How to Enhance SD-WAN Efficiency with DNS-Based Application Routing
May 27, 2020

Jim Offutt
EfficientIP

Share this

Keeping networks operational is critical for businesses to run smoothly. The Ponemon Institute estimates that the average cost of an unplanned network outage is $8,850 per minute, a staggering number. In addition to cost, a network failure has a negative effect on application efficiency and user experience.

One area where networks tend to fail is in app delivery continuity. As multi-cloud environments grow more and more popular for hosting apps, finding the best way to route users across networks to their desired applications is becoming challenging. Not only are there a larger number of network exit points, but it is more difficult to define the best path to take for a user to access an app.

Typically the best path includes parameters like performance of the app itself or availability of the app, meaning that the app should be reachable via the path defined. Finding the best path can be a reasonably straightforward task, but only if all network components are functioning properly. As networks become more complex, a scenario where an application becomes unreachable (such as due to WAN failure) is all too likely.

The more complex the network, the higher the cost of failure. Enterprise Management Associates assessed the damage of one hour of WAN downtime in a 100-branch enterprise and a 1,000-branch enterprise; they found that a 100-branch enterprise loses $300,000 per hour of downtime, while a 1,000-branch enterprise could lose up to $1 million per hour.

Fortunately, a variety of solutions exist that could prevent such losses. One is a home-made multi-WAN vendor routing diversity; however, this is best for large enterprises with IP networking experts I&O.

A simpler solution is SD-WAN, or software-defined wide area network. SD-WAN automatically selects the route to take to reach an IP destination. But like any IP routing solution, it does not select the destination to go to; it tells you how to go, not where to go. It is a popular option for many companies, since it is excellent in efficiency and redundancy and can apply political or financial routing rules, not just technical IP routing.

However, a main drawback is that if any component on the path goes down, SD-WAN just drops the application traffic — it is unable to propose a new path to reach the same app hosted on a different server or in a different datacenter. Therefore, SD-WAN alone is not enough to ensure app delivery continuity; while it can control access to apps, SD-WAN is unable to guarantee that the app being requested is reachable by the user. For that, you need an application-aware routing solution to augment your network.

This is where DNS-based routing comes in. Before knowing how to go somewhere (with SD-WAN), you need to know where you want to go. DNS already performs the role of selecting the destination, and the best way to detect that the app is reachable is from the viewpoint of the user. Intelligent routing decisions should therefore be taken as close as possible to users, to enable "application aware routing"; a recursive DNS located near enterprise users is ideally placed.

Indeed, putting app routing control functionality into DNS located at the edge of the network makes sense. This is essentially how a DNS Global Server Load Balancer (GSLB), located at the network edge, would work; by continuously checking availability of app resources, following the same network path that will be used by the user to reach the app. The DNS GSLB could quickly detect an application access failure and "force" an alternative destination (a new IP address for the same application name).

Early failure detection, followed by automatic failover, would ensure that users are always routed to the app in an accessible datacenter. This would guarantee the desired app availability.


Adding DNS GSLB capability at the network edge covers scenarios that SD-WAN cannot handle. This includes detecting application access failure (IP path or server infrastructure or configuration), reacting on the user’s behalf on WAN failure, and selecting the best destination based on application response time metric. The bottom line is that everyone already uses DNS; it would therefore make sense to incorporate the GSLB functionality, and provide it at the edge.

DNS GSLB and SD-WAN are complementary to each other. SD-WAN chooses the how, DNS chooses the where, and adding DNS GSLB functionality as close as possible to users offers increased intelligence on the where. Moving DNS GSLB to the edge is disruptive in that it offers a smarter approach for controlling app traffic routing, one that is simple to implement and efficient in use.

Jim Offutt is Senior Solutions Architect at EfficientIP
Share this

The Latest

September 27, 2022

Users have high expectations around applications — quick loading times, look and feel visually advanced, with feature-rich content, video streaming, and multimedia capabilities — all of these devour network bandwidth. With millions of users accessing applications and mobile apps from multiple devices, most companies today generate seemingly unmanageable volumes of data and traffic on their networks ...

September 26, 2022

In Italy, it is customary to treat wine as part of the meal ... Too often, testing is treated with the same reverence as the post-meal task of loading the dishwasher, when it should be treated like an elegant wine pairing ...

September 23, 2022

In order to properly sort through all monitoring noise and identify true problems, their causes, and to prioritize them for response by the IT team, they have created and built a revolutionary new system using a meta-cognitive model ...

September 22, 2022

As we shift further into a digital-first world, where having a reliable online experience becomes more essential, Site Reliability Engineers remain in-demand among organizations of all sizes ... This diverse set of skills and values can be difficult to interview for. In this blog, we'll get you started with some example questions and processes to find your ideal SRE ...

September 21, 2022

US government agencies are bringing more of their employees back into the office and implementing hybrid work schedules, but federal workers are worried that their agencies' IT architectures aren't built to handle the "new normal." They fear that the reactive, manual methods used by the current systems in dealing with user, IT architecture and application problems will degrade the user experience and negatively affect productivity. In fact, according to a recent survey, many federal employees are concerned that they won't work as effectively back in the office as they did at home ...

September 20, 2022

Users today expect a seamless, uninterrupted experience when interacting with their web and mobile apps. Their expectations have continued to grow in tandem with their appetite for new features and consistent updates. Mobile apps have responded by increasing their release cadence by up to 40%, releasing a new full version of their app every 4-5 days, as determined in this year's SmartBear State of Software Quality | Application Stability Index report ...

September 19, 2022

In this second part of the blog series, we look at how adopting AIOps capabilities can drive business value for an organization ...

September 16, 2022

ITOPS and DevOps is in the midst of a surge of innovation. New devices and new systems are appearing at an unprecedented rate. There are many drivers of this phenomenon, from virtualization and containerization of applications and services to the need for improved security and the proliferation of 5G and IOT devices. The interconnectedness and the interdependencies of these technologies also greatly increase systems complexity and therefore increase the sheer volume of things that need to be integrated, monitored, and maintained ...

September 15, 2022

IT talent acquisition challenges are now heavily influencing technology investment decisions, according to new research from Salesforce's MuleSoft. The 2022 IT Leaders Pulse Report reveals that almost three quarters (73%) of senior IT leaders agree that acquiring IT talent has never been harder, and nearly all (98%) respondents say attracting IT talent influences their organization's technology investment choices ...

September 14, 2022

The findings of the 2022 Observability Forecast offer a detailed view of how this practice is shaping engineering and the technologies of the future. Here are 10 key takeaways from the forecast ...