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

Masataka Ohta mohta at necom830.hpcl.titech.ac.jp
Sat Jan 28 12:06:18 UTC 2012

Saku Ytti wrote:

> 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.

The required amount of memory is merely 150KB.

> Now if you add QoS on top of this, you probably need 100 per each class you
> are going to support.

If you have 10 classes, it is still 1.5MB.

> And if switch does support QoS but operator configures only BE, and
> operator does not limit BE queue size, operator will see buffer bloat,

1.5MB @ 10Gbps is only 1.2ms, which is not buffer bloat.

					Masataka Ohta

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