Beyond SDN: Micro-Segmentation, Macro-Segmentation or Application-Segmentation Part-1

Software Defined Networking (SDN) originally came out of work done to extend the functionality of the Java software framework as early as 1995. In 1998 a number of the key people from Sun Microsystems and Javasoft left to found WebSprocket the first commercial implementation of SDN. Two years later Gartner had recognized SDN as an emerging market and created a new category to track commercial efforts engaged in this space. Now some 15+ years later we have cyber warfare, espionage, and financially motived hackers constantly questing for the chewy center that is our enterprise data. While SDN has addressed some of the deficiencies found in the perimeter only systems, it’s still not comprehensive enough. Some have proposed, and possibly even implemented, setting up zero-trust zones for key enterprise servers where the default policy for access to these systems is “Deny All”. Then as applications are added to a server, specific access controls are added to the switch port of that server to enable the new functionality. The problem with this approach is that it can quickly become very tedious to craft and daunting to maintain. This still leaves several problems.

The smallest practical unit on which security can be applied is the IP address, while a switch can have different policies for each Virtual Machine’s (VM) unique IP address the switch itself will never see VM to VM traffic within the same server. Using switch Access Control Lists (ACL) to enforce security policies at the application and server port layers can quickly tax a switches Content Addressable Memory (CAM). Finally, we have maintenance, can you quickly resolve why a given switch or firewall has a specific security policy or rule? Most organization are incapable of knowing the origin of every single rule as often there is no centralized, cross-vendor, auditable database that exists.

To address some of these issues VMWare and Cisco crafted a new approach they named Micro-Segmentation which defines a new overlay framework where a software management layer takes control of both the hypervisor’s virtual soft switch and the enterprise switching fabric providing a single management perspective. VMWare branded this NSX, and it offers three major advantages: management to the virtualized Network Interface Card (NIC), automated deployment of the security policy with the VM, extending the management framework to include legacy switching. Including legacy, switching isn’t just for compliance, but it’s to address all the issues around deployment across the entire enterprise. Cisco calls this Application Centric Infrastructure (ACI).

Not wanting to be left out of the post-SDN ecosystem Arista Networks added to this by crafting a Macro-Segmentation view. Rather than using an overlay framework instantiated as a series of services woven into hypervisor they are leveraging existing firewall services in both software and hardware. These firewalls can then be easily stood up or reconfigured between servers by leveraging existing software & hardware from well-established firewall vendors like Fortinet and Palo Alto Networks. Actually weaving together a management layer that includes switching and firewalls is much more coherent.

The best solution though resides somewhere between Micro-Segmentation and Macro-Segmentation, and some have called it Application-segmentation. Because in the end, all we really care about is the security of the applications we deploy on our infrastructures. So while VMWare, Cisco & Arista have taken a sort of bottom-up approach, a new breed of network security orchestration applications from companies like Illumio and Tuffin have entered the fray taking a top-down, an Application-Segmentation approach to the same problem. More on this to come in Part-2 of Beyond SDN.

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