Residential and enterprise users alike are demanding more from telecommunications services.
Their expanding appetite for high-bandwidth, high-quality multimedia applications places significant new stresses on metro networks. These stresses revolve around delivery of unprecedented amounts of Ethernet and IP-centric bandwidth—bandwidth that is now of a much higher quality than that of previous generation metro packet services. To complicate the situation, service providers must also deal with a complex multiprotocol environment that not only satisfies this new deluge of high-quality Ethernet and IP traffic demand but addresses the still-growing demand for TDM circuits.

How are service providers going to evolve their metro networks to respond to these challenges?

This article discusses key developments in optical networking. It explains how these technology advances are vital for service providers as they build manageable and scalable networks to meet consumer and enterprise demands for multimedia Ethernet and IP services—the connected experience.

There are over 50 million broadband users in the U.S., and the rate of adoption continues to increase. Residential users are devouring peer-to-peer social networking, online entertainment and e-commerce services. According to a recent Nielsen poll, five of the top ten fastest-growing Web brands are user-generated multimedia content sites, each of which is enjoying 200% to 400% annual growth in traffic.
Several million U.S. homes already have high-definition television (HDTV) sets in service, and the adoption is expected to grow to nearly 80 million by 2010. Online gaming subscriptions are now held by over 12 million users and the number is forecasted to increase to 30 million by 2009.

Enterprise users are also looking for more from IP-based services. Enterprises are turning to a variety of applications that involve the real-time sharing of multimedia content—applications such as telepresence and remote collaboration, telemedicine and medical imaging content sharing and distributed workforce innovation.

As new network services emerge and form the connected experience, they force significant new requirements onto metro aggregation and transport networks:

•    Cost-effective bandwidth. HDTV content, which can occupy 19 Mb/s per stream for video-on-demand (VOD), is today driving dramatic bandwidth increases. The sharing of rich Internet content, including digital photos and user-generated video, forces a dramatic increase in demand for Internet access bandwidth.

•    Stringent service requirements. Not only is more bandwidth required but also loss and latency requirements for the applications are tightening. Packet loss for video can cause visible pixelation or momentary screen blanking. Latency requirements for mobile voice and remote collaboration are also placing new stresses on packet networks.

•    Multiprotocol networking. While networking moves in general toward packet-based IP and Ethernet services, there is still growing demand for TDM access circuits and TDM-based bulk bandwidth management. Because most of today’s metro network is circuit-based, the future network must handle a complex, multiprotocol traffic mix. The challenge will be how to scale Ethernet while addressing ongoing TDM requirements.

•    Very large-scale operations (VLSO). Increasing bandwidth and service stringency force the network to be managed and operated in the most efficient means possible. Opportunities exist to reduce the number and types of elements in the network. Improvements in the level of network automation and the ability to rapidly and precisely troubleshoot in a more complex and service-rich environment become increasingly important.

Optical networking technologies play important roles in addressing the four dimensions of manageable scalability. Photonic technology delivers cost-effective bandwidth and streamlines operations. MPLS-based connection-oriented Ethernet transport delivers private-line-equivalent packet-based services. Sonet technology provides inexpensive, granular pipes that support the multiprotocol access network. There are also a number of operational capabilities from the optical networking heritage that uniquely deliver VLSO.

Photonic networking provides the foundation for network scalability from both a capital cost and operational point of view. ROADM technology provides the lowest cost-per-bit for bypass traffic, providing a 90% cost reduction compared with IP service elements. By providing this low-cost optical bypass, ROADM systems allow service providers to offload more costly IP service elements. Service providers who add a flexible and reconfigurable photonic layer can recover the initial added cost with as little as 2 Gb/s of traffic per site. ROADM deployments are critical for the economical delivery of residential video services.

Operationally, the addition of a new wavelength across an entire network can be accomplished by touching only the wavelength end points. Optical power levels are adjusted automatically at intermediate points, eliminating the need to visit those locations. One very large U.S. customer recently used ROADM technology to deploy an entire metro network that would otherwise have required 30,000 individual fiber installations.

