In SDN optical networks, centralized control and scalability

Technology for SDN optical networks is emerging and with it comes centralized control and dynamic bandwidth provisioning in the WAN.

Optical networks are critical for handling increased bandwidth demands, yet they can be inflexible, difficult to provision and challenging to manage.

Over time, SDN will change that and bring programmability, centralized control, dynamic provisioning and support for multi-vendor environments to optical networks. While technology for SDN optical networks is not yet as advanced as SDN for the data center, it will ultimately have a significant impact on high-speed transport in the wide area network (WAN).

Benefits of SDN optical networks

In metro and long-haul optical networks, transmission is sent over the fiber optical cable and routers that handle the data network protocols (IP, MPLS, etc.).  One of the key challenges in designing and operating optical networks is the interaction, control and management between the optical and routing layers.

SDN's benefits for the optical network include:

  • The ability to scale network bandwidth up or down rapidly by facilitating deployment of optical bandwidth and IP resources
  • Added resource utilization efficiency by optimizing the path taken through the multi-layer network
  • Lower Opex by automating operations across the network layers, eliminating device-by-device configuration and coordinating provisioning functions

SDN's centralized view of the network enables it to evaluate individual layers of the network to determine where and how to best send traffic. With SDN, a network transports information over the most efficient technology, not just the predefined transport technology. If bandwidth is limited in some portion of the network, SDN can reroute traffic around the point of congestion.

SDN optical networks standards emerge

Multiple standards bodies are currently working on developing SDN standards for the optical network. The two main standards/protocol efforts related to SDN in the optical network are OpenFlow and GMPLS.

OpenFlow was designed specifically for L2-4 transport (Ethernet packets) and needs modification to provide SDN-like control to the optical layer. The Optical Transport working group within the Open Networking Foundation (ONF) is addressing SDN and OpenFlow control capabilities for optical transport networks. The work includes identifying use cases, defining a target reference architecture for controlling optical transport networks incorporating OpenFlow, and creating OpenFlow protocol extensions.

GMPLS differs from traditional MPLS in that it supports multiple types of switching, including optical transport. GMPLS is often used as the control plane for optical switching. It is a proposed IETF standard to simplify the creation and management of IP services over optical networks, and it is often used as the control plane for optical switching.

The state of SDN optical networks technology

More on SDN and optical networks

One company uses SDN for optical bandwidth provisioning

Self-service WAN with Vello Systems

SDN programmability across optical and packet layers

Cisco extends its Insieme APIC controller to control WAN and LAN

Cyan's Blue Orbit ecosystem for SDN WAN

Many optical network and router suppliers have introduced SDN enhancements to their products to improve the agility, programmability and traffic handling capabilities of optical networks. A couple of notable deployments show the benefits of SDN for optical network deployments:

  • DukeNet Communications, a regional fiber carrier in North Carolina, has deployed an SDN orchestration process to link virtual machines and virtual services across a multi-vendor network. This deployment uses technology from Cyan and Accedian Networks and leverages OpenFlow to fulfill dynamic bandwidth requests.
  • Marist College in New York State is using OpenFlow to spin up and tear down wavelengths between data centers and to migrate virtual machines workloads among them. The Marist team tied three data center sites together with optical connections through Internet2 with its technology partners IBM, NEC and Adva Optical Networking.

Other leading suppliers working on SDN optical networks include Huawei Technologies, Infinera, Ericsson, Cisco, Ciena, Juniper Networks, Alcatel-Lucent, Vello Systems, BTI Systems and Fujitsu.

Conclusions

Optical networks need the capabilities of SDN to respond to market demands for dynamic bandwidth provisioning and lower operation costs. Implementing SDN can help optimize packet/optical transport by leveraging the most efficient paths in the network. The programmability enabled by SDN helps spark innovation and enables a wealth of new network features. SDN can ease provisioning challenges and provide end-to-end control of traffic.

Yet, despite the promise of SDN, implementation in the optical network is very much in the early stages compared to data center SDN. SDN optical standards, including OpenFlow and GMPLS, are a couple of years away from full implementation. Designing and implementing SDN in multi-vendor environments will be challenging until SDN for optical networks reaches maturity.

This was first published in February 2014

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