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SD WAN Overview

Benefits of SD WAN

Having explored the definition of SD WAN, let’s consider some of the benefits that people hope to enjoy from an SD WAN deployment.


The SD WAN market grew from the US, partly as an easier way for large enterprises to deploy and manage networks. One of the key benefits of SD WAN was that it offered a centralised GUI-based management and allowed people to take advantage of the reduced cost and delivery lead time of locally-sourced internet connectivity compared to MPLS circuits.

This was further supported by inhouse applications moving to platforms such as Amazon Web Services (AWS) and by Software as a Service (such as being consumed from public clouds and accessed via the internet. SD WAN promised to offer private line-like performance over the public internet, a claim which can have some merit when an Optimised IP solution is also included.

The SD WAN CPE solution isn’t necessarily a revolution; more an evolution of existing technologies all brought together under the CPE and rebranded as SD WAN.

Simpler Hybrid Networks

Hybrid Networking has been available and deployed by Managed Service Providers like SAS for years so there’s nothing particularly new in utilising locally-sourced internet, either as a primary or secondary active circuit. SD WAN makes deploying and managing Hybrid Networking solutions easier, and adds monitoring and alerting for those that didn’t have it already.


SD WAN helps with each deployment, since the device calls home to receive its configuration. This also leads to standardisation across regions, and the central controller acts as an inventory repository for all devices and configurations.

Monitoring and visibility

The ability to monitor the entire IP path is a key challenge for businesses as they digitalise their businesses and move applications to the Cloud. In the absence of a complete solution in the market, we had to develop our own monitoring solution over many years, and carriers are also recognising the need to offer advanced monitoring.

Now, SD WAN promises to create greater visibility of the network. Visibility on the utilisation of your connectivity and applications across the network can give insight to what’s actually happening. This allows you to right-size your WAN and to understand what traffic might be offloaded to the internet. The SD WAN benefit here is not so much the ability to do this but the ability for this to be included as part of the CPE solution.

If you don’t have access to a world class monitoring, alerting and reporting system then the inclusive offering within the SD WAN CPE solution will be a good starting point. However, if an application is running slowly due to a database query then SD WAN monitoring is not going to give you everything you need: you’ll also want to see the LAN, Server, Virtual machine, database and application. For those who want to see all that in a form that’s meaningful, rather than as a long list of nodes, Critical Path Monitoring will be a great help.

Easier deployment

Another problem that SD WAN, or one of the facets of SD WAN, addresses is that it is sometimes difficult to deliver new routers to remote locations. Issues with customs and local engineers as well as in country hardware replacement can be an issue. The SD WAN CPE function can be delivered as virtual devices, basically as software sitting on a standard X86 server. As long as you have the IT staff at site who are knowledgeable on the IT Infrastructure side, SD WAN can help circumvent this issue.

Dynamic path selection

Dynamic Path Selection is another feature that isn’t really new. Performance routing has been available with Cisco edge devices for many years but tended to be very expensive. SD WAN CPE vendors have included this feature at a more palatable cost point. The problem this solves is that an application can now be given its own SLA in terms of latency, packet loss and jitter. If the primary connection suffers from a degradation in performance, known as a ‘brown out’ then the SD WAN CPE device will measure any other connectivity available and if it meets the SLA criteria, switch the traffic to that link.