Version 133 (modified by trac, 11 years ago) (diff)


Hacking Firefox for Maximum Performance with Tor


Tor is known for being secure but slow. If you want to improve browsing speed a bit, please follow the following simple instructions for tweaking the Firefox web browser's settings:

Procedure 1

First, open Firefox's advanced settings menu by running about:config from the address bar. Upon entering this address, you will see a long list of internal settings. Modify the following ones and set them to the suggested values shown here for maximum performance:

{{{ network.http.keep-alive.timeout:600 (300ms default is OK usually, but 600 is better.) network.http.max-persistent-connections-per-proxy:16 (Default is 4) network.http.pipelining:true (Default- false. Some old HTTP/1.0 servers can't handle it.) network.http.pipelining.maxrequests:8 (No default) network.http.proxy.keep-alive:true (Default- true, but double check) network.http.proxy.pipelining:true (Default- false) }}}

Afterwards, just restart the browser and experience the difference! For some automated additional performance hacks, check out FireTune. Currently, FireTune is only for Win32, but you can do the same tweaks manually with the help of this page. Additionally, there is the FasterFox extension that is easy to install, and is also platform independent!

Procedure 2 - an update and addendum to Procedure 1

These results were arrived at empirically, using the win32 bundle, Tor & Privoxy & Vidalia bundle:

You will need the following tools...

Tor Button - enable / disable TOR access in FireFox

This provides an optional button or text in the bottom right of the browser window in Firefox. This allows you to switch Tor on and off.

FasterFox - Modify performance related settings in FireFox

This plugin modifies the networking and cache settings for Firefox. The following settings need to be modified.

  • You need to select 'Optimized' in the FasterFox Options.

Prio - Increase Vidalia / TOR process Priority (win32)

You will also realise a substantial increase in performance by increasing the process priority for the Vidalia process. You can do this in Task Manager after you identify vidalia.exe. If you want to persist the process priority you will need a Task Manager addon. This will allow the same process priority each time the OS loads Vidalia. An effective tool for doing this is Prio. This tool can only be used in a non-commercial setting, unless you license it. I dont recommend modifying the process above 'high'. If Vidalia crashes or freezes, the Windows OS will become unresponsive. Setting it to 'Above Normal' is a good start.

You can also elect to not load Vidalia at all. This seems to result in slightly improved performance.

TCP/IP - Optimise 2K/XP's throughput (win32)

Windows XP has a self-tuning IP stack, but it can still benefit from a little help. Using the TCP Optimiser tool from above you can tune the RWIN, SACK OPTS (rfc 2038), and tcp1323opts controlling window scaling. The tool has one button optimise. This setting is sufficient to benefit from immediate increases to Tor throughput. To increase throughput further you can try experimenting with lower values of the IP TTL (Time To Live). Values as low as 32 will work and result in improved performance. Also try experimenting with smaller TCPWindowSizes. This setting is automatically adjusted when you move the slider marked 'Connection Speed' of the TCPOptimizer tool. Maximum throughput occurs when TCPReceiveWindow sizes < 65536 are applied. Currently theory is that above this size, TCP Receive Window Scaling comes into effect on Windows 2K/XP. The current theory is that TOR does not negotiate Scaling Receive Windows very well, which causes the IP stream to stall, reducing overall throughput.

Remove the limit on TCP connection attempts XP SP2 (win32)

Remove the limit on TCP connection attempts has an interesting article detailing this restriction introduced in XP SP2. Microsoft have restricted the amount of half-open TCP/IP connections with the proviso that it would reduce the pace that worms spread. As noted by SpeedGuide, internet worms spread isotropically (multi-directionally) and so their infecton rate is exponential. As such, placing a constant (limit) on the rate of connection creation for every computer running XP SP2 will slow the rate of worms spreading (for that group of computers) but not by much. Consider the population of humans on the planet. Its over ~6 billion.

Supposing all these people are running Windows XP SP2, with rate limited half-open connections. Rate limiting is set to 10 half-open connections per second. To infect the entire population of computers would take: We are assuming optimum forward infection here. In the first second we have infected 10 machines. The 2nd second to elapse will cause (10 x 10) + 10 = 110 computers to be infected. The 3rd second to elapse would cause:

( (10 x 10) x 10 ) + (10 * 10) + 10 = 1110 computers to be infected. So the number of computers infected for every second that elapses is : computers infected = ~ 10 elapsedSeconds

In 12 seconds, we would have 10 12 = 1 billion computers infected. Full infection occurs before 13 seconds have elapsed !

This is all skewed by network topologies and routing algorithms, but they would affect a non-limited network in an identical manner. So the affect is a theoretical maximum of 13 seconds of additional notice to act against the worm. To all intents and purposes, this is useless.

Of much more interest is the effect on ANY network that relies on many open connections, such as Tor and a host of P2P applications. The effect here is a slow down of communications, with the limit acting as the catalyst.

Use the Event ID 4226 Patcher to mitigate against this.

DNS - reducing latency

For faster DNS performance generally (on win32 only i'm afraid) see...

When TOR starts it will report if it is using localhost to resolve DNS addresses. When you install FastCache, it sets up a local, cached and persistent store of DNS addresses. DNS resolves cost TOR a lot in terms of latency. A large part of TOR's reduction in speed is caused by setting up the path to the Onion routers that are servicing the request. Reduce DNS latency and the time cost of setting up the TOR channels are reduced.

