Enhancing SD-WAN Efficiency with Edge DNS GSLB for Improved UX

For organizations to survive in today’s highly competitive digital world, it’s vital that their businesses run smoothly. Users and customers need to be able to access their important work applications and services, at all times and from anywhere. Unfortunately, network complexity is increasing the likelihood of apps becoming unreachable due to scenarios such as WAN failure. SD-WAN can assist to some extent, but is helpless when any network component on the routing path goes down. This is where adding DNS GSLB functionality brings value.

Each unplanned network outage causes devastating financial impact – average cost around $8,850 per minute, according to the Ponemon Institution. Issues can be related to IP routing (e.g. route disappearing), increased latency due to layer 2 re-routing (taking a backup link rather than the main / xDSL vs optical fiber), failure of the protocol optimization system, firewall rules filtering out part of the traffic, or SD-WAN incorrectly deciding the best application route. As well as damages to a company’s bottom line, network failure also has disruptive effects on application efficiency and end-user experience.

Ensuring Application Delivery Continuity in multi-cloud

An important area of concern relates to application delivery continuity. With apps being hosted more and more in multi-cloud environments, the number of network access points has considerably increased, making it far more complex to decide the best way to route a user to the applications they desire. The ‘optimum path’ normally includes parameters such as actual performance of the app or its availability, meaning that the app must be reachable via the specified path. If not all network components are functioning properly, finding the best path can be a tricky task.

Naturally, the cost of failure rises with complexity of the network. For a 100-branch enterprise, Enterprise Management Associates estimates a loss of $300,000 per hour of WAN downtime, compared to a 1,000-branch enterprise losing up to $1 Million per hour.

Fortunately, such losses can be avoided using a variety of different solutions, the first of which being a home-made multi-WAN vendor routing diversity. That, however, is suitable only for large enterprises with I&O teams containing IP networking experts.

SD-WAN offers a simple but incomplete solution

A more simple solution is to use a software-defined wide area network, commonly known as SD-WAN, to automatically decide which route to take for reaching an IP destination. The downside, just like any IP routing solution, is that it does not select the destination to go to; while it tells you how to go, it does not specify where to go. SD-WAN has been adopted by lots of companies because it enhances efficiency and redundancy and allows political or financial routing rules to be applied, rather than only technical IP routing.

However, a main disadvantage is that if there is a failure on any component along the path, SD-WAN simply drops the application traffic. Even though the app is most likely also hosted on a different server or in another datacenter, SD-WAN is not able to propose a new path for reaching it. So while it’s able to control access to apps, SD-WAN cannot guarantee that an app being requested by the user is always reachable. The conclusion is that for ensuring app delivery continuity, using just SD-WAN on its own is not viable. For that, you need to enhance your network with an application-aware routing solution.

Edge DNS GSLB brings intelligent application aware routing

This is where DNS-based routing brings real benefit. Ideally, you need to know where you want to get to – i.e. the destination – before deciding how to actually get there. DNS is great at performing the role of selecting the optimal destination, and the best way to detect that the app is reachable at that destination is from the viewpoint of the user. Hence for routing decisions to be intelligent they need to be taken as near as possible to users, thus enabling “application aware routing”. For this, a recursive DNS located close to enterprise users is ideally placed.

Consequently, incorporating app routing control functionality into DNS located at network edge makes sense. This is essentially how EfficientIP’s Edge DNS GSLB operates; taking the same network path that the user will follow to reach the app, it constantly checks availability of app resources. Edge DNS GSLB rapidly detects any application access failure and “forces” routing to an alternative destination – a new IP address for the same application name. Thanks to this early failure detection, followed by automatic failover, users are sure to be always routed to the app in a datacenter which is accessible. App availability is hence guaranteed.

As a result, Edge DNS GSLB is able to cover many scenarios which SD-WAN cannot handle. They include detection of application access failure (due to problems with server infrastructure, IP path or configuration), reacting on behalf of the user for WAN failure, and selecting the ideal destination based on the application response time metric. In addition, DNS is already used by everyone so it makes sense to leverage existing investments and use DNS GSLB at the edge.

Complementing SD-WAN with Edge DNS GSLB improves end-user experience

Edge DNS GSLB is without doubt complementary to SD-WAN. The latter chooses the how, whereas DNS chooses the where, and Edge DNS GSLB offers additional intelligence on the where. Events logged at the Edge DNS GSLB engine level can be used from a supervision standpoint to detect network issues early and without the need to deploy specific sensors at each location.

Bringing a disruptive but smarter approach for controlling routing of application traffic, Edge DNS GSLB is really simple to implement and certainly efficient in use. Bearing in mind the increasing complexity of IP networks and optimization solutions to improve user experience, organizations would do well to consider Edge DNS GSLB whenever SD-WAN is being utilized.