Network Management Moves to a New Level

March 2001
By Christian B. Sheehy

An all-optical switching platform brings added flexibility to ease constraints on connectivity.

A new type of optical networking software will enable bandwidths of light to be redistributed in response to fluctuating data traffic. The technology allows individual streams of photons to be moved when and where they are needed, ensuring greater network reliability and near real-time communication.

As demands on capacity continue to increase, fiber optics is moving toward multiple wavelength channeling to relieve the congestion in overcrowded fiber links. The challenge will be to simultaneously manage numerous data routes and to accommodate the rapid evolution of networking in general.

Based on an all-optical architecture developed by Lucent Technologies, Murray Hill, New Jersey, the software enables carriers to increase network capacity by continuously switching between multiple wavelengths of light to carry information. The availability of numerous mobile data paths results in increased usable bandwidth and improved transmission reliability. This product was developed to meet the commercial need to manage increasing amounts of data on system networks as optical data transmission technology transitions from point-to-point, single-channel fiber communications to multiple channels.

According to Rod Alferness, Lucent’s chief technical officer for optical communications, traditional techniques in data management and security during transmission were built around methods in synchronous digital hierarchy in which units of light bandwidth are first divided into smaller, more manageable segments. Next, the optical signals are converted to electrical signals to be rerouted through the use of digital cross-connects and add-drop multiplexors. The signals must then be converted back to optical signals before being sent on their way. The optical-electrical-optical (O-E-O) conversion is costly and slow, making this approach increasingly impractical.

To combat potential information gridlock, Lucent’s Bell Laboratories’ Optical Services Manager (OSM) software, accompanied by WaveStar LambdaRouter technology, eliminates the O-E-O conversion. This breakthrough allows networks to be scaled up to the limits of the optical management capability. Rather than disturbing wavelength structure to free more bandwidth on a length of fiber, multiple wavelengths of data on each fiber are redistributed throughout the network to improve the use of available space. “We can now take multiple fiber connections between businesses and demultiplex the fibers into individual wavelengths that can then be optically cross-connected with other fiber lines, ensuring that no one fiber is overcrowded,” Alferness remarks.

The rapid growth of centralized hub networks such as the Internet makes it difficult for service providers to predict future growth, he adds. Emphasis on network protection through node ring formations has enabled the isolation of inoperable links by routing signals around damaged areas. This approach works well in a static environment where growth potential is limited and network predictability is high. In the Internet, constant change in network topology has dramatically reduced this predictability because new nodes are continually increasing the complexity of traffic pathways running through systems, Alferness indicates.

“With the introduction of OSM software and LambdaRouter technology to a multiple wavelength fiber network, the system becomes more mesh-like, allowing for greater connectivity because all hubs are connected,” Alferness explains. “This connectivity at the wavelength level allows for better control over network functionality, making the whole system easier to chart and predict.” Lucent’s optical switching methodology uses wavelength channeling to make network communications more flexible by providing bandwidth capacity where and when appropriate, he says.

Within a network, beams of data-carrying photons enter the LambdaRouters positioned at major system nodes. Each incoming wavelength of photons is initially part of a color spectrum on one incoming fiber. Using dense wavelength division multiplexing (DWDM) technology, the wavelengths are separated into individual colors on single, smaller fibers, before entering the LambdaRouter as an input optical fiber bundle.

The interior of each LambdaRouter is made of a fabric composed of 256 pairs of microscopic mirrors. Precisely positioned, the mirrors reflect, or switch, the wavelengths of light, repositioning the streams by color refractivity. Regrouped as part of an output bundle, the wavelengths are then routed to the proper fiber pathway. Using DWDM technology and optical switching, instead of electrical cross-connects, light signals on multiple-wavelength-carrying fibers are routed seamlessly through each LambdaRouter, resulting in near-real-time transmission quality.

Unlike many data networking systems that receive optical signals and break their content down before transmitting them, LambdaRouter technology uses optical switching to route information more efficiently. When incoming wavelengths are bound for different locations, OSM-controlled optical switching cross-connects the signals by reorienting the mirrors to provide transmissions in near real time. All-optical OSM/LambdaRouter networking enables the reconfiguration of sender-receiver connectivity to help increase network efficiency by avoiding transmission losses related to high traffic or damaged connections.

