Feeds

Routing instability causes net traffic chaos

Interweb routing chart snarl-up

The Essential Guide to IT Transformation

Surfers experienced problems accessing parts of the internet Monday, following the flare-up of router instability problems.

Security watchers pinned the problem on "garbage" being thrown into global BGP (Border Gateway Routing) lookup tables, causing entries to become unnecessarily long. Some backbone routers with older software versions are unable to process this traffic, resulting in sessions getting dropped and problems reaching parts of the internet as a result.

BGP is a core routing protocol which, put simply, maps the best available routes for traffic to flow across the interweb. These routing tables have become snarled up with junk in the loose equivalent of motorists being instructed to go around a roundabout 20 times before proceeding with their journey. As a result traffic has become snarled up and, in some cases, may only be able to access parts of the net via the back-roads.

"The source of the problem appears to be with AS 47868 causing AS paths to become too long," writes Marcus H Sachs, director of the SANS Internet Storm Center. "Not much you can do about it unless you have access to your BGP router, in which case you might want to either block AS 47868 or limit the length of any AS path."

BGP autonomous system (AS) numbers represent unique routing domains, which are typically linked to administrative domains. These work something like place names, indicating the fastest routes on the information super-highway, with the important difference that these routing tables are not fixed but periodically updated.

Danny McPherson, chief security officer at Arbor Networks, explained that routers still running versions of Cisco software older than three years old didn’t allocate enough buffer space for "silly long AS paths, and so they blow chunks when they receive the update".

"However, other vendor implementations and patched versions happily propagate the update, apparently through numerous intermediate ASes, so seemingly random sets of BGP routers in the routing system were taking a dump, or dropping sessions with malformed AS path complaints," he notes.

Similar problems caused global routing instability five years ago, McPherson notes in a detailed technical dissection of the problem here.

The practical upshot of the problem is not altogether clear.

UK traffic stats from LINX look normal, but elsewhere Slashdot reports a "single mis-configured router is apparently able to cause a DOS for a huge chunk of the net". ®

The Essential Guide to IT Transformation

More from The Register

next story
Sysadmin Day 2014: Quick, there's still time to get the beers in
He walked over the broken glass, killed the thugs... and er... reconnected the cables*
VMware builds product executables on 50 Mac Minis
And goes to the Genius Bar for support
Auntie remains MYSTIFIED by that weekend BBC iPlayer and website outage
Still doing 'forensics' on the caching layer – Beeb digi wonk
Multipath TCP speeds up the internet so much that security breaks
Black Hat research says proposed protocol will bork network probes, flummox firewalls
Microsoft says 'weird things' can happen during Windows Server 2003 migrations
Fix coming for bug that makes Kerberos croak when you run two domain controllers
Cisco says network virtualisation won't pay off everywhere
Another sign of strain in the Borg/VMware relationship?
Forrester says Australia, not China, is next boom market for cloud
It's cloudy but fine down under, analyst says
prev story

Whitepapers

Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.
The Essential Guide to IT Transformation
ServiceNow discusses three IT transformations that can help CIO's automate IT services to transform IT and the enterprise.
Maximize storage efficiency across the enterprise
The HP StoreOnce backup solution offers highly flexible, centrally managed, and highly efficient data protection for any enterprise.