On 2/24/2021 12:34 PM, William Kane wrote:

Thank you for running obfs4 bridges with iat_mode != 0, only very few obfs4 bridges support the additional traffic obfuscation in both directions.

Kudos to you my friend.

• William

Should I take this as a recommendation to update my bridges to support iat_mode=2.

Cheers.

2021-02-23 1:18 GMT, torjoy south_america_bridges@protonmail.com:

...

Hi All,

I work with time and frequency references and run some tor bridges. What is the objective of "iat_mode" setting? Is an good timming reference important for this setting? For now, i'm adminstrating 3 briges, one with iat_mode=0, iat_mode=1 and iat_mode=2. Could you explain or forward me to some reading about it?

Best regards,

Luiz

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Thanks for all your answers guys! Now i know that i'm doeing good running bridges in different iat modes. Actually I'm running 4 bridges, and two have iat_mode set to 0 and two others set to 1 and 2 respectively.

I also have a question about bridges speed. It seems that when I do use of my bridge (that is in same network of my PC) the connection is too slow (~1Mbps using relays in a circuit that clearly (by seeing it in tor metrics) has high bandwidth). I do use it as a guard relay. But, when i disable the settings, using the same circuit or an very similar one I can see that the speed bumps to more than 4 Mbps. Is there any optimizations that I can do in my bridge relay? I have 20 Mbps uplink and 200 Mbps downlink here. Set my speed setting to 10 Mbps maxium in torrc. I can also see that bridge is not overloaded (no high cpu usage and low number of connections around 180 for now).

Best regards,

Luiz

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‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ Em segunda-feira, 1 de março de 2021 às 10:38, William Kane ttallink@googlemail.com escreveu:

If you run more than three bridges, run an even distribution of bridges with iat_mode set to 0, 1 and 2, if you run only three bridges, one with each setting, if two, then 0 and 2, if only one, run it with 2 due to the lack of bridges supporting it, et cetera.

That's how I would handle it..

• William

  2021-02-24 23:44 GMT, Eddie stunnel@attglobal.net:

...

On 2/24/2021 12:34 PM, William Kane wrote:

...

Thank you for running obfs4 bridges with iat_mode != 0, only very few obfs4 bridges support the additional traffic obfuscation in both directions. Kudos to you my friend.

• William Should I take this as a recommendation to update my bridges to support iat_mode=2.

Cheers.

...

2021-02-23 1:18 GMT, torjoy south_america_bridges@protonmail.com:

...

Hi All, I work with time and frequency references and run some tor bridges. What is the objective of "iat_mode" setting? Is an good timming reference important for this setting? For now, i'm adminstrating 3 briges, one with iat_mode=0, iat_mode=1 and iat_mode=2. Could you explain or forward me to some reading about it? Best regards, Luiz Sent with ProtonMail Secure Email.

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"ServerTransportOptions obfs4 iat-mode=2" in torrc

On February 25, 2021 11:16:52 AM GMT+03:00, "Toralf Förster" toralf.foerster@gmx.de wrote:

On 2/24/21 9:34 PM, William Kane wrote:

...

Thank you for running obfs4 bridges with iat_mode != 0, only very few obfs4 bridges support the additional traffic obfuscation in both directions.

At my client I have iat_mode=2 set but I do wonder how to set that as default at a bridge?

-- Toralf

On 2/24/21 9:34 PM, William Kane wrote:

Thank you for running obfs4 bridges with iat_mode != 0, only very few obfs4 bridges support the additional traffic obfuscation in both directions.

SO why is this not the default?

-- Toralf

On 2/25/21 6:32 PM, niftybunny wrote:

And why did I read about this the first time in a mailing list?

+1

-- Toralf

On Thu, Feb 25, 2021 at 06:30:35PM +0100, Toralf Förster wrote:

SO why is this not the default?

The feature introduces a substantial performance penalty for a dubious and poorly understood privacy gain. If I were to write an algorithm to detect obfs4, I wouldn't bother dealing with its flow properties; there are easier ways to identify the protocol. In hindsight, it was probably a mistake to expose the iat option to users and bridge operators.

Cheers, Philipp