How does SD-WAN compare to VPN?

When enterprises compare SD-WAN vs. VPN services, choosing between the two technologies should consider factors such as cost, cloud computing usage and application awareness.

Software-defined WANs are sometimes marketed as an upgraded version of virtual private networks on the global Internet, and many IT teams are confused about the fundamental differences and similarities between SD-WAN and VPN services.

While the preferred connectivity option for SD-WAN platforms is indeed based on the Internet (public IP, to be specific), the technology is not about network connectivity. SD-WAN marketing teams may want users to believe that Internet connectivity is the primary choice for SD-WAN, but the original concept of software-based networks still supports a variety of interfaces.

To choose the right option, enterprise IT teams will want to cut through the hype surrounding SD-WAN by comparing various aspects of SD-WAN vs. VPN.

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Understanding VPNs

For decades, the basic task of basic IPsec VPNs has been to discard packets that do not come from authenticated endpoints. All traffic between endpoints is encrypted at the highest level, which forms the basis of VPNs on the global Internet. VPNs are simple and cost-effective, but they also have problems in guaranteeing network performance.

At the most basic level, a VPN can prioritize applications and traffic before encrypting it. However, the value of doing so is limited. Once traffic is in an encrypted tunnel, it is impossible to prioritize it from the perspective of the provider network because the headers are encrypted and cannot be viewed. What is left is the best effort of the network to support the traffic at a reasonable performance level.

For small businesses that run their business on a single IP backbone, a typical VPN is fine. However, for larger enterprises with multiple locations, IPsec VPNs often cause problems for voice and video applications due to high latency or congestion on the network.

Here are the pros and cons of VPNs that enterprises should consider when evaluating SD-WAN vs. VPN:

• Standard VPNs provide simple WAN creation using authenticated tunnels and encryption.
• VPN services are simple, generally low cost, and easy to deploy.
• Latency-sensitive applications require more than VPNs provide with encryption and authentication capabilities.
• Cloud-based services require global internet connectivity with optimization and advanced next-generation security, features that VPNs cannot always provide.

Learn about SD-WAN

Once an enterprise adopts and relies on cloud computing services or requires application awareness, remote access, and granular security, SD-WAN technology begins to make sense. Although SD-WAN does not have end-to-end quality of service (QoS) like Layer 3 MPLS VPN, SD-WAN meets the challenge by providing the ability to sense network conditions and prioritize applications locally. SD-WAN's local quality of service (QoS) is much more advanced than basic Internet VPN services due to its granular support and features such as caching or application acceleration.

When organizations need cloud computing services, they should consider security and application awareness. SD-WAN devices and clients are generally more comprehensive in feature sets, consistent with people's current work habits, such as working from home, coffee shops or hotels. With the enhanced control of SD-WAN, IT teams or providers can limit and protect traffic based on user profiles and traffic types.

In many cases, simplified self-management with easy-to-use GUIs is driving SD-WAN adoption. Traditional Cisco IOS VPN configuration requires expertise and certification, while SD-WAN configuration is based on a point-and-click approach.

The promise of SD-WAN is to support any type of network connection, from Multiprotocol Label Switching (MPLS) to Virtual Private LAN Service (VPLS) and, of course, Internet VPN. With SD-WAN's application-based routing capabilities, it can take advantage of multiple paths, such as the global Internet, 4G, or Multiprotocol Label Switching (MPLS). However, at present, it is still less expensive to deploy a simple IPsec device to create a standard VPN connection.

SD-WAN can use several types of connections.

At the same time, SD-WAN devices and clients will offer all the functionality in a simple, easy-to-use, basic form factor. When each device or client is just a fast track to a centralized management server, the original promise of SD-WAN will begin to become a reality. In other words, enterprises will be able to use their most basic SD-WAN services or more complex elements, depending on their overall needs, essentially using cloud network function virtualization capabilities.

SD-WAN technology doesn't exist yet, as most providers are pushing for cost savings by using low-cost global internet connections, and hardware that can still be individually programmed. It does, however, need to be configured from a server.

Disadvantages of SD-WAN

While it may seem difficult to find any SD-WAN disadvantages with such a rich technology, it does have some drawbacks that can be considered.

(1) Using the Internet as a WAN connection can reduce repair time and service levels. Transitioning from MPLS to an Internet-based WAN with SD-WAN can often be a shock when problems such as power outages occur. The company's network operations center responsible for MPLS configuration and ongoing support has extensive expertise and responsive service levels. This is not to suggest that every Internet provider provide a reduced level of support, but IT teams should consider the requirements of the service level agreement (SLA) and determine how to support the business when major problems occur.

