Re: IPv4 Address Exhaustion Effects on the Earth

[Jared Mauch <jared () puck nether net>]

On Apr 5, 2011, at 6:07 PM, Jim Gettys wrote:

> On 04/05/2011 05:59 PM, Michael Proto wrote:
> > On Tue, Apr 5, 2011 at 5:38 PM, Jared Mauch<jared () puck nether net>  wrote:
> > > On Apr 4, 2011, at 4:30 PM, Jim Gettys wrote:
> > >
> > > > Note that the paper "Characterizing Residential Broadband Networks" by Dischinger, et. al. indicates that a large 
> > > > fraction (in their 2 year old sample, 30% or so) of broadband head ends are running without RED, and should be 
> > > > doing so if at all possible; alternatives are years out by the time they are tested and deployed, and operators 
> > > > running without it in congested systems are inflicting pain on their customers.
> > > Something I've observed is if you are sending data 'upstream' on the cable modem setup i have (16 down/ 2 up) and 
> > > you saturate the upstream, the buffering destroys any downstream capability at the same time.  I'm not even sure 
> > > where to start diagnosing to explaining this to the carrier involved, as this isn't the desired behavior of a 
> > > "business class" service.
> > >
> > > - Jared
> > Isn't this just a case or prioritizing outbound ACKs?
> >
> > http://www.benzedrine.cx/ackpri.html
>
> Nope.  Your acks get delayed to what you are sending upstream, behind the downstream traffic.
>
> Bufferbloat hurts both directions, once saturation occurs and your latencies start to go up.
>
> Note that on many of these links, the RTT becomes (literally) as though you are half way (or further than) the moon.
>     

I sent a private reply, but I guess i'll post some of it here:

1) there are no ways to identify the devices doing the buffering and/or drop counts
2) I can obviously feed the cable modem much faster on the lan vs what it can send upstream

Doing things like rate-limiting/QoS are merely just papering over the problem.  I would take a T1 and rate-limit it to 
1.2Mb/s for TCP to allow VoIP to work.  Junipers can buffer up to 1 second on these low-speed interfaces, which 
obviously creates the problems you describe.

There are a lot more problems with the gateway devices, such as the forcible dns proxy that exists.

- Jared