The History of Wide Area Networks (WANs)

Wide Area Networks (WANs) connect users and devices across many locations to services, applications, and data that reside in data centers and cloud providers. Every 10 – 15 years, WANs go through a revolution on how they are designed and built. Early WANs used modems to transmit data over phone networks. Second generations used frame relay and ATM, and third generation WANs used MPLS. Software Defined Wide Area Networks (SD-WANs) are the fourth and most current generation of WANs. Traditional WANs are designed to serve traditional network architectures and requirements of businesses. In these architectures, the focus was on applications served from self-owned or private data centers thus, utilized dedicated lines that were typically MPLS. Enterprise networks designed to support these requirements are not relevant for current and future enterprise needs. As applications move to the cloud, a growing need for network agility, application variety and increasing user mobility, networks need to evolve, welcome to SD WAN.

SD-WAN Benefits

SD-WAN vendors build their solutions in different architectures and philosophies. If you would ask a network administrator that deployed SD-WAN what is an SD-WAN and what did his/her organization gain from it, the typical answer would include the following SD-WAN benefits:

• Faster
• Better
• Lower cost
• More secure

Faster

Faster networks – The disaggregation of transport and applications where enterprise networks become transport agnostic, allow to utilize multiple WAN interfaces for achieving better (faster) application delivery to end users. SD-WAN services typically offer the capabilities for defining routing policies based on business needs (application prioritization and quality of experience based decisions), this is basically one of the primary pillars of what is SD-WAN technology. Typically, SD-WAN vendors offer in their products or services the option to route traffic from branch offices directly to the internet. This option of Direct Internet Access (DIA) is an important requirement for improving the speed of your network. Some of the SASE services do require backhauling all traffic through central points of presence and over a dedicated backbone of the SASE service provider. This network architecture should be carefully examined as in many cases, it increases latency and results in higher cost. Although Gartner does include backhauling of data through cloud POPs in its recommendation, one needs to consider this recommendation with reference to its specific enterprise requirements for performance, security and cost.

Agile network architectures – Network agility is also an important item on the SD-WAN benefits list. Different from traditional WANs, being software defined and centrally managed, network architecture of hub and spoke, full mesh or any combination of these architectures, can be quickly provisioned and changed as required on SD-WAN networks. Different from the fixed nature of traditional networks, SD-WAN architecture gives agility in the hands of network administrators, through automation, network performance may grow and shrink as workloads and associated business requirements change. Backup network interfaces may be added or removed as network requirements change. This completely changes the traditional paradigm of fixed connectivity contracts and network designs that inhibited flexibility.

Better

Reliability of the network – One of the important SD-WAN benefits relates to network reliability. In the past, a site would lose its connectivity due to failure of a single dedicated line that serves the site. Even if several connections were available, the routing policies would be fixed so some of the applications or users in the organization would lose their connectivity in the case of such network failure with no way for network admins to define dynamically policies based on importance of services or users. SD-WAN changes this as a typical SD-WAN product would allow to define failover and load balancing policies that would ensure better and more reliable delivery of specific applications even when network conditions deteriorate or even in cases of specific network interfaces failure. This benefit of network reliability is one of the key elements of what is an SD-WAN solution all about.

Network automation – Both on-boarding of new locations as well as the on-going operation of the network and adaptation to changing network conditions and workloads are automated in SD-WAN. Through zero touch provisioning (ZTP) devices are connected to power and ethernet and automatically provisioned in the central management system. Policies for changing routing logic are defined and pushed to network edge devices from this central management system and come to action automatically as changes are identified by the system. Additionally, DevOp tools can be utilized so that networking bandwidth and associated routing and security policies can be provisioned dynamically as compute and storage change.

Cheaper

Reduced OPEX – Being transport and service provider agnostic is another pillar of SD-WAN benefits. An enterprise can choose which Network Service Providers (NSP) to purchase connectivity from, moreover, the enterprise can purchase different types of network connections such as broadband, 4G or 5G cellular connections or even MPLS, define the utilization of these different network connections based on quality, cost and other enterprise requirements. Additionally, such policies can be dynamically changed from one central management system. The nature of centrally managed SD-WANs also results in the reduction of IT people required for managing the network, instead of logging into each edge device and configuring it through a Command Line Interface (CLI), all edge devices can be centrally configured and managed.

Reduced CAPEX – This is one of those SD-WAN benefits that is many times neglected in the decision making process. Although one of the promises associated with the definition of what is SD-WAN was hardware agnostic, some of the SD-WAN vendors continue to require a bundle of hardware and software resulting in high Total Cost of Ownership (TCO) and greater vendor lock-in. Being hardware agnostic is an important requirement enterprises and service provider should present to SD-WAN vendors. Being able to run on commodity hardware devices, on virtual machines or in public/private clouds gives enterprises choice, more control and lower capital costs.

More secure

End-to-end encryption – Most of the cloud SaaS applications encrypt the traffic of their applications, but not all enterprise data sent between locations is encrypted. Even many of the voice and video communications services don’t encrypt the payload (the actual data of voice and video). The SD-WAN architecture typically allows for secure (encrypted) tunnels between locations of edge devices (software and hardware) thus making sure that all traffic in motion will be encrypted. In this regard, it is important to analyse the architecture of some of the SASE vendors. When looking at the Gartner definition of recommended SASE architecture, you would find a fixed network architecture of hub and spoke where all enterprise traffic is routed through cloud Points of Presence (POPs) of the SASE vendor or service provider. This SASE architecture would typically require a man in the middle decryption of the traffic. It doesn’t mean that this type of SASE network architecture doesn’t have merit, it does mean that enterprises should understand the details of how the SASE service is provided to them and understand the pros and cons of each option. flexiWAN allows for more flexibility and choice in all relevant areas of SD-WAN and SASE deployments. This includes network architecture, routing policies, the security services used and how each specific data or application is routed according to those selected choices of security and network architectures.

Zero trust networks – This capacity of zero trust is one of the SASE benefits although it is not always offered by all SASE vendors. Given the strong relationship between SASE and SD-WAN, zero trust is also achieved with secure SD-WAN solutions. Providing 1:1 micro-segmentation between users and devices communicating with services, applications, and data. Whitelist security policies of what is allowed in a least privileged model instead of a blacklist model that defines where network traffic cannot go. Anomaly detection provides early detection if a user is misbehaving or a device has been infected with malware.