BGP leaks causing internet outages in Japan and beyond

Doesn't the following indicate that neither does Verizon?

In this case it appears Verizon had little or no filters, and accepted most if not all BGP announcements from Google which lead to widespread service disruptions. At the minimum Verizon should probably have a maximum-prefix limit on their side and perhaps some as-path filters which would have prevented the wide spread impact.

There are two (main) flavors, but here eBGP (external) is the relevant one. Instead of explaining how it'll route traffic through itself, Google can tell its neighbors that it can reach, say, Vodafone (but with a certain cost).

Importantly, this approach allows for autonomous systems to decide which routes to advertise to which neighbors. Content providers generally don't also provide transit, e.g. Google typically doesn't carry traffic from AT&T customers to Comcast customers free of charge, even if it is directly connected to both of them.

Now if Red and Blue get a cable connecting the two of them, they'll start speaking BGP to each other. Green will continue advertising the indirect path, but Red's routers and Blue's routers will see that they have a more direct path to each other, and not go through green. So while network engineers need to tell their routers about their direct connections, BGP will automatically help distant ISPs figure out the best indirect paths.

It looks like what happened is that Google, which is not an ISP but peers directly with a bunch of ISPs (so they get better performance than being behind a single ISP, as most smaller companies do), started advertising routes that looked more efficient than the actual routes between various ISPs. Technically, those packets can flow over Google, although Google doesn't have the capacity to route traffic on behalf of the internet at large (it's not an ISP), and probably has routing rules configured to not actually accept packets that aren't destined for Google sites.

So two things happened. The first is that internet connectivity was disrupted. The second is that we got to see, a bit, what Google's peering relationships look like, because of the routes that Google advertised.

You can think of an ASN as representing a (routinely changing) bundle of different IP prefixes. A large ISP will have several ASNs. A very big company that manages its own multihomed connectivity might have one. Most companies on the Internet do not have one; their ISP handles it for them. The fact that virtually no ISP will peer with you† explains why you can't easily subscribe to two ISPs and multihome through both of them.

BGP basically accomplishes two things:

1. It establishes which network operators have claims on which specific IP networks.

2. It establishes which network operators (via their ASNs) are connected to which other network operators, so that a participating router can figure out where to send traffic to an arbitrary IP address.

† for random message board values of "you"

edit: the point being, how to do it is not an issue. they're not in the position to do it. ...but if you were thinking of censorship or outright disruptive terrorism via BGP, you'd be looking for infiltrating network operator jobs, not developing an attack. the attacks themselves are trivial, well-documented, and often happen accidentally.

edit2: "sorry we broke the internet" http://seclists.org/nanog/1997/Apr/444