Software-defined wide area network (SD-WAN) is the host application driving transformation at the edge of the network. Enterprises and telcos are replacing closed SD-WAN and other appliances with virtualized software implementations running on universal customer premises equipment (uCPE), which is often standard servers from leading manufacturers.

The question now facing these enterprises and telcos is: What’s the best way to implement virtualized SD-WAN? And how do you best combine it with other applications such as firewalls and internet of things (IoT)?

Starting with bare metal is a dead end

Many initial deployments of SD-WAN were implemented as a software virtual network function (VNF) running directly on the uCPE server. This approach is known as bare metal, because there is no virtualization layer. Telcos adopted this approach because it was simpler than a hosted approach. Some SD-WAN suppliers assert that they can also host other VNFs. Even so, their portfolio of VNFs is small and doesn’t include other SD-WAN suppliers. 

In taking this path, users lost many of the benefits of uCPE. But we have seen a shift in the market. Now, operators who initially deployed SD-WAN on bare metal are moving to an open hosting platform. We’re also seeing demand from enterprises for a cloud-centric or hosted model.

Benefits of uCPE and a virtualization layer

uCPE by itself helps in breaking open the closed appliance model. But, by combining uCPE with an open virtualized hosting layer (as shown below), users can get all of the benefits of the cloud.

• A true multi-vendor system with separate suppliers of servers, hosting software, and VNFs. This approach enables selection of best-of-breed at each layer, eliminating lock-in and powering innovation. 
• Separation of hosting from network functions enables dynamic service deployment and eliminates the vendor lock-in seen when VNFs also provide hosting.
• De-risking SD-WAN selection. There will continue to be consolidation in the SD-WAN space, with some suppliers going away. Separating the SD-WAN function from the hosting layer provides a recovery path for replacing SD-WAN VNFs due to technical or commercial reasons. 
• Optimization at each layer. An open hosting layer enables innovation to occur separately at each layer. You can add a new server with lower cost or higher performance, while keeping the VNFs unchanged. Likewise, VNFs can be combined in a service chain to deliver innovative features and to meet customer requirements for particular VNF suppliers.
• Networking and operational features. An optimized hosting layer goes beyond just providing a home for VNFs. It also enables advanced networking and operational features, such as zero-touch provisioning, advanced networking, fault and alarm management, and security.
• Support for a wide range of COTS servers. A dedicated hosting layer will support a much broader range of hardware platforms and features than will an SD-WAN VNF that also provides hosting.

Result: open, neutral and cloud-centric hosting

With an open hosting layer, users of uCPE can get all of the benefits they expect. They can use best-of-breed components to provide features and reduce risk. They can build dynamic services, changing them as needed without changing the network. And with the large number of SD-WAN suppliers in the market, they can reduce the risk of picking the wrong one. Leading telcos like Verizon, Colt and others are taking this path for SD-WAN. Shouldn’t you?