Lucent will be adding optical network navigation system (ONNS) intelligent software as part of each LambdaRouter. This component technology will allow LambdaRouter optical switches to communicate with the OSM to continuously inventory network resources, log changes in network topology and determine optimal signal paths between end points. In an all-optical mesh environment, ONNS will enable the LambdaRouters to identify key changes in the network, such as the introduction of new nodes or the presence of a fiber cut. The LambdaRouters, in accordance with the OSM, will then have the information needed to determine more efficient routing through the network.

“Networking is turning increasingly away from voice-telephony-based communications and more toward data-oriented asynchronous transfer mode [ATM] and Internet protocol [IP] switching,” Alferness notes. “The DWDM or transport layer of a network serves these data-driven applications by providing a means of managing available bandwidth on a macro-optical level as opposed to a microcomponent level.” The concept of a mesh-like network, where central hubs are interconnected, promotes the standardization of activity throughout systems like the Internet. DWDM technology is rooted in the notion that it makes sense to use existing capacity as efficiently as possible before creating more, he adds.

When additional data capacity is needed, the ONNS software within each LambdaRouter will have a dynamic signaling capability for allocating wavelengths on other fiber strands according to the information’s destination. As end-point routers and ATM or IP switches detect limitations in connectivity, these components will contact the OSM software by way of network LambdaRouters to request additional or rearranged bandwidth. “We will be able to handle the demand for greater capacity based on the needs of these ATM and IP elements,” Alferness indicates.

Michael Coghill, senior vice president of global engineering, Global Crossing Limited, Rochester, New York, notes that the whole point of moving to an all-optical mesh network is to decrease the time spent tuning it and increase the time spent using it. The company is currently testing uses of the WaveStar LambdaRouter to protect transoceanic links between the United States and Europe. The firm has employed the technology to switch data back and forth between cable connections to supply added security and reliability to trans-Atlantic transmissions.

“Using the LambdaRouter as a switch, we can transfer signal wavelengths from one path to another depending on traffic demands or network conditions,” Coghill indicates. “The ability to use bandwidth dynamically without having to tinker with equipment inside the network will help us save time in the communications process, money in the form of fewer internal system adjustments and energy in the number of people needed to make it all happen.”

According to Coghill, the advantage of transitioning to a contiguous wavelength all-optical network is the ability to employ multiterabit optical-routing capabilities within mesh networking environments. “Increased capacity is no good unless you have the capability to protect all your data,” Coghill emphasizes. “If you have to constantly change equipment to provide information security and reliability, this affects the scalability of your network as upgrades are added. With major system operations at the optical level, modifications can be achieved by simple commands instead of cumbersome electrical grooming.” For peripheral network monitoring, the maintenance of an existing O-E-O framework to accommodate communications with external networks will likely remain essential, he adds.

Including ONNS technology in the existing LambdaRouter format will bring a measure of intelligence to mesh networks by increasing data path restoration capabilities. When fiber cuts occur, ONNS components will furnish information to LambdaRouters to locate alternate fiber routes. Theoretically, this will ensure the seamless transmission of data between network end points. Alferness explains that ONNS software will automatically discover any lost connectivity and give the LambdaRouter needed data to properly reroute a transmission. ONNS software will make redirection possible without OSM or human intervention, he adds.

“With the combination of OSM, LambdaRouter and ONNS platforms within a network, businesses will be able to rapidly provision wavelength services to meet consumer demand,” Alferness notes. Using OSM software, a network operator can remotely direct a LambdaRouter to increase or decrease the number of wavelengths being sent to other locations based on the data needs of each site. In single wavelength fiber optics, bandwidth trading is restricted to the reallocation of all the data being carried by a fiber. Multiple wavelength fiber communications allow information streams to be transferred selectively from fiber to fiber, boosting network efficiency, he adds.

Besides reassigning data paths to provide increased bandwidth capacity, additional wavelengths can be established between points in a network by using OSM software to electrically control LambdaRouter function. If greater connectivity is required than originally allotted between two or more locations, the network operator will be able to supplement fibers with rerouted wavelengths. “Wavelengths that may have initially supported a connection between Chicago and Denver may now be supporting communications between Chicago and New York,” Alferness declares.

OSM software will provide the flexibility necessary for business applications to offer a high quality of service in the evolving virtual environments of the Internet and private networks, he says. The WaveStar LambdaRouter currently has a 256-signal capacity and is being tested for scalability to 1,024 signals by April 2001. Now commercially available, OSM software was demonstrated in combination with LambdaRouters at a 2000 trade show in Atlanta, Georgia, according to Alferness. Lucent plans to begin controlled introduction of its ONNS software in the third quarter of 2001, with commercial availability scheduled for September 2001.