What is SD-WAN? Why SD-WAN is needed?
A Software-defined Wide Area Network (SD-WAN) is a software defined overlay approach to manage WAN networks that allows enterprise to use any combination of transport medium including MPLS, Internet Satellite and 4G/LTE and others to securely connect users to applications by decoupling the hardware from its control mechanism.
To securely and intelligently direct traffic across the WAN, an SD-WAN employs a centralized control mechanism. This improves application efficiency and provides a high-quality user interface, resulting in higher business productivity, greater agility, and lower IT costs due to transport independence across different connection types.
Why is it changing the network game?
Traditional WANs based routers were never intended for cloud use. They usually require backhauling all traffic from branch offices to a center, headquarters, or data center, where specialized security inspection services can be implemented. Backhaul delays degrade application performance, resulting in a bad user experience and productivity loss. Traditional large scale WANs are usually cost effective as it includes expensive network appliances like firewalls, IP/IDS, router and switches and expensive private network carriers and it is time consuming to configure and manage decentralized and complex network devices.
In SD-WAN, as control plane is centralized, the connectivity between data plane and control plane will have complexity of O(n) while in the case of traditional network where control plane and data plane is integrated, the complexity of the connectivity is O(n²). So SD-WAN based architecture is highly scalable.
Why SD-WAN is needed?
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, IaaS and SaaS services such as Office 365, MEGA and Dropbox, while delivering the highest levels of application performance as applications are moving to cloud. Enterprises need continuous UP time and quick and secure access to every location in the work whether it is data center located or cloud based hosted.
SD-WAN dynamically uses multiple available connections (Satellite, MPLS, Internet, 4G/LTE) to find the best distribution route for traffic across the entire network, shaping bandwidth as required to minimize jitter and packet losses, and providing the best user experience regardless of location. The more advanced solutions would attempt to automatically direct traffic to the optimal link and if there is any transport issue, on-demand action will automatically be triggered based on the policies to ensure performance of the link.
Benefits of SD-WAN
Network Agility:
Because SD-WAN is cloud-delivered and software based, it allows for fast adaptation to evolving needs, such as adding connections to cloud-based services, setting up new branches or remote offices, and dynamic routing of all traffic for optimized application and data delivery, since it is cloud-delivered and software-based.
Ease of Deployment:
SD-WAN allows for various deployment options including completely cloud or software or hardware based, or a hybrid. When SDWAN enabled device gets onboard, configurations are pushed from centralized control plane.
Central Management and Control:
A centrally located control plane or virtual manager monitors all network activity including transport health, UP time of devices and alerting of problems, and enabling the remote remediation of issues. The control plane allows the automatic push of templates and configuration to each network node and add accessibility to common software platforms to every location quickly and efficiently. In addition, it delivers real-time analytics and reporting.
Cost Reduction:
As per Gartner report, SD-WAN deployment is 2.5 times less expensive than traditional WAN architectures. The root of this reduction is attributed to:
· Using existing infrastructure to transmit all traffic and access cloud applications (MPLS, Internet, Satellite, 4G/ LTE).
· Payment plans allow pay-as-you-go plans helps in reducing the cost as you have to pay for what you have used and no on-going maintenance and upgrade fees.
· ZTP (Zero touch provisioning) that allows quick site deployments and time to accessibility as all deployment functions are managed from the central location.
· No need to deploy application-specific hardware or software as each branch is accessing remote cloud based applications.
With SD-WAN, applications can be deployed on cloud, On-Premise or Multi-tenant and any services can be used and deployed like Branch security, cloud security, voice and collaboration by using any transport like MPLS, Internet, Satellite, 5G/LTE and from any location.
Separating functionality into control and data planes
SD-WAN separates functionality into a control plane and a data plane.
· The control plane is the part of the network that is responsible for forwarding of traffic based on routing decisions and policies. Control plane is the brain of the network. All intelligent decision making is done at control plane
· The data plane (forwarding plane) is part of the network that carries application and user data. It forwards the data from one port of the network device to the other.
Overview of SD-WAN Architecture
In traditional network, IO module (data or forwarding plane) and supervisor engine (CPU or control plane) resides within a device and the communication and connectivity between IO module (Data plane) and CPU (Control plane) is done by using switch fabric. In SDN technology, these two planes (data and control) are now being separated. Edges devices (routers, switches and etc.) now only have IO modules in it and its control plane module is now shifted to separate centralized location and transport (MPLS, data and Internet, 5G/LTE) plays the role of switch fabric. This is illustrated in the figure.
