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Software Defined Wide Area Network🤖 (SD-WAN)

Technology | 2021-07-18

A Software-defined Wide Area Network (SD-WAN) is a virtual WAN architecture that allows enterprises to leverage any combination of transport services – including MPLS, LTE and broadband internet services – to securely connect users to applications.

An SD-WAN uses a centralized control function to securely and intelligently direct traffic across the WAN. This increases application performance, resulting in enhanced user experience, increased business productivity and reduced costs for IT.

Traditional WANs based on conventional routers are not cloud-friendly. They typically require backhauling all traffic – including that destined to the cloud – from branch offices to a hub or headquarters data center where advanced security inspection services can be applied. The delay caused by backhaul impairs application performance resulting in a poor user experience and lost productivity. Unlike the traditional router-centric WAN architecture, the SD-WAN model is designed to fully support applications hosted in on-premise data centers, public or private clouds and SaaS solutions such as, Workday, Office365 and Dropbox, while delivering the highest levels of application performance.

📌Why SD-WAN?

As applications continue to migrate to the cloud, networking professionals are quickly realizing that traditional WANs were never architected for the cloud.

Applications are no longer hosted solely in enterprise data centers. They are also hosted in:

- On-premise data centers

- Public or private clouds

- Subscription-based Software as a service (SaaS) solutions such as, Workday, Office365, Box and Dropbox

📌SD-WAN benefits for enterprises

Increase business productivity and user satisfaction

Enhance business agility and responsiveness

Improve security and reduce threats

Simplify branch WAN architecture

Reduce WAN costs by up to 90 percent

📌How does an SD-WAN work?

SD-WAN for cloud-first enterprises: An SD-WAN uses software and a centralized control function to more intelligently steer or direct traffic across the WAN. An SD-WAN handles traffic based on priority, quality of service and security requirements in accordance with business needs. The conventional router-centric model distributes the control function across all devices in the network - routers simply route traffic based on TCP/IP addresses and ACLs.

Sending SaaS and IaaS traffic directly across the internet delivers the best application Quality of Experience for end users. However, not all cloud-bound or web traffic is created equal. Many cloud applications – and their providers – natively apply robust security measures. Accessing these “trusted” applications directly from the branch, across the internet provides the needed security to protect the enterprise from threats. A few examples include Salesforce, Office365, ServiceNow, Box, and Dropbox.

The intelligence and ability to identify applications provides an application-driven way to route traffic across the WAN instead of simply using TCP/IP addresses and ACLs. This software-driven approach delivers a much better QoEx than possible with router-centric WAN model.

Actively use any transport including MPLS, Broadband and LTE: An SD-WAN virtualizes WAN services including Multiprotocol Label Switching (MPLS), broadband internet services and 4G/LTE, treating them as a resource pool. But why aren’t more internet connections used for enterprise WAN services? Simple. Historically, the internet was a best-effort amalgam of networks. It wasn’t secure or reliable enough to meet business needs. And it certainly didn’t perform well enough to support latency-sensitive or bandwidth-intensive business applications.

Overcoming the challenges of broadband: With internet access redefining the economics of networking, the time is now to actively use broadband services in the enterprise SD-WAN. That is, as long as concerns over performance, reliability and security can be overcome. The solution is to shift to a business-driven SD-WAN platform that unifies SD-WAN, firewall, segmentation, routing, WAN optimization and visibility and control functions in a single platform.

Advanced software-driven security and performance features enable enterprises to securely, reliably and actively use broadband to transport application traffic instead of simply using it as an idle backup. By augmenting or even replacing MPLS with broadband, enterprises can significantly increase WAN bandwidth while lowering overall WAN costs.

📌Two key SD-WAN capabilities

Centralized Orchestration: By centralizing the configuration of an SD-WAN as well as application performance and security policies, enterprises can significantly reduce WAN operational expenses.

Zero-Touch Provisioning (ZTP): With ZTP, configurations and policies are programmed once and pushed to all branch locations without having to manually program each device individually using a CLI. It eliminates the need to send specialized IT resources out to branch locations whenever a new application is added or a policy is changed. ZTP also reduces human errors, resulting in more consistent policies across to enterprise.


Software-defined Networking (SDN) concepts and the OpenFlow protocol were introduced in 2011 to deliver increased agility, flexibility, operational efficiency and choice to data networking. Fundamental to SDN was the separation or disaggregation of the control or management function (plane) from the data forwarding function (plane) of the network. SDN proposed centralizing control while leaving the data forwarding function distributed amongst network elements (switches and routers).

The SD-WAN architectural model is similar to SDN in many ways: Centralized management or orchestration – the control plane, Distributed data forwarding function – the data plane and Application-driven traffic routing policies.

SD-WAN, similar to SDN solutions, do not support interoperability between vendors. However, various SDN and SD-WAN industry working groups continue to propose and debate the creation of industry standards.

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