While Software Defined Networking (SDN) in data centers has garnered all the attention over the last few years, with products and solutions from many incumbent network vendors and a number of startups available today, this year is widely expected to be a break-out for Software Defined Wide Area Network (SD-WAN).

Though traditional networking has always offered global scalability and resiliency, enterprises have struggled with policy based routing, centralized provisioning and management. In addition, distributed enterprises have also struggled with long lead times for MPLS deployment and high bandwidth costs which has made WANs complex and expensive to build and operate.

SD-WAN promises to lower costs and reduce operational complexity by borrowing many of the same paradigms of SDN in data center to bring about easier provisioning, intelligent path selection, improved visibility into application performance and traffic analytics.

While enterprises have a choice to deploy hybrid WANs or even Internet as WAN to optimize costs independent of SD-WAN technologies, the incumbent network vendors and emerging SD-WAN vendors are beginning to deliver on the promises of centralized provisioning, management and visibility functionalities that provide compelling use cases for enterprises to experiment with and eventually deploy SD-WAN in production networks.

Compared to SDN in data center where network must be integrated with server virtualization, L4-7 services, automation and orchestration tools to be able to provide effective return on investments, SD-WAN can be considered as a pure network solution with minimal technology adjacencies. Therefore, the success of SD-WAN projects are expected to be much higher.

SD-WAN promises to lower costs and reduce operational complexity by borrowing many of the same paradigms of SDN in data center

What to look for in SD-WAN solutions

To gain agility and efficient utilization of WAN bandwidth through centralized provisioning and policy management, SD-WAN, as an integrated solution, must deliver on the following essential features and functionalities.

Device Form Factor & Controller Location

Edge devices should be available in both physical and virtual appliance formats. As enterprises are increasingly looking at the flexibility provided by hardware and software decoupling, virtual appliances running on COTS hardware can be integrated with other virtualized network functions to create best-in-class network services at the WAN edge. Public cloud instances should be available to seamlessly extend the WAN boundaries of enterprises adopting public cloud. The WAN controller should be available either on premise or on cloud to suit the needs of enterprises.

Path Selection

Recognition or finger printing of common enterprise applications and the ability to create custom application signatures is essential to classify traffic flows and enable prioritized treatment of traffic based on link costs, network and application performance requirements across all available WAN links. Policy based routing has been challenging in traditional networking, therefore, path quality monitoring along with path symmetry are other key features that enable better application performance under varying network conditions

Routing Protocols

The solution must support commonly deployed protocols such as BGP towards service provider networks and OSPF towards branch networks.

IPv6 Support

With the depletion of IPv4 address space, the SD-WAN solution must support IPv6 or at least have a clearly defined IPv6 roadmap.

Overlay & Underlay Transport

The overlay network must support partial and full-mesh topologies. The underlay transport network support should include Ethernet, 3G/4G cellular interfaces and optional support legacy transport such as T1/E1.

Secure Multi-Tenancy

The solution must support standards- based cryptography and must provide ability to create scalable network partitioning to support multi-tenancy requirements to address mergers, acquisitions and divestitures.

Service Insertion & Chaining

The solution must provide proven mechanisms for co-existence with other network functions such as firewall, WAN optimization and voice gateway services. Enterprises that have deployed legacy voice gateways on WAN devices must carefully evaluate their options as legacy voice support may not be available from newer vendors in the market.

Resiliency

It is important to understand what network functions are centralized to ensure traffic gets forwarded even during controller outages or non-reachability.

Integration into Existing Networks

The solution must offer integration mechanisms into existing networks to enable phased migrations. Non- disruptive mechanisms (e.g., in-path appliances) are preferred which enable SD-WAN devices to be added into existing networks for proof-of-concept, pilots and phased migrations.

Provisioning, Management & Reporting

As the most important feature of SD-WAN, the solution must provide a single-pane-of glass management to enable zero touch provisioning, centralized policy management and enforcement, role-based access controls, application performance monitoring & diagnostics, SLA reporting, executive summaries & detailed views, traffic analytics, integration into NMS and SIEM tools, and finally, open interfaces for integration into network automation and orchestration tools.