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Software-defined wide area networks

Versatile Connections

Article from ADMIN 40/2017

By Julian Frede

A natural consequence of software-defined storage and software-defined data centers is the software-defined wide area network, or the Internet connections between locations and cloud services.

The term "software-defined" usually refers to a technology that entered the IT market in the 2000s: virtualization. Although virtualization has been customary in a server environment for many years, the question arises as to how such basic structures as wide area network (WAN) routes can be virtualized and what their inherent benefits might be. A software-defined WAN (SD-WAN) comprises multiple components:

Virtualization: frees the network from the physical infrastructure.
Zero-touch provisioning: allows the timely addition of routes to the virtual infrastructure.
Centralized management, automation, and the technologies of dynamic path conditioning.
WAN optimization technologies: compression and deduplication, as well as high-speed TCP packet order correction and forward error correction.

Some manufacturers do without the last set of technologies listed; however, two definitive vendors, Silver Peak [1] and Riverbed [2], come from exactly this sector and continue to use their (partly) patented technologies for this new product line.

Network virtualization is the basis on which SD-WANs are built. At this level, the overlay network (logical connections) abstracts itself from the underlay network (physical connections). Examples of underlay networks include private multiprotocol label-switching (MPLS) networks leased from providers, directly leased point-to-point routes, and simple xDSL (i.e., ADSL, SDSL, etc.), cable, and LTE/UMTS Internet connections.

Separating the Network Layers

A well-known technology is used to separate the underlay networks from the logical (overlay) network: VPN connections that work with 256-bit IPsec encryption on all well-known SD-WAN products. These VPN connections form the underlay tunnel

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