Tor network parameters This file lists the recognized parameters that can appear on the "params" line of a directory consensus. Table of Contents 1. Network protocol parameters 2. Performance-tuning parameters 3. Voting-related parameters 4. Circuit-build-timeout parameters 5. Directory-related parameters 6. Pathbias parameters 7. Relay behavior 8. V3 onion service parameters 9. Denial-of-service parameters 10. Padding-related parameters 11. Guard-related parameters 12. Relay behavior X. Obsolete parameters 1. Network protocol parameters "circwindow" -- the default package window that circuits should be established with. It started out at 1000 cells, but some research indicates that a lower value would mean fewer cells in transit in the network at any given time. Min: 100, Max: 1000, Default: 1000 First-appeared: Tor 0.2.1.20 "UseOptimisticData" -- If set to zero, clients by default shouldn't try to send optimistic data to servers until they have received a RELAY_CONNECTED cell. Min: 0, Max: 1, Default: 1 First-appeared: 0.2.3.3-alpha Default was 0 before: 0.2.9.1-alpha Removed in 0.4.5.1-alpha; now always on. "usecreatefast" -- Used to control whether clients use the CREATE_FAST handshake on the first hop of their circuits. Min: 0, Max: 1. Default: 1. First-appeared: 0.2.4.23, 0.2.5.2-alpha Removed in 0.4.5.1-alpha; now always off. "min_paths_for_circs_pct" -- A percentage threshold that determines whether clients believe they have enough directory information to build circuits. This value applies to the total fraction of bandwidth-weighted paths that the client could build; see path-spec.txt for more information. Min: 25, Max: 95, Default: 60 First-appeared: 0.2.4 "ExtendByEd25519ID" -- If true, clients should include Ed25519 identities for relays when generating EXTEND2 cells. Min: 0. Max: 1. Default: 0. First-appeared: 0.3.0 "sendme_emit_min_version" -- Minimum SENDME version that can be sent. Min: 0. Max: 255. Default 0. First appeared: 0.4.1.1-alpha. "sendme_accept_min_version" -- Minimum SENDME version that is accepted. Min: 0. Max: 255. Default 0. First appeared: 0.4.1.1-alpha. "allow-network-reentry" -- If true, the Exit relays allow connections that are exiting the network to re-enter. If false, any exit connections going to a relay ORPort or an authority ORPort and DirPort is denied and the stream is terminated. Min: 0. Max: 1. Default: 0 First appeared: 0.4.5.1-alpha. 2. Performance-tuning parameters "CircuitPriorityHalflifeMsec" -- the halflife parameter used when weighting which circuit will send the next cell. Obeyed by Tor 0.2.2.10-alpha and later. (Versions of Tor between 0.2.2.7-alpha and 0.2.2.10-alpha recognized a "CircPriorityHalflifeMsec" parameter, but mishandled it badly.) Min: 1, Max: 2147483647 (INT32_MAX), Default: 30000. First-appeared: Tor 0.2.2.11-alpha "perconnbwrate" and "perconnbwburst" -- if set, each relay sets up a separate token bucket for every client OR connection, and rate limits that connection independently. Typically left unset, except when used for performance experiments around trac entry 1750. Only honored by relays running Tor 0.2.2.16-alpha and later. (Note that relays running 0.2.2.7-alpha through 0.2.2.14-alpha looked for bwconnrate and bwconnburst, but then did the wrong thing with them; see bug 1830 for details.) Min: 1, Max: 2147483647 (INT32_MAX), Default: (user setting of BandwidthRate/BandwidthBurst). First-appeared: 0.2.2.7-alpha Removed-in: 0.2.2.16-alpha "NumNTorsPerTAP" -- When balancing ntor and TAP cells at relays, how many ntor handshakes should we perform for each TAP handshake? Min: 1. Max: 100000. Default: 10. First-appeared: 0.2.4.17-rc "circ_max_cell_queue_size" -- This parameter determines the maximum number of cells allowed per circuit queue. Min: 1000. Max: 2147483647 (INT32_MAX). Default: 50000. First-appeared: 0.3.3.6-rc. "KISTSchedRunInterval" -- How frequently should the "KIST" scheduler run in order to decide which data to write to the network? Value in units of milliseconds. If 0, then the KIST scheduler should be disabled. Min: 0. Max: 100. Default: 10. First appeared: 0.3.2 3. Voting-related parameters "bwweightscale" -- Value that