Futureproof the edge: With today's accelerating traffic demands and cutthroat competition, the diversity of edge devices is a barrier to growth and profitability. Service providers need a new solution

The demands on service providers have never been greater. Internet traffic is doubling every 100 days, the Department of Commerce reports. Just to stay even, service providers must expand their facilities at an unprecedented rate.

The explosive growth has had a profound effect on wide area technology. Data has deposed voice as the driving force in WAN design, and packet switching has replaced time division multiplexing (TDM) as the basis for bandwidth management and service provisioning. Internet protocol (IP) is now the common language of electronic commerce, while asynchronous transfer mode provides economical transport for data, voice and video.

At the transmission layer, optical fiber is replacing copper throughout the public infrastructure. Sonet/synchronous digital hierarchy (SDH) backbones running at OC-48/STM-16 (2.5 Gb/s) are now commonplace. Dense wavelength division multiplexing (DWDM) promises even greater capacity.

Meanwhile, deregulation has spawned competition in all shapes and sizes. New players are intent on stealing customers from established providers. Incumbents are rushing to defend their turf and penetrate new markets.

To attract and hold customers, service providers must offer an ever-lengthening list of services-Internet access, frame relay, native ATM, circuit emulation, virtual private networks (VPNs), systems network architecture (SNA), and emerging services such as voice over IP. Time-to-market with new services has dropped from 30 months to nine months and continues to fall.

But just rolling out new services isn't enough. To compete successfully, service providers also must promise lower prices. And therein lies the challenge. How can service providers expand their networks and support more services while driving down costs?

The battle at the edge The battle to deliver more services at lower cost must be fought at the edge of the public network. The edge is where the service provider meets the customer and differentiates itself. The core of the network serves the edge by providing transport (Figure 1).

Core switches move traffic between the edges to support IP traffic and ATM cells with the appropriate quality of service (QOS). Edge devices handle myriad protocols and media types, including frame relay, IP, SNA and native ATM. Edge devices take voice calls from PBXs, voice over frame relay and voice over IP. They terminate connections as slow as DS-0 (56 to 64 kb/s) and as fast as OC-12/STM-4 (622 Mb/s).

Edge devices cooperate with customer premises equipment to manage congestion, set up connections, negotiate QOS parameters and use expensive access circuits efficiently. And now they must convert everything to a consistent set of IP and ATM flows into the core.

A barrier to growth Unfortunately, today's edge devices are highly specialized, and carriers need a different platform for each service-a frame relay switch for frame relay traffic, a frame relay access device for SNA, a router for IP, an ATM switch for ATM and an access concentrator for voice. This division of labor reflects the evolution of WANs. As each new service was conceived, a special platform was created to support it.

But the number and diversity of edge devices is a problem. Each platform consumes space and power. Each must be managed individually. And often, each platform represents a separate routing node.

A point of presence (POP) at the edge of the public infrastructure can be a complex network (Figure 2). Ensuring efficient routing and resource use even within the POP is a daunting and operationally expensive task. To make matters worse, many vendors have introduced proprietary protocols to unite the two.

Furthermore, lack of integration between IP and ATM compromises network performance. ATM switches build Layer 2 links between routing nodes, and routers find Layer 3 paths through the network, but no attempt is made to coordinate the two. That means IP and ATM are often at odds, resulting in inefficient bandwidth usage and diminished QOS.

Worse yet, the spread of specialized devices impedes service growth and flexibility. Some products that support broadband connections are inefficient at narrowband speeds. Certain legacy frame relay switches won't accept ATM connections, and they will not scale to broadband speeds.

Every new service or performance enhancement entails more platforms and added complexity. Equipment and operating costs rise faster than revenue.

Preparing for the future To grow and prosper in today's overheated market, service providers must futureproof the edges of their networks. They need a next generation WAN edge switch that supports both today's and tomorrow's services and ends the proliferation of separate platforms. They need a solution that will adapt flexibly to future demands without requiring a crystal ball.

POPs vary widely in size, and access speeds range from kilobits to megabits per second. So the new switch must be more scalable than existing products, support interfaces from DS-0 to OC-48c/STM-16 and expand to accommodate thousands of low-speed ports.

The new switch must be more versatile than current products. Besides the usual IP and frame relay features, it must accept legacy protocols such as SNA and enable emerging services such as VPNs and voice over IP.

To help service providers diversify, the next generation WAN edge switch should handle voice traffic as effectively as data. It also should support standard PBX connections, voice over frame relay, voice over ATM and voice over IP. And it should allow interworking on numerous dimensions, not only between frame relay and ATM,but also among the various voice technologies.

Most important, the next generation edge switch should include Layer 2 switching and full-function Layer 3 routing in a single node (Figure 3). With only one node per site, network operation becomes much simpler, less costly and more responsive to change.

For improved end-to-end performance, the new switch should tightly integrate IP and ATM. Using Tag Switching from Cisco Systems Inc., which encompasses multiprotocol label switching, an emerging standard from the Internet Engineering Task Force, ATM switches and IP routers can cooperate to build optimal paths through a multiservice network.

Cost-effective migration Most service providers, even relatively new ones, have a huge investment in existing equipment. Few, if any, can afford a complete forklift upgrade just to boost performance or add a new service. Therefore, to be useful in existing networks, the next generation edge switch must have network management capabilities that let service providers manage within