BT’s Cohen on share ratios
p2pnet.net News:- BitTorrent creator Bram Cohen says he’s not willing to help private BitTorrent trackers, “accusing them of being destructive to sharing”.
Some private BitTorrent trackers watch members to make sure they upload as much as they download, says a Zeropaid interview with Cohen.
“Supporters say monitoring the upload/download ratio encourages sharing, resulting in faster download speeds. Those who do not reach the minimum ratio are normally banned from using the tracker,” says the story.
“To monitor user ratios’, trackers depend on clients reporting their true upload and download statistics. Programmers are increasingly exploiting this vulnerability by developing software which falsifies upload and download reports to the tracker.
“The exploit was first widely publicized over a year ago, but no solution has yet been found. Only standard code is sent to the tracker, which is impossible to verify using the current BitTorrent protocol.”
But just a ratio cheating software is becoming easier to use and more readily available, “the pressure is on Bram Cohen and BitTorrent Inc to update the protocol to catch ratio ‘cheats’,” says Zeropaid.
However, retorts Cohen, “[Leechers are] engaging in perfectly reasonable and non-destructive behavior and the site is trying to punish him for it, thus fostering the creation of clients which lie about their statistics. This is the site’s fault, and the result could do serious damage to the value of BitTorrent statistics generally. Sites which do this are being extremely destructive, and the way they grandstand about how they’re fostering sharing really ticks me off.”
In the Q&A, he argues the tit-for-tat nature of protocol is enough to stop destructive leeching; that the BitTorrent protocol is sufficiently robust to handle file sharers who limit their upload and don’t seed after files are downloaded and, “Even if almost everyone quit the instant their download was completed you’d still have decent download rates, they’d just be closer to everyone’s upload rates.”
“To encourage sharing beyond the tit-for-tat system, Cohen suggests that user ratios should not be monitored at the peak of each swarm, or if a torrent is heavily seeded,” says Zeropaid. “Alternatively, he suggests adapting an alternative method for calculating the ratio, which takes into consideration the health of a torrent.”
So far, it adds, “the BitTorrent world has not been turned on its head by ratio cheating software, but there is no accounting for the future. Without support from BitTorrent Inc. to upgrade the protocol, private tracker administrators who want to keep ratio monitoring may be forced to develop a new protocol.”
Also See:
Zeropaid - Bram Cohen Refuses BitTorrent Ratio Exploit Patch, October 11, 2006
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October 13th, 2006 at 3:07 pm
he’s right, if a tracker is making money on ads, they should seed the content themselves. which private trackers are complaining about this??
October 16th, 2006 at 7:22 pm
The author totally misses the point of share ratios. Share ratios are broken as a mechanism. Consider two examples: 1) unpopular torrents, and 2) widely seeded torrents.
If I download a set of rarer, unpopular torrents, I may not find people to upload to. As a result my share ratio suffers and I am prevented from downloading new files. The tracker only knows about files that it tracks, thus if I only downloaded unpopular torrents from the tracker, I may NEVER be able to recover my share ratio now matter how much I want people to uploade the unpopular torrents.
If a torrent is widely seeded, a similar situation arises. When there are more people uploading then downloading, few downloaders are downloading from me. It may take an enormous amount of time to recover the share ratio.
In neither scenario above was the victim peer misbehaving. They are simply scenarios under which share ratios should not be applied.
October 23rd, 2006 at 3:36 pm
It’s funny really. Every new “feature” proposed by researchers, hackers, ect always seem move in the direction of breaking the single most important philosophy of bittorrent which makes it work.
Which is that clients can’t trust each other and trackers should not trust clients. The ONLY data being exchanged is actual data and address/port information. The data is checked via checksum, and well adress/port is checked by if you can actually connect to the client (or tracker).
Any attempt to add data for ratios means somebody can cheat or lie.
I’m behind BT. Leave it alone. It works BECAUSE of the paranoid model!