Re: 10GE TOR port buffers (was Re: 10G switch recommendaton)

[Joel jaeggli <joelja () bogus com>]

On 1/27/12 14:53 , bas wrote:
> While I agree _again_!!!!!
>
> It does not explain why TOR boxes have little buffers and chassis box
> have many.....

you need purportionally more buffer when you need to drain 16 x 10 gig
into 4 x 10Gig then when you're trying to drain 10Gb/s into 2 x 1Gb/s

there's a big incentive bom wise to not use offchip dram buffer in a
merchant silicon single chip switch vs something that's more complex.

> On Fri, Jan 27, 2012 at 11:36 PM, George Bonser <gbonser () seven com> wrote:
> > > Buffers in most network gear is bad, don't do it.
> >
> > +1
> >
> > I'm amazed at how many will spend money on switches with more buffering but won't take steps to ease the congestion. 
> >  Part of the reason is trying to convince non-technical people that packet loss in and of itself doesn't have to be 
> > a bad thing, that it allows applications to adapt to network conditions.  They can use tools to see packet loss, 
> > that gives them something to complain about.  They don't know how to interpret jitter or understand what impact that 
> > has on their applications.  They just know that they can run some placket blaster and see a packet dropped and want 
> > that to go away, so we end up in "every packet is precious" mode.
> >
> > They would rather have a download that starts and stops and starts and stops rather than have one that progresses 
> > smoothly from start to finish and trying to explain to them that performance is "bursty" because nobody wants to 
> > allow a packet to be dropped sails right over their heads.
> >
> > They'll accept crappy performance with no packet loss before they will accept better overall performance with an 
> > occasional packet lost.
> >
> > If an applications is truly intolerant of packet loss, then you need to address the congestion, not get bigger 
> > buffers.