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<< Back to Blog  |   6 Minute Read    |   Topic: [WAN, SD WAN]

Benefits of SD WAN (and challenges too)

SD WAN Benefits

Having explored the definition of SD WAN elsewhere, I'd like to consider some of the benefits that people hope to enjoy from an SD WAN deployment.

SD WAN Benefits

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 in-house 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.

Download our free introduction to SD WAN to help guide you through the myths and jargon you may come across along your journey to implementing your own solution.

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.

What problems does SD WAN create?

A number of SD WAN CPE vendors want to take the credit for the cost savings of Hybrid Networking without accepting the responsibilities for its DIY shortcomings.

The challenge of managing SD WAN yourself

If SD WAN helps you swap your expensive international MPLS connection with locally bought internet at a fraction of the price (not always true!) then they are also suggesting that you become your own Managed Service Provider to scour the local market, order, install, support and bill that circuit.

It takes a great deal of in-country expertise and effort to achieve and support this and hope that the local teams maintain records and pass on the local contacts and knowledge.

You’ll need carrier savvy IT staff in every office or at the least, region. It’s very easy to compare the cost of international MPLS against local internet circuits but more difficult to quantify the management overhead both locally and centrally of having multiple providers.

Carrier-delivered SD WAN can make it harder to get the benefits you seek from Hybrid WAN

A recent development of SD WAN is a move by the carriers to incorporate SD WAN with their connectivity. The logic on this is sound – once the carrier’s systems are integrated with SD WAN CPE devices, customers will be able to get a quote to change their bandwidth and then the systems will make changes to the network as well as the router at the same time. This is something that the SD WAN CPE vendors can’t do because they don’t supply the connectivity.

The downside of this approach for customers is that it goes against one of the potential advantages of Hybrid Networking:  which is that you can connect each site with the best carrier and technology. For example, you could buy a local internet connection to make considerable savings over International MPLS.

Are there really benefits of SD WAN versus MPLS?

If you have a primarily UK based network then the cost differential between MPLS and Internet may not be large on a like for like basis (it depends who has supplied your MPLS and Internet).  However, there are a number of performance related benefits to SD WAN, some of which bring their own cost benefits. You might like to read our Guide to SD WAN Benefits for more information.

If you do have international sites, a better solution may be to use a Managed Services Providers who can integrate several carrier networks to give you the best pricing, performance and delivery speed at every site. 

Benefits of SD WAN - guide
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