[149110] in North American Network Operators' Group
Re: 10GE TOR port buffers (was Re: 10G switch recommendaton)
daemon@ATHENA.MIT.EDU (Masataka Ohta)
Sat Jan 28 07:06:50 2012
Date: Sat, 28 Jan 2012 21:06:18 +0900
From: Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>
To: nanog@nanog.org
In-Reply-To: <20120128100724.GA7455@pob.ytti.fi>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
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
