SD-WAN - Symbiosis Without Compromise

WAN infrastructures are highly persistent due to typically enormous investments in their dedicated hardware and management tools. WAN services like MPLS have undoubtedly been beneficial and enduring, but enterprises and IT departments require more flexible and economical solutions to provide employee access to corporate resources and cloud-based applications. SD-WAN promises to fulfill these needs with software-based, cloud-based solutions - running on commercial off-the-shelf hardware platforms - to connect their various branch offices.

For more than a decade technologies like leased lines, VPNs and MPLS were the dominant architectures connecting enterprise entities. Proven to be highly secure and reliable, they nevertheless lack flexibility and typically entail high costs for limited bandwidth. On the other hand, the ubiquity and ease of using the Internet have influenced users' demands for access to corporate resources and services from wherever they are, and with the devices of their choice. Unfortunately, the Internet is handicapped by a paucity in reliability and security. Predictably, there are many attempts to combine these worlds - one example being the Metro Ethernet Forum's (MEF) concept of the Third Network, launched several years ago, with the exact goal of melding the more desirable characteristics of both Carrier Ethernet services and the Internet.

SD-WAN - A Compelling Alternative
Software-defined networking (SDN) has emerged as a technology to increase agility in enterprise networks through decoupling the control and decision making surrounding network traffic, known as the control plane, from the underlying traffic forwarding methods, the data plane. Organizations like the Open Networking Foundation (ONF) have defined, and driven acceptance of, open protocols within the vendor and provider space.

Software-Defined WAN (SD-WAN) applies SDN principles to wide area networking for connecting branch offices of medium and large enterprises to headquarters, data centers and the private and public clouds where applications reside.

SD-WAN is gaining considerable momentum. In the Ashton, Metzler & Associates report The need to rethink the WAN, analysts identify three key market developments driving the need for new approaches to Wide Area Networking: the growing number and importance of branch offices, increasing worker mobility, and the accelerating adoption of cloud computing. In addition to these three drivers, organizations must ensure excellent performance for business-critical applications, with special emphasis on real-time applications such as video and voice. At the same time organizations are constrained by the characteristics of current WAN services including high cost, complexity, rigid architectures that inhibit the adoption of cloud applications, and the glacial rollout of private line connectivity in many locations to implement new network services. A recent ZK Research study revealed that it takes an average of four months to implement a new service due to architectural challenges and high complexity in branch deployments.

WAN Reinvented
IT professionals and corporate users are increasingly frustrated by the inability of traditional WAN architectures to support the cloud era. SD-WAN offers a compelling alternative by leveraging and virtualizing multiple types of connections between business locations, data centers and cloud resources. SD-WAN is transport agnostic - using all available links including Internet, MPLS and 4G-LTE - and overlays controls to ensure quality of experience, reliability, predictability, security, manageability, and deliver all these benefits at a reduced cost.

From a technical standpoint SD-WAN is a software control overlay comprised of the following key elements: a management dashboard that provides easy administration by IT professionals with negligible effort by staff in field locations; a highly automated control plane that actively and intelligently manages and routes network traffic using all available transport technologies in accordance with business priorities; a business policy framework that encodes requirements and baselines for security, quality of service, cost controls, user experience and application priorities. SD-WAN controls may be located within a traditional data center, but optimally it runs in the cloud, equally accessible to all business locations, and is managed as Software-as-a-Service (SaaS) to reduce the workload and cost of corporate IT.

Edge devices are deployed at branch offices in either a physical or virtual form factor. Sophisticated edge device functionality recognizes a large number of popular applications (2,500+) and routes traffic over the optimal connection based on business policies and continuous real-time monitoring of link performance. Advanced technologies such as dynamic multi-path optimization steer traffic over the most optimal path on a per-packet basis - using private, public and hybrid connections - and even ensure quality over single links using advanced remediation techniques.

Virtualizing the Network
SD-WAN offers a network-independent overlay to carry application traffic independent from the underlying physical or transport layer. All available links - different technologies, capacities, and connections from different service-providers - constitute a pool of resources in a virtual WAN ensuring high availability and performance. Link utilization is increased and the network is simplified. Links can be readily added as there is no static relationship between a link and an application. Virtualization also provides self-healing as links are experiencing degraded performance.

SD-WAN architecture is differentiated from other technologies attempting to improve traditional WAN performance: it is not a conventional WAN optimization technology only applicable to private MPLS links; it is not merely multilink bonding with path control; it is not just a last mile solution with a cloud gateway to provide caching and acceleration technologies.

Instead, SD-WAN virtualizes the network, enables a secure overlay, simplifies service delivery and provides real interoperability. Sophisticated SD-WAN technologies leverage cost-effective off-the-shelf hardware, and support significant automation within business policy frameworks and open networking. It enables managed services and continuously monitors usage and performance metrics to support heterogeneous networks including dual Internet and broadband links, wired and wireless links as well as public and private links. Individual links can have a great variation in performance characteristics based on type or time. To maximize the benefits of multiple connections, SD-WAN measures the performance of upstream and downstream links separately to allow independent steering decisions for each direction.

Paths of Adoption
Given the benefits, SD-WAN is an appealing alternative to improve the performance, reliability, manageability and cost of traditional enterprise WAN infrastructures. Happily, complete replacement of the existing infrastructure is not the only path of adoption. The whitepaper SD-WAN Business Value by the Enterprise Strategy Group (ESG) describes several ways to transition a network depending on the current infrastructure, business needs or existing contracts. The benefit of SD-WAN is that it works with what organizations already have today. The deployment does not require a complete network conversion - existing links and contracts can continue while alternatives are introduced step-by-step.

ESG details four different paths of adoption: First, if the company and its branches are already migrating applications to SaaS, it is a good opportunity to re-architect the branches to optimize cloud access. Second, organizations looking to add new branches can simply purchase two broadband connections from different Internet providers instead of purchasing an MPLS link and deploy a router. Third, organizations wanting to augment an existing branch network can install an SD-WAN edge device and broadband connection alongside the existing MPLS router and link. And finally, the expiry of an MPLS network contract is a perfect time to switch to SD-WAN.

Choosing the Appropriate SD-WAN
For IT professionals and budget decision makers a compelling new technology is only one side of the coin. The other is to make the correct choice regarding the best solution and partner. The ZK Research whitepaper WAN is a business Imperative establishes several key requirements to satisfy when seeking the appropriate SD-WAN solution provider. In this report, the most important criterion cited is the ability to enable a transport-independent overlay for a hybrid network consisting of private, wired broadband and wireless circuits, ideally with dynamic steering and optimization techniques. The SD-WAN provider should offer flexibility by supporting either physical or virtual appliances within the branch offices. Furthermore, the ability to provision an SD-WAN from the cloud ensures that the complexity of integrating the various technologies can be masked from the customer.

Another requirement is that the provisioning of new locations should be easy and not require a local IT person, and a scalable pay-as-you grow pricing model must be available. One of the key benefits of SD-WAN is reduced cost, therefore the solution of choice should offer minimal initial investment with incremental cost commensurate with scaling the infrastructure.

The SD-WAN service of choice must connect to all major IaaS and SaaS providers to ensure optimized performance of cloud services. The portal for administration must offer rich functionality with a complete and cohesive view of network and application performance. Finally, the SD-WAN solution must automatically recognize applications, classify them and prioritize traffic appropriately.

Frost & Sullivan stated - in a comment accompanying the recent product leadership award given to VeloCloud - that an SD-WAN solution gives enterprises a much-needed control mechanism to deploy, run and manage WANs to help improve operational efficiency and reduce total cost of ownership.