This brings us to another objection to partitioning networks into physical and virtual realms--namely, as Cisco's Warrior contended, "It fails to provide full real-time visibility of both physical and virtual infrastructure."
Warrior argued that segregating networks into physical and virtual realms forces users to cobble multiple third-party components into a consolidated management platform, thus complicating IT operations and creating silos of different security policies, log data and orchestration processes. The rest of her post recounts the benefits of Cisco's ACI (Application Centric Infrastructure, an outgrowth of the Cisco ONE SDN strategy), which bridges network control with application services.
But abstract talk, like that in an earlier blog post by Warrior, of an "object-oriented design" with "dynamic policy management across physical and virtual resource pools" via a "deeply programmable" system for rapid application provisioning and placement sounds good on paper, does little to solve existing network challenges as the majority of workloads become virtualized and increasingly nomadic between physical systems.
However, the added management complexity that Warrior described appears to be the biggest downside of decoupling physical and virtual networks. As Greg Ferro wrote in "VMware NSX Caution Signs:" "The level of internal change at organizations that would adopt VMware vCloud 5.5 (the management platform for VMware NSX) is not be underestimated. For example, networking teams must have access to vCenter, security policies must be overhauled and reapproved, and server teams need to understand networking as part of their build practices. If IT infrastructure groups were unionized, there would demarcation disputes, walk outs and management action plans." Of course, adopting Cisco's ACI vision would mean the same type of changes for the server team as Cisco tools replace vCloud or Microsoft System Center Virtual Machine Manager.
At this point of SDN evolution, the modular approach of virtual network overlays on a programmable physical network fabric taken by NSX and vendors such as Embrane, Midokura and Nuage, offers the best balance of features, flexibility/adaptability and ease of deployment on existing hardware while allowing both physical and virtual networks to evolve on independent technology cycles. Traditional network equipment vendors intent on owning the entire cloud hardware/software stack will resist, but vertical integration hasn't been a winning strategy since the mainframe era--a fact the age of SDN and virtual networks is unlikely to change.
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