ROADM technology is evolving in two directions:

•    Sub-wavelength transport capabilities are being integrated onto cards in standalone ROADM elements. These ADM-on-a-card capabilities reduce the function of a single standalone ADM onto a card pair. As a result, they provide very cost-effective sub-wavelength grooming and transport for a light concentration of services.

•    ROADM functionality is similarly being reduced to cards that can be deployed in other types of optical networking systems. Like ADM-on-a-card approaches for stand-alone ROADMs, ROADM-on-a-card functionality allows for straightforward capacity upgrades while accommodating cost-effective grooming for light service concentrations. Since the ROADM-on-a-card concept can be applied to a variety of network element types and configurations, ROADM functionality can be economically added to chassis that are accomplishing grooming of a heavy concentration of sub-wavelength traffic.

There has been substantial demand for Ethernet, driven by the desire to scale bandwidth, add services and support IP based applications. The single universal Ethernet jack delivers multiple types of services and allows users to increase their bandwidth without a truck roll.

For Ethernet to replace TDM-based services, service providers must be able to deliver Ethernet connections that provide a private-line-equivalent quality of service (QOS). Private-line-equivalent QOS provides robust connection performance—loss, latency, and jitter—and the reliability assured by protection switching.

To provide this QOS, Ethernet (a connectionless technology) must be transported over a connection-oriented technology. A connection-oriented technology (such as MPLS) reserves bandwidth and queuing resources for each Ethernet connection through the network and assures that each connection will not have to compete unexpectedly for overbooked network resources.

MPLS technology is an excellent choice for delivering connection-oriented Ethernet. MPLS technology originated in the router world but can be adapted for the optical networking environment. A pseudowire encapsulates an Ethernet connection and maps it into a traffic-engineered MPLS tunnel, which preserves all of the Ethernet operation administration and maintenance (OAM) and QOS requirements for that Ethernet connection. Standards-based network protection schemes for MPLS assure the reliability of each connection.

MPLS supports all of the physical layers in the network including Ethernet, OTN, Sonet and WDM, thus assuring that access mechanisms can be diverse. MPLS also meets network cost and performance requirements.

Sonet technology delivers inexpensive pipes that support multiprotocol network needs. In fact, most of the access for IP services continues to be over a DS1 and DS3-based TDM infrastructure.

Sonet provides add/drop, grooming, switching, sub-wavelength bandwidth management capabilities and finer levels of granularity than defined by OTN. SONET also provides access network redundancy, moving traffic from a customer’s site to the serving central office (CO) in a resilient manner.

Optical networking elements have traditionally provided substantial operations capabilities that allow service providers to build expansive aggregation and transport infrastructures. These capabilities include in-service software upgrades, foolproof management interfaces, precision OAM for fault sectionalization, in-service card replacement and GMPLS-based control planes. By leveraging these capabilities and adapting them to a packet-centric environment, service providers can continue to deploy manageable large-scale metro aggregation and transport infrastructures.

From asynchronous systems to Sonet, ADMs to MSPPs, and from DWDM systems to ROADM systems, optical networking gear has continued to evolve to meet new networking challenges. Now, a whole new class of optical networking gear—the packet optical networking platform (Packet ONP)—is emerging to address the substantial packet-centric challenges imposed by user demands for the connected experience.

The Packet ONP is a modular, chassis-based fusion of:

•    ROADM-on-a-card technology for cost-effective bandwidth delivery in the core, aggregation and access portions of the metro network.

•    Connection-oriented Ethernet to provide private-line-equivalent QOS for packet services.


•    Next-generation Sonet capabilities to address the continued need for multiprotocol access and sub-wavelength grooming.

Each of these technologies exists within a single addressable optical-class element.

By leveraging packet ONPs for their aggregation and transport infrastructure, service providers can make efficient use of costly router-based service elements, provide a complete range of high-quality services to a geographically dispersed customer base, and leverage the installed base of optical networking equipment and operational procedures. Most importantly, these providers can deploy manageable and scalable metro networks that support the rigorous demands of the connected experience.