"ARPANet Co-Founder Predicts An Internet Crisis" (slashdot)

Thu Oct 25 21:40:36 UTC 2007

Paul Vixie wrote:
> "Dr. Larry Roberts, co-founder of the ARPANET and inventor of packet
> switching, predicts the Internet is headed for a major crisis in an article
> published on the Internet Evolution web site today. Internet traffic is now
> growing much more quickly than the rate at which router cost is decreasing,
> Roberts says. At current growth levels, the cost of deploying Internet
> capacity to handle new services like social networking, gaming, video, VOIP,
> and digital entertainment will double every three years, he predicts, creating
> an economic crisis. Of course, Roberts has an agenda. He's now CEO of Anagran
> Inc., which makes a technology called flow-based routing that, Roberts claims,
> will solve all of the world's routing problems in one go."
> 
> http://slashdot.org/article.pl?sid=07/10/25/1643248

So I seem to recall flow cached l3 switches being rather common. ;)

Over here in the firewall business we offload flows from the firewall
policy enforcement engine into flow cached forwarding engines. In both
cases (switch/firewall) you trade one expense (fib lookups) with another
(keeping track of flow state for the purposes of forwarding). Since
statefull inspection firewalls have to track flow state anyway paying
the flow state tax is a built in assumption.

The problem of flow cached switches was the first packet hitting the
processor from each flow. Most of the flows are rather short so the
processor ended up with more than it's share of the heavy lifting for
the prevailing internet style traffic workloads. I suppose if one pushed
flow caches down into the forwarding engines of current router asics you
could reap the benefits of not performing a longest match match lookup
on every packet, though mostly you just have another look aside
interface and yet more memory contributing additional complexity that's
poorly utilized in worse case workloads...

Like I said if you're buying a firewall or a load balancer you probably
get to pay this tax anyway, but the core router customer voted with
their wallets a while ago, and while revisiting the issue occasionally
is probably worth it I wouldn't expect flow caching to be the revolution
that got everyone to swap out their gear.