SD-WAN: Advantages and Disadvantages

This article explores the pros and cons of SD-WAN (Software Defined Wide Area Networking).

What is SD-WAN?

Introduction: SD-WAN separates the functions of networking devices into two distinct planes: the control plane and the data plane.

• The control plane is responsible for signaling traffic and routing decisions.
• The data plane handles the actual transfer of application and user data.

In traditional WAN setups, each instance of the data plane contains its own control plane. However, in SD-WAN, a single, logical control plane manages multiple instances of the data plane (typically switches and routers). This separation simplifies the programming and control of all transport mediums.

SD-WAN is a technology that distributes traffic between branch offices and data center sites using the most appropriate transport mediums, leveraging software-defined networking (SDN) concepts. This makes SD-WAN “transport-agnostic.”

Key Features of SD-WAN:

• Centralized Control Plane: SD-WAN uses a centralized control plane architecture, where the control plane manages a large and diverse set of data plane components.
• Standard OpenFlow Protocol: It often utilizes the OpenFlow protocol for communication between the control plane and data plane components. Viptela (now part of Cisco) developed the Overlay Management Protocol (OMP) specifically for SD-WAN. SD-WAN often eliminates the need for protocols like OSPF and BGP within the SD-WAN overlay.
• Transport Independent, Secure, and Reliable Network: SD-WAN delivers a network that’s independent of the underlying transport, while maintaining security and reliability.
• Standard Encryption: SD-WAN uses standard encryption methods like AES to provide secure connectivity over any type of transport medium. Some SD-WAN services also use IPsec to authenticate network traffic between branch offices and data center sites.
• Easy Migration: Migration from traditional WAN to SD-WAN is made easier through different approaches like inline path, out of path, and thin branch. These approaches typically use BGP to interface a legacy branch with the SD-WAN branch.
• Simplified Management: SD-WAN provides users with an easy-to-use management console for traffic management, policy assignment, and device configuration (switches, routers, firewalls, etc.).
• Network Simplification through Automation: SD-WAN simplifies the network by automating tasks such as deployments, configurations, and operations.
• Cost-Effectiveness and Flexibility: SD-WAN improves cost-effectiveness and flexibility by leveraging commercially available hardware, network devices, or servers.

For more details, refer to the difference between SD-WAN vs Traditional WAN.

Benefits or Advantages of SD-WAN

Here are the key benefits of SD-WAN:

• Automatic Failover: SD-WAN offers automatic failover to another transport medium if one fails. For instance, if an SD-WAN router is connected to DSL, fiber, and LTE, and the DSL connection fails, the router will automatically send traffic using fiber or LTE.
• Cost Savings: SD-WAN provides significant cost benefits by leveraging public internet connections over expensive MPLS circuits. Low-priority, less sensitive data can be sent over the cheaper public internet, while private links (e.g., MPLS) are reserved for critical and time-sensitive data like VOIP.
• Easy Migration for Existing MPLS Users: Organizations already using MPLS can easily migrate to SD-WAN solutions without having to completely overhaul their existing MPLS network.
• Improved Application Performance: SD-WAN dynamically shifts traffic to links with higher bandwidth availability. This, combined with WAN optimization techniques, improves application performance. It ensures application performance continuity, and enables rapid deployment and automation.
• Scalable Secure Communications: It provides scalable and secure communications over any transport medium.
• Efficient WAN Utilization: SD-WAN unifies all available WAN links to deliver aggregate capacity, leading to efficient WAN utilization.
• Simplified IP Stack: It offers a simple, consolidated IP stack to the edge of the existing network, making it easy to insert SD-WAN into the existing network.
• Incremental Resource Addition: SD-WAN provides the ability to incrementally add resources and interoperate with existing devices and circuits.

Drawbacks or Disadvantages of SD-WAN

Here are some of the potential drawbacks of SD-WAN:

• Requires IT Staff: SD-WAN requires IT staff for planning, design, implementation, and ongoing maintenance.
• Potential for Jitter and Packet Loss: There is a possibility of jitter and packet loss, especially when relying heavily on public internet connections.
• Not Immune to Slow Performance: The system is not 100% immune from slow performance, as it still depends on the quality of the underlying network connections.
• Limited On-Site Security: SD-WAN does not typically offer built-in, on-site security functionality. It often relies on external security solutions.