bandwidth-weights are divided by. If not present then this defaults to 10000. Min: 1 First-appeared: 0.2.2.10-alpha "maxunmeasuredbw" -- Used by authorities during voting with method 17 or later. The maximum value to give for any Bandwidth= entry for a router that isn't based on at least three measurements. First-appeared: 0.2.4.11-alpha "FastFlagMinThreshold", "FastFlagMaxThreshold" -- lowest and highest allowable values for the cutoff for routers that should get the Fast flag. This is used during voting to prevent the threshold for getting the Fast flag from being too low or too high. FastFlagMinThreshold: Min: 4. Max: INT32_MAX: Default: 4. FastFlagMaxThreshold: Min: -. Max: INT32_MAX: Default: INT32_MAX First-appeared: 0.2.3.11-alpha "AuthDirNumSRVAgreements" -- Minimum number of agreeing directory authority votes required for a fresh shared random value to be written in the consensus (this rule only applies on the first commit round of the shared randomness protocol). Min: 1. Max: INT32_MAX. Default: 2/3 of the total number of dirauth. 4. Circuit-build-timeout parameters "cbtdisabled", "cbtnummodes", "cbtrecentcount", "cbtmaxtimeouts", "cbtmincircs", "cbtquantile", "cbtclosequantile", "cbttestfreq", "cbtmintimeout", "cbtlearntimeout", "cbtmaxopencircs", and "cbtinitialtimeout" -- see "2.4.5. Consensus parameters governing behavior" in path-spec.txt for a series of circuit build time related consensus parameters. 5. Directory-related parameters "max-consensus-age-to-cache-for-diff" -- Determines how much consensus history (in hours) relays should try to cache in order to serve diffs. (min 0, max 8192, default 72) "try-diff-for-consensus-newer-than" -- This parameter determines how old a consensus can be (in hours) before a client should no longer try to find a diff for it. (min 0, max 8192, default 72) 6. Pathbias parameters "pb_mincircs", "pb_noticepct", "pb_warnpct", "pb_extremepct", "pb_dropguards", "pb_scalecircs", "pb_scalefactor", "pb_multfactor", "pb_minuse", "pb_noticeusepct", "pb_extremeusepct", "pb_scaleuse" -- DOCDOC 7. Relay behavior "refuseunknownexits" -- if set to one, exit relays look at the previous hop of circuits that ask to open an exit stream, and refuse to exit if they don't recognize it as a relay. The goal is to make it harder for people to use them as one-hop proxies. See trac entry 1751 for details. Min: 0, Max: 1 First-appeared: 0.2.2.17-alpha "onion-key-rotation-days" -- (min 1, max 90, default 28) "onion-key-grace-period-days" -- (min 1, max onion-key-rotation-days, default 7) Every relay should list each onion key it generates for onion-key-rotation-days days after generating it, and then replace it. Relays should continue to accept their most recent previous onion key for an additional onion-key-grace-period-days days after it is replaced. (Introduced in 0.3.1.1-alpha; prior versions of tor hardcoded both of these values to 7 days.) "AllowNonearlyExtend" -- If true, permit EXTEND cells that are not inside RELAY_EARLY cells. Min: 0. Max: 1. Default: 0. First-appeared: 0.2.3.11-alpha "overload_dns_timeout_scale_percent" -- This value is a percentage of how many DNS timeout over N seconds we accept before reporting the overload general state. It is scaled by a factor of 1000 in order to be able to represent decimal point. As an example, a value of 1000 means 1%. Min: 0. Max: 100000. Default: 1000. First-appeared: 0.4.6.8 "overload_dns_timeout_period_secs" -- This value is the period in seconds of the DNS timeout measurements (the N in the "overload_dns_timeout_scale_percent" parameter). For this amount of seconds, we will gather DNS statistics and at the end, we'll do an assessment on the overload general signal with regards to DNS timeouts. Min: 0. Max: 2147483647. Default: 600 First-appeared: 0.4.6.8 8. V3 onion service parameters "hs_intro_min_introduce2", "hs_intro_max_introduce2" -- Minimum/maximum amount of INTRODUCE2 cells allowed per circuits before rotation (actual amount picked at random between these two values). "hs_intro_min_lifetime", "hs_intro_max_lifetime" -- Minimum/maximum lifetime in seconds that a service should keep an intro point for (actual lifetime picked at random