Twitter is obviously one of the big stories to come out of the Iranian election. And it's been a remarkable development -- no argument there. The tweets have been inspiring and courageous. And there's an aesthetic dimension to them that's hard to resist.
But understand... the tweets could be stopped (more on that below). In fact, I worry that Twitter's success in Iran will create a false confidence that the Internet can't be stopped, and that people's digital voices can't be silenced. They can -- and we should understand that keeping an open global Internet requires aggressive effort and activism.
I'm not a network guy, so techies please jump in and help me out. But here's my understanding of why Iran could stop the tweets if they really wanted to. In short, they could just turn off the Internet, much like Myanmar did.
From my tentative understanding, Iran's network is a lot like China's in that it's very centralized. This post explains (and illustrates) that the Iranian Internet traffic passes through a centralized bottleneck. (Imagine if the Holland Tunnel were the only way into Manhattan).
With this bottleneck in place, it's easy to filter traffic. Just like the post office could theoretically block every envelope going to San Francisco, Iran can block packets going to the IP address for "Facebook" or "Twitter." (Great NYT article on these basics here).
So here's where "proxies" come in (and techies, please help me out here if my understanding is off). Let's say you want to send a letter to San Francisco, but the post office doesn't allow it. Well, if you know that some dude in Kansas would forward your letter on to San Francisco, then you could go ahead and mail your SF-bound letter, but it would appear to the post office like it's going to Kansas.
So that's how tweets are getting through. They're essentially being sent to "middlemen" proxy servers -- which, in turn, allows the information to pass "in disguise" through the filter. It's like a digital Underground Railroad. (Great overview of proxies and services like Tor here).
But here's the thing -- they're only getting through because Iran has (for now) left its networks open, even though the government has apparently tried to limit bandwidth to prevent videos and pictures from getting out.
So assuming my descriptions are accurate, the point is that the Iranian government could in fact shut down the Internet, which would essentially strangle the tweets. I'm not sure why they haven't -- maybe the PR would just be too terrible.
So, yes, so long as the Internet remains open, it will be hard to limit people's voices. But that shouldn't disguise the depressing fact that governments exert enormous control over Internet access -- and could shut the whole thing down. For those interested in this very theme, I'd recommend the Wu/Goldsmith book Who Controls the Internet: Illusions of a Borderless World.
(Obviously, none of this is intended to downplay the extraordinary role Twitter and its users have played under truly frightening circumstances. It's inspiring. My only point is that it shouldn't give way to an excessive Internet triumphalism. An open Internet depends on policy choices -- it's not a independently-living organism that can overcome repressive policies.)