Building on the foundation of the fiber-optic network

Dec. 1, 1998

Building on the foundation of the fiber-optic network

Sprint?s new ION initiative builds on the company?s previous investment in fiber-optic technology to anticipate future communications demands.

Marty Kaplan Sprint Corp.

In life as well as in business, goals are rarely met without years of planning, preparation, and implementation. Although it is difficult to forecast the future, it is vital for businesses to expect the unexpected and work to solve tomorrow`s problems today. Because the communications network of the future will be built on the technologies of today, tomorrow, and yesterday, Sprint has spent the past decade preparing its network to not only meet the communications demands of the future but also to surpass them.

Today`s foremost communications challenge is meeting the demands that the Internet is placing on the fiber-optic network. The next phase of the Internet`s evolution is to fulfill its role as a primary form of communication, and the world is looking to the telecommunications industry to make the promise of integrated voice and data communications possible. Telecommunications capacity needs are growing at unprecedented rates as business demands change. Many trends have increased bandwidth requirements and hastened the technology development needed to expand existing telecommunications networks. Internet usage, which some analysts predict will grow 700% annually in coming years, is threatening to overwhelm networks and overwork the fiber backbone because the same fiber-optic backbone that carries the Internet also carries frame relay, Asynchronous Transfer Mode (ATM), and other data and voice traffic.

Greater customer demands

More than five years ago, engineers at Sprint realized the limitations of the network to meet the needs of the 21st century. They foresaw that customers would soon demand a data network as reliable as the public switched telephone network. They would always want to be connected. They would want access as fast as their television. And they would want to be able to communicate seamlessly and cost-effectively with people on or off the Internet, by phone or PC, independent of device, protocol, or distance.

Thus began the initial development of Sprint ION (Integrated On-Demand Network), a new network platform that integrates voice, video, and data over a single, existing connection to the home or business. ION will enable virtually unlimited bandwidth and next-generation entertainment, information, and communication applications.

But before Sprint could realize its vision for service integration, it had to build a network that would provide the necessary survivability, quality of service, and scaleability.

Since the early 1980s, telecommunications infrastructure has changed through the use of computers and fiber-optic cables. Synchronous Optical Network (SONET) has increased network bandwidth, efficiency, and reliability as well as allowed carriers to shift to fiber-optic cable. In the early 1990s, SONET equipment supporting 4-fiber bidirectional line-switched rings (BLSRs) became available. In this architecture, every network segment has a working fiber and a protect fiber, and traffic is sent only in the required direction during normal operation. When service on a network segment is interrupted, traffic is routed around the break and sent to the endpoint in the opposite direction. Since that time, Sprint has predominately deployed 4-fiber rings and has more than 130 rings operating in the network.

While many carriers chose to deploy SONET in a star or linear design, Sprint`s SONET network was deployed on a ring-based architecture designed for survivability. Traffic on the network can be re-routed in as little as 60 msec, so fast that it is virtually transparent to the user.

Although SONET has improved transmission speeds and utilized fiber networks effectively, bandwidth demands continue to outgrow existing network capacity. Today`s business network must support all traffic types as well as the growing number of multimedia applications. These networks must support a wide range of uses and applications through a fiber-optic architecture and subnetworks that include frame-relay service, ATM, videoconferencing, and messaging.

New data applications in use today include scientific and engineering super computers, video-on-demand, computer-aided design, media imaging, and interactively controlled, virtual-reality applications. Each of these applications relies on high-speed, dynamic bandwidth; therefore, networks must be able to transmit electronic information rapidly.

With the amount of data carried in the network soon to surpass that of voice traffic, the future long-distance network will be a design based on the requirements of data circuits. To install additional bandwidth, many carriers are choosing to deploy dense wavelength-division multiplexing (DWDM). By early 1999, DWDM will multiply the capacity on a fiber by 96 times with greater increases in the year 2000. The technology increases the capacity to 240 Gbits/sec on each fiber pair, which is enough data to move 3600 three-hour movies around the world in one second.

Using light wavelengths, DWDM simultaneously transmits densely packed data streams on a single fiber. By combining DWDM with a special amplification method and precise filtering techniques, telecommunications has realized unprecedented bandwidth expansion. Multiplexing these data streams with DWDM allows carriers to increase each fiber strand`s transmission capacity. The cost of boosting existing cable capacity with DWDM is substantially less than that of installing additional fiber, and it provides a virtual-fiber path with frequency channels that serve as single STM-16/OC-48 (2.5-Gbit/sec) carriers.

Another technological advancement developed over the past four years in preparation for Sprint ION is the ability to carry high-quality voice traffic over an ATM network and to connect seamlessly to any public-switched network. Four recurring principles have driven the evolution of the Sprint network to prepare for the introduction of ION. These principles include providing quality of service on a per-application basis, dynamic bandwidth control, customers` control of their own communication services, and total integration of services over a common infrastructure to decrease costs dramatically.

Implementing convergence

Sprint ION`s integrated platform uses advanced software and hardware components to combine and convert different protocols into ATM cells that can be used to send e-mail, download Web pages, check voice mail, or make a phone call (see figure). All communication devices plug into one central hub through standard telephone jacks. Information or signals are sent to the integrated-services hub where they are simultaneously converted into digital packets. Those packets then travel to a metropolitan-area fiber-optic ring over a single phone line using digital subscriber loop (xDSL) technology. On the ring, the packets are switched to the Sprint service node to receive instructions, download applications, or process calls. The service manager within the service node manages those instructions and ensures the transmission gets to its destination over the core network.

Sprint ION, which was announced last June, allows businesses to expand their local- and wide-area networks and dynamically allocate bandwidth. Thus, they will pay only for what they use rather than having to purchase a set high-bandwidth capacity that often sits idle. The network will also provide high service reliability using SONET rings across the United States.

While today`s Internet is useful for casual communications, it cannot support real-time mission-critical applications that consumers need today. Sprint ION will make full use of quality-of-service characteristics, enabling customers to assign different transport priorities to their various applications on the network. For instance, if your fax services or intra-company calling do not require quite the same quality as mission-critical voice and data services, customers can assign slightly lowered "class of services" to the lesser services and benefit from lowered pricing.

The network architecture delivers the ability for discrete networks/services to be integrated onto an all-services single network, simplifying management and reducing business and network costs. ION`s cost efficiencies will help Sprint cut its total network costs by 70%.

Using today`s network tomorrow

The goal of new data-centric ap proaches to transport is to provide protection and restoration and to use available bandwidth efficiently. New technologies must be developed to meet changing demands, and DWDM systems are poised to evolve into a component of the next-generation transport network.

One way to carry high-bit-rate traffic is to interface directly from the Internet protocol (IP) router to the DWDM system. This implementation is referred to as "direct on wavelength." The direct-on-wavelength implementation removes the SONET architectural elements from the system. Therefore, protection and restoration must be provided by other means such as the recent deployment of point-to-point OC-48/STS-48c IP router connections, deployed directly on the DWDM system without SONET terminating transport equipment.

Increasing the capacity per fiber is one of the primary objectives of long-distance carriers. When more capacity is required, more wavelengths can be added to accommodate the demand. The fundamental building block of the optical network is the DWDM system, which is already in place. u

Marty Kaplan is senior vice president and chief technology officer at Sprint (Westwood, KS).

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