Review: Cisco ACI shakes up SDN

Hands-on with Cisco’s highly scalable data center network fabric driven by -- surprise -- a completely open API

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At a Glance
  • Cisco ACI 1.1(3f)

InfoWorld Editor's Choice

The promise of software-defined networking -- namely simpler, more flexible network operation through centralized, software-driven control -- has been tangible for a few years now, though like many new concepts, it has suffered from misunderstandings and confusion due to amorphous definitions thrust upon it by eager marketing teams. On top of the many definitions, we’ve also seen a number of different approaches, with the OpenFlow model leading the way from the beginning.

Leave it to Cisco to come up with yet another way of doing SDN. Cisco’s Application Centric Infrastructure (ACI) is an SDN solution at odds with the OpenFlow approach, and as such, it diverges from the original direction of the OpenDaylight SDN project, of which Cisco is a founding member. Cisco continues to be a large presence in the OpenDaylight initiative, but is clearly favoring its own technology with ACI.

ACI communicates with network devices using OpFlex, Cisco’s operations control protocol, not OpenFlow, which is the OpenDaylight standard. The critical distinction is that OpFlex places the actual network configuration decisions in the network, not in the controller. The controller abstracts the higher-level configurations instead. You might imagine this as the controller telling the fabric what needs to be done, not how to do it. The fabric is responsible for implementing the controller’s instructions and reporting back on success or failure.

Cisco claims this approach scales better than OpenFlow, which relies on the controllers to perform network configuration tasks. It also allows users to configure the network in terms of application requirements, through a higher-level policy model, rather than worrying about the underlying configuration details. Cisco has OpFlex agent support commitments from Microsoft, IBM, F5, Citrix, Red Hat, and Canonical among others, and it has proposed OpFlex as an IETF standard and as part of OpenDaylight.

While ACI’s SDN internals may operate with OpFlex and not OpenFlow, it’s certainly not traditional networking. It’s hopefully also an indication of Cisco moving toward more open integration, as ACI is built around a complete RESTful API and relies heavily on the Python programming language, providing an open source SDK and tools publicly available on GitHub.

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