The Heady Potential of Software-Defined WANs

Carl Weinschenk
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The Top Challenges for Network Engineers in 2015

The advantages of software-defined networks (SDN) have been widely described. The focus on software-defined wide-area networks (SD WAN), as the name implies, is deeply related to the more conceptual term SDN. The term SD WAN adds specificity and context to the value proposition of SDNs.

Andrew Froehlich at Network Computing describes these SD WAN advantages. In the old world, two approaches were possible: Multiprotocol label switching (MPLS) and Metro Ethernet. In an SD WAN environment, the intelligence in the network can determine in real time whether those two – as well as cellular and broadband links -- are the best bet, judged by network-determined parameters.

Thus, if MPLS fits the bill for one part of the data’s journey and Wi-Fi for another, an SD WAN can handle the complex management necessary to take advantage:

Besides the obvious benefits of WAN link aggregation, next-generation WAN technologies also leverage end-to-end network visibility and feedback in order to improve transmission efficiencies on the fly. SD-WANs can detect the fastest path (or paths) from source to destination in real-time and dynamically re-route packet flows across links to improve performance. Routing decisions are made based on data such as latency, load and types of QoS policies applied.

David Hughes, the founder and CEO of Silver Peak, told FierceEnterpriseCommunications that SD WANs can save as much as 90 percent over legacy approaches. The savings, he said, come from reduced bandwidth needs and operational and capital (opex and capex) savings. Bandwidth savings, the story says, are the easiest to quantify. Opex is saved because complicated and manpower-intensive branch office management is eliminated. Capex is cut because the density and duplication of equipment is drastically reduced.

The rationale for SD WANs is consistent. Indeed, the advantages pointed to by Froehlich and Hughes are echoed by consultant Keith Townsend, who described his experience in deploying an 85-site video conferencing network. Performance differs over different providers’ WAN links and shaping the traffic – the ability to tap into the best option in a unique situation – is difficult in legacy scenarios, he writes. SD WANs are built to confront this challenge. A bonus is that deeper information is available about conditions on the network, so options that perhaps would not have been apparent in the legacy world can be used:

Because the network controller is an x86 device or a cluster of x86 devices, the analysis capacity is more than any existing network protocol running on dedicated network devices. The controller can analyze traffic and determine optimal network paths for individual applications as well as individual flows. SD WAN solutions enable a greater level of circuit flexibility; an organization can leverage several inexpensive broadband circuits and reduce the reliance on dedicated connectivity.

SDNs are a great example of technology that is developed with a keen eye forward and backward. Planners are looking forward in the sense that the future needs of telecommunications and enterprise network administers are anticipated. The backwards look is to confront inefficiencies that were designed into earlier networking topographies and remove them as limiting factors.

Carl Weinschenk covers telecom for IT Business Edge. He writes about wireless technology, disaster recovery/business continuity, cellular services, the Internet of Things, machine-to-machine communications and other emerging technologies and platforms. He also covers net neutrality and related regulatory issues. Weinschenk has written about the phone companies, cable operators and related companies for decades and is senior editor of Broadband Technology Report. He can be reached at and via twitter at @DailyMusicBrk.

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