Re: [ncrg] SDN addresses control plane complexity, not data plane

David Meyer <dmm@1-4-5.net> Thu, 14 March 2013 14:26 UTC

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Date: Thu, 14 Mar 2013 10:26:17 -0400
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From: David Meyer <dmm@1-4-5.net>
To: Bob Briscoe <bob.briscoe@bt.com>
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Cc: "ncrg@irtf.org" <ncrg@irtf.org>, Rui Aguiar <ruilaa@ua.pt>
Subject: Re: [ncrg] SDN addresses control plane complexity, not data plane
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So the message was that scalable evolvable systems have certain
architectural structures. One of them is the bowtie (or hourglass,
depending on whether you view a systems' layering to be horizontal or
vertical). In general the Internet has an "hourglass" architecture
(mod all of the variations) which is part of what has allowed both
scale and innovation above/below the "waist".

That said,  the question I posed is how was essentially "how is
OpenFlow (specifically *not* SDN) related to the Internet hourglass
(if at all)"?

--dmm


On Thu, Mar 14, 2013 at 10:15 AM, Bob Briscoe <bob.briscoe@bt.com> wrote:
> Dave,
>
> At one point in your talk on SDN & complexity, you pointed to just under the
> neck of the classic TCP/IP hourglass as the point that the originators of
> SDN chose to address.
>
> The message wrt complexity is really the reverse. SDN doesn't attack the
> narrowest (least diverse) layer, it attacks the fattest (most diverse)
> layer, in an attempt to narrow it to a single standard (cutting out
> complexity).
>
> Reason: The hour-glass represents the data plane. SDN concerns the control
> plane (specifically routing). The equivalent of the hour-glass in the
> control plane has evolved into an inverse hour-glass - a fatty-glass. See
> slide #8 or even #15 in Rui's presentation here:
> <https://www.net.t-labs.tu-berlin.de/arcadia/talks/Aguiar.pdf>
> or the paper: "Some comments on hour glasses"
> <http://dl.acm.org/citation.cfm?id=1452346>
>
> The more important a layer is for interoperability, the thinner the layer.
> All the different routing protocols make the control plane into a
> fatty-glass, because there is no /operational/ need for interop between
> routing protocols within different ASs.
>
> SDN attempts to narrow the control fatty-glass by standardisation of
> intra-domain policy-routing at build time, which implies the industry is
> maturing from a focus on run-time conformity (between operators) in the data
> plane by adding build-time conformity (between vendors) in the control
> plane.
>
>
> Bob
>
>
>
> ________________________________________________________________
> Bob Briscoe,                                                  BT