between these two values). "hs_intro_num_extra" -- Number of extra intro points a service is allowed to open. This concept comes from proposal #155. "hsdir_interval" -- The length of a time period. See rend-spec-v3.txt section [TIME-PERIODS]. "hsdir_n_replicas" -- Number of HS descriptor replicas. "hsdir_spread_fetch" -- Total number of HSDirs per replica a tor client should select to try to fetch a descriptor. "hsdir_spread_store" -- Total number of HSDirs per replica a service will upload its descriptor to. "HSV3MaxDescriptorSize" -- Maximum descriptor size (in bytes). "hs_service_max_rdv_failures" -- This parameter determines the maximum number of rendezvous attempt an HS service can make per introduction. Min 1. Max 10. Default 2. First-appeared: 0.3.3.0-alpha. "HiddenServiceEnableIntroDoSDefense" -- This parameter makes tor start using this defense if the introduction point supports it (for protover HSIntro=5). Min: 0. Max: 1. Default: 0. First appeared: 0.4.2.1-alpha. "HiddenServiceEnableIntroDoSBurstPerSec" -- Maximum burst to be used for token bucket for the introduction point rate-limiting. Min: 0. Max: INT32_MAX. Default: 200 First appeared: 0.4.2.1-alpha. "HiddenServiceEnableIntroDoSRatePerSec" -- Refill rate to be used for token bucket for the introduction point rate-limiting. Min: 0. Max: INT32_MAX. Default: 25 First appeared: 0.4.2.1-alpha. 9. Denial-of-service parameters Denial of Service mitigation parameters. Introduced in 0.3.3.2-alpha: "DoSCircuitCreationEnabled" -- Enable the circuit creation DoS mitigation. "DoSCircuitCreationMinConnections" -- Minimum threshold of concurrent connections before a client address can be flagged as executing a circuit creation DoS "DoSCircuitCreationRate" -- Allowed circuit creation rate per second per client IP address once the minimum concurrent connection threshold is reached. "DoSCircuitCreationBurst" -- The allowed circuit creation burst per client IP address once the minimum concurrent connection threshold is reached. "DoSCircuitCreationDefenseType" -- Defense type applied to a detected client address for the circuit creation mitigation. 1: No defense. 2: Refuse circuit creation for the length of "DoSCircuitCreationDefenseTimePeriod". "DoSCircuitCreationDefenseTimePeriod" -- The base time period that the DoS defense is activated for. "DoSConnectionEnabled" -- Enable the connection DoS mitigation. "DoSConnectionMaxConcurrentCount" -- The maximum threshold of concurrent connection from a client IP address. "DoSConnectionDefenseType" -- Defense type applied to a detected client address for the connection mitigation. Possible values are: 1: No defense. 2: Immediately close new connections. "DoSRefuseSingleHopClientRendezvous" -- Refuse establishment of rendezvous points for single hop clients. 10. Padding-related parameters "circpad_max_circ_queued_cells" -- The circuitpadding module will stop sending more padding cells if more than this many cells are in the circuit queue a given circuit. Min: 0. Max: 50000. Default 1000. First appeared: 0.4.0.3-alpha. "circpad_global_allowed_cells" -- DOCDOC "circpad_global_max_padding_pct" -- DOCDOC "circpad_padding_disabled" -- DOCDOC "circpad_padding_reduced" -- DOCDOC "nf_conntimeout_clients" -- DOCDOC "nf_conntimeout_relays" -- DOCDOC "nf_ito_high_reduced" -- DOCDOC "nf_ito_low" -- DOCDOC "nf_ito_low_reduced" -- DOCDOC "nf_pad_before_usage" -- DOCDOC "nf_pad_relays" -- DOCDOC "nf_pad_single_onion" -- DOCDOC 11. Guard-related parameters (See guard-spec.txt for more information on the vocabulary used here.) "UseGuardFraction" -- If true, clients use `GuardFraction` information from the consensus in order to decide how to weight guards when picking them. Min: 0. Max: 1. Default: 0. First appeared: 0.2.6 "guard-lifetime-days" -- Controls guard lifetime. If an unconfirmed guard has been sampled more than this many days ago, it should be removed from the guard sample. Min: 1. Max: 3650. Default: 120. First appeared: 0.3.0 "guard-confirmed-min-lifetime-days" -- Controls confirmed guard lifetime: if a guard was confirmed more than this many days ago, it should be removed from the guard sample. Min: 1. Max: 3650. Default: 60. First