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The SDN Transformation: A Framework for Sustainable Success

A Change is Required

There is a great opportunity waiting for service providers, driven by the widespread adoption of cloud-based applications by both enterprises and consumers. It’s a chance to capitalize on the elastic network needs of on-demand cloud computing and storage to create new sources of revenue and better control CAPEX/OPEX costs. Unfortunately, the lack of elasticity in most of today's static networks makes it difficult for service providers to deliver the on-demand bandwidth necessary to support dynamic applications in a fast, cost-effective and profitable way.

The on-demand nature of cloud-based applications makes for unpredictable traffic volumes, often characterized by spikes in usage. These dynamic traffic volumes present service providers with another challenge as they try to plan and engineer appropriate levels of network capacity to satisfy users' bandwidth demands.

The fast-growing popularity of cloud-based applications has rendered service providers' traditional business models obsolete. In today's fiercely competitive networking market, service providers clearly need a new business model, which enables them to capitalize on the proliferation of cloud-based applications and services. To construct that new business model, service providers are seeking networking solutions built on Software Defined Networking (SDN) architecture.

An SDN-based solution transforms today's rigid transport infrastructure into a highly programmable network, one that is just as flexible, efficient and seamlessly scalable as data-center computing and storage resources. With this new, highly-adaptive network, service providers can make their transport networks sufficiently flexible to deliver, on demand, the bandwidth that consumer and business end users need for their cloud-based applications.

SDN Equips the Network to Support Applications

SDN is an innovative network architecture that shifts control of the network from within the network elements to an external centralized controller and abstracts the underlying hardware infrastructure from the applications. The external controller now decides which network paths packets should take.

Then, using a standardized interface such as the OpenFlow protocol, conveys its instructions to the forwarding plane, which remains within network elements such as routers and switches.

With software now in control, the SDN-enabled network has the following characteristics:

  • programmability based on abstracted, simplified and open interfaces
  • a flexible, dynamic optical/data layer which supports Layer 0 through Layer 3 switching
  • an optical controller and a packet controller, along with a network orchestrator, to coordinate both controllers and provide a global, end-to-end view of the network, across multiple layers and multiple vendor platforms
  • de-coupled control and data planes, enabling each to evolve and to be updated independently
  • path computation across multiple network layers, including legacy layers

Basically, SDN integrates network resources to create a unified network operating system, making it possible for service providers to tailor connectivity according to a given application's specific requirements – across multiple layers, domains, vendors, and technologies. Compared to the traditional, hardware-centric network's reliance on pre-defined sets of resources, the SDN-enabled, application-centric network brings together the resources necessary to support all aspects of a given application. The SDN-enabled network's ability to align its resources to satisfy a given application's performance requirements positions service providers to monetize network properties such as differentiated resiliency and lower latency. Consequently, SDN produces direct as well as indirect financial benefits for service providers.

Transform the Network, Migrate to the Future at Your Own Pace

Service providers want an SDN solution that enables them to implement this innovative approach to networking, and also fully leverage the value of existing assets, including their network resources, networking expertise, and investments in the network brand. By deploying an SDN solution that combines dynamic multi-layer (L0-L3) transport with dynamic control, service providers can transform their network and service-delivery model while also maximizing return on their embedded investments. Such a solution enables the now-programmable network to respond to applications, rather than forcing applications to respond to the network, as they have done historically. Using the network intelligence that is logically centralized in the external controller, the network can update dynamically, in real time, to accommodate the needs of a given application.

The Critical Attributes of a Successful SDN Solution

Not all SDN solutions are created equal. If service providers expect to realize the full range of SDN capabilities and benefits, they need to deploy a solution such as the Coriant Dynamic Optical Cloud™, which features three essential attributes:

Programmability enables the network to adapt to the dynamic requirements of end users and applications, making it possible for service providers to introduce and modify services very quickly. With multi-layer (Layers 0-4) programmability, service providers can adapt to real-time network changes, reduce overall network complexity, use network resources more efficiently and cost-effectively, and seize new revenue opportunities.

Multi-layer, multi-vendor end-to-end integrationis critical as more applications and services move to the cloud. Service providers must be able to integrate computing and storage resources, flexibly and efficiently, across:

  • multiple vendors' platforms
  • multiple segments of the network – access, metro and core
  • multiple optical and packet protocol layers (0-4), including wavelength, Optical Transport Network, Ethernet and IP/MPLS

SDN helps manage and orchestrate this diverse ecosystem of resources, including optical-layer advances such as flexible grid, ROADMs and photonic mesh, to deliver an end-to-end global view of the network.

Openness is an essential attribute because packet-optical transport networks comprise multiple vendors' platforms and multiple technologies. They depend on standards-based protocols for interoperability at the physical layer. Emphasizing maximum network programmability, SDN's open and collaborative software-based development process focuses on applications and accelerates innovation. A truly open SDN solution is one that implements a standards-based orchestrator (OpenDaylight), a standards-based application programming interface (OpenFlow), and standards-based management capabilities (NETCONF, SNMP). By deploying a truly open SDN solution, service providers can easily introduce new functions and applications written by vendors, third-party developers and service providers themselves.

