What is SD-WAN or Software-Defined WAN?

Software-defined wide-area network (SD-WAN) is a service that grants the enterprise with the ability to dynamically connect branch offices and data centers on a global scale. As companies utilize a growing number of cloud-based applications, traditional WAN networks are unable to maintain strong speeds and optimized connectivity. Scaling multiprotocol label switching (MPLS) solutions to overcome this challenge is costly and time-consuming. SD-WAN has emerged as a more cost-effective solution that can deliver results with previously impossible agility and efficiency.

Compared to a traditional routing hardware deployment, SD-WAN offers the flexibility to control connection efficiency even during periods of high network demand. The cost and operational benefits of SD-WAN are becoming increasingly apparent, and the business sector is taking notice. Gartner estimates that 25 percent of users will leverage SD-WAN in 2019, with revenue from vendors growing 59 percent annually. Gartner expects the SD-WAN market to be worth $1.3 billion by 2020.

What are the benefits of SD-WAN solutions?

SD-WAN solutions offer many benefits to meet the demands of modern enterprise networks, including:

  • Improved application performance and quality of service for remote and branch workers
  • Reduced WAN costs and scaled capacity through the use of lower-priced broadband and mobile connections
  • Increased flexibility to prioritize business-critical applications over other network traffic
  • Improved business continuity and disaster recovery capabilities that maintain connectivity even during multiple network failures
  • Increased connection security across the WAN as applications and data migrate to the cloud
  • Reduced branch networking complexity by consolidating services into an integrated WAN edge appliance and centralizing management and policy definition

How does SD-WAN technology work?

SD-WAN provides IT stakeholders with better tools to manage several types of internet connections, including broadband and MPLS, as well as 3G/4G/LTE. As with internal software-defined networking solutions, SD-WAN solutions leverage policy management tools to improve IT's ability to optimize how data moves between office branches, data centers and cloud.

SD-WAN is perhaps best understood within the context of the data plane and control plane. The data plane describes the flow of information packets through a network infrastructure. Meanwhile, the control plane tells the data where to go, as defined by a developer or network engineer. Traditionally, an administrator would define rules and manually program policies. In a large enterprise, distributing policies across the network in this manner is not only prone to error but also incredibly time consuming.

In the new paradigm, SD-WAN centralizes parts of the control plane, which gives administrators the power to distribute new rules, policies and configurations across a network of any scale within seconds. Should an error occur in the network, it is much easier to identify the issue and deploy a solution at a network level, rather than deploying scripts or commands to individual routers.

Beyond application deployments, SD-WAN also makes it easier for administrators to shape bandwidth and prioritize traffic from mission-critical applications. Policy makers can decrease the traffic priority of non-essential software, such as time-wasting social media applications. SD-WAN optimization features allow administrators to define a hybrid network to route critical data through high-speed channels, leaving slower connections for auxiliary traffic.

Why use SD-WAN vs MPLS?

Networks that use the MPLS technique for data package management rely on each piece of hardware to make forwarding decisions. In this case, a router receives an IP packet, determines where that packet needs to go based solely on its network-layer header, and sends it to the next node. Over large networks, multiple routers must continually make this decision.

Network administrators need to use command line codes and other manual processes to create rules for these routers to follow. If a network contains ten routers and an application requires ten rules, it means 100 rules would need to be distributed across the network. If each rule takes ten seconds to process, it would take 16 minutes to distribute the rule-set before the application could be distributed appropriately. As the list of rules grows, the distribution time expands exponentially.

SD-WAN centralizes the rule definition and distribution processes, allowing administrators to group rules and manage policies with a single application, simultaneously. For example, a stakeholder could define a rule telling the network to send critical communications over a VPN connection, and application updates over a broadband circuit.

What are the advantages of SD-WAN?

Today's enterprise infrastructure are supported by WANs but often experience issues due to the high volume of traffic. Organizations that leverage MPLS and other networking solutions may encounter service outages, traffic congestion and packet loss. A clear example of this issue is the low quality of VoIP calling and video streaming that occurs when network demand is high.

SD-WAN addresses these problems seamlessly. Ultimately, end users won't even know if their network uses SD-WAN because their applications and services will simply work as intended. The ability for SD-WAN to dynamically route traffic through a hybrid network means that WAN traffic is reduced overall, and network agility increases.

Other benefits of SD-WAN include better quality of service for mission-critical applications, faster routing between network points and increased visibility into the WAN paths. With these advantages, network administrators can troubleshoot issues with greater agility and ultimately realize cost reductions at scale. Meanwhile, the majority of SD-WAN solutions leverage IP-SEC encryption to protect data wherever it goes.

Who are the top SD-WAN vendors and providers?

As SD-WAN grows in popularity, the number of suppliers increases. However, each vendor does not offer the same level of service. Citrix SD-WAN offers optimized features for organizations at any scale. See Microsoft Azure and Citrix Sd-WAN partnership.

Compared to other providers that monitor path selection on a per-session basis, Citrix SD-WAN offers packet-based path selection for rapid adaptation to any network changes. Furthermore, the Citrix solution detects failures quickly, eliminating any impact to an application session. Likewise, other providers do not support asymmetric routing. Citrix understands that applications are not symmetric, so symmetric measurement and unidirectional path selection may be inefficient. Asymmetric selection delivers optimal efficiency.

Learn about Citrix SD-WAN

Increase WAN throughput and reliability while improving the application experience for branch and mobile users with Citrix SD-WAN.

Related terms: Software-Defined Networking (SDN), branch office networking, business continuity

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