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

  • From: Ross Vandegrift
  • Date: Fri Oct 26 11:01:32 2007

On Thu, Oct 25, 2007 at 05:36:11PM -0400, Scott Brim wrote:
> On 25 Oct 2007 at 17:02 -0400, Jason Frisvold allegedly wrote:
> > Anyone have any experience with these Anagran flow routers?  Are they
> > that much of a departure from traditional routing that it makes a big
> > difference?
> There's no difference in routing per se.  Rather it's in-band
> signaling of QoS parameters to provide feedback to queue management.

I read over the vendor's site when that article was sent, and I'll be
honest, a lot of what they are trumpeting are steps backwards in
router performance.

While the site is pretty light on the details, Anagram's "Fast Flow
Routing Architecture" sounds very similar to dated multilayer switching
approaches.  CEF-like adjacency certainly provides higher routing
throughput with less overhead.  So if it's a win, it must be a win
because the cost of going back to a flow-caching is offset by a gain
in better QoS.

Their QoS details are a bit sketchy, but this would worry me:

	BTC basically '"watches" every flow. By constantly comparing each
	flow's behavior over time against a simple set of operator-defined
	rules per flow class, BTC can identify "suspect" flows that by virtue
	of their duration, byte count, source/destination, or other criteria,
	require some form of corrective or policing action.

So now there's a "flow table" that in the forwarding plane.  What
happens when the flow table overflows?  How does the router decide
when to age-out a flow?  

I have yet to see a flow-centric filtering device save the network
when it's flow/session table is what's under attack.

Ross Vandegrift
[email protected]

"The good Christian should beware of mathematicians, and all those who
make empty prophecies. The danger already exists that the mathematicians
have made a covenant with the devil to darken the spirit and to confine
man in the bonds of Hell."
	--St. Augustine, De Genesi ad Litteram, Book II, xviii, 37