Software-defined networking has emerged as a response to complex and static network architectures, and has been a major topic in the hosting world. SDN essentially adds a software layer between the network hardware and the software controlling it. This abstraction between the network control plane and underlying data forwarding plane provides network operators greater vendor choice and agility, as well as automation of network operations.
While it’s still in its infancy, many web hosts are seeing adoption of SDN as a way to gain greater efficiency, but also to be part of a new wave of networking that promises to connect us like never before.
Understanding Software-Defined Networking
“The basic concept of SDN is you’re decoupling the control plane from the data plane, so the data plane is the device itself and the control plane is how it’s configured,” Ellen Roeckl, corporate relations director at open-source SDN company Big Switch Networks says. “What creates that flexibility is that by separating those two things, the hardware essentially becomes just the infrastructure that things run on, and the software becomes a way of centralizing and automating things.”
This programmability and automation greatly reduces the time spent by staff provisioning and maintaining the network device-by-device, effectively increasing agility. It also gives data centers more choice in networking hardware than on the proprietary model, and with this competition comes downward pressure on hardware prices.
For web hosting providers, SDN has opened up greater possibilities for creating more isolated multi-tenant cloud hosting environments in which each tenant has access to compute, storage, and networking from a common resource pool. With SDN endpoints as virtual devices that are part of the hypervisor environment, SDN frees tenants from having to share their network with those they share servers with, and have different throughput or security characteristics than their neighbors.
The Big Shakeup in Network Architecture
“There’s a massive re-architecture of the network going on, and by massive I mean it’s the kind of disruptive change that only happens once every 20 years,” Kelly Harrell, VP and GM of Brocade’s software networking business unit says.
To understand the scale of the change that SDN will have on networking, perhaps the best comparison is the transition from mainframe computing where software and hardware was in the same box to open systems which allowed the architectural separation of hardware from software.
“If you look at what’s happening in the networking industry right now is that the networking industry is going through its first ever open systems revolution,” says Harrell. He says that we’re in the midst of a shift from blackboxes that constrain software and hardware towards a system where software can be used on top of standard equipment. And just like in the open systems revolution that happened in computing, being able to mix and match hardware and software will result in radically better economics and tremendous flexibility.
The SDN Revolution may not be Smooth
Despite all the enthusiasm surrounding SDN, Roeckl notes that there are still a lot of risks.
“It’s not going to be a smooth transition,” she says.
For instance, some say traditional firewalls may not be equipped to manage the requirements of an SDN data center. Others say splitting up the control plane from the data plane makes the SDN controller and the virtual infrastructure new targets for potential security attacks. Also, because you’re now dealing with physical network infrastructure, network virtualization can potentially make it difficult to identify problems when you can’t see the hardware in the network.
From a hardware standpoint, there may also be resistance from networking equipment providers that are used to providing a proprietary stack of operating system, interfaces, and applications. Dealing with a new model of networking that’s less integrated and more open, Roeckl says, would be sacrificing their high-margin sales of proprietary and vertically integrated systems.
Why SDN is Needed Now
Traditional networking is stretched to its limit partly due to virtualization. Instead of a server running a single application, they often run dozens of virtual machines, which makes the direction of traffic more complex. Harrell says, “Now when that traffic goes into the server, how does it know what to do? How does it know what VM to go to? How does it know if that particular traffic needs to be firewalled or routed in a specific way?”
“Basically, with virtualization, that layer of abstraction, that hyper-visor has broken the physical networking model. Now you need the network technology to network to extend its way into the server to finish the new job, and that’s where software networking comes into play. It’s complementary to the hardware.”
The Open Systems Interconnection model acts as the standard classification system of communications components, grouping functions into protocol layers numbered from one to seven. Each layer supports the next, ranging from Layer 1 (the physical layer) to Layer 7 (the application layer). There’s no replacing all network hardware from one to seven, but SDN promises to move more of the work done in Layer 3 to 7 to the server.
And because these functions can be done on generic hardware, less money goes to specific network devices that may only serve one function, meaning that hardware is more flexible and adaptable. “Instead of buying a big box, now you can distribute that workload across the servers using virtual machines,” Harrell says.
SDN will Change Hosting
The way networking has worked over the past few decades has largely been seen by web hosts as more-or-less a given – a constraint with which they had to live. Their main way of improving and streamlining operations was through servers and server software. But networking is now becoming adaptable and will become a source of advantage.
“What SDN promises to do is to make networking operate a lot more like servers operate now,” Roeckl says. “There’s a tremendous amount of choice, not only in hardware, but also in applications and orchestration systems.”
At the recent VMworld 2013 conference in San Francisco, VMware CEO Pat Gelsinger announced: “This is the coming out party for network virtualization.” This is just one of many indicators that networking will be a greater focus in 2013, and that this long-ignored aspect of service delivery is getting its due attention.
As SDN is implemented more in the real world, especially in the web hosting space, it will help prove its benefits but also work out the kinks and establish its limitations. By that time, we’ll be preparing for the next innovation in networking.