SDN is proving very good at highlighting industry fault-lines and one of those long-standing fractures is surely at the packet/optical layer - on one side of the line are the optical vendors who tend NOT to favour the complete integration of packet and optical into a single managed entity.

On the other, of course, their opposites from the IT side of the industry tend to advance the packet network as the overriding (as it were) thing, with optical reduced to point-to-point links. Those are two extremes in the debate, but you get the idea.

SDN implementation naturally becomes a forum for this political wrangle as it involves 'managing' the whole and therefore must make assumptions.

As Uwe Fischer, CTO of Coriant, the recent optical spin-out from Nokia Siemens Networks points out, some vendors want the packet layer and its management to dominate with the optical layer subservient "and the elements there commoditised". Fischer and Coriant would prefer to see an effective hybrid approach, he claims.

"There's so much [a separate] transport network can do if it's managed properly to optimise performance end-to-end," claims Uwe. SDN promises to provide that sort of granular management and Fischer resents the lack of attention the transmission network is currently getting in the SDN upsurge currently rocking the industry.

To help redress the balance Coriant has announced the commercial availability of its Intelligent Optical Control (IOC) which Uwe claims is the industry's first 'concrete' SDN solution at the optical layer.

Things that an SDN controlled optical layer can do end-to-end? First of course, lower latency. Less delay-inducing packing and unpacking packets on their journey across the infrastructure. This will clearly be a very valuable option if and where SDN makes it possible to selectively stuff flows with delay-sensitve traffic.

Coriant is also claiming vast savings on CAPEX and (for similar reasons) service implementation and general agility also get a boost.

"Operators can now implement new services up to 90 per cent faster," claims the Coriant blurb. "Tests confirmed, for example, that the set-up time for a 100G data center service dropped from hours to minutes."