Re: Why do we need congestion control?

--- On Wed, 4/10/13, Fred Baker (fred) <[email protected]> wrote:

> From: Fred Baker (fred) <[email protected]>
> Subject: Re: [e2e] Why do we need congestion control?
> To: "<[email protected]>" <[email protected]>
> Cc: "<[email protected]>" <[email protected]>, "<[email protected]>" <[email protected]>
> Date: Wednesday, April 10, 2013, 1:44 PM
> 
> On Apr 10, 2013, at 1:06 PM, Daniel Havey <[email protected]>
>  wrote:
> 
> >> In the face of this, what I don't understand is why
> this
> >> thread has gone on for so long.  Surely it
> should be
> >> allowed to die, given that the core -- possibly
> reasonable
> >> -- concern was long-ago answered.
> > So I don't understand this.  The so called
> "bufferbloat" problem is solved in the core?  But
> pragmatically speaking it still exists?  This wont get
> me a PhD, but, one has to ask, why?  Does the core drop
> segments?  Or does it buffer them?
> 
> It does. Not often, but it does when it needs to.
> 
> http://www.ieee-infocom.org/2004/papers/37_4.pdf
> 
> Most buffer bloat behavior is at the edge - WiFi, Mobile
> telephone, broadband. There are other cases. But think about
> dumbbell networks - two fast networks connected by something
> slower. That's where you'll find it.

I agree.  The segments fly through the core then probably slam into a rate limiter at the edge of the ISP.  Either that, or they blow through the rate limiter and hit a slow wireless hop.