appeared: 0.3.0 "guard-internet-likely-down-interval" -- If Tor has been unable to build a circuit for this long (in seconds), assume that the internet connection is down, and treat guard failures as unproven. Min: 1. Max: INT32_MAX. Default: 600. First appeared: 0.3.0 "guard-max-sample-size" -- Largest number of guards that clients should try to collect in their sample. Min: 1. Max: INT32_MAX. Default: 60. First appeared: 0.3.0 "guard-max-sample-threshold-percent" -- Largest bandwidth-weighted fraction of guards that clients should try to collect in their sample. Min: 1. Max: 100. Default: 20. First appeared: 0.3.0 "guard-meaningful-restriction-percent" -- If the client has configured tor to exclude so many guards that the available guard bandwidth is less than this percentage of the total, treat the guard sample as "restricted", and keep it in a separate sample. Min: 1. Max: 100. Default: 20. First appeared: 0.3.0 "guard-extreme-restriction-percent" -- Warn the user if they have configured tor to exclude so many guards that the available guard bandwidth is less than this percentage of the total. Min: 1. Max: 100. Default: 1. First appeared: 0.3.0. MAX was INT32_MAX, which would have no meaningful effect. MAX lowered to 100 in 0.4.7. "guard-min-filtered-sample-size" -- If fewer than this number of guards is available in the sample after filtering out unusable guards, the client should try to add more guards to the sample (if allowed). Min: 1. Max: INT32_MAX. Default: 20. First appeared: 0.3.0 "guard-n-primary-guards" -- The number of confirmed guards that the client should treat as "primary guards". Min: 1. Max: INT32_MAX. Default: 3. First appeared: 0.3.0 "guard-n-primary-guards-to-use", "guard-n-primary-dir-guards-to-use" -- number of primary guards and primary directory guards that the client should be willing to use in parallel. Other primary guards won't get used unless the earlier ones are down. "guard-n-primary-guards-to-use": Min 1, Max INT32_MAX: Default: 1. "guard-n-primary-dir-guards-to-use" Min 1, Max INT32_MAX: Default: 3. First appeared: 0.3.0 "guard-nonprimary-guard-connect-timeout" -- When trying to confirm nonprimary guards, if a guard doesn't answer for more than this long in seconds, treat lower-priority guards as usable. Min: 1. Max: INT32_MAX. Default: 15 First appeared: 0.3.0 "guard-nonprimary-guard-idle-timeout" -- When trying to confirm nonprimary guards, if a guard doesn't answer for more than this long in seconds, treat it as down. Min: 1. Max: INT32_MAX. Default: 600 First appeared: 0.3.0 "guard-remove-unlisted-guards-after-days" -- If a guard has been unlisted in the consensus for at least this many days, remove it from the sample. Min: 1. Max: 3650. Default: 20. First appeared: 0.3.0 12. Relay behavior "assume-reachable" -- If true, relays should publish descriptors even when they cannot make a connection to their IPv4 ORPort. Min: 0. Max: 1. Default: 0. First appeared: 0.4.5.1-alpha. "assume-reachable-ipv6" -- If true, relays should publish descriptors even when they cannot make a connection to their IPv6 ORPort. Min: 0. Max: 1. Default: 0. First appeared: 0.4.5.1-alpha. X. Obsolete parameters "NumDirectoryGuards", "NumEntryGuards" -- Number of guard nodes clients should use by default. If NumDirectoryGuards is 0, we default to NumEntryGuards. NumDirectoryGuards: Min: 0. Max: 10. Default: 0 NumEntryGuards: Min: 1. Max: 10. Default: 3 First-appeared: 0.2.4.23, 0.2.5.6-alpha Removed in: 0.3.0 "GuardLifetime" -- Duration for which clients should choose guard nodes, in seconds. Min: 30 days. Max: 1826 days. Default: 60 days. First-appeared: 0.2.4.12-alpha Removed in: 0.3.0. "UseNTorHandshake" -- If true, then versions of Tor that support NTor will prefer to use it by default. Min: 0, Max: 1. Default: 1. First-appeared: 0.2.4.8-alpha Removed in: 0.2.9. "Support022HiddenServices" -- Used to implement a mass switch-over from sending timestamps to hidden services by default to sending no timestamps at all. If this option is absent, or is set to 1, clients with the default configuration send timestamps; otherwise, they do not. Min: 0, Max: 1. Default: 1. First-appeared: 0.2.4.18-rc Removed in: 0.2.6