AT&T MPLS / BIB Routers

Jim Gettys jg at freedesktop.org
Wed Feb 16 17:09:50 CST 2011


On 02/16/2011 05:44 PM, Mikeal Clark wrote:
> We just put in a AT&T MPLS and are having a pretty negative experience with
> the "Business in a Box" routers they are using for our smaller sites.  We
> are seeing extremely high latency under load.  Anyone have any experience
> with these devices that could shed some light on this?  Are they really this
> bad?
>

There is excessive buffering in all sorts of devices all over the 
Internet. This causes high latency under load (along with higher packet 
losses, and lots of other problems.

It's what I've been blogging about on http://gettys.wordpress.com. These 
buffers fill; and they are so large they have defeated TCP congestion 
avoidance to boot, with horrifying consequences.

So far, I've found this problem (almost) everywhere I've looked:
	o ICSI has good data that bufferbloat is endemic in DSL, Cable, and 
FIOS.  Delays are often measured in seconds (rather than milliseconds).
	o some corporate and ISP networks run without AQM, in circumstances 
that they should.
	o Windows, Mac OSX and Linux all have bufferbloat in their network 
stacks, at a minimum on recent network device drivers, and often elsewhere.
	o Every home router I've tested is horrifyingly bad.
	o 3g networks & 802.11 have this in spades.

Why should AT&T's MPLS be any different?

My next topic will be "transient" bufferbloat, having to do with 
defeating slowstart.

Come start helping fix this: please join us at bufferbloat.net, as we
try to get people to fix it.  Already there are some experimental 
patches for the Linux Intel wireless driver.
			Jim Gettys
			Bell Labs




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