#8494: Document MaxAdvertisedBandwidth in the bandwidth list spec -------------------------------------------------+------------------------- Reporter: alphawolf | Owner: juga Type: defect | Status: | assigned Priority: Low | Milestone: Tor: | 0.3.5.x-final Component: Core Tor/Tor | Version: Severity: Normal | Resolution: Keywords: tor-spec, consensus, bandwidth, | Actual Points: MaxAdvertisedBandwidth tor-relay tor-dirauth | needs-insight tor-bwauth | Parent ID: #25925 | Points: Reviewer: | Sponsor: -------------------------------------------------+-------------------------
Comment (by juga): Collecting all commented lines and including the examples, we would have: Bandwidth generators MUST limit the relays' measured bandwidth based on the MaxAdvertisedBadwidth. A relay's MaxAdvertisedBandwidth limits the bandwidth-avg in its descriptor. bandwidth-avg is the minimum of MaxAdvertisedBandwidth, BandwidthRate, RelayBandwidthRate, BandwidthBurst, and RelayBandwidthBurst. Therefore, generators MUST limit a relay's measured bandwidth to its descriptor's bandwidth-avg. This limit needs to be implemented in the generator, because generators may scale consensus weights before sending them to Tor. Generators SHOULD NOT limit measured bandwidths based on descriptors' bandwidth-observed, because that penalises new relays. sbws limits the relay's measured bandwidth to the bandwidth-avg advertised. Torflow partitions relays based on their bandwidth. For unmeasured relays, Torflow uses the minimum of all descriptor bandwidths, including bandwidth-avg (MaxAdvertisedBandwidth) and bandwidth-observed. Then Torflow measures the relays in each partition against each other, which implicitly limits a relay's measured bandwidth to the bandwidths of similar relays. Torflow also generates consensus weights based on the ratio between the measured bandwidth and the minimum of all descriptor bandwidths (at the time of the measurement). So when an operator reduces the MaxAdvertisedBandwidth for a relay, Torflow reduces that relay's measured bandwidth. > What do you think about these subsections? > > > > No Zero Bandwidths > > > Bandwidth Aggregation > > > Bandwidth Scaling > > > MaxAdvertisedBandwidth Sounds good, just not sure how you have in mind to include them. A possibility would be: "bw=" Bandwidth [Exactly once.] The measured bandwidth of this relay. No Zero Bandwidths: Tor accepts zero bandwidths, but they trigger bugs in older Tor implementations. Therefore, implementations SHOULD NOT produce zero bandwidths. Instead, they SHOULD use one as their minimum bandwidth. If there are zero bandwidths, the parser MAY ignore them. Bandwidth Aggregation: Multiple measurements can be aggregated using an averaging scheme, such as a mean, median, or decaying average. Bandwidth Scaling: Torflow scales bandwidths to kilobytes per second. Other implementations SHOULD use kilobytes per second for their initial bandwidth scaling. If different implementations or configurations are used in votes for the same network, their measurements MAY need further scaling. See Appendix B for information about scaling, and one possible scaling method. MaxAdvertisedBandwidth: Bandwidth generators MUST limit the relays' measured bandwidth based on the MaxAdvertisedBadwidth. See Appendix C for more information. [...] C. MaxAdvertisedBandwidth [The text above without 1st sentence] Does this sounds good? > Please open another ticket for changes to other specs. i've created #26478 -- Ticket URL: <https://trac.torproject.org/projects/tor/ticket/8494#comment:19> Tor Bug Tracker & Wiki <https://trac.torproject.org/> The Tor Project: anonymity online
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