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

Saku Ytti saku at ytti.fi
Sat Jan 28 04:07:24 CST 2012


On (2012-01-27 22:40 +0100), bas wrote:

> But do you generally agree that "the market" has a requirement for a
> deep-buffer TOR switch?
> 
> Or am I crazy for thinking that my customers need such a solution?

No, you're not crazy. If your core is higher rate than your customer, then
you need at minimum serialization delay difference of buffering.
If core is 10G and access 100M, you need buffer for minimum of 100 packets,
to handle the single 10G incoming, without any extra buffering.

Now if you add QoS on top of this, you probably need 100 per each class you
are going to support.
And if switch does support QoS but operator configures only BE, and
operator does not limit BE queue size, operator will see buffer bloat, and
think it's clueless vendor dropping expensive memory there for the lulz,
while it's just misconfigured box.

When it comes to these trident+ 64x10GE/48x10GE+4x40G, your serialization
delay difference between interfaces is minimal, and so is buffering demand.

-- 
  ++ytti



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