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Tor network 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
First-appeared: Tor 0.2.1.20
"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
"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
"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
"min_paths_for_circs_pct" -- DOCDOC
"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
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)
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 indepedently. 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)
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 4294967295. Default 50000.
First-appeared: 0.3.3.6-rc.
"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.
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 params.
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
onion key lifetime parameters:
"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.)
8. V3 onion service parameters
Hidden service v3 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 new proposed extension if available by the introduction
point (for protover HSIntro=5). Min: 0. Max: 1. Default: 0. 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
DoSCircuitCreationDefenseTimePeriod period.
"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.
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
"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
"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
"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
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