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

Keith Jones <> Thu, 14 March 2013 15:02 UTC

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From: Keith Jones <>
To: Bob Briscoe <>, Dave MEYER <>
Date: Thu, 14 Mar 2013 14:58:51 +0000
Thread-Topic: [ncrg] SDN addresses control plane complexity, not data plane
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Subject: Re: [ncrg] SDN addresses control plane complexity, not data plane
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Hi all,

I am very new to SDN's and the architecture, but unlike many here, old enough to remember SS7. This whole SDN architecture reminds me of SS7 I wonder if there are any leassons we can learn from that?

Feel free to shoot me down.

all the best

"If you can not measure it, you can not improve it." Lord Kelvin
From: [] On Behalf Of Bob Briscoe []
Sent: 14 March 2013 14:15
To: Dave MEYER
Cc:; Rui Aguiar
Subject: [ncrg] SDN addresses control plane complexity, not data plane


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:
or the paper: "Some comments on hour glasses"

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 Briscoe,                                                  BT

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