Agnitum's Outpost firewall provides a DNS cache and is worth installing just for this feature. In combination you can use another firewall of your choice if you wish. If you choose to use another firewall with Outpost just acting as a DNS cache, make sure you disable all of Outposts additional plugins and all networking modifications that it can make.

Having completed testing, TOR addresses do appear in AnalogX FasterCache and Agnitum. FasterCache itself may prove unstable on occasion, with its icon stuck in its 'Red' - problem state. Try it and possibly update this page with your results.

--- N.B. the effect of FasterCache on TOR is still undetermined, although the 'DNS latency reduction' theory still applies. Also for all OS'es see...

Procedure 3

If you follow the previous authors work you should have well performing access. To go that bit further lets consider the ideal behaviour of our TOR client.

You will need: The on-line reference to TOR properties, that can be placed in torrc. Always back up this file before editing.

Lets think of a Service Level requirement we might like to place on our TOR client.

  • we want it to establish circuits as quickly as possible. If it takes too long ignore them, by timing out the building of circuits quickly.
  • now we have circuit build time-outs occuring more frequently as we don't wait too long for circuits to establish, we need to encourage TOR to try to generate circuits more often.
  • Once we have established a circuit, we are assuming its a good one and we dont want it being timed out by firewalls or anything else. We need to make sure a ping occurs on the circuit to prevent this.

Given this SLA, lets come up with some properties that may help satisfy it.

  • CircuitBuildTimeout NUM

Try for at most NUM seconds when building circuits. If the circuit isn't open in that time, give up on it. (Default: 1 minute.) Force circuits that are quick to establish and thus likely to push traffic more quickly. Values as low as 2 seconds have been tried with good results, although the author is not sure on the effect on anonymity.

  • KeepalivePeriod NUM

To keep firewalls from expiring connections, send a padding keepalive cell every NUM seconds on open connections that are in use. If the connection has no open circuits, it will instead be closed after NUM seconds of idleness. (Default: 5 minutes)

  • NewCircuitPeriod NUM

Every NUM seconds consider whether to build a new circuit. (Default: 30 seconds) Lets make TOR ready to establish a new circuit more readily.

The values to populate torrc with are as follows.

  • CircuitBuildTimeout 10
  • KeepalivePeriod 60
  • NewCircuitPeriod 15 (or try values as low as 2)

Bringing it all together - a typical configuration file for Windows

# This file was generated by Tor; if you edit it, comments will not be preserved
# The old torrc file was renamed to torrc.orig.1 or similar, and Tor will ignore it

# The advertised (external) address we should use.
# Limit the maximum token buffer size (also known as burst) to the given
# number of bytes.
BandwidthBurst 8192KB

# A token bucket limits the average incoming bandwidth on this node to the
# specified number of bytes per second.
BandwidthRate 4096KB

#MaxAdvertisedBandwidth N bytes|KB|MB|GB|TB If set, we will not advertise more than this amount of bandwidth for our BandwidthRate. Server operators who want to reduce the number of clients who ask to build circuits through them (since this is proportional to advertised bandwidth rate) can thus reduce the CPU demands on their server without impacting network performance.
MaxAdvertisedBandwidth 50KB

# Administrative contact information to advertise for this server.
ContactInfo NAME at ISP dot com
#Try for at most NUM seconds when building circuits. If the circuit isn't open in that time, give up on it. (Default: 1 minute.)
CircuitBuildTimeout 2

# If set, Tor will accept connections from the same machine (localhost only)
# on this port, and allow those connections to control the Tor process using
# the Tor Control Protocol (described incontrol-spec.txt).
ControlPort 9051

# Serve directory information from this port, and act as a directory cache.
DirPort 9030

# Send a padding cell every N seconds to keep firewalls from closing our
# connections while Tor is not in use.
KeepalivePeriod 60

# Where to send logging messages.  Format is minSeverity[-maxSeverity]
# (stderr|stdout|syslog|file FILENAME).
Log notice stdout

# Force Tor to consider whether to build a new circuit every NUM seconds.
NewCircuitPeriod 15

# Set the server nickname.
# Advertise this port to listen for connections from Tor clients and servers.
ORPort 9001

# Let a socks connection wait NUM seconds unattached before we fail it. (Default: 2 minutes.)
SocksTimeout 30

# If we have keept a clean (never used) circuit around for NUM seconds, then close it. This way when the Tor client is entirely idle, it can expire all of its circuits, and then expire its TLS connections. Also, if we end up making a circuit that is not useful for exiting any of the requests we're receiving, it won't forever take up a slot in the circuit list. (Default: 1 hour.)
CircuitIdleTimeout 600

#NumEntryGuards NUM
#    If UseEntryGuards is set to 1, we will try to pick a total of NUM routers as long-term entries for our circuits. (Defaults to 3.)
NumEntryGuards 8

The proof is in the pudding

With the changes made from Procedure 2 and 3, you can realise a sustained throughput of >100k, peaking at ~200k or more. These figures are based on the highest TOR bandwidth settings (>1.5mbps), through a 2mb connection. TOR at version 0.1.2.x uses an Asynchronous DNS resolver, the DNS tips above are still indeterminate for TOR traffic.

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