An SDN solution that addresses these critical attributes is the foundation of the programmable network necessary to support and empower cloud-based applications and thereby enhance service providers' long-term market strength and profitability.

SDN Opens Up a Growing List of Use Cases

As SDN-enabled solutions move from laboratory trials to field trials, the hard evidence in support of the SDN business case is growing. There are potentially, dozens of overall SDN use cases that arise out of the programmability capabilities of SDN. Every use case typically falls into one or more general categories: services, efficiency and availability.





Bandwidth on Demand




Network Slicing




Network Defragmentation




Application-based Forwarding




Bandwidth on Demand, one of the leading use cases, falls within the services, efficiency and availability categories. A dynamic network enables applications and end users to request network resources, such as bandwidth, on demand. For example, an end user or an application may request temporary bandwidth between data centers, a lower latency on an existing connection (performance bursting) or an increase in bandwidth for cloud bursting.

When the SDN-enabled network receives these requests, it determines the optimal path through the network by examining existing flows and the resources necessary to fulfill the request. An optimal path is one that meets but does not exceed the requested performance criteria. For example, a service provider does not want to allocate a 10 Gb/s link if a 1 Gb/s link suffices. Similarly, a service provider does not want to allocate a 5-millisecond (ms) path to fulfill a request for a 10-ms delay if a 10-ms path is available. The goal is always to use the network's least-cost resources first.

Allocating network resources on demand benefits both the service provider and the customer. The service provider utilizes the network more efficiently and cost-effectively, thereby increasing revenues. The ability to create bandwidth interconnection services also increases network availability in terms of QoS, redundancy levels and protection. The customer gets the elastic bandwidth necessary to match their changing compute and storage needs, and also potential long-term cost savings.

Network Slicing is a use case that falls into both the services and efficiencies categories. It is a process by which the service provider virtually apportions segments of the network, across multiple products and layers to satisfy the specific requirements of a particular end user. For example, a service provider could use network slicing to partition services for a retail carrier in a wholesale environment or for a large enterprise. By eliminating the need to virtualize every single network element, the SDN-enabled network enables the service provider to deliver precisely what the end user needs – and do so much more easily, faster and cost-effectively than before. Service providers can also use this SDN-enabled capability to manage a hybrid-networking environment much more efficiently than was possible before.

Network Defragmentation falls into the services, efficiency and availability use-case categories. As service providers add and remove network traffic flows over time, the network resources can become fragmented. As new connection requests are received they may not be able to be fulfilled even if the network has the aggregate unused capacity. The solution is to optimize the existing connections to pack them in a more efficient manner on the network.

Operating across both the optical and packet layers of the network, SDN-enabled network defragmentation packs flows to improve the network utilization. Because of SDN's ability to provide a multi-layer, end-to-end view of the network, service providers can boost network utilization by 50- to 90-plus percent. Packing flows to enhance network utilization translates into the service provider's ability to provision more services on the network.

Another goal of defragmentation is to utilize resources with the optimal level of availability in mind when modifying paths. It can also help free up bandwidth and paths that can be utilized for redundant backup path alternatives.

Application-based Forwarding is one of SDN's efficiency use cases. Basically, SDN allows a service provider to set up the desired flow for an application, according to that application's specific requirements, rather than having to provision that application flow step-by-step across multiple network layers. For example, a service provider needs to upload into the data center all the data associated with an enterprise resource planning (ERP) system backup. Given the security and reliability requirements of that ERP system backup, it’s unlikely the service provider would choose the lowest-cost path to route that application through the network. Contrast that application's requirements with those of a mobile user's video application. When downloading that application, the user wants a lot of throughput and a low-cost connection, not necessarily a low-latency connection. SDN enables the service provider to take into consideration all the factors concerning a specific application's requirements and come up with a recipe for the most appropriate and efficient flow through the network.

SDN and Its Benefits Provide a Framework for Sustainable Success

SDN is the concept driving the ongoing network revolution. By transforming the transport network into a more elastic, adaptable and ultra-scalable entity, SDN creates for service providers a framework in which they can create new, billable applications and services. Equally important, that framework brings with it the tools and techniques service providers need to create more sustainable business models and strengthen their ability to compete with both traditional and new rivals in the marketplace.

SDN promises to deliver significant financial and competitive benefits, notably by enabling service providers to:

  • respond to changing market conditions by creating new applications and launching new services faster than was possible before
  • shorten dramatically the time required to dimension and provision the network resources necessary to support specific applications
  • satisfy end-user requirements for on-demand bandwidth in an efficient and profitable manner
  • reduce operational complexity through network simplification and automation
  • reduce CAPEX and OPEX by a) enabling customers to tailor their application-specific connections and b) enabling service providers to distribute loads, with maximum speed and efficiency, among the most appropriate network resources
  • free themselves from being locked in to specific vendors' solutions and associated cycles of forced platform upgrades
  • generate additional revenues that strengthen their margins


By deploying the right SDN-enabled solution, service providers can capitalize on the opportunity to migrate their multi-layer transport networks according to their individual business strategies and budgetary considerations. In doing so, they can protect their existing investments in switches/routers, optical transport platforms and network management systems in a programmable network that is essential for long-term success in an application-driven ecosystem.

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