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:

1. 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.
2. 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.
3. 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.
4. 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.
5. Scalable Secure Communications: It provides scalable and secure communications over any transport medium.
6. Efficient WAN Utilization: SD-WAN unifies all available WAN links to deliver aggregate capacity, leading to efficient WAN utilization.
7. 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.
8. 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:

1. Requires IT Staff: SD-WAN requires IT staff for planning, design, implementation, and ongoing maintenance.
2. Potential for Jitter and Packet Loss: There is a possibility of jitter and packet loss, especially when relying heavily on public internet connections.
3. 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.
4. Limited On-Site Security: SD-WAN does not typically offer built-in, on-site security functionality. It often relies on external security solutions.