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Feature Article
April 2001


The New Carrier Core: Make It Truly Scalable


Due to declines in legacy business and a perceived market slowdown, carriers are under heavy competitive pressure to grow their networks in a way that squeezes maximum margin out of their existing legacy services while readying for the inevitable growth of more profitable IP-based services. But the mismatch is widening between current-generation router performance and the demand for more capacity to support IP traffic, new services, and to keep pace with advances in the optical transport network. Emerging next-generation routers bring truly scalable routing to the network core in order to support these new requirements.

While awaiting those revenue-driving new IP services, we've already seen Internet traffic mushroom. Fueled by swarms of new users and faster access speeds, it's doubling every few months, expected to be a full 90 percent of network traffic by 2003. That translates to a 150-million terabyte per month load by 2003 -- up from a mere 350,000 terabytes per month in 1999, according to industry estimates from analyst firm RHK. So as carriers offer best-guess forecasts of future bandwidth requirements and which services they'll need to support, competitive carriers now should be considering shifting to this new routing paradigm.

The solution must deal with a hydra-headed dilemma facing carriers. First, it must accommodate the unpredictable nature of the Internet itself. It must be able to increase the capacity of network links to carry swelling data traffic. It has to let carriers provision new services quickly to take advantage of fast-surfacing opportunities to increase profitability. And, bottom line, it needs to translate into minimized operational (and capital) costs needed to run networks supporting these new requirements. To appreciate the potential, compare the traditional method of scaling to what is possible with a legitimately scalable, carrier-class, multiservice core backbone.

In the past, service providers met bandwidth demand by increasing the interface speeds of existing routers or adding more routers. This model is increasingly cost prohibitive and impractical for several reasons. Using multiple routers and/or displacing a core router with the next bigger box disrupts the network and negatively impacts the provider's ability to deliver reliable service.

For example, a customer has a fixed-configuration router with eight slots, each with OC-48 connections. To add another OC-48 interface, the customer must buy another such router. Once installed, it must be interconnected to the first by two OC-48s. To get one more OC-48's worth of capacity, the customer has to purchase a new router and three OC-48's worth of capacity.

This method also uses valuable router interfaces just to interconnect routers. And as the router cluster grows, more ports are needed, only compounding the problem. Clustering increases the cost per port since the ports used for interconnection are not serving customer links (and therefore not generating revenue). This is an expensive proposition, and causes disruption to the network, as well as the need to dispatch scarce IP talent to install and configure new routers.
Current fixed-configuration routers are not well suited for the core of large service provider networks, and are increasingly being pushed to the edge of large networks, or employed only by smaller providers. Carriers no longer can afford to run their networks constrained by such underlying network topology and are seeking equipment footprints that can scale along with requirements while the network remains in service.

Carriers have no choice but to deploy scalable routers to future-proof their networks and grow bandwidth on demand, and it was only a matter of time before they began adopting a non-disruptive and incremental method of scaling. New core routers incorporate a distributed architecture with backplane interconnects. This allows for continual in-service upgrades so a carrier can easily grow from OC-3 to OC-192 -- or even OC-768 -- in the same platform. The undeniable reliability of such a system, combined with advanced quality of service (QoS) and multi-protocol label switching (MPLS) capabilities, lets carriers support legacy services and sell new revenue-generating services such as VPNs, VoIP, and video-on-demand (VoD).

A key differentiator of next-generation routers is the ability to perform at wire rate, regardless of route prefix length, route table size, MPLS label swapping, QoS, or multicast. This means QoS needs to be hardware-based and buffers must be dynamically configured to support both real-time, delay sensitive and non-real-time, delay-insensitive applications. For competitive differentiation, service providers obviously need to possess advanced QoS features in order to offer enhanced service level agreements (SLAs).

Using inherently scalable technologies at the heart of the network will evoke multiple benefits with tangible reductions in both capital and operational costs, as well as increased operational efficiency, performance and reliability. This will become more apparent as the solution grows in size, since capacity grows on a linear basis. In large and high-speed networks, where the rate of growth is high or likely to be high, the use of scalable core routers will prove a compelling core-network value proposition.

A scalable router approaches the issue of growth in a fundamentally different way than traditional architectures and offers an array of advantages by affording the ability to scale over time as a single router. Such specific operational cost savings include:

Administration of Route Tables
The burden and operational cost of making changes to route tables and having to send out scarce IP experts is eliminated. A single route table is maintained even when the router itself has scaled to many hundreds of interfaces and multiple routers' worth of capacity.

Network Simplification
Having a single router with a single route table dramatically simplifies the network for upgrades, design, management, and operations. Power, cooling, maintenance, and spare requirements are static. These are unknown quantities in a multi-router architecture. The design process can be reduced to minor revisions each year, rather than an ongoing planning and product evaluation process involving lab and architecture groups.

Day-to-Day Operations
A network designed with a scalable router will make it easier to back up configuration files, easier to apply new system-wide policies, and easier to cable manage. Day-to-day operations will be simple and familiar to operations staff. As the POP scales in size, the router will still look the same and have the same field support requirements.

Software Upgrades
Networks are constantly changing to keep the service offerings competitive and feature rich. Software upgrades therefore will be a necessity and something that operations will be asked to perform regularly. By using a secure software upgrade solution with fast fall back (dual servers, dual images), a single, scalable router can provide simple and reliable upgrades. The multiple-router approach is more complex due to node count and multiple hardware and software revisions.

Time To Provision
New service offerings can be rolled out quickly. Time-to-market advantage will be a critical success factor for both incumbent carriers and new service providers hoping to compete with the market leaders. The increased abundance of inexpensive bandwidth will provide nimble carriers with the opportunity to quickly introduce new services and fill up network pipes with attractive offerings. We are rapidly migrating from bandwidth expansion to service creation.

The new carrier core will be comprised of routers specifically designed for carrier and ISP backbones. These routers will offer the scalability, resiliency and port density to enable just-in-time bandwidth provisioning, high reliability, and network availability -- all with the quality of service needed for carriers and ISPs to support mission-critical applications of the future. 

Esmeralda Swartz is the director of strategic marketing at Avici Systems, Inc., a developer of core routing solutions providing scalability, resiliency, and port density; and enabling just-in-time bandwidth provisioning, high reliability, and the quality of service needed for carriers and ISPs to support mission-critical applications of the future such as video streaming, VoIP, and Multi-protocol Label Switching VPNs. 

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