May 21, 2002

By Charles Waltner, News@Cisco

Resilient Packet Ring (RPR) technology is known by some as a metropolitan area network (MAN) technology that service providers are using to solve network bandwidth bottlenecks and deliver new IP services. In reality, the range of applications and customers for RPR is far broader.

Cisco's RPR technology, known as Dynamic Packet Transport (DPT), is supported on an array of Cisco Internet routers and optical equipment and is being used in new applications and market segments by millions of subscribers worldwide. Why? According to customers, DPT/RPR provides unparalleled network simplicity, scalability and reliability in delivering high-bandwidth Internet Protocol (IP) services over an optical infrastructure - with a lower total cost of ownership.

Today, more than 200 companies worldwide are using DPT/RPR. They are using the technology not only in MAN and regional environments but in intra-POP, campus, inter-exchange, and cable networks.

The Genesis of RPR

The rapid growth of IP services has been a double-edged sword for service providers. New demand for data and converged voice/video/data IP-based services is generating new revenue opportunities for service providers. But many providers have struggled to adapt their existing Time Division Multiplexing (TDM) networks - typically designed for circuit-based voice traffic - to handle these new services and traffic while keeping capital and operational costs down.

Traditional SONET/SDH-based networks, while optimal for delivering TDM services such as voice, were not originally designed to support the enormous growth in IP data traffic and have proven sub-optimal for IP services delivery. Ethernet (and Gigabit Ethernet) and DPT/RPR have become the compelling architectures for delivering IP services. DPT/RPR provides enormous bandwidth utilization benefits with statistical multiplexing, as well as SONET/SDH-like carrier-class reliability with sub-50 millisecond failover recovery time, while Ethernet offers the ultimate customer access interface for IP services delivery.

Many providers are finding the optimal solution combines DPT/RPR, Ethernet and IP/MPLS (Multiprotocol Label Switching). Cisco's 12000 and 10700 Internet Routers enable providers to enjoy the benefits of DPT/RPR for high-speed optical connectivity, Ethernet for cost-effective customer connectivity, and a robust IP/MPLS control plane feature set for services delivery.

Network operators of large campus networks and cable operators have also jumped on the DPT/RPR bandwagon. While they've often started with an IP and optical infrastructure as opposed to a TDM network foundation, they're enjoying the same scalability, reliability and efficiency benefits of DPT/RPR.

DPT/RPR in Action Globally

DPT/RPR is proving itself in the field with deployments by some of the world's most sophisticated network operators.

One such operator is Ebone. Operating one of the most extensive networks in Europe, Ebone specializes in offering hosting services, IP Virtual Private Networks, and SDH services to large providers and corporations. In addition, Ebone has invested in city metropolitan and regional area networks to reach a customer base of Internet exchange points, multi-tenant building and facilities operated by carriers.

Ebone turned to Cisco's DPT/RPR solutions when its rapid growth made it difficult for the company to keep up with ever-increasing network bandwidth demands. Expansion of its older point-to-point network would have been a time-consuming and expensive process, requiring new equipment and extensive periods of network interruptions for installations. Ebone avoided such profit drains by using Cisco's DPT/RPR solutions. With far less equipment overhead and installation, the Cisco solution helped Ebone expand network capacity more cost effectively. Today, Ebone's DPT/RPR networks carry more than 35 percent of Europe's Internet traffic.

Another organization which has reaped the benefits of Cisco's DPT/RPR technology has been SUNet, or the Swedish University Network. SUNet provides all data communications to Sweden's 30 universities. Some of SUNet's links had become overloaded because of increasing university attendance coupled with the rapid growth of data traffic from Internet usage. The network operators of SUNet decided to build a new 10 Gbps network, with 2.5 Gbps access to each university. They found that Cisco's DPT/RPR solutions made the best use of their infrastructure investment. DPT/RPR makes the network far more reliable and, because of its excellent use of available bandwidth, it's allowed them to access the universities much more cost effectively.

Dubai Internet City in the United Arab Emirates is offering managed voice, video and data service thanks to DPT/RPR. The showcase of Dubai Internet City's offerings will be Ethernet-based broadband connectivity, ranging from speeds of 10 Mbps to a Gigabit. Dubai Internet City's mission is to become the regional hub for IT and telecommunication companies in the Middle East. It is committed to offering the highest levels of service and to provide its customers with access to an advanced network infrastructure. It now has more than 300 companies operating on its network.

DPT/RPR Continues to Grow

Cable is one of the fastest growing market segments adopting DPT/RPR. Cable MSOs support tens of millions of subscribers with DPT/RPR today. They are using the technology to provide regional connectivity and hub/access solutions. This industry, in particular, wants to quickly deliver profitable IP services, leveraging existing fiber rings and a much less expensive alternative to SONET/SDH.

New applications for DPT/RPR are also springing up. One interesting application is server farm interconnection for mission-critical voice, video and storage. Companies are finding that the benefits provided by DPT/RPR for networks are also provided for servers. They're using the technology to interconnect servers and routers for increased performance and reliability at lower cost than FDDI rings. As a result, server vendors have seen great interest in this application from their customers. For example, Sun Microsystems recently announced a new Packet Over SONET adapter that allows network engineers to connect Sun servers directly onto a DPT/RPR network, improving efficiency and network reliability. The adapter provides high-bandwidth network connections at OC-48 speeds, or up to 2.4 Gbps.

There's no doubt we'll continue to see DPT/RPR penetrate new businesses and be used in new ways. The technology's superior features and economics are major assets for any company.

Charles Waltner is a freelance writer based in Oakland.