Service delivery's traffic meets at the optical/electrical crossroads

Communications News,  Oct, 2001  by Rajiva Dhar

• E-mail
• Print
• Link

Optical switches speed past their electrical ancestors along the provider highway.

Content distribution is becoming vital, as more businesses rely on service providers for content hosting, data mirroring and data backup. Delivery of these services requires high bandwidth, guaranteed connectivity and strict enforcement of service-level agreements (SLAs) to guarantee network performance.

Service providers positioning their networks for these sophisticated product offerings are already sold on optical switches--not just because optical switches deliver greater capacity and reliability than their electrical ancestors, but because the total cost of network ownership comes in significantly lower with optical switches. Optical switching is frictionless; no heat is generated in the process. Optical components and modules require

less power to operate than electrical architectures. Usually smaller, they demand less space in central offices and data centers.

While the future of transporting packets lies in the optical domain, the processing, routing and storing of those packets will remain in the electrical domain for some time to come. Providers rolling out application services are also searching for ways to bring efficiency and accuracy to managing these electrical and optical heterogeneous communication infrastructures. This challenge is exacerbated at the network edge where the optical and electrical domains cross.

Most of today's optical-edge devices are not capable of supporting service differentiation. New "service-aware" systems are emerging that have been designed specifically for harnessing application services on intelligent optical networks. These systems groom traffic at the network edge--unshackling all-optic switches in the core to simply switch wavelengths of light.

Each of these new solutions has attributes that hold different degrees of relevance for different metro service providers:

* Tight integration among IP, synchronous optical network (SONET) and wavelength division multiplexing (WDM) network layers and control software. Today, no existing standards govern how requests are signaled between IP, SONET and WDM devices. This communication gap forces the equipment at each layer to guess at traffic loads to be processed at the other layer, and the fallout is inefficiency in service provisioning. Integrating all the layers of the network architecture simplifies this process.

* The ability to reprovision metro rings as customer bandwidth needs fluctuate. To ensure efficient utilization of network resources, service providers must be able to create and reconfigure network topologies within a physical ring without expensive truck rolls. Tunable lasers can reprovision the optical network based on the changes in customer bandwidth needs.

* Flexible service packages. Traditional, generic SLAs--prescribing acceptable thresholds for guaranteed bandwidth, burstable bandwidth, latency characteristics and other network-resource metrics--will no longer adequately address business customers' reliability and cost requirements. SLAs in the new services environment must broker additional meaningful attributes, such as number of mailboxes, maximum allowed storage space, over-subscription factor and security aspects, such as authentication and encryption levels, each with an associated cost. With the advances in optical-Internet technologies, business customers will be granted the flexibility to pick a service package based on the type of applications they intend to run on their networks.

* Multiple routing protocol support. Newer services, such as bandwidth trading and IP transit, are appearing on the horizon, requiring a network to support information exchange at all levels within the network. Support for these services requires protocols that enable efficient allocation of bandwidth among users in a flexible and dynamic manner. Routing protocols like open shortest path first, intermediate system to intermediate system, multiprotocol label switching, differentiated services and border gateway protocol are key enablers for these services.

* Multilevel protection for reliability. In a worst-case scenario, network restoration speeds can be as high as a few minutes. Integrating SONET's rich fault-detection and fault-isolation capabilities with optical protection provided by tunable lasers, where a box can be switched in and out of network, is a technique that provides resiliency and survivability.

As metro access and core networks evolve to meet growing demands, some of the requirements imposed on them are higher bandwidth needs, application-level service differentiation, guaranteed service-level agreements and bandwidth dilation on demand. In order to facilitate these by avoiding the costly option of using multiple devices, a new approach to networking is needed, combining the benefits of optical networking and resiliency of SONET with the intelligence and flexibility of the IP and application layers.

An integrated architecture enables going beyond today's fiber or bandwidth leasing model and moving toward metered application services and on-demand bandwidth dilation. A tight integration of the WDM, SONET and IP layers allows service providers to control customer traffic using a wider variety of network parameters, therefore offering more meaningful service-level agreements to their customers.