Will the popular SD-WAN really kill MPLS?

[[419147]]

Arguably, no network technology has received more attention than SD-WAN (software-defined wide area network), and for good reason.

A large number of network professionals are either already deploying SD-WAN or are planning to do so in the near future. The reason is that SD-WAN architecture is optimized for cloud computing, while traditional WAN was designed during the era of client/server computing.

With the trend of working from home, more applications have moved to the cloud, and the pace of enterprise adoption of SD-WAN has also accelerated.

Is SD-WAN an MPLS Killer?

The short answer is no. In reality, the two technologies complement each other, so it is important to understand how to use each to design a network that is the most affordable and cost-effective.

However, many SD-WAN vendors have been positioning SD-WAN as an MPLS (Multi-Protocol Label Switching) killer because this new technology can make full use of multiple broadband links to connect branch offices. Many vendors, especially start-ups, have expressed the view that enterprises can abandon traditional MPLS networks and save a lot of telecom costs. Broadband links are indeed cheaper than MPLS, but this does not mean that MPLS has no place in enterprise WANs.

Benefits of MPLS

MPLS is a network protocol that controls the traffic that travels between two locations. MPLS networks are dedicated private networks that use advanced routing protocols to send different types of traffic over different paths on the network. For example, video and voice require a low-latency route to ensure high performance, while general Internet traffic can choose a less congested route because latency is not a big issue for it. The advantage of MPLS is that it guarantees fast, reliable packet delivery, making it ideal for high-performance or real-time applications.

Cost of MPLS

A major drawback of MPLS is cost; long-distance global connections can be expensive.

Traditional MPLS networks have a characteristic that they use an active/passive architecture. This means that enterprise customers must purchase two links, but can only transmit traffic through the primary link unless the primary link fails completely; only when the primary link fails completely will the traffic be retransmitted through the passive link. In fact, in order to obtain this higher network reliability, customers pay for bandwidth twice for a single connection.

Cost Advantages of SD-WAN

SD-WAN is an overlay on an existing network that may include MPLS, but most commonly uses broadband for the last mile and the Internet for the middle mile. The technology enables enterprises to take advantage of multiple network connections in an active/active architecture where traffic is routed over the best connection determined in real time. Deciding factors include: the latency sensitivity of the traffic, the time of day, cost, and the current state of each link.

Using the internet and broadband connections is cheaper and more reliable than using MPLS because it provides multiple paths and offers greater flexibility. The flexibility comes from the software-defined nature of SD-WAN, which separates the control aspects of the network from the hardware, so that routing changes across the entire network can be centrally managed and executed quickly, in a much shorter time than a full MPLS WAN.

Lower costs, improved network reliability and centralized management are all potential benefits of SD-WAN.

Disadvantages of SD-WAN

The downside of SD-WAN is that application performance can be unpredictable if the network is built entirely on broadband Internet, which has variable and unpredictable performance. In this case, SD-WAN's multipathing capabilities improve reliability, but application performance can be difficult to manage.

Latency comparison

When designing an SD-WAN, there is a general tendency to make it all broadband because long-distance MPLS connections can be very expensive, often costing thousands of dollars for a transoceanic connection compared to local broadband.

Businesses must ask themselves: what is more important, cost or predictability? There is no one right answer, as all businesses are different, but for most businesses, if broadband and Internet are unpredictable, certain applications will not run smoothly, which may put the business at risk, such as transaction systems, real-time CAD programs, and voice and video.

Differences in response time

I recently compared the performance differences between using MPLS or the Internet to connect cities that are far apart. The average response time between Dallas, Texas and Dubai, United Arab Emirates was about 50 milliseconds using MPLS, while the average response time was about 600 milliseconds using the Internet.

Even more striking is the change between the shortest and longest times.

Dallas to Dubai response times vary by 12% using MPLS and 153% using the Internet. Similarly, Dubai to Mumbai response times vary by 15% using MPLS and 212% using the Internet. Even across continents, San Jose, California to Washington, D.C., there is a significant difference: 5% using MPLS and 82% using the Internet. Once link lengths drop to about half the east-west distance in the United States, the magnitude of the difference is much smaller, making a full broadband WAN the obvious choice.

The problem with such large differences is that it can cause some applications to run smoothly some days and poorly some days. This inconsistency is detrimental because it negatively impacts application performance, which in turn reduces productivity. Small and regional companies can use an all-Internet WAN and the user experience may not be greatly affected because the connection length is short enough for important traffic. But this is not the case for national or global enterprises.

For widely distributed enterprises, optimizing cost and performance requires using SD-WAN, an architecture that combines broadband and the Internet with MPLS to achieve the best of both worlds.

This can be achieved by using broadband for last-mile connections and the Internet and MPLS for long-haul connections. Multiple broadband connections ensure resilient connections, and the decision to transport traffic over MPLS or the Internet can be made based on the performance required by the application. High-performance, real-time, mission-critical applications will transport traffic over MPLS, while best-effort traffic will use the Internet. In this way, enterprises can reduce their spending on MPLS by adjusting the specifications of these lines, providing priority connections only for those business applications that require high-performance networks.

The savings from MPLS often exceed the investment in SD-WAN infrastructure, so with careful planning and upfront preparation, companies can reduce the overall cost of running their network.

The rise of SD-WAN has led to the question of which is better, SD-WAN or MPLS. The answer is that both are excellent because they are used to solve different problems. One will not replace the other, instead, they complement each other.

Author: Zeus Kerravala is founder and principal analyst at ZK Research, providing a variety of tactical advice to help clients adapt to the current business environment as well as long-term strategic advice.

Original URL: https://www.networkworld.com/article/3226371/is-sd-wan-better-than-mpls.html