In this techtorials, we aim to provide an introduction to the concept of SD-WAN for those who are either new to the topic, or perhaps just firming-up their understanding before assessing whether it is the right solution for their business’ needs. To that end, the following provides a beginner’s guide to SD-WAN, and how it can be understood as an evolution of the traditional WAN. We’ll also provide next steps for those looking to further advance their understanding.
SD-WAN: A Definition
In a nutshell SD-WAN stands for ‘software defined WAN’ or ‘software defined wide area networking’.
SD-WAN can be defined as an evolution of the wide area network (WAN), to use a centralized software defined (SD) control function to bring efficiencies and enhanced IT capabilities.
To truly understand what SD-WAN is, we need to look at these phrases in turn:
WAN: Wide Area Network
A private network that can connect across distinct sites, using technologies such as leased lines & multi-protocol label switching (MPLS), allowing organizations to share data & applications within an integrated, controlled & secure environment, irrespective of geographical locations. Traditional WANs rely on most control functions (e.g. routing of traffic or implementation of IT policies) to be managed individually for each location. This approach uses separate hardware appliances or ‘tin’ (e.g. branch routers, switches, gateways etc…) to perform each network function.
The use of software to automate the management and configuration of these network functions & appliances. Rather than being required to manually configure each network appliance individually, network administrators are able to instruct software with the logic of what they are trying to achieve & rely on it to automate the specific configurations. Networks that employ these automations are referred to as software defined networks, or SDNs. SD-WAN can be considered as an application of these SDN techniques to the WAN.
Bringing SD and new networking capabilities to the WAN goes hand-in-hand with the ability to replace physical tin with more flexible virtualized network functions (known as network function virtualization or NFV) and the centralization of these functions for more efficient and coherent network management.
How Does SD-WAN Work?
When beginning to explore exactly how SD-WAN works, it is useful to consider the characteristics of a typical SD-WAN setup. Individual SD-WAN capabilities can vary considerably as a result of business requirements and the specific strengths of different SD-WAN providers, but the following represents the constituent aspects of a typical offering:
The SD element of SD-WAN allows a WAN’s control functions to be managed centrally from a single software interface. This ‘single pane of glass’ is provided natively rather than requiring separate solutions that attempt to tie configuration of those disparate functions together.
With traditional WAN control functions, the network management and control planes would be spread far and wide across network locations. When network administrators are required to update network configurations, in response to changing IT requirements or policy updates, they would need to roll these out to the appliances within each location individually, with the all the associated strain on resources – not to mention the opportunity for inconsistencies in deployment.
SD-WAN, however, can bring the opportunity of centralised orchestration, whereby a single point of control – a central brain – allows network configuration updates, fixes, policies etc, to be programmed and automatically disseminated to branch locations and devices. This in turn can allow the efficient and rapid roll out of consistent policy and access controls across a WAN, as well as easier onboarding of devices throughout its locations.
Whilst traditional WAN can utilise multiple connectivity options, incorporating multiple elements (such as broadband or mobile connectivity alongside more traditional technologies) to create a smarter network can be a challenging, complex, and laborious process for network administrators. Consequently, many traditional WANs are largely dependent on MPLS or direct leased lines to provide secure connectivity between network locations.
SD-WAN abstracts away the differences in the underlying connectivity to an extent, and so can incorporate MPLS alongside broadband and even mobile networks, to allow flexibility in connectivity options. Using tunnelling technology, differences between connectivity types are minimised and data can be sent through each. Decisions about how traffic is routed can in effect become connectivity agnostic. What’s more, SD-WAN’s network management software can then react dynamically to ensure that the flow of information through these connectivity types best meets business requirements.
Business reliance on cloud-based applications for critical functions is already well established and rapidly growing due to the features, efficiencies, and scalability that they provide. The easier incorporation of public connections can allow internet breakout from network locations to access SaaS applications such as Office 365 or Salesforce, whilst keeping these connections within the network’s central control and policies. This addresses the latency issues that can arise when routing SaaS requests via the data centre (i.e., data centre backhaul), or the security concerns of allowing unsecured internet breakout.
The traditional WAN model primarily relies on address-based routing, with individual local branch routers utilising TCP/IP and access tables to manage the use of network resources. It can therefore require complex and time-consuming configuration of the network conditions around an application to provide individual applications with the access and bandwidth that they need to meet business requirements and maximise their productivity. Bringing new applications online can sometimes prove time consuming and problematic, particularly when those applications live in the cloud.
Building on traditional WAN configurations, SD-WAN can make it easier to deliver application-aware traffic management, whereby the software will recognise specific applications and allow configuration directly on a per-application basis. Consequently, routing and bandwidth allocation can be managed in accordance with the priority and demands of applications to ensure that business critical functions are maintained.
Intelligent Path Control/Flexible Steering
As mentioned above, the move away from low-level labour-intensive manual network configuration to software-based solutions allows SD-WANs to deliver automatic traffic steering based on current network conditions, application requirements, and variations in user demand.
With the evolving profile of business applications and the increasing reliance on high bandwidth streaming for voice and video conferencing, the need for networks capable of dynamically handling fluctuating demand, whilst maintaining QoS, continues to grow.
