28632 to
    • Property Summary changed from WTF-PAD: Test and improve circuit RTT measurement to Ensure circuit padding RTT estimate handes var cells/wide creates
    • Property Points changed from to 2
    • Property Sponsor changed from to Sponsor2
    • Property Milestone changed from Tor: 0.4.0.x-final to Tor: unspecified
  • Ticket #29084 – Description

    initial v7  
    1 From TODO file:
    2 {{{
    3   - Circuit RTT measurement will break on var_cell/EXTEND2 cells
    4     - Are there any heuristics we can use here?
    5       - If RELAY_EARLY is only for the first cell of an EXTEND2 series,
    6         we can use that. But the proposal currently says MAY, but not MUST
    7         for this behavior.
    8 }}}
     1The use_rtt_estimate field in the circuit padding machines lets machines offset the inter-packet delays by a middle-node estimated RTT value of packets that go from the middle to the exit/website.
     3We abort this measurement if we get two or more cells back-to-back in either direction, as this indicates that the half-duplex request/response circuit setup and RELAY_BEGIN sequence has finished.
     5However, if we switch to a multi-cell circuit handshake, then we will need to take that into account when measuring RTT.
     7If RELAY_EARLY is used only for the first cell of a multi-cell EXTEND2 payload,
     8then we can just count time between RELAY_EARLIES. But the proposal currently says MAY, but not MUST for this behavior.