The chronology of software defined networking
Virtualized Data Centers
The modern data center has virtualized its server and storage equipment so that new services and capacity can be quickly and easily provisioned. Virtualization is an essential ingredient in what we now call the cloud. Witness Dropbox, Apple iCloud, Amazon Web Services and Microsoft Azure being able to easily store more of your data at the click of a button, or host your new application in a matter of seconds, all at ever-diminishing prices. This has been made possible in part by the simplification of the elements within the data center. Behind the curtain at AWS, or at any other modern data center, lies a new design where vanilla hardware runs intelligent software that can now be centrally provisioned to provide compute and storage services more quickly and at a lower cost than before.
The goal of Software-Defined Networking (SDN) is to make network services as agile and flexible as compute and storage elements are in the modern data center. This is achieved by setting what each individual piece of networking equipment has to do from a central controller. Network managers can configure, manage, secure, and optimize network resources, set policy across the entire network and deliver services to where they are needed, quickly and dynamically. Explaining how this works and is implemented quickly descends into a morass of esoteric networking terms and diagrams — OpenFlow, control/forwarding planes, recursion/arbitration/orchestration, etc. Suffice it to say that SDN might be rolled out if you have a large network, many IT professionals and a large budget for buying new equipment, or some combination thereof. Thus, SDN has mainly been deployed within Fortune 5000 LANs and service provider networks.
VIRTUALIZED DATA CENTERS -> SDN -> SD-WAN -> ABOVE SD-WAN
Software-Defined Wide Area Network (SD-WAN) is the application of SDN ideas to wide-area connections, which include commodity Internet through DSL or cable, Ethernet-over-fiber, MPLS and leased lines. The premise of SD-WAN is that enterprise traffic can be automatically and dynamically shaped and then forwarded across the most appropriate path based on network conditions, the security and quality-of-service (QoS) requirements of the application, and the cost of the circuit. As with SDN, control is centralized, so changes in policy or provisioning can be managed from a single interface and automatically distributed to the relevant network device(s).
SD-WAN sounds great in theory, but in practice it has not delivered on the promise. Complex provisioning and maintenance, incompatibility with existing network elements and other issues have led to iffy cost savings and opaque quality improvements. Making matters worse, most SD-WAN vendors have tried to solve all possible network ills with a Swiss Army Knife approach.
By taking certain elements from the SD-WAN toolbox it is possible to create a justifiable reason for deployment that will make your boss happier, through cost savings, and your end users sing your praises, through higher quality user experiences. For example, by focusing on a specific application such as interactive communications, it’s now possible to make reliable IP telephony calls and experience smooth videoconferencing over any network connection, all the time.