(2) Using services from multiple Internet providers will create an unpredictable environment. Many SD-WAN providers advocate using multiple network service providers (ISP) backbones to save money. This strategy makes sense unless the enterprise experiences latency and jitter issues between applications due to traffic routing across multiple service providers. Using services from multiple network service providers (ISPs) may not be a problem when deployed on a larger scale, but global enterprise customers should carefully consider deploying their WAN using the lowest-cost provider in their region.

(3) No end-to-end QoS. One of the key drivers behind MPLS is end-to-end QoS. SD-WAN counters MPLS with sophisticated path selection, application isolation sensing, and granular local prioritization. However, the fact remains that MPLS is still the only option for maintaining application SLAs end-to-end. The result is typically a per-application SLA that can be delivered back to the business.

(4) Cost savings are not always achievable. Whether SD-WAN cost savings are achieved depends on several factors, but perhaps the most important is connectivity. For example, in the UK, the cost of the Internet is comparable to Multiprotocol Label Switching (MPLS), which can result in an improvement in the overall business model when complex SD-WAN equipment and services are added to the connectivity. The US market is different because the cost of global Internet is generally much lower than Multiprotocol Label Switching (MPLS). IT teams need to conduct a business analysis of the market in each country.

(5) Researching SD-WAN providers is often a daunting task. One of the drawbacks of selecting an SD-WAN provider is the large amount of hype and marketing that often leads to a difficult decision-making process. Many providers and vendors tout significant cost-saving benefits and advanced features, making it difficult for enterprises to gain the clarity needed to make comparisons.

The Difference Between SD-WAN and VPN

The main difference between standard IPsec VPN and SD-WAN is based entirely on the capabilities of software-defined networking (SDN), which SD-WAN technology is based on. SDN consolidates options into a single platform that can be used as hardware, virtualized, or client access. Similarly, SD-WAN is a collection of different aspects of WAN functionality that are consolidated into a single platform for easy management.

VPNs provide authenticated WAN security between two or more endpoints to protect communications between headquarters and branch offices. End-to-end VPN encryption is only a small part of overall security as IT teams are responsible for supporting users with remote cloud-based work partners, productivity applications, and more.

Both ends of a VPN transmission need to protect traffic, reduce access based on permissions, perform WAN optimization, and select the best path. Standard VPNs typically do not include the intelligence to route traffic based on the best path with optimization and security. That said, some enterprises still need to deploy VPN services without SD-WAN capabilities, such as temporary office deployments or locations with simple requirements.

Can SD-WAN replace VPN?

Enterprises can replace VPNs with SD-WAN based on business needs or after seeing clear adoption benefits. Many enterprises have found that SD-WAN provides far more capabilities than WAN connections associated with Multiprotocol Label Switching (MPLS) or IPsec VPNs.

SD-WAN has the ability to manage and report at the network and user level, which enables enterprises to support and facilitate application access through a single interface, which is not possible with VPN services. SD-WAN can also transform business by consolidating LAN, WAN, users, security and application performance into a single platform, rather than just another VPN service.

While SD-WAN can serve as a lifesaver for these large networks, enterprises still face end-to-end traffic flow issues. So, why would an enterprise choose IPsec VPN over SD-WAN?

Enterprises comparing SD-WAN vs. VPN should make their decision based on a sound alignment of business processes, applications, and policies. Fundamentally, they should consider the following questions:

• Does the business need to guarantee application performance, or can it do best effort?
• Does the enterprise use the cloud and support remote, insecure networks?
• Should enterprises manage their own WAN?

For businesses that want to implement a cost-effective and best-effort VPN service, using traditional VPN equipment with a simplified feature set, a simple router or client with IPsec capabilities can be used. The cost of deploying such a service is usually minimal. Some businesses deploy VPN services with broadband for less than $100 per month.

SD-WAN vs. VPN: How to Decide

While it is difficult to predict the future, enterprises will undoubtedly seek the best network performance, security, and flexibility at a relatively low cost.

The goal of SD-WAN is to take business elements and map them into business support. With SD-WAN, the network becomes more granular, enabling better reporting, security, and application performance. Unlike standard Internet VPNs, SD-WAN can sense network conditions to ensure predictable performance levels no matter where the client is connected.

When comparing SD-WAN vs. VPN over the global Internet, SD-WAN is more comprehensive. SD-WAN technology has the potential to enable basic Internet VPNs and terminate global Multiprotocol Label Switching (MPLS) and VPLS networks.

However, when considering any network technology, enterprises need to be wary of the hype and publicity that may lead them to purchase SD-WAN after buying a specific service provider product with specific key elements.

As IT teams continue to move forward, technology acceleration and product capabilities will continue to evolve, eventually making simple VPNs a thing of the past. Enterprises will need to take a more targeted approach to protecting and processing application traffic to avoid hacker attacks or poor distribution performance, all of which can impact business development.