Rather than conducting regular low-level configuration reviews to optimise the performance of the network, administrators can program an SD-WAN with parameters that reflect the importance and requirements of each application or network function within the business setting. The software can then deliver intelligent path control, or flexible steering, by assessing the current network capabilities and performance in real-time and automatically routing traffic as needed to meet those requirements.
WAN optimisation is achieved through a combination of acceleration and data reduction. Acceleration is achieved through TCP/application proxying, thus reducing the effect of protocol inefficiencies experienced when messages need to travel back over long distances. Data reduction occurs through compression and deduplication techniques to ensure that less data has to traverse the WAN.
Additional Network Enhancement Techniques
In addition to intelligent routing and the aforementioned remediation techniques, SD-WAN services may incorporate further WAN enhancements that deliver networks with lower latency and packet loss, redundancy and sub-second downtime on critical applications. Again, these rely on real-time monitoring of network performance degradation but can include load sharing and automated remediation to detect and clean ‘dirty’ network paths.
If there is then a spike in user demand for a business-critical application, or such an application is generating higher data loads, network resources can be automatically and dynamically redeployed to it from less-critical applications to ensure the smooth running of business functions, without the need for complex manual intervention.
Remediation can be described as the combination of packet loss, jitter, and out-of-order remediation techniques:
- Packet loss remediation is the process of using backup information which can be used to repair data if it is lost during data transfer. SD-WAN generates this backup information, referred to as ‘parity’, which travels with the main information, meaning it can be used if data has been lost by the time packets reach their destination.
- Jitter remediation is used is used where latency fluctuates dramatically – usually caused by contention in the transit path. Packets are kept back to enable them to be sent with a consistent latency.
- Out-of-order packet remediation is employed where data is separated during transfer. This prevents packets from arriving in the wrong order – so if part of the data stream is delayed, packets can be kept back to wait for preceding packets to arrive. Once the delayed packets have caught up, they are presented in the correct order.
The above is only an introduction to the characteristics of SD-WAN. If you’re considering investing in SD-WAN for your organisation read our ‘Buyer’s Guide’ for an insight into what you need to know.
What is SD-WAN?
GTT’s Rich Vidil, VP of Sales Engineering, gives an easy-to-understand explanation of what SD-WAN is and how it works.
The Benefits of SD-WAN
Many of the benefits of SD-WAN have been touched upon above, and while they can vary considerably in accordance with the features installed, the main reasons why SD-WAN may be the best WAN solution for enterprise can be categorised as follows:
The below can all provide opportunities for increased productivity:
- Improved network performance, particularly for applications requiring high network quality such as voice and video.
- Access to cloud applications with low latency connections.
- Prioritisation of business-critical applications across all network users and locations enables your staff to work more effectively and has a significant impact on productivity.
Enhanced Customer Experience
Improved networking capabilities can increase the delivery speed and quality of service for a business’ customers, whether they are accessing those networks directly (e.g., cloud apps) or indirectly (e.g. high street retail).
More efficient use of existing network capacity, the incorporation of broadband and mobile connectivity (perhaps in place of fixed network capacity), increased utilisation of SaaS applications in place of fixed computing capacity and streamlined network management with intelligent routing can all help a business maximise its returns on investment in network architecture with SD-WAN.
Meanwhile, even for those who take a DIY approach to their network management, the move from manual to automated configuration can drastically reduce the demands on network administrators who no longer need to update hundreds or thousands of network appliances individually.
Instead, their time and expertise can be better deployed, expanding the capabilities and efficiency of the network with the new tools at their disposal.
For those who opt for managed services, however, the efficiencies are even more pronounced as they can benefit from the wealth of specific SD-WAN expertise that a managed service provider can bring, to optimise network performance and minimise labour demands.
Scalability & Responsiveness
Businesses can find scaling both up and down more manageable with SD-WAN. Increased cloud computing opportunities, low-touch provisioning that can allow devices and branches to be brought online far quicker, and the ease of upgrading software instead of hardware, can help to future-proof a business’ networks for whatever may be around the corner.
Control & Compliance
Central orchestration ensures configurations and policies can be updated and deployed consistently to all network locations, on an automated basis, thus reducing discrepancies between locations and any resulting performance and security issues. Enhanced visibility of network performance can also help diagnose and eliminate any discrepancies and issues should they arise.
Tunnelling with end-to-end encryption, on all forms of connectivity, can help to achieve high levels of network security across the board, which can be complemented by consistent security policies resulting from centralised network management.
SD-WAN can be summarised as the movement of WAN management away from physical hardware that is deployed and managed in each network location to a software-based system with a centralised control function. The specifics of any deployment can vary, however through the use of software for low-level network configuration, real-time monitoring and optimisation, any enterprise should be able to find a solution that boosts their operational efficiency and productivity.
For a deeper understanding of the topic read our other techtorialss:
- SD-WAN vs. MPLS: Which service is right for your business?
- SD-WAN Architecture vs Traditional WAN: What’s the Difference?
- SD-WAN security: Protecting your traffic without losing efficiency
Alternatively, if you are ready to explore how SD-WAN can help your business, you can learn about our own SD-WAN services or get in touch directly with one of our experts using the form below.