Servers and storage have been the key beneficiaries of virtualisation over the last decade, resulting in an increasing number of applications moving to the cloud.

However, network architectures have remained closed and proprietary thereby resulting in cumbersome, non-scalable and inflexible implementations. The network has been seen as a roadblock for innovation and leveraging the cloud to its full potential.

This is changing. One of the key demand drivers for networking technology is the need to provision massive amounts of bandwidth to handle the growing demands of the internet, including video and cloud applications located inside domestic and global data centers. With 120 million internet users, India has the third largest user base in the world. Research from McKinsey estimates that India will add more internet users than any other country-between 330 – 370 million by 2015. These customers will come not only from cities but also from rural locations, and they will consume and generate more and more content and applications. Currently, operators struggle to build the ideal infrastructure required to meet these demands because this growth requires huge capital investments, and these networks need to be virtualised to provide flexibility and efficient utilisation. Multi-vendor networks today remain static, inefficient and operationally complex due to the lack of interoperability between the different products.

To address these challenges, transport software-defined networking (Transport SDN) has been conceptualised to enable unified control and programmability across a network of heterogeneous physical and virtual networking devices. SDN is a an architectural approach that leverages the availability of computing resources now found in data centers around the globe, and uses that power to virtualise and represent large heterogeneous networks in a simple and easy to provision way. SDN uses standards-based protocols and open interfaces so that it is not tied to a single vendor.

Current Implementation of SDN

SDN has been used and focused on devices within data centers and is now recently being demonstrated in wide area networks.

However, SDN can now be extended to the transport layer. The potential for Transport SDN to showcase its real power is in managing multiple elements from multiple vendors across multiple layers of the network, including the IP/MPLS layer, the optical transport network switching layer and the optical transmission layer. This centralised control and ability to consider the entire network state across multiple devices and layers when making network decisions is one of the key value propositions of Transport SDN.

Transport SDN: Extending SDN to the transport network

While SDN appears to have the potential to simplify networks at the IP and Ethernet layers, service providers have large capital and operational investments in their transport networks as well. There is unfortunately no solution that coordinates and optimises between various layers that has been successfully deployed in production service provider networks today. Therefore, what typically ends up happening in a multi-layer scenario is that all traffic is required to pass through a router, and if the router needs more capacity at the transport layer then there is a set of manual communications and processes that has to take place between the data and the transport departments, which is time-consuming, inefficient, and costly.

By extending SDN to transport this management across layers and vendors, network management can be virtualised and automated and all layers can be exposed as network resources to applications running on top of the SDN controller. Transport SDN can represent the reality of a multi-layer network as a single virtualised abstract view, allowing either service provider operations staff or applications to simply ask for a connection from point A to point B with bandwidth and quality of service without having to know all of the specifics of the multiple layers. All of the resources in the network at all layers are now treated as resource pools that can be shared by any service or application.

The SDN controller, after examining this pool of virtualised resources across all layers, can calculate the most cost-effective path to satisfy the constraints, simulate the change before it goes into production and then automatically set up the service across multiple devices with little or no human intervention.

The key benefits of extending SDN to the transport layer and delivering on a multi-layer, multi-vendor and multi-domain solution would be:

• Network scalability through the quick deployment of optical bandwidth to support routers and other bandwidth-intensive application demands.
• Efficient resource utilisation by optimising the path taken through the network based on application requirements and by establishing more deterministic failover scenarios to minimise overprovisioning.
• Lowered operating expenditure through automating the network across layers, eliminating device-by-device configuration at the router layer and coordinating with the transport layer.
• Speed time to revenue by allowing the network and any changes to be simulated in software ahead of time and then, once finalised, radically pushed to the network.
• Increased reliability with more deterministic and faster protection.

Transport SDN: A Summary

In order for SDN to be truly useful in multi-domain, multi-vendor and multi-layer networks, it needs to extend its control to include the emerging next-generation converged optical transport layer, where integrated switching adds substantial network value and has significant impact on overall network architecture—including what happens at higher layers. Extending SDN to transport requires a hardware and software architecture that supports an ability to abstract optical wavelengths into pools of optical capacity and to be able to map any service from 1-100GbE into those pools. Virtualising transport layer resources for more dynamic and efficient management will give service providers the flexibility, speed and capacity to manage exactly when, where and how they grow. This will ultimately result in both increased revenues and lower operating expenses on those large capital and operational investments that they’ve already made in their transport networks.