BitTorrent Throttling: Interview With Gemini Project

Every week there is more controversy as ISPs continue to limit, throttle and otherwise interfere with P2P traffic. For those people who think their ISP is meddling with their traffic, there is a new system available to confirm it. TorrentFreak catches up with the creators of Gemini Project.


For years now, many ISPs have sought to limit P2P traffic as they try to reduce bandwidth consumption due to their lack of preparation for the online video and music sharing boom. When it was first revealed that Comcast had been using hacker techniques to limit the effectiveness of BitTorrent traffic, there was quite an uproar and this even led to a FCC hearing.

Of course, it’s not just Comcast messing with transfers, there are many other ISPs around the world using a wide range of techniques to limit P2P traffic. As file-sharers become more aware that ISPs aren’t necessarily giving their subscribers what they hoped they’d already paid for (unlimited traffic etc), slow speeds or erratic transfers often raise suspicions of meddling.

However, ISPs aren’t forthcoming about these activities so asking them often gets people nowhere. Now, thanks to some new software, file-sharers can find out for themselves. TorrentFreak caught up with and the Gemini Project for the low-down.

TF: What was the inspiration for Gemini Project? Who chose this project name and why?

[_SHIN_]: Well… as to the first part of the question, we can’t but think of a negative inspiration. We’re referring to the much-trumpeted slogan “Internet without limits” dominating the ads for almost all the ISPs. What makes it negative is the fact that the slogan is all about false promises masking a real inability of the providers to recognize the natural evolution of the transmissions over the Internet. Inability that becomes unsustainable when it comes to adjust the physical structures to the ever-developing nature of Internet communications. We all know there’s a general discrimination against peer-to-peer.

The aim of our project is to help the users lamenting over filters and slow downs to find evidence of ISP manipulations.

As to the name, «Gemini» stands for the synchronized activity of the two systems (Gemini A and Gemini B), where the first knows exactly what to expect from the latter, and vice versa.

TF: When did work on the Gemini Project begin? Who is involved and how much time has been spent?

[_SHIN_]: Neither the core application nor the method which that is based upon are original creations by we’ve just limited ourselves to put some points of the EFF detailed guide into practice, always keeping in mind that in order to check ISP filters, there needs to be a traceable communications between two hosts, with a given ISP in between.

In about a month, some members of staff had discussed and technically developed the project. The point we’ve worked on most has been the creation of a system that would be simple for newbies to use while preserving those requirements pointed out by the EFF as necessary in order to get valid, non-altered results.

The test ambiance requires a definite setup that’s overtly invasive, as it involves installing softwares of packet inspection and analysis, disabling NAT and firewall, modifying the configuration for Ethernet cards, and so on.

We thought the best solution was to use a Live operating system in two versions, with the needed software and analysis tools already installed on it, so that users would not have to intervene too much in the process.

TF: Would you tell us a little about the technical aspects of the project, such as the software/systems used and why they were chosen?

[_SHIN_]: The operating system we used as a base is Ubuntu Gutsy Gibbon 7.10, on which we’ve pre-installed and configured the following elements: Wireshark, a BitTorrent client/tracker, a ZIP file containing mp3 to be transferred from A to B, pcapdiff. We’ve chosen BitTorrent protocol because it is, as far as we know, one of the most filtered, together with the eMule network.

TF: How does the system work?

[_SHIN_]: Each Gemini user launch his/her version of the system (A or B) and type the other user’s IP address. When the two systems locate one another’s presence, clocks are synchronized (via time server) and network-card setups are performed, and the requirements for a valid test (NAT and firewall disabled) are checked. If all the requirements are met, Gemini_A creates the .torrent file out of the ZIP, generating the tracker and the seed.

Gemini_B starts the download. Transmission is recorded on both hosts using Wireshark. After a predetermined period (the default is 4 minutes), Gemini_A sends Gemini_B the Wireshark log, so that Gemini_B can perform a traffic comparison through pcapdiff, producing a final report.

TF: How can the users interpret the data they get from these tests?

[_SHIN_]: The final report is a text file that’s easy enough for an ordinary user to interpret. We’d say it’s self-explanatory. The report shows:
– the overall number of sent/received packets
– the number of forged packets
– the number of dropped packets.

The number of dropped packets should be relatively low, while the number of forged packets should approach zero. Whoever performs the test and needs help to interpret the results, is invited to open a thread in the forum dedicated to Gemini Project – we’ll help them to understand if his/her ISP is really jamming peer-to-peer traffic.

TF: Thanks for taking the time to speak with us. Do you have anything to add?

[_SHIN_]: There are other things (i.e extensions to the python pcapdiff script, new methods of analysis, etc.) we’re planning to develop and include into coming versions of the project. But improvements and add-ons will depend on community interest and Gemini circulation.

Further information and operating details are available on the forum.

The Gemini ISOs can be downloaded from

Gemini A and Gemini B

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