Can I ask a pretty newbie question - how is BGP connected to IP, TCP and DNS protocols? Is it sitting "below" them, "on top" of them, or is it somewhere else?
Why Google Went Offline Today and a Bit about How the Internet Works
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Re: Why Google Went Offline Today and a Bit about How the Internet Works
#52Since I use DuckDuckGo for searches, I probably wouldn't notice this. Not receiving Gmail for a while wouldn't be noteworthy (at least for the first half hour or so). I'm confused about the times the author gives, though. The article is dated today (11/6) and he says this happened 'today' at 6:24pm PST / 02:24 UTC. But unless I'm mistaken, that is a time currently in the future ( http://time.gov/timezone.cgi?Pacific/…
You're counting across the dateline, so for you it was 11/5.
Am I? Not snark: if I'm misunderstanding this, I truly want to know. I'm in central US, CST, and the article gives PST. That conversion has always just been +2 hours.
Re: Why Google Went Offline Today and a Bit about How the Internet Works
#53Can I ask a pretty newbie question - how is BGP connected to IP, TCP and DNS protocols? Is it sitting "below" them, "on top" of them, or is it somewhere else?
BGP runs on top of TCP, which runs on top of IP.
DNS runs on top of UDP (or sometimes TCP), which runs on top of IP.
Edited to elaborate: most computers on the internet don't need to know anything about BGP. It's not directly involved when you establish connections. Think of it as an automatic configuration system running on the various routers.
Re: Why Google Went Offline Today and a Bit about How the Internet Works
#54Can I ask a pretty newbie question - how is BGP connected to IP, TCP and DNS protocols? Is it sitting "below" them, "on top" of them, or is it somewhere else?
First, TCP and DNS don't come into it: they both piggyback on IP (TCP directly; DNS via UDP in typical use), so IP is all that's really relevant.
BGP is how routers communicate with each other. Every major edge router for a network is typically connected to many other edge routers for other networks. Each router announces what amounts to their complete routing table: i.e., for every IPv4/IPv6 address that they know how to route, they announce what networks it traverse on the way to the destination.
When a router is deciding which router an IP packet should hop to next, it looks at the packet's destination IP address and consults an in-memory data structure that it has constructed based on the BGP announcements of the routers to which it's connected. Modulo refining nuances (MED/PREF), it looks for two things:
1. It routes the packet according to the most specific network it saw announced. If it sees a packet destined for 1.2.3.4, and one connected router A is announcing a route for 1.2.3.0/24, and another connected router B is announcing a route for 1.2.0.0/16, it will pass along the packet to router A, all other things being equal.
2. As a tiebreaker for announcements with the same network specificity, it looks at the "AS path": the set of networks that the packet will traverse. It picks the router with the shortest path: the least number of traversed networks.
So the answer to your direct question is that BGP is "somewhere else": it's what routers use to communicate to each other "How will you route this IP packet?" and then make reasonable decisions about how they should send packets around the network.
Re: Why Google Went Offline Today and a Bit about How the Internet Works
#55Can I ask a pretty newbie question - how is BGP connected to IP, TCP and DNS protocols? Is it sitting "below" them, "on top" of them, or is it somewhere else?
BGP is comprised of long lived TCP connections between routers. The IP of the other router is well known and hard coded in the config afaik but I'm not a network engineer.
Re: Why Google Went Offline Today and a Bit about How the Internet Works
#56Can I ask a pretty newbie question - how is BGP connected to IP, TCP and DNS protocols? Is it sitting "below" them, "on top" of them, or is it somewhere else?
Re: Why Google Went Offline Today and a Bit about How the Internet Works
#57Earlier quoted context omitted.
There's a trend to use VoIP on cellphones too (see LTE). So in the future this will not help at all.
Is there some way to say "ignore DNS results from this provider", such that were you to spot an issue you could block that provider's information (and anyone replicating their version of the truth) and thus find a valid path. If that were possible you wouldn't be reliant on a third party to resolve the issue to get your system working, and once your system worked, you could contact them to resolve the issues for all.
If someone is giving out bad DNS records, you can just choose to use a different DNS server.
But in this case the problem was bad routes. You can certainly force your own routers to use fixed routes instead, but that doesn't help you unless everybody else along the path also does it. So it's not easy. There are tricks one can play -- like advertising your network as a set of smaller, more-specific networks (since routers will usually favor more-specific routes over more general ones).
Re: Why Google Went Offline Today and a Bit about How the Internet Works
#58It really makes one wonder about the fragility of the internet.
I would say the resilience is what impresses me here. The fact that it's decentralized means that anyone can fix the internet. The fact that this one specific problem was fixed within 26 min by individuals realizing the problem and acting to fix it gives me a warm feeling.
I think what you mean is that anyone can break the internet (in this case a random ISP from Indonesia) and that in that case only very specific people could fix it (probably at least a senior network engineer at said ISP).
Re: Why Google Went Offline Today and a Bit about How the Internet Works
#59Earlier quoted context omitted.
You're counting across the dateline, so for you it was 11/5.
Am I? Not snark: if I'm misunderstanding this, I truly want to know. I'm in central US, CST, and the article gives PST. That conversion has always just been +2 hours.
As I read it that was 18:24 yesterday in PST, or 02:24 today in UTC. The use of "today" may just be sloppy dating-- or it may reflect that it was today for most of those affected.
Re: Why Google Went Offline Today and a Bit about How the Internet Works
#60If you're interested in peering (couldn't resist the pun) behind the curtain, read the NANOG[1] mailing list. These are the real guys keeping the Internet up and running :)