Theoretically, network virtualization technology, often lumped under the banner of software-defined networks, provides IT departments with a single point of control for enterprise networks, which speeds up service deployments, eases administrative tasks and reduces costs.
Virtualization has swept through servers, working its way to storage systems, and now has taken aim at enterprise networks.
However, delivering such capabilities requires largely ripping out and replacing current network infrastructure. This massive undertaking means significant investments in new network equipment, a long -- perhaps painstaking -- process of upgrading network nodes and a dramatic retooling of network engineers' skill sets. While the change offers many long-term potential benefits, significant angst is expected in the short term.
Industry observers see software-defined networks as a natural step in the increasing virtualization of data centers; server virtualization is becoming commonplace, and storage virtualization is being adopted. Bringing such capabilities to networks is the next stage in the evolution of the data center.
In a nutshell, software-defined networks essentially change how networks function. Currently, tedious, time-consuming, administrative tasks -- setting up addresses, routing traffic -- are linked to and performed on expensive hardware. With a software-defined network, these tasks are decoupled from the hardware and instead become software functions running on commodity hardware.
Making this switch to network virtualization presents companies with a number of potential benefits. Network intelligence -- from directing traffic to minimizing latency to security -- moves from closed switches and routers to open, software-based controllers. Because network control is implemented via software, network complexity is reduced. In addition, data center technicians work one common interface for all devices rather than a variety of proprietary vendor-specific solutions.
Theoretically, network management becomes much simpler. "A majority of organizations use ticket systems, followed by phone calls and then emails to communicate adds, moves and changes to the network team," said Andre Kindness, principal analyst at Forrester Research Inc. "This manually driven way of communicating infrastructure change drags out response time."
The potential paradigm shift to virtualized networks has caught network equipment vendors' attention. As a result, suppliers are outlining various plans to add such features to their product lines. Established vendors, such as Brocade Communications Inc., Cisco Systems Inc., Dell Inc., Extreme Networks Inc., Hewlett Packard Co., and Juniper Networks Inc., want to ride the software-defined-network wave. In addition, startups like Adara Networks Inc., Big Switch Networks, Inc., Contextream Inc., Embrane Inc., Vello Systems Inc. and Vyatta Inc. have entered the fray.
As evidence of the market's potential, VMware paid $1.26 billion in July for software-defined network startup Nicira Inc. "The price that VMware paid was much more than anyone expected," said Bob Laliberte, senior analyst for Enterprise Strategy Group (ESG).
While this market has generated a lot of buzz, it has also produced virtually no deployments. "If the SDN market was a baseball game, the pitchers would still be warming up," said Zeus Kerravala, principal analyst with ZK Research. "We have a long way to go before enterprises start to realize the benefits that SDNs offer."
One reason is the changes taking place are multifaceted, not one-dimensional. To reap software-defined network benefits, businesses need to change three network elements: the physical controllers, their network software and the application programming interfaces that enable applications to call network services.
Network virtualization technology in the wild
Only one element, the physical controllers, has started to take shape. Researchers at Stanford University created the OpenFlow Switching specification in 2008. Since they did not have a commercial interest, they relied on an open-source model to spread their work.
OpenFlow allows software running on multiple routers to determine the path of data packets through a network of switches. This separation of the control information from the forwarding data allows for more sophisticated traffic management than what is feasible using traditional approaches, like access control lists and routing protocols.
About a year ago, vendors started to outline plans to deliver products based on OpenFlow. The group includes established vendors like Google Inc., HP and IBM, as well as startups, such as Big Switch Networks Inc. and Vello Systems.
In March 2011, Deutsche Telekom, Facebook, Google, Microsoft, Verizon and Yahoo founded the Open Networking Foundation (ONF), a consortium designed to promote the use of OpenFlow. The group has released two iterations of OpenFlow; coordinated interoperability demonstrations at events, like Interop; and worked with Indiana University to establish an interoperability testing laboratory. ONF membership has now passed 70 partners and continues to grow steadily.
While OpenFlow has garnered support, many of the other needed elements are in the blueprint, rather than the delivery, phase. As vendor plans and new products take shape, possible hurdles could emerge, starting with scalability. Through the years, networks have evolved so they now support millions of nodes. Software-defined networks have not yet proven they work outside the lab, let alone on such large networks.
Also, a software-defined network consolidates dispersed information in a central location, which introduces a single point of failure. Consequently, vendors need to add resiliency to their solutions and develop robust management tools in case problems arise.
Cost is an open question. Vendors have also been nebulous regarding product pricing. Analysts expect these solutions to cost about the same as traditional network gear but deliver much more functionality.
However, network virtualization will not be the "no-brainer" that server virtualization has been. "With server virtualization, companies reduced costs by eliminating a lot of underused hardware," said ESG's Laliberte. "That won't be as likely with SDNs because network connections remain in place."
Understanding how to deploy and manage these new devices could also create challenges. "The networks of tomorrow require new skill sets from the personnel, organization changes and process standardization," said Forrester's Kindness. "Otherwise I&O will be installing solutions that won't offer any benefits and could possibly cause more inefficiencies."
Software-defined networks have a lot of potential and are garnering a great deal of ink. However, they are not the slam-dunk that other types of virtualization have been, so many enterprises are proceeding with caution.
About the Author: Paul Korzeniowski is a freelance writer who specializes in cloud computing and data-center-related topics. He is based in Sudbury, Mass., and can be reached at firstname.lastname@example.org.
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