Do not use this page! It's heavily outdated.

No offense to the author(s). This article was probable written decades ago, where browser fingerprinting wasn't well researched and frequently discussed. You shouldn't add any optimization to the Tor Browser Bundle, because it will let you stand out from the other Tor Browser users. Resulting in being more pseudonymous than anonymous. The page has not been deleted, because wiping knowledge is almost ever a bad idea. It's useful to document the history and perhaps one or another optimization might be proposed for the Tor Browser Bundle. Are you up to it?

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) - See NOTE1 below.

Afterwards, just restart the browser and experience the difference! For some automated additional performance hacks, check out the FasterFox extension. You also can do the same tweaks manually with the help of this page.

NOTE1: Proxy pipelining may not be well supported by Privoxy. For this reason, you may want to install Polipo and use that instead of Privoxy to get the performance benefits of pipelining. If you use Torbutton (which you should, if you want any anonymity at all), all of the Tor-relevant privacy scrubbing features of Privoxy are no longer necessary.

NOTE2: Do not use page prefetching. Disable this if it is enabled. Prefetching is a speculative feature, which assumes that you will read the pages referenced by the links in the current page you are viewing. This places undue load on the Tor network and clog your circuits with unnecessary traffic. Its unlikely you will read all the pages referenced by the current page, especially in the case of search engines results.

Using Polipo Proxy (example assumes Windows - adjust accordingly)

Polipo as a proxy instead of Privoxy has been discussed in some places online, with reports that it is more performant. To use this proxy:

  • Install Polipo to the default location
  • Set Vidalia's Proxy application to:

'C:\Program Files\Polipo\polipo.exe' - without quotes.

  • Set Vidalia's Proxy application arguments to:

-c "C:\Program Files\Polipo\config"

You will not see a shell window for Polipo, but the process will be created and visible in the Task Manager. Check the process exists to assure it is working correctly.

Advanced Tuning of Tor

If you follow the previous authors work you should have well performing access. To go that bit further lets consider the ideal behavior 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.

A Tor Non-Functional Requirement (NFR)

Lets think of a Non-Functional 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 to do this ignore them, by timing out the building of circuits quickly.
  • now we have circuit build time-outs occurring more frequently, 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 don't want it being timed out by firewalls or anything else. We need to make sure a ping occurs on the circuit to prevent this.

In order to accomplish this, use the latest tor 0.2.2.x-alpha as circuit based timings are automatic and enabled by default.

Advanced Tuning of Polipo

Within Polipo's config file, add the following parameters at the top:

allowUnalignedRangeRequests = true
disableLocalInterface = true
maxPipelineTrain = 32
proxyName = "Polipo"
proxyPort = 8118
serverMaxSlots = 32

allowedClients = ""
cacheIsShared = false
censoredHeaders = from,accept-language,x-pad,link
censorReferer = maybe
chunkHighMark = 50000000
maxConnectionAge = 300s
maxConnectionRequests = 30000
tunnelAllowedPorts = 1-65535

The settings above enable Polipo to replace Privoxy, but still enables the Tor toggle button to operate, if you are using the Tor FireFox plugin.

Advanced Tuning of Privoxy

Privoxy is set to be a 'straight-through' proxy server, with the toggle switch. Its buffer is reduced to below that of RWIN. This is because RWIN represents the largest TCP receive window. Its value is chosen to be above Tor default socks size = 252KB

-- --
Privoxy:buffer 265 (KB)
toggle 0

Advanced Tuning of Windows

This section has been included last for those who are technically capable.

Processor Scheduling (win32)

Windows enables the program running in the foreground to have heightened processor resources. If this option is switched to 'Background Processes', Tor appears to return consistently higher performance. This option can be found in 'My Computer | Right click | Properties | Advanced Tab | Performance Settings | Advanced tab again.

!TCPOptimizer - 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 MTU, RWIN, SACK OPTS (rfc 2038), and tcp1323opts controlling window scaling. The tool has one button optimize. 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.

Windowsin TCP Optimizer
-- --
RWIN TCPOptimizer max setting
MTU 576, 1500 or 1492 - try all 3 settings
Window Scaling On
TcpIP TTL 128 (hops)
LANBufferSize 65535 (bytes)

You can view your connection parameters and their effects on your connections, both with Tor and without Tor, at DSLReports

Event ID 4226 Patcher - 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 infection 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 Catching time

Reducing DNS caching time reduces the risk of an invalid DNS resolve, given Tor servers may be operating in a DHCP environment that updates the IP each time the network connects.

Windowsregistry:TCPIP service
-- --
DNS Cache 36000(seconds (10 hours)) set in registry by hand, HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters
Last modified 6 years ago Last modified on Sep 11, 2012, 10:03:01 PM