The use of software-defined networking (SDN) solutions is currently limited to data centres for integrating automated systems, building virtual networks, and amalgamating service chains. However, data centres are not the only part of IT infrastructure that may require SDN technology. SDN solutions can also be deployed in enterprise wide area networks (WANs) to reduce their costs and complexities.
A WAN is used to connect branch offices to a central corporate network, and data centres that are separated by distance. WAN connections have traditionally used technologies that require special proprietary hardware, which are often complex and expensive. Meanwhile, SD-WAN solutions use a software approach to migrate a large part of the network control to cloud.
SD-WAN technology
SD-WAN technology uses real-time WAN link performance monitoring and data packet inspection to autonomously manage the distribution of network traffic across multiple heterogeneous WAN links. It aims to improve and optimise WAN performance to meet business requirements.
SD-WAN solutions shift traffic monitoring and management from physical devices to applications by leveraging SDN’s flexibility and agility. This helps create a secured pool of private and public connections, and brings in automation, centralised network control and agile, real-time traffic management over multiple links. In addition, the technology helps the network administrator to remotely program appliances through a central controller, thereby reducing provisioning time and minimising or eliminating the need to manually configure traditional routers at branch locations.
While SD-WAN products and services vary by vendor, most of the enterprises deploy hybrid WAN by dynamically routing traffic over both private and public links, such as leased multi protocol label switching (MPLS). An SD-WAN architecture allows administrators to reduce or eliminate the reliance on expensive leased MPLS circuits by sending lower priority, less-sensitive data over cheaper public internet connections and reserving private links for mission-critical or latency-sensitive traffic such as voice over internet protocol. This flexible nature of SD-WAN reduces the need for over-provisioning, and brings down overall WAN expenses.
SD-WAN drivers
Enterprise customers are now demanding more flexible, open and cloud-based WAN technologies, instead of specialised solutions that often involve expensive, fixed circuit and proprietary hardware. To meet this requirement, SD-WAN eliminates the need for expensive routing hardware by providing connectivity and services through cloud. Since SD-WAN connectivity can be controlled through cloud, a customer has the flexibility to scale up connectivity during times of peak demand. In addition, SD-WAN can conveniently handle situations when broadband quality is inferior. Besides, it can shunt traffic over private links with guaranteed quality as and when needed. As a result, organisations are able to invest in larger and cheaper broadband links and minimise the size of their expensive private links.
With SD-WAN, an enterprise is able to rely more on broadband and less on private links. SD-WAN also takes active measurements between endpoints to ascertain whether the broadband link is capable of carrying voice or video traffic reliably. Moreover, the emerging SD-WAN offerings can be used to improve and secure internet connectivity, making them more competitive with expensive legacy WAN technologies such as T-1 or MPLS.
Key concerns
While evaluating the decision to adopt SD-WAN technologies, the principal concern of enterprises is return on investment. The capex and opex of the SD-WAN solution needs to be compared with the overall cost of the WAN. A hybrid WAN uses low-cost broadband and requires smaller private links. However, some offices might not deploy private links at all. In downsizing or eliminating private circuits, most carriers lock their enterprise customers in a multi-year contract. Thus, penalties for early termination or service-level changes further impact the return on investment.
Another consideration for evaluating SD-WAN technology is that of vendor lock-in. There are several SD-WAN products, and they are all different and incompatible. While some get incorporated into the existing WAN; others replace the WAN hardware completely. An evaluation process should carefully consider the long-term commitment to the vendor.
Conclusion
SD-WAN is a compelling use-case for SDN, with the potential to offer significant cost savings while improving the overall connectivity of branch locations with the central office and the cloud. In addition, it is easier to deploy for pilot testing, making it conducive for enterprises that are reluctant to adopt new solutions.
Going forward, SD-WAN is likely to be used not just for WAN connectivity at branch offices and data centres, requiring less proprietary equipment, but also for virtual private networks, network as a service, and application policy control.
