IT managers are turning towards automatically switched optical networks to unite their infrastructures and meet the demand of new bandwidth-intensive applications. Dieter Will of ADVA Optical Networking (below) explores the current network landscape and assesses the technologies that are revolutionising the telecommunications industry

Hardware and software vendors have responded to this shift and are now bringing to market technology that enables dynamic bandwidth delivery to any location at any time. Referred to as Automatically Switched Optical Networks (ASONs), these are automated, demand-responsive and self-healing optical networks that can provision wavelengths and bandwidth on demand, rapidly reducing data bottlenecks and ensuring network optimization without significant expansion or alteration.

Many IT professionals still believe that more bandwidth is the solution, but this will not reduce the time spent manually reconfiguring the network or help to reduce long-term operation and administration costs (OAM). ASONs will. Across the globe, leading enterprises from a number of business markets (including manufacturing, healthcare and research and education) are deploying ASON solutions and noticing a return on investment (ROI) in less than 12 months. This is because ASONs help to define network simplification.

Currently, networks require large IT teams of trained staff to manage operations and ensure data is transported when and where it needs. In this environment there is a great deal of redundancy, not only for the IT staff whose work load can be intermittent but crucially for network resources that can often become stranded or redundant after completing data transfer. If not administered manually, these resources sit idle whilst awaiting their next task. Automatic reconfiguration eliminates this redundancy and reduces manual intervention, harnessing all the elements of a network into a productive heterogeneous environment.
With an increasing number of enterprises seeking to automate their operations, share resources and respond to data demands, ASONs present a compelling proposition and an unquestionable business case. While assessing the motivations for change, it is important for an enterprise to remember the sound financial basis for this transition. Although there will be initial capital expenditure costs (CAPEX), the key business opportunities ASONs present will not only help recoup initial costs, but also deliver excellent future growth opportunity. The key points to consider are:

• Simplicity – ASONs simplify the management of IT infrastructures, streamlining equipment, reducing server sprawl and eliminating redundancy.
• Flexibility – ASONs improve business responsiveness and operational speed by dynamically re-allocating resources as needed, matching business cycles and responding to network demands.
• Cost savings – ASONs reduce the total cost of ownership (TCO) by making better use of IT assets and drastically reducing operation, administration and maintenance (OAM) costs.
• Automation – intelligent middleware enables automated resource provisioning that reduces manual intervention and enables the network to act according to programmed rules.

There are two enabling technologies that are vital to an ASON’s success. From a hardware perspective, optical switching capability is essential. Two- and multi-degree reconfigurable optical add/drop multiplexers (ROADMs) deliver this functionality. If an enterprise seeks flexibility within its infrastructure, ROADMs provide the capability to dynamically establish circuits and light paths across the optical network via simple requests.

The ability to dynamically switch light paths to multiple network ports is a feature of ROADMs that contain Wavelength Selective Switch (WSS) functionality, allowing any-port connectivity across supported topologies. WSS is a significant advancement in ROADM technology and will have considerable impact on reducing OAM costs.

A WSS is an optical device that provides switching and wavelength equalization. Responding to software commands, it performs all wavelength multiplexing (mux), de-multiplexing (demux), optical switching and power level equalisation functions. Initially, ROADMs featured Dynamic Channel Equalizers (DCE) that performed only block-or-pass functions. Now, with WSS integration, ROADMs have the ability to fully switch wavelengths. Figure 1 shows the interconnection of two rings with a multi-degree ROADM using WSS technology, enabling reconfigurable services and bandwidth-on-demand.

Modern ROADM architectures such as this offer two distinct advantages:

• The ability to add two-degree or multi-degree ROADMs when and where they are needed. Without having to plan for unknown traffic demands, ROADMs eliminate stranded equipment and drive CAPEX and OAM costs down.

• The significant lengthening of the lifecycle of the hardware due to the use of software automation.

In addition to the hardware, an ASON requires intelligent, unifying control software; a decentralized control plane that is able to provide the necessary signalling and routing commands and automation. Generalized Multiprotocol Label Switching (GMPLS) offers the solution. GMPLS is the next step in the Multiprotocol Label Switching (MPLS) evolution.

A GMPLS control plane simplifies network operation and management by automating end-to-end provisioning of connection-oriented services, managing network resources, providing a high resilience to network failures and a strict Quality of Service (QoS) level. Figure 2 shows this unifying solution. The control plane requires intelligent Connection Controllers to manage data-forwarding network elements. These control units form the control plane and are complemented here by an optional centralized monitoring system.

Of significance here is that within the GMPLS platform, the International Engineering Task Force (IETF) has extended MPLS signalling and routing protocols and applications beyond Internet Protocol (IP) networks. Consequently, GMPLS offers a control plane that can finally function across a number of dissimilar networks, including: IP, MPLS, Asynchronous Transfer Mode (ATM), Synchronous Optical Network (SONET), Synchronous Digital Hierarchy (SDH), Optical Transport Hierarchy (OTH) and Wavelength Division Multiplexing (WDM).

The use of ROADM and GMPLS technology in ASONs results in a high level of automation that enables rapid service provisioning, effective resource sharing and continuous network optimization with limited manual intervention. Those enterprises that have already used ASONs to unite their IT infrastructures are finding that their networks are adaptable and resilient, driving down operational costs and, most importantly, providing their organisation with a competitive edge to respond to changing business demands.