What is SD-WAN? Technology and Practical Applications

SD-WAN addresses the increasing enterprise demands driven by IoT, SaaS, and Cloud alongside escalating cybersecurity needs, where applications demand prioritization and optimization while enterprises require reductions in deployment costs, operational labor, and time.

What is SD-WAN?

SD-WAN (Software-Defined Wide-Area Network) is an application of SDN (Software-Defined Networking) concepts to transmit traffic over WAN links. SD-WAN automatically leverages predefined policies to determine the most optimal routes for traffic moving from branch sites to headquarters, Cloud-hosted applications, and the Internet.

With the zero-touch provisioning feature of SD-WAN, users achieve significant cost savings by eliminating the need to physically visit each branch site for configuration. Instead, administrators configure policies via a centralized management appliance, after which configurations automatically synchronize down to branch site devices. As of late 2020, leading global vendors delivering SD-WAN technology included Cisco Viptela, Cisco Meraki, Fortinet, Checkpoint, Juniper, Palo Alto, and others.

SD-WAN resolves traditional WAN challenges such as operational complexity and security deployment difficulties. The standout advantage of SD-WAN is its application-aware QoS capability (Layer 7) as opposed to legacy IP- and port-based QoS found in traditional WAN.

The SD-WAN solution natively integrates comprehensive routing and security protocols. Key advantages of SD-WAN include:

- Simplified centralized management via an integrated GUI and CLI.

- Flexible deployment (appliances can be deployed on-premises, in the Cloud, or in a hybrid topology. vEdge routers can be physical appliances or virtualized network instances).

- Security: end-to-end data encryption capabilities, device certificate authentication, and built-in next-generation Firewall capabilities.

Granular analytics that facilitate accelerated troubleshooting and provide actionable recommendations for efficient capacity planning.

SD-WAN Architecture

According to Cisco, core architectural components of SD-WAN comprise:

- vBond orchestrator performs initial authentication of vEdge appliances and facilitates control-plane connections between vSmart and vEdge. Furthermore, vBond distributes vSmart and vManage information across all vEdge devices.

- vManage serves as the centralized network management system (NMS), delivering a graphical user interface (GUI) for streamlined monitoring, provisioning, and troubleshooting of SD-WAN fabric components.

- vSmart Controller establishes a secure control plane connection to each vEdge router and advertises routes and data/routing policies via the Overlay Management Protocol (OMP), operating as a Route Reflector. vSmart constructs and maintains the network topology, orchestrating traffic path decisions.

- vEdge routers represent physical or Virtual Router appliances deployed at branches, offices, or Cloud environments, providing secure site-to-site connectivity across single or multiple WAN transports. vEdge is responsible for data-plane traffic forwarding, security enforcement, encryption, QoS, and traditional routing protocols such as Border Gateway Protocol (BGP) and Open Shortest Path First (OSPF).

Practical Applications of SD-WAN

SD-WAN enables enterprises to construct WAN networks delivering comparable or superior throughput and reliability by repurposing and aggregating disparate WAN links, including broadband Internet, LTE, and MPLS. Practical use cases for SD-WAN deployment include:

Geographic corporate scaling: When organizations expand operations into new geographic regions or execute mergers and acquisitions, they simply leverage available commodity connectivity alongside SD-WAN to seamlessly integrate new environments into the corporate network.

Cloud migration: SD-WAN mitigates network transport concerns when accessing Cloud-based workloads, leveraging application-based routing mechanisms to deliver optimal end-user experience. Most SD-WAN features are readily accessible on modern routers, switches, or firewall appliances.

Additionally, SD-WAN can be deployed across virtualized network functions (VNFs) or directly within public clouds such as AWS. This enables enterprises to realize immediate operational gains when migrating workloads from corporate on-premises servers to cloud-native SaaS services such as Salesforce.com or Google Workspace applications.

Multi-branch and Cloud SD-WAN deployment model

WAN transport optimization: For enterprises running hybrid Internet and private links, SD-WAN intelligently routes designated internal enterprise traffic over public Internet connections to offload private circuits, while rigorously preserving security posture via underlying encryption protocols such as IPsec.

WAN performance enhancement: SD-WAN continuously and dynamically evaluates transport quality to route traffic along the optimal path on an application-by-application basis, facilitating dynamic load balancing across diversified uplinks. Should a WAN circuit fail, traffic failover occurs automatically to alternate links without service degradation for end users. This is critical for organizations operating latency-sensitive workloads like voice and real-time video.

Conclusion

We hope this article has provided valuable technical insights into enterprise networking. Looking forward, we will continue developing advanced SD-WAN capabilities integrated into the Vcloudia Cloud ecosystem, partnering with enterprise customers to resolve the architectural limitations of traditional WAN.

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