# Possible Discrepancy in Tor Project Webpage Setup Guide

**URL:** https://forum.torproject.org/t/possible-discrepancy-in-tor-project-webpage-setup-guide/7959
**Category:** Websites Feedback
**Tags:** tor-browser
**Created:** [June 12, 2023, 10:05am UTC](https://forum.torproject.org/t/possible-discrepancy-in-tor-project-webpage-setup-guide/7959 "2023-06-12T10:05:16Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![ukmr](https://forum.torproject.org/user_avatar/forum.torproject.org/ukmr/32/510_2.png) [@ukmr](https://forum.torproject.org/u/ukmr)
#### Post date: [June 12, 2023, 10:05am UTC](https://forum.torproject.org/t/possible-discrepancy-in-tor-project-webpage-setup-guide/7959/1 "2023-06-12T10:05:16Z")

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Hi!

I’ve observed what appears to be a discrepancy in the Tor Project’s obfs4proxy Debian / Ubuntu setup guide web documentation, regarding iat-mode.  
The Tor Project’s post-installation guide states,

“Paste the entire bridge line into Tor Browser:  
Bridge obfs4 : cert= iat-mode=0  
You’ll need to replace , , and with the actual values, which you can find in the tor log.”

> **[Tor Project | Post-install](https://community.torproject.org/relay/setup/bridge/post-install/)**
>
> Defend yourself against tracking and surveillance. Circumvent censorship. | Post-install

However, the Tor Project’s obfs4 Bridge Relay configuration guide webpage doesn’t state the requirement of the inclusion of iat-mode=0 in the torrc configuration file provided at:  
[https://community.torproject.org/relay/setup/bridge/debian-ubuntu/](https://community.torproject.org/relay/setup/bridge/debian-ubuntu/)

Therefore the individual following this guide, when they view the bridge relay’s full fingerprint found inside the Tor Data Directory, for example, in Debian/Ubuntu at /var/lib/tor/pt\_state/obfs4\_bridgeline.txt" then the iat-mode=0 parameter is not printed.

I’m not interested in contributing to the recent debate regarding “iat-mode=0/1/2” I’m merely stating what appears to be an omission in the Debian/Ubuntu Bridge obfs4 relay webpage configuration guide for a standard obfs4 Bridge relay.

In this neutral context if the obfs4 Bridge relay is to communicate iat-mode=0 to Tor Browser clients who might be configured with iat-mode=1/2 & connecting to this obfs4 bridge relay, is the inclusion of:

ServerTransportOptions obfs4 iat-mode=0

a mandatory requirement to be added to the torrc provided at [Tor Project | Debian / Ubuntu](https://community.torproject.org/relay/setup/bridge/debian-ubuntu/) ?

Would the exclusion of iat-mode=0 in the torrc be sufficient, technically, to notify any connecting Tor Browser clients utilising iat-modes 1&2 that these modes are not available on this obfs4 Bridge relay, or does the torrc explicitly require the inclusion of ServerTransportOptions obfs4 iat-mode=0 to communicate to the Tor Browser client that iat-mode is not available on this obfs4 Bridge relay?

Is it imperative that a obfs4 Bridge relay communicates the iat mode, if so then this should probably be stipulated in the instructions at [Tor Project | Debian / Ubuntu](https://community.torproject.org/relay/setup/bridge/debian-ubuntu/)  
to tally with the advice on the post install page which states,

" Paste the entire bridge line into Tor Browser: Bridge obfs4 : cert= iat-mode=0

To summarise, if iat-mode=0 is excluded from the torrc then the iat-mode will not be included in the full obfs4 Bridge relay fingerprint, displayed on the obfs4 Bridge relay Post Install webpage guide at [Tor Project | Post-install](https://community.torproject.org/relay/setup/bridge/post-install/)

To reiterate, this post is not intended to reignite the debate surrounding the use of iat-mode.  
It’s to help clarify the need/no need for the inclusion of ServerTransportOptions obfs4 iat-mode= in the torrc of a standard configuration of a obfs4 bridge relay.

If anyone feels prompted by this post to engage in further discussion regarding the use of iat=mode, please start a new topic. Thanks.