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

Joel jaeggli joelja at bogus.com
Fri Jan 27 23:32:20 UTC 2012


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 at 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.
>>
>>
> 
> 





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