Maximising SD-WAN Performance: Strategies for Overlay and Underlay Networking

By Geoff Dornan, Group Chief Technical Officer at CMC Networks.

When deploying software-defined wide-area networks (SD-WAN), it is vital to pay close attention to the underlay network. The SD-WAN overlay inherits the attributes of the underlay networks. So, low-latency underlay networks will ensure higher performing SD-WAN with less packet loss and jitter, whereas underlays with higher latencies will be mirrored by the SD-WAN and result in a poor user experience. The SD-WAN market is generating rapidly growing revenues year over year, with Research and Markets estimating the overall global market to reach a huge $7.8 billion by 2027.

Enterprises are seeking easier management of their wide-area network (WAN) connectivity to improve application performance and user experience with SD-WAN. On top of this, they need to keep up with cloud demands with an agile network that can route multi-cloud and hybrid cloud workloads securely.

For today’s cloud-first enterprises, traditional underlay services like MPLS cannot always keep up with their requirements. They need a network that can provide visibility, flexibility and scalability, on top of the high-performance and low-latency connectivity MPLS is known for.

To maximise the value of SD-WAN, the synergies between underlay and overlay network services are vital. Enterprises need to assess various underlay options for SD-WAN including Dedicated Internet Access (DIA), to ensure their WAN can operate efficiently, intelligently, and keep up with their evolving cloud requirements.

Defining SD-WAN MEF defines an SD-WAN service as “a service that provides a Subscriber with a virtual overlay network that enables application-aware, policy-driven, and orchestrated connectivity between SD-WAN User Network Interfaces (UNIs). It also provides the logical construct of a L3 Virtual Private Routed Network for the Subscriber that conveys IP Packets between Subscriber sites.” MEF 3.0 is an important certification that enables service and technology providers to validate that their SD-WAN services conform to the MEF 70 standard. Rather than utilising connectivity services based on a single transport facility, MEF 3.0 SD-WAN services can take advantage of multiple Underlay Connectivity Services to deliver differentiated capabilities.

MEF 3.0 SD-WAN services are defined as overlay services, and MEF 3.0 Optical Transport, Carrier Ethernet and IP services can be used as Underlay Connectivity Services to support the SD-WAN overlay service.

SD-WAN can provide highly effective link remediation capabilities that showcase the power of this technology. These include deploying forward error correction, revertible failover,

packet duplication, dynamic path optimisation and more, to mitigate low performance, best effort underlay connectivity services.

MEF is also taking Service Operation, Administration and Management (SOAM) and Service Acceptance Testing (SAT) very seriously. Due to this, standards have been explored like MEF 66 and MEF 61.1 to ensure the performance of the Underlay Connectivity Service and the subsequent impact on the SD-WAN overlay.

One of the top drivers for enterprises utilising SD-WAN is to achieve better WAN and application performance regardless of the device location or access technology type. A poor underlay will ultimately result in in a poor Application Quality of Experience (AppQoE).

SD-WAN is now in a mature state of adoption, where the hype cycle of pure cost savings has passed. A much stronger focus needs to be given to the design and selection of the Underlay Connectivity Service so that the SD-WAN overlay can power the application performance and user experience required by enterprises.

Cloud-First Capabilities

With cloud adoption on the rise, enterprises need an underlay service that can deliver reliable, highly available, low latency and low packet loss connectivity in collaboration with SD-WAN.

One of the key drivers for SD-WAN adoption is this demand for a reliable, low latency and low packet loss route to different cloud providers. For over two decades, MPLS has delivered predictable metrics around latency, jitter, packet loss and availability. So, how do you ensure Internet access technologies can provide a similar service to MPLS, while leveraging the many advantages a next generation SD-WAN can provide?

Traditional routing protocols like MPLS form adjacencies and distribute link state information with a limited and static view of the entire path an application will need to traverse, both in the transmit and receive direction. This does not provide the full visibility required for key elements to make application-aware routing decisions or deliver on the AppQoE, however segment routing can address some of these legacy setup drawbacks.

Software, Insights & Intelligence

To enhance operations with an intelligent network, enterprises should consider software-defined options that can provide better visibility and insights compared to legacy underlay services like MPLS.

A next generation software-defined network (SDN) backbone that leverages Artificial Intelligence (AI) can provide a full map and state of the entire topology of the global network. The right product and partner should ensure the fastest route to the desired content or service, as well as providing a key focus on application-level visibility and performance.

With SDN, the application traffic can be routed autonomously to ensure service levels are maintained when connecting the user to the required service. These networks should also provide an enhanced service level offering of Dedicated Internet Access (DIA).

A DIA-Focused Future

DIA can provide enterprises with an underlay that performs just as well, if not better than MPLS, with the addition of diversity, scalability and flexibility.

Whether the enterprise’s requirement is Site to Site, Site to Cloud, Site to CDN or Site to Internet Exchange, the right DIA service will provide purpose-built Service Level Agreements for DIA to meet site availability, latency and packet loss requirements.

SD-WAN can completely transform an enterprise’s network, operations and services – they just need to ensure the underlay network supports the overlay SD-WAN service to achieve the desired outcomes.

Intelligent SD-WAN, paired with an efficient and high-performance DIA underlay, can transform enterprise networks with a forward-thinking solution that can pivot and scale with changing business requirements.

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