Utp | The Official BitTorrent Blog

I was recently invited to participate in a workshop sponsored by the GIIC, an organization of telecom and technology executives who ponder large scale Internet and information infrastructure questions. The purpose of this workshop was to consider changes to the Internet infrastructure that would allow cost transparency, an upgrade to the Internet platform that could have wide ranging implications for the economic models that currently prevail online.

While that topic is worthy of exploration on its own, some of the many areas explored during this particular gathering were in matters of policy and the recently announced rulemaking proposal by the FCC towards a principle of network neutrality. And throughout the many discussions, it became apparent that those on the “market” side of this debate have a very difficult challenge ahead of them: How can they frame the debate in a way that doesn’t have them come across as online versions of Strom Thurmond? This is no small challenge given the basic issues of equality are wrapped into our national identity and any implications of inequality tug at the strings of that identity. So as a starter, I’d suggest attempts at branding users (customers) as bandwidth hogs will not yield a useful approach toward this end. Does society favor discrimination against those who over-eat? Even on an increasingly green political landscape, any definition of a “reasonable consumption level” is going to be, to say the very least, “sensitive”.

Some defensible ground remains in the areas of network congestion if one can stake out clear and reasonable technical arguments and actions defending those principles. Being the target of a great many technologies currently deployed to shape, block and throttle (i.e. discriminate) it would be easy for BitTorrent to assume the role of victim in our little analogy. I suspect there is a great deal of mileage to be had in this approach amid the fury of debate. But this isn’t our plan. Instead, we’ve spent considerable energy developing technologies in µTP to combat the underlying premise of discrimination, Internet congestion. And while it remains to be seen how the market will react to these developments, whether the DPI currently deployed will be modified to discriminate against µTP as well, there is an opportunity for one side of the debate to stand behind their principles and in so doing demonstrate the potential of self regulation to the benefit of all.

–Eric–

μTP or “micro-Transport Protocol” is a new protocol from BitTorrent, Inc. that is at the heart of the new major release of our popular BitTorrent clients “μTorrent” and “BitTorrent Mainline”. It is going to be available as the default transport mechanism in both μTorrent v2.0 and BitTorrent v7.0. So what’s the big deal? And why do we want this to be the centerpiece of our future software?

The fact is that our BitTorrent clients have become incredibly popular with users downloading large files over the internet. So much so that some observers claim that BitTorrent traffic accounts for 30%, 50%, or even more of all Internet traffic. Regardless of the actual numbers (which we have no way of knowing), it is clear that the popularity of BitTorrent is putting such a burden on ISP networks that they sometimes react by slowing down or interfering with that traffic.

Now there is a whole “net neutrality” debate, partly about whether ISPs should be allowed to interfere with internet traffic from one particular app simply because it is “too popular” – some argue that perhaps ISPs could invest more so that supply meets demand – but this debate is not the focus here. At BitTorrent we like to be a bit more pragmatic, to assert that there is responsibility on the part of both the ISPs and authors of popular applications like BitTorrent to make sure that the internet scales smoothly to meet demand.

Which brings us back to μTP:

News of μTP started to leak to the public late last year with some wild and totally untrue reporting that we were trying to make BitTorrent more greedy and were somehow “declaring war” on users of other applications. In fact completely the opposite is true, as was subsequently acknowledged by the initial author’s follow-up article.

μTP is a completely new implementation of the BitTorrent protocol with a major new design objective – μTP is designed to be network friendly – to not swamp network connections when there are other apps trying to send and receive – and to resolve the key problem that ISPs use to justify interference with BitTorrent traffic.

If BitTorrent traffic volume is so great that it overwhelms end-users’ connections (leading to service calls from consumers whose internet doesn’t work), then μTP eliminates this problem by being better at only using bandwidth when there is no other traffic competing, and automatically slowing or stopping BitTorrent transfers before network connections seize up.

Legacy BitTorrent traffic uses the standard internet “TCP” protocol to govern when it tries to go faster or slow down. The problem with TCP is that it can only detect a problem by waiting to see if packets are dropped. Unfortunately, by the time packets are being lost, the problem is already acute and the consumers connection has already drastically slowed or stopped. TCP is a lot like trying to drive with your eyes closed. You only notice something’s wrong when you hit something.

μTP is like driving with your eyes *open* – μTP is able to see problems coming and make much more modest adjustments to ensure the problems don’t cause a car wreck. It does this by being able to detect congestion on a network based on how long a packet takes to be sent from one peer to the next. If things start to take longer, then μTP adjusts the rate of sending accordingly.

As it happens, this trick has required some very deep engineering work – the way the client talks to other clients has had to be completely re-built. As a side effect, because the new protocol so different, it is practically invisible to some of the nasty traffic shaping techniques that some ISPs have been using. We doubt whether this happy result will last for long, and nor is it the point of the technology. The point is to reduce the need for such gear rather than to evade it.

Overall, when we get μTP stable, we’re excited about the potential benefits that this could bring to ISPs by reducing the effective burdens on their networks. Although we stand to gain nothing financially from them for implementing it, we hope to maintain the lead enjoyed by μTorrent and BitTorrent Mainline software as the most popular BitTorrent clients, and hopefully demonstrate how innovation from responsible stakeholders on a neutral internet can lead to winning outcomes all-around.

– Simon–