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Deploying Global SD WAN across the Internet?

Written by Robert Sturt

Robert Sturt is Managing Director of Netify, an SD-WAN, SASE security & connectivity market network where you can login free to compare and shortlist vendors.

Is there an implication of selecting multiple ISPs based on cost? In this article, we discuss the challenges for Global businesses deploying SD WAN services. We've added the key international SD WAN data points to our IT Managers buyers framework.

Global SD WAN Buyers Framework

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Cisco state 'Voice networks should not exceed the accepted 150 ms one-way delay limit.”When looking at SD WAN architecture for Global companies, businesses need to become more mindful of application performance across backbones between international networks. If your data originates in the UK and is destined for a return trip to China (for example), the Enterprise cannot simply rely on the feature set of SD WAN technology. The laws of physics cannot be broken, no matter what the service providers marketing may try and suggest. (!)

Below. Multiple ISP backbones across SD WAN.

SD WAN over the Internet 2

In order to better understand the impact of a multiple low-cost ISP strategies, we need to segment user type. Where head office to branch connectivity is concerned, many companies are still looking toward MPLS VPRn (Virtual Private Routed Networks.

  • Type 1 Corporate to Branch office: MPLS, VPLS or Point to Point / Multipoint circuits.
  • Type 2 Small branch office: MPLS, VPLS or Internet SD WAN.
  • Type 3 Remote users: SD WAN.

What is important to know when buying Global SD WAN?

Learn about our SD WAN provider & vendor Mindmap. An at-a-glance overview of SD WAN features you need to consider with a comparison of 14 major UK/Global providers & vendors.
  1. Select a single backbone provider where possible.
  2. Consider latency and jitter for international traffic.
  3. Remember, an SLA is a commercial document and not technical.
  4. Managing Global implementation is challenging vs national counterparts.
  5. Global software vendors may have low resources in your particular country.

Does using a single ISP backbone result in SD WAN suitability for all connectivity types?

In our opinion, where a single ISP strategy is implemented, global connectivity with reliability and predictability is a possibility.

Figure 2, a single Global ISP backbone.

SD WAN Single ISP Backbone

Figure 2 demonstrates how latency and jitter are broadly similar when compared to MPLS. The major differentiator surrounds the lack of an end to end guarantee of traffic performance per Class of Service when using the Internet.

However, overall the cost of Internet connectivity is lower. In addition, some would argue the granular support of SD WAN traffic via Quality of Service is enough to not worry about Internet latency, Global or otherwise. SD WAN capability not only prioritises local traffic but also senses variability in latency and packet loss. Where MPLS QoS adds priority regardless of network conditions, SD WAN offers a significant upgrade with regards to data packet treatment.

Whether or not your business is willing to trust in the technology to ensure traffic is predictable is a conversation with the service provider or SD WAN partner of choice.

Traffic is one element, what about support?

An overlooked element of SD WAN using low-cost Internet providers is the management of connectivity issues. Where connectivity is impacted, pinpointing the issue is often protracted as IT teams work to establish where the issue may exist. If we focus on site type 1, this may be one step too far in terms of business risk. Where remote users and small offices are concerned, clearly using the Internet and the risks associated are acceptable.

The Internet is really the enabler to many of the benefits when discussing SD WAN, the flexibility across cloud access and other applications with security, control of connectivity state and failover, the technology is very compelling.

Is Hybrid WAN the answer?

Network design is all about aligning business requirements with connectivity and managed services. Where the ISP connectivity is considered based on fix times, network performance, support and so forth, the result is an informed buying decision.

Hybrid architectures is one of the major development points of Software Defined Networking (SDN) as the original vision is one of agnostic devices taking instructions from cloud-based management services.

With DIY implementations of SD WAN, the opportunity to terminate connectivity of choice is clearly one of your buying decisions. If your business is looking more toward managed SD WAN, IT must be mindful of the capability positioned by the managed service provider. Where Internet only provisions are at the core of their proposition, the service is not connectivity agnostic and the detail behind which ISP backbones form their core connectivity must be requested.


The future of networking is certainly behind software based, flexible architectures. The need for application access with security from whichever location our users decide to work from is almost mandatory rather than a nice to have feature.

Where Global connectivity is required, there really is only a certain amount of providers capable of meeting 90% of an international demand. With this in mind, the procurement process should request firm detail on coverage in order to understand the impact on your business.

Will ISP connectivity replace MPLS? The marketplace take up of SD WAN suggests the demise of MPLS is happening right now. With the Internet growing in scalability and reach every year alongside the demand for lower costs and on-demand access to almost everything, this trend cannot be denied.

There are certain sectors where privacy will be of primary concern, think financial or government organisations. Where full data privacy is a requirement, point to point or multipoint dedicated fibre circuits are often the only choice. Software WAN services may well become the dominant force in networking but the case will always remain for other types of connectivity.

Aligning your specific requirements with the service provider market will output the relevant technologies and associated features including security.


Robert Sturt insider@netify.co.uk Last Updated: 12.10.2019