Feature Story

May 25, 2004

By Nick Wreden, News@Cisco

Worldwide telecommunications networks are on the cusp of a great transformation. Increasing bandwidth and digital technology will generate new applications, spread knowledge, and create unprecedented communications capabilities. To put this transformation in context, it is useful to both look back at telecommunications' history and forward to the new services that packet-switched networks, driven by the new Cisco Carrier Routing System, will make possible.

The Legacy: One-Track Calls

In the late 1800s, telephone networks were in their infancy. When a call came into a central office, an operator would plug a line into a "cord board" and shout across the room to the operator who was handling the customer being called. That operator would then plug into the same line to complete the call.

Although there were electro-mechanical and digital advances that speeded call completion and coped with massive increases in volume, that same methodology of establishing dedicated connections essentially remained in public telephone networks for the next century. Despite the inefficiencies of having the equivalent of a train ferry travelers from station to station on one, dedicated track, that system-technically called circuit-switched-worked well until the advent of the computer age.

Since the 1980s, both private firms and telephone companies responded to the increasing volumes of data (digital) as well as voice (analog) traffic in several ways. In some cases, they built separate data networks, since existing networks were optimized for voice. In other cases, a variety of band-aids, such as bridges, gateways, multiplexers, and digital cross-connect systems, were used to ensure that data and analog communications played well together.

But circuit-switched equipment was expensive to buy and maintain. It was also increasingly inadequate at carrying exponential increases in traffic that ranged from local calls to credit card and ATM verifications to even digital images.

The Present: An IP Revolution

The industry responded to these infrastructural inadequacies in two ways. The first was to offer space and capacity-called bandwidth-to carry more traffic more cheaply. The enabling technologies for such bandwidth were fiber optics, which can carry more than 3 trillion bits per second, and the high-speed SONET transmission standard. The industry response was to move from a circuit-switched to a packet-switched infrastructure based on IP (Internet protocol), the same protocol behind the World Wide Web.

Packet switching involves putting voice or data information into the digital equivalent of envelopes called packets, complete with a destination address and other information. These packets are then independently sent along the best available paths before being reassembled at their final destination. Packet switching also involves replacing centralized switches with distributed routers, each with multiple connections to adjacent routers. In effect, instead of having an exclusive railroad track with only one train to ferry travelers, packet switching enables data to travel on any track that's temporarily free at any time. Ironically, packet switching resembles the technology of an even earlier era-the telegraph.

Packet-switching has multiple cost-reduction advantages, one reason why it has formed the strategic cornerstone for billion-dollar investments by major carriers like Sprint and Verizon, as well as such organizations as cable companies. Multiple phone calls or Internet connections can share the same line; meaning less bandwidth is wasted maintaining connections. Transmissions are gracefully adapted to existing traffic to optimize capacity. As a result, packet switching is anywhere from three to 100 times more efficient than circuit switching (depending on the information being transferred). Other savings result from fewer host facilities, or "points of presence," that are required in packet-switched networks. The various add-on technologies in primary backbone networks can be "converged" onto a single IP-based, non-proprietary technology, reducing support and infrastructural costs.

But more importantly from the carrier perspective is the revenue potential from packet switching and the opportunity to build customer loyalty through personalized capabilities. Customers are willing to pay for higher bandwidth that lets them use applications that support profitable or compelling activities. For example, a high-bandwidth, packet-switched network can let branch offices simultaneously discuss and review spreadsheets. Another application, "unified messaging," executes the vision of "any message, from any device, at any time" by permitting emails to be heard over the phone or voice mails to be read. Multicasting permits streaming audio and video for broadcasting entertainment over the Web and distance learning. Packet switching also lets telecommunications companies segment customers, helping them provide different applications, custom services, and rates depending on the customer's traffic volume needs and other factors. Network operators either cannot provide these services on circuit-switched networks or face very cumbersome modifications to their infrastructures.

One of the packet-switching capabilities that gets the most attention is voice-over-IP (VoIP), also called Internet telephony. VoIP was initially plagued by quality problems, but those have largely been addressed by improvements in IP's quality-of-service (QoS) capabilities. Essentially, QoS means that packet-switching networks are able to prioritize packets based on the application. Using this ability, delays that once compromised voice calls have generally been eliminated. Based on a survey by the research firm In-Stat/MDR, an estimated 2 percent of all U.S. firms are using IP telephony, and the number is expected to grow to about 19% of all firms by 2007.

The Future: The Revolution Continues

If the advantages of packet-switched networks are so overwhelming, why has it taken so long for telecommunications carriers to make the change? Now that quality and operational consistency issues have been addressed, the primary reasons are financial and technical. The carriers have a major investment in the Class 4 and Class 5 digital circuit switches that do today's heavy lifting for voice and data traffic. Carriers are understandably reluctant to abandon this investment, especially after the financial tsunamis that have hit the telecom industry. Technical reasons include the lack of sophisticated hardware that can both handle the bandwidth of fiber networks as well as evolving business and consumer applications' demands.

But those concerns can now be met with the introduction of the Cisco Carrier Routing System (CRS-1), a next-generation router designed for carrier-class IP networks. From the chips to the line cards to a new operating system, Cisco CRS-1 has been optimized for scalability, availability and the ability to handle big-gulp bandwidth totaling 92 terabits per second (Tbps). That's enough to transfer the entire collection of the U.S. Library of Congress in fewer than five seconds. The CRS-1 gives carriers the ability to combine separate "overlay" networks into a single, converged network for voice, video and data communications. CRS-1 can also help carriers save significant overhead expenses through PoP consolidation and other benefits. Also, service quality will be better because packet-switched networks are more reliable and redundant.

The CRS-1 will enable carriers to take advantage of such trends as the move toward broadband IP. Over the next coming months and years, broadband IP will enable carriers to offer true video-on-demand (complete with pause, fast-forward and rewind), interactive gaming and other capabilities, including music, video, and other content. And for businesses, broadband IP, for example, will enable carriers to offer remote enterprise management, allowing them to control complex networks for companies from afar.

Circuit-switched networks optimized for point-to-point communications are at the end of a long and productive lifecycle. They have grown obsolete thanks to the fiber optic driven growth in bandwidth, the digitization of business, and the need to converge separate voice, data and images onto a common multimedia platform.

The move to a global, packet-based communications network is as important as the long-ago establishment of the first phone lines. What has brought these changes to a tipping point is the introduction of the telecommunications workhorse, the Cisco CRS-1, which offers the required scalability, availability, intelligence and throughput necessary to usher in the Information Age.

Nick Wreden is a freelance journalist in Atlanta, Georgia.