[Cerowrt-devel] trying to make sense of what switch vendors say wrt buffer bloat

[Ketan Kulkarni]

some time back they had this whitepaper -
"Why Big Data Needs Big Buffer Switches"
http://www.arista.com/assets/data/pdf/Whitepapers/BigDataBigBuffers-WP.pdf

the type of apps they talk about is big data, hadoop etc


On Mon, Jun 6, 2016 at 11:37 AM, Mikael Abrahamsson <swmike at swm.pp.se>
wrote:

> On Mon, 6 Jun 2016, Jonathan Morton wrote:
>
> At 100ms buffering, their 10Gbps switch is effectively turning any DC it’s
>> installed in into a transcontinental Internet path, as far as peak latency
>> is concerned.  Just because RAM is cheap these days…
>>
>
> Nono, nononononono. I can tell you they're spending serious money on
> inserting this kind of buffering memory into these kinds of devices. Buying
> these devices without deep buffers is a lot lower cost.
>
> These types of switch chips either have on-die memory (usually 16MB or
> less), or they have very expensive (a direct cost of lowered port density)
> off-chip buffering memory.
>
> Typically you do this:
>
> ports ---|-------
> ports ---|      |
> ports ---| chip |
> ports ---|-------
>
> Or you do this
>
> ports ---|------|---buffer
> ports ---| chip |---TCAM
>          --------
>
> or if you do a multi-linecard-device
>
> ports ---|------|---buffer
>          | chip |---TCAM
>          --------
>             |
>         switch fabric
>
> (or any variant of them)
>
> So basically if you want to buffer and if you want large L2-L4 lookup
> tables, you have to sacrifice ports. Sacrifice lots of ports.
>
> So never say these kinds of devices add buffering because RAM is cheap.
> This is most definitely not why they're doing it. Buffer memory for them is
> EXTREMELY EXPENSIVE.
>
> --
> Mikael Abrahamsson    email: swmike at swm.pp.se
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>
>
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