SD-WAN offers flexibility, bandwidth benefits, centralized management, and other advantages. However, it should be carefully compared to modernized networking architectures like SASE.
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Software-defined wide area networking (SD-WAN) is a flexible, software-based approach to connecting local area networks (LANs) across large distances. It is essentially a virtual overlay that runs on top of the physical underlay of networking infrastructure. SD-WAN is often used by organizations with multiple branch locations instead of traditional multiprotocol label switching (MPLS), leased line, or dark fiber for connectivity. SD-WAN offers a number of benefits compared to MPLS and other networking models, but it is not without its downsides.
| SD-WAN pros | SD-WAN cons |
| Flexibility | Security limitations |
| Bandwidth | Inconsistent performance |
| Centralized management | More administrative overhead |
| Initial cost savings | Complex cost structure over time |
MPLS networks have hardwired, dedicated network paths provided by carriers who are bound by quality-of-service (QoS) agreements. MPLS is reliable, but inflexible, and it tends towards having network chokepoints that slow down performance. It is also ill-suited to cloud adoption or remote work. SD-WAN was intended to solve for some of these challenges.
Some other WAN configurations, like virtual private LAN service (VPLS), also use the MPLS protocol and have similar drawbacks.
SD-WAN allows for connecting sites via low-cost options like broadband or LTE, rather than MPLS circuits. This can result in cost savings, though the amount depends on the contracts with ISPs and the amount of hardwired MPLS connections an SD-WAN configuration still relies on.
SD-WAN network routes are far less rigid than MPLS routes. The result is fewer bottlenecks and less tromboning. This especially helps with cloud-hosted application performance, when the applications might be hosted in faraway data centers. Dynamic path selection ensures more efficient connections between users and the cloud.
SD-WAN allows for flexibility. It can incorporate multiple connectivity options, including leased lines, 5G, the public Internet, and cloud network routes.
SD-WAN has no native bandwidth limits, unlike MPLS networks in which capacity is rigidly fixed. SD-WAN can add bandwidth as needed by combining multiple connections and leveraging the fastest connectivity available.
SD-WAN management is centralized. Administrators can make changes to the entire network via single-pane-of-glass interfaces. Security and routing policies can be applied across all branch locations and for on-premises and remote users alike from a central location.
Often, security must be layered on top of SD-WAN; it is not natively included in the network itself. SD-WAN is often paired with other disjointed security tools: this creates more overhead, and inconsistency in how security rules are applied.
While MPLS is provided as a service, SD-WAN has to be configured and maintained internally. Organizations that set up SD-WAN themselves may find their administration needs increase by quite a bit, so many turn to managed service providers for SD-WAN.
Maintaining hardware and private lines at every branch location becomes increasingly expensive. Transitions to SD-WAN, while intended to lower costs, often introduce new,
complex layers of "overlay" configurations that keep operational overhead high. Organizations often end up double paying for bandwidth and security user licenses. If SD-WAN is operated by a managed service provider, their fees often rise over time as well.
Even though it is defined by software, SD-WAN is rooted in hardware. SD-WAN deployments may not always require routers or MPLS, but most connection types still require hardware and dedicated lines of some kind (firewall appliances, for instance). Reconfiguring or scaling the network may still require costly hardware installation and maintenance. Most organizations that rely on SD-WAN also need to maintain a VPN server to support remote workers, which also inhibits scalability while introducing security risks (see Castle-and-moat model).
Forcing traffic through central hubs for security introduces latency, frustrating users further from main offices. While SD-WAN often improves office-to-office speeds, remote users remain tethered to slow, unreliable VPNs that cause traffic bottlenecks and introduce inefficient routing.
SD-WAN was designed to connect buildings, not individuals. As a result, SD-WAN remains location-bound, treating the corporate network as a destination to reach for security and connectivity.
Secure access service edge (SASE) is a cloud-based architecture with a user-centric approach, shifting networking and security policies to the cloud and designing them around the user, not the office. SASE replaces location-dependent rules with a unified set of policies and experiences that remain identical whether a user is at an office or remote.
SASE also positions organizations well to fully adopt AI. AI applications require large amounts of consistent bandwidth and low latency for real-time processing. Because SD-WAN relies on the public Internet for many of its paths, it cannot always guarantee the consistent data delivery AI needs. SASE can help an organization reach a state of AI readiness thanks to its unified, consistent, cloud-delivered network paths.
| SD-WAN | SASE |
| Separate security, disjointed policies | Native zero trust security |
| Rooted in hardware | Cloud-delivered |
| Not optimized for AI | Optimized for AI |
| Built for branch networking | Built for hybrid workforces |
Networking is evolving, and network modernization positions organizations well to take advantage of emerging technologies like AI. However, a hard cutover to a completely new networking model like SASE is not in the cards for most organizations. Too many essential services may depend on MPLS connections or on-premises services.
Approaching network modernization or SASE adoption as a journey can help organizations adapt to the realities of the modern-day competitive environment, AI, global connectivity, and hybrid workforces. To learn how to start modernizing, see How to prepare for network modernization projects.
Or, explore the contrasts between SD-WAN and SASE more thoroughly.
Many businesses transition to SD-WAN to gain better flexibility and cost efficiency. Unlike multiprotocol label switching (MPLS), which uses rigid, hardwired paths, SD-WAN allows companies to connect various sites using more affordable options like LTE or standard broadband.
SD-WAN uses dynamic path selection to find the most efficient routes between users and the cloud. By reducing the rigid routing requirements common in traditional networks, it minimizes bottlenecks and "tromboning," which keeps applications responsive even when hosted in distant data centers.
SD-WAN offers centralized management through a single interface, often called a "single-pane-of-glass." This allows administrators to apply routing and security policies across all company locations and for remote employees simultaneously from one location.
Security is typically not a native part of the SD-WAN network itself. Organizations often have to layer separate security tools on top of the connection, which can lead to increased administrative work and inconsistent security policy application across the network.
While SD-WAN can save money initially, it can become expensive over time due to the need for hardware maintenance at every branch office.