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Understanding SDN components and where they're going

What is SDN, and how does it differ from NFV? In part two of this series, IT expert Andrew Froehlich explains SDN technologies and where we can expect to see them in the future.

In any discussion surrounding the topic of next-generation networking, network functions virtualization and software-defined...

networking are undoubtedly part of that conversation. In part one of this series, we sought to explain what NFV is, and where virtual network functions, or VNFs, fit into the equation. In this article, we will turn our focus toward SDN to tell you what it is, how the approach differs from NFV and where SDN components are being implemented in current enterprise networks.

Unlike NFV, which focuses on the virtualization of physical network appliances or functions, the goal of software-defined networking is to centralize network intelligence -- whether network components are physical, virtual or both. The purpose of centralizing is to provide end-to-end visibility for data flows and create the ability to automate processes. This visibility can also be used to automate dynamic routing, so data can flow across optimal paths toward its destination.

SDN separates networking functions into two groups, or planes. The control plane is the centralized decision-making part of the architecture that determines the optimal paths for data packets. The data plane is then responsible for the actual forwarding of data. The data plane intelligence remains distributed on network hardware throughout the campus LAN, data center or WAN.

The differences between NFV and SDN are clear: NFV focuses on the ability to rapidly provision and control network functions through the process of virtualization, while SDN works to decouple network intelligence to provide a more intelligent routing architecture that can be automated. That being said, it's then easy to understand how the two can be combined to complement one another to create highly flexible networks. One approach will virtualize and streamline network function deployments, and the other will optimize data transport.

SDN components taking hold slowly, but surely

You're really not seeing many companies rushing to rip and replace their entire networks so they are fully SDN-capable. Instead, most are looking to address specific pain points.

One frequently asked question is where SDN is being implemented. In reality, you're really not seeing many companies rushing to rip and replace their entire networks so they are fully SDN-capable. Instead, most are looking to address specific pain points within their infrastructure that can most easily take advantage of end-to-end visibility and routing intelligence.

The WAN is a perfect example. For years, network architects have struggled with the limitations of connecting remote sites using a limited number of connectivity choices -- many of which are quite expensive. These limited choices often resulted in connections that were sparked outages, created bottlenecks and suffered from high latency. WAN optimization technologies helped, but ultimately fell short due to a lack of end-to-end visibility across the entire WAN. SD-WAN technologies solve this problem by centralizing the control plane of the entire WAN, so the most optimal routing choices can be made. They also allow for the abstract pooling of multiple, disparate circuits to provide far more potential paths for the data to take. The end result is increased data performance -- often while using lower-cost lines due to the architecture's ability to intelligently route traffic across the most optimal route.

Another area of the enterprise network seeing significant deployments of SDN components is the data center. The benefits of SDN here are twofold. First, SDN allows for the elimination of manual provisioning for new services, applications and other network functions. It does so by not only centralizing network intelligence, but also compute, storage and security. From a network perspective, auto-provisioning can be implemented to program the bandwidth, quality of service, access rules and any other policies within the data center. This significantly speeds up provisioning times and eliminates time-consuming tasks previously performed by a network administrator.

The other appealing benefit for SDN in the data center is data flows can be automated at a level of granularity never before seen. The vast majority of modern data center traffic flows in an east-west fashion within the data center. Because of this, centralizing the control plane not only ensures consistent policies among server applications, middleware and data stores, but it also optimizes routing at a per-application level.

Eventually, SDN components will start to catch fire within the campus LAN, and we'll finally see a complete, end-to-end network with fully automated intelligence for both routing and automated provisioning. But until there are real drivers mandating major network architecture overhauls, expect your first exposure to SDN to start at the edge with the WAN -- or within the data center.

Next Steps

How can SDN and network virtualization work together?

SDN's effect on campus LAN

Build a software-defined WAN business case

This was last published in September 2016

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