CALIENT Technologies

Move the light, not the fiber

Dream of Flexible Telecom Network Becomes Real with SDN and Optical Circuit Switching

In the early part of this decade, the “next big thing” for service provider networks was colorless, directionless, contentionless (CDC) networks.

This optical network architecture was designed to allow flexible reconfiguration of optical transport networks for both capacity planning and more short-term optimization of routes based on demand. The longer-term dream included the ability to achieve multi-layer optimization – for example allowing layer 3 devices to reconfigure the optical transport topology and capacity from a service level, thereby achieving the lowest possible cost per bit.

In the intervening years, some CDC networks were built but the revolution didn’t really get off the ground except for some isolated network islands. The dream hadn’t died, but carriers knew that more network control capabilities were needed to sense and control data flows across the various network segments to provide the desired interconnectivity.

These capabilities have now arrived in the form of software-defined networking (SDN) technology that is able to provide a unified control plane that can make better global traffic forwarding decisions. The challenge, however, is that many of the legacy networks in place today are not SDN-compatible and without a network-wide control capability, the value proposition of SDN is somewhat limited.

This is where Optical Circuit Switches (OCS) like CALIENT’s S320 can play a significant role in accelerating SDN deployment. By deploying SDN-enabled OCS switches at the edges of the network and between network domains, the entire optical network, including legacy transport systems, can fall under SDN umbrella control.

The result is that the entire optical network, including all vendor, domain, and legacy network islands become “one giant optical switch” providing any client device access to any network resource.

Transport Interconnect Network Architecture Debuts

We call this the Optimized SDN Transport Architecture and we first introduced it at this year’s Optinet China Conference in Beijing.

In the diagram below, you can see how core routers at a customer’s data center are connected to the CALIENT S-Series OCS. The S-Series provides any-to-any connectivity to the legacy DWDM network and ROADM/DWDM network that provides metro / wide area networking. The SDN controller manages traffic flows and network topology from the edge Routers through the OCS and MAN/WAN. By virtue of the OCS’s switching capabilities, the controller can select the best optical-layer path available, regardless of vendor or domain.


Based on the feedback we’re hearing from service provider customers, we’re very excited about this architecture. Some customers estimate that putting this in place can cut 35%-50% of core-router CAPEX costs.

We’ve put together some webpages to help you get a better understanding of the transport interconnect architecture:

  • Press release: announcing our demonstration at Optinet and a presentation by our technical director for China.
  • Solution Page: With a description of the architecture and two videos that provide a thorough background.
  • SDN Transport Whitepaper: This document provides an in-depth examination of the transport interconnect architecture and its benefits.

If you are looking to re-ignite the dream of a flexible, telecom network I hope you will check out one of these resources.


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