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Re: Katrina Network Damage Report

  • From: Alan Spicer
  • Date: Sun Sep 11 06:53:27 2005


love IPv6 more than you guys would ever give to a sole. Shoot I could run a big ISP on a single 48. God bless America.

Bring it on... Why are you so afraid?

---
Alan Spicer ([email protected])
----- Original Message ----- From: "Steve Gibbard" <[email protected]>
To: <[email protected]>
Sent: Sunday, September 11, 2005 12:35 AM
Subject: Re: Katrina Network Damage Report


On Sat, 10 Sep 2005, Todd Underwood wrote:

interesting discussion.  at least we're talking about networking now.
:-)

wrt sean's comment, the only thing i can think he means by 'partition'
is that the networks may have power may be in some routing table but
just not the routing table of any of renesys's (or routeviews or ripe)
peers.  in that case, i guess i would agree.  our use of 'outage' is a
special case of 'partition' where the whole internet is on one side
and it's possible that the networks in question are on the other.
they may route somewhere.  just not to the internet.
The difference between a partitioning and a complete outage can depend a lot on what's on each side of the partition.

If my DSL line goes down, I suppose that's technically a partitioning. I can still get to the DNS server in the basement, or to my neighbors' computers on my wireless network, but not to anything else. Meanwhile, the rest of the Internet can't get to anything in my or my neighbors' houses, but is otherwise functional. Complaining that that was anything less than a complete outage would be at best extremely pedantic, since there's likely nobody on my home network who particularly cares about being able to get to other things on my home network.

However, the same sort of partitioning can happen on a much bigger scale. There are some countries or large regions that have several ISPs, an exchange point they use to connect to eachother, locally hosted content, and a single path out to the rest of the world. In those areas, it's possible for the international link to fail but for connectivity to the nearby portions of the Internet to work fine. In those cases, it's far less clear-cut to say, "they don't have access to the Internet," and might be more accurate to say that their part of the Internet had been cut off from the rest of the Internet.

(I gave a talk on this at NANOG and a few other conferences last spring. The associated paper is at http://www.pch.net/resources/papers/Gibbard-mini-cores.pdf)

From what I understand of the Renesys methodology, the difference between a partitioning and a total outage wouldn't be visible. A router in a region that wasn't able to send data to Florida wouldn't be able to send data to your collector (which doesn't mean the Renesys system isn't really cool for answering all sorts of other questions -- it is).

That said, I haven't heard any reports of a large scale partitioning happening in New Orleans. It sounds like most of what was down was down due to local infrastructure being under water or without power, so my guess is that the Renesys view was pretty accurate in this case. Thanks for sharing it.

-Steve


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