We recently noted that uTorrent, now owned by BitTorrent, released a new version of their client that lays uTP, the micro transport protocol, on top of UDP. That decision results in better congestion control, but it also prevents the kind of TCP RST packet attacks Comcast has used to throttle upstream P2P traffic, and in some cases allows users to skirt ISP throttling. BitTorrent insists to us their intention was a more Internet and network-friendly client, not to evade throttling.

While it may not have been BitTorrent's intent, our resident throttled Bell Canada & TekSavvy customers are using the client to dodge ISP throttling, albeit with mixed results. Many users who only saw P2P download speeds of between 20-50k/s, are now seeing speeds closer to 150-300k/s. Others however, claim the new beta client, which BitTorrent reiterates isn't yet prepped for general release, makes no difference in reducing throttling.

To be clear, bypassing Bell Canada throttling is not anywhere in the alpha's design motivation. It is just a coincidence. -BitTorrent's Simon Morris

According to network expert Robb Topolski, the BBR user who first discovered Comcast's use of forged packets to kill upstream P2P delivery, the new client should help all users skirt ISPs who are using RST packet resets to cripple P2P (he's written a guide in our forums, here).

However, it won't be of much use to those hoping to evade Comcast's new protocol agnostic throttling system, which throttles a user back if a particular CMTS port is congested, and if that user has been consuming more than 70% of his allotted throughput for more than fifteen minutes.

Regardless, Topolski says the new client is designed to avoid congestion. "Users using uTP will not likely ever trigger the 70% threshold on a congested network port," he says. "uTP will detect the congestion condition through increased round-trip-times and start backing off before any packets get de-prioritized." He notes that while Comcast's throttling system takes 15 minutes to kick in, uTP does it in real time.

By this point you're probably grokking the larger point that the new client is actually fairly friendly to congested networks and the Internet, contrary to the hyperbolic tirade by Richard Bennett that garnered the Register oodles of hits last week as outlet after outlet pointed out that Bennett was wrong. Bennett's primary goal was to use the uTorrent announcement as a lectern for his anti-network neutrality positions, suggesting that neutrality laws would block ISPs from filtering any shift to a UDP-driven P2P platform -- causing the Internet to explode.

Bennett contacted me this week to suggest that the title of our original post on the new uTorrent client (New UDP uTorrent Takes Aim At Throttling), was at least partially responsible for his proclamation that Bittorrent had "declared war on VoIP, gamers," and was ushering forth digital oblivion. Bennett has since penned a follow up piece at El Reg that takes a drastically different tone from the first (the comments are worth reading).

I went back to the source to confirm that evading throttling was nowhere on BitTorrent's radar when designing the new uTorrent client, and spoke to Simon Morris, head of Product Management at BitTorrent.

"To be clear, bypassing Bell Canada throttling is not anywhere in the alpha's design motivation," says Morris, head of Product Management at BitTorrent. "It is just a coincidence." According to Morris, the client really won't be all that useful for anybody not dealing with throttling more sophisticated that TCP RST resets.

"If an ISP were relying completely on forged TCP reset packets to throttle Bittorrent traffic, then uTP would certainly evade this method," says Morris. But he notes there's some serious limitations to this. "Our client only talks uTP to other clients that talk uTP," he says - noting that the forged-TCP-reset-packet throttling method "would only be evaded completely in swarms consisting entirely of our new uTorrent 1.9 alpha client and uTorrent 1.8 clients" (which accept incoming uTP connections but default to TCP when trying to make outgoing connections).

"Of course there are many Bittorrent clients out there, and for now only some uTorrent clients will speak uTP," he notes. "I suspect this is what is behind the variable effects reported by your users."

Meanwhile, Topolski says ISPs have no real technical excuse to take specific aim at UDP P2P, not least of which being that protocol agnostic throttling systems really don't care. "Being more congestion-responsive than any other Internet use, it cannot congest the last mile," he says. "If some ISP decides they want to buy new updated DPI products to detect and throttle this too, they will be unable to use congestion as the excuse for doing so."