I've heard a lot of talk lately about software-defined networks (SDN). Just about every networking vendor is at least nodding to the concept, particularly as a way of handling more complex cloud-based environments. There have been a couple of high-profile announcements lately, and the technology is very interesting. While it seems like this is not quite ready for most businesses yet, it does offer the potential to change how complex networks work, and eventually to present some big changes for networks and customers of all sizes.
Today's corporate networks use open standards such as the IP protocol and Ethernet connectivity, but configuring the networks themselves often requires lots of manual tasks because each device on the network has separate policies and consoles.
Making significant changes in the network – even with existing hardware – can be time-consuming, potentially taking a week or two. With the move toward server virtualisation and cloud computing, this has gotten even more complex, which is one of the reasons why a number of organisations and companies have been focused on solving the issues.
The concept behind software-defined networking (SDN) essentially moves the "control plane" of the network away from each individual device on the network to a controller that works with all the devices, including both virtual and physical devices. This allows for a single controller to configure or manage the complete network, as opposed to each device managing its own functionality and being programmed individually. To accomplish this, you typically hear about the network using the OpenFlow protocol, which was created at Stanford University and the University of California at Berkeley, but is now run by the Open Networking Foundation.
With SDN, a standard software program can control the network, specifically letting it manage the resources that it needs. I've often heard SDN talked about in terms of allowing network virtualisation, which is certainly one application.
But, as Gartner analyst Joe Skorupa puts it: "SDN is not about network virtualisation. It is about changing how we design and build and operate networks to achieve business agility."
He notes that the big promises of SDN include allowing applications to be rolled out in hours instead of weeks, and potentially using lower cost hardware since each device will not be doing its own control functions. This, therefore, could be a big market transition.
A number of companies have announced solutions using OpenFlow. NEC had one of the first switches and at the most recent InterOp show, HP introduced a broad line of OpenFlow products, including a controller and an application called Security Sentinel.
But no company has been talking about SDN and OpenFlow more than Big Switch Networks. A few weeks ago, it finally announced its product line, including its Big Network Controller platform and a couple of applications that run on top of it. One difference, the company says, is it that all of these products are generally available now.
Big Switch's controller is based in part on the FloodLight open source OpenFlow kernel with extensions, and the company describes it as essentially a platform for running OpenFlow applications.
Big Switch says its controller will work with products from 27 partners. These include hypervisors from Citrix, Microsoft, Canonical, and Red Hat; and physical switches from Arista, Brocade, Dell, Extreme Networks, and Juniper. In addition, the company says it has tested with IBM and HP switches, and that it has also tested with VMware. (Big Switch has only limited support for VMware today, though it expects to have more robust support in 2013).
Big Switch's first two applications, which go on top of that, are Big Virtual Switch, which provides data centre network virtualisation, and Big Tap, a network monitoring tool. Virtual networks is the topic I hear most about with SDN, as setting up and reconfiguring "virtual networks" is time consuming, especially in a virtualised or cloud environment. Big Switch says its tool will make this easier, and will also allow more virtual machines per rack. It can work as an overlay on a traditional network, in a pure OpenFlow network, or most importantly, in a hybrid network.
But SDN is supposed to go beyond virtual networks toward applications, and the company's Big Tap unified network monitoring tool is an example of this.
Big Switch says it has nearly two dozen partners working on applications that can run on top of its platform. Of these, the groups that seem most ready for it include the OpenStack and CloudStack platforms for running cloud data centres. Other applications include Cariden's traffic engineering application and a Coraid application for managing storage in multi-tenant environments.
The other SDN company that is getting a lot of attention lately is Nicira, which was bought by VMware this summer. Nicira talks about its Network Virtualisation Platform (NVP), essentially software designed to create an intelligent abstraction layer between hosts and the existing network – in other words, an overlay network. This is meant to be a series of virtual switches (which it calls Open vSwitch) and to be part of a Distributed Virtual Network Infrastructure (DVNI) architecture.
VMware has talked about Nicira being part of its "software-defined data centre" concept, which seems to fit in with its Pivotal Initiative focused on cloud computing.
Another interesting approach comes from Midokura, a smaller Japanese-US start-up that is offering MidoNet. This is aimed primarily at virtualised hosts in an Information as a Service (IaaS) environment, and fits at the hypervisor layer. The concept is to provide network isolation and fault-tolerant distributed environments without an intermediating network. The company says this does not require any new hardware, but simply IP connectivity among network devices, and it’s "truly scalable." This was announced at the recent OpenStack conference.
There are other alternatives to OpenFlow for separating the data plane and control plane, and cloud platforms such as OpenStack and CloudStack could work with or without OpenFlow controllers. But the concept is certainly pushing companies such as Cisco, Juniper, and Alcatel-Lucent to provide more open access to their networking products via APIs.
Cisco has itself promoted the concept of software-defined networking, saying its switches support the concept of network virtualisation and have for years, and will at some point support OpenFlow. But the company sees the big benefit in software-defined networking as getting the applications to be more intelligent about the network and the resources it consumes.
SDN is often seen as a way of reducing the cost of networking, of making networks more open, and of making the management of virtual machines and virtual data centres much easier. As such, it provides both opportunities and challenges for Cisco (the leading network vendor), VMware (the leading virtual machine vendor), and for many smaller companies that seem more likely to embrace the open source and OpenFlow concepts more fully, believing it gives them a new weapon against the more proprietary products that dominate the market today.
Overall, the concept strikes me as very intriguing, though probably not something most businesses are ready for yet, in part because the products are all so new and the standards are still evolving.
Right now, the big beneficiaries will be organisations that run big cloud data centres, whether public or private, as they face the issues of dealing with network complexity and a need for faster changes. Over time, though, we could see more network-aware applications, which could be much more important. Placing the control with the applications rather than the administrators is a big change, and teaching programmers how to create applications for this – and indeed, figuring out which applications will be able to really take advantage of this – seems like it will be a challenge. Still, the concept has a lot of promise, even if it is still very early days.
For more on SDN, check out our article on how Google is helping lead the charge to a swifter Internet.
Image Credit: Daniel Cortes
Michael J. Miller is Chief Information Officer at Ziff Brothers Investments, a private investment firm. Mr. Miller, who was editor-in-chief at PC Magazine from 1991-2005, authors this blog for PC Magazine to share his thoughts on PC-related products. No investment advice is offered in this blog. All duties are disclaimed. Mr. Miller works separately for a private investment firm which may at any time invest in companies whose products are discussed in this blog, and no disclosure of securities transactions will be made.
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