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Upgrading to a real-time IP network

Posted: 16 Jan 2004 ?? ?Print Version ?Bookmark and Share

Keywords:real-time ip? ip network? web? internet? atm?

The Internet and IP networks have grown tremendously during the past decade; fueled primarily by best-effort applications like e-mail, Web browsing and non-critical data services. Despite this impressive growth, IP networks have not succeeded in supporting real-time applications and converged legacy services, which demand greater levels of stability and reliability.

As service providers look to decrease the number of backbone networks, they require a routing solution that supports the graceful migration of legacy Layer 2 services to IP while providing the stability, QoS, reliability and convergence improvements to support new real-time IP services.

Finances and technology are driving the migration to an IP-based network. New IP services are critical to improving top-line revenue. Decreasing the number of networks needed to support legacy and new real-time services is essential to improving profitability. New IP/MPLS routers are capable of delivering telco-grade availability, ATM-like QoS, convergence improvements and scale.

Service providers recognize that profitability depends on achieving higher margins from real-time services and cost efficiencies of converged networks. Best-effort services such as e-mail can withstand the significant delay, packet reordering and outages common in most IP networks. But real-time services, such as VoIP, video, streaming media and interactive gaming, demand a higher level of network performance with low latency and high network availability. Essential services that currently reside on ATM and frame-relay switches cannot be transitioned to a network that is neither stable nor delivers the QoS-level agreements required.

Network disruptions were acceptable for popular best-effort applications such as e-mail and Web browsing because those applications exist independently of variations in latency and throughput. But new applications like interactive gaming, VoIP, music and video-on-demand are already commercial services for carriers. The newer class of services will not tolerate the service interruptions that are accepted in best-effort traffic. As real-time applications continue to increase, network outages will become more visible, and service providers will have to react or lose customers to other carriers.

For IP networks to support demanding real-time applications and converged legacy networks, carriers must overcome five obstacles: poor router reliability, lack of link protection, disruptive operations, slow convergence time and multiservice support.

Router reliability

Two primary causes of IP network downtime are router hardware and software failure. In contrast to traditional central-office equipment such as voice and ATM switches, IP routers were not designed to support carrier-grade 99.999 percent availability.

To accommodate the lack of telco-grade reliability, carriers have become accustomed to the costly practice of duplicating core routers in their points of presence to compensate for the lack of reliability in a single router. Next-generation routing platforms have achieved 99.999 percent availability by providing full hardware and software redundancy in a single router.

A key component is delivering fail-safe route controller protection. Non-stop routing implementations use one or more backup route controllers to maintain the pertinent routing state and supporting adjacencies with surrounding routers, preserving connectivity to peers. In-service software upgrade, whereby a carrier loads a new software image on a backup route controller while the primary continues to operate, is also a requirement.

A study by the University of Michigan observed that link failures accounted for 32 percent of the outages in a large regional IP network. Networks have relied on the ability of routers to route around failed links. But there's a glitch: The approach produces unacceptable disruption to real-time and converged services.

To avoid triggering protocol convergence and affecting services, link protection must occur locally and achieve failover in less than 45ms. Powerful new SONET/SDH link aggregation mechanisms such as composite links enable up to 64 physical links to be grouped into a single logical link.

Another major reason IP networks fail has to do with operational changes, such as software and hardware upgrades, link expansion and configuration changes.

A new generation of core routers offers in-service hardware scalability and hitless in-service software upgrades. By migrating to such platforms, carriers can eliminate hardware and software upgrades as a source of disruption in the network.

- Esmeralda Swartz

Director of Strategic Marketing

Avici Systems Inc.

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