IPv4 Address Exhaustion Effects on the Earth

Jared Mauch jared at puck.nether.net
Tue Apr 5 17:17:56 CDT 2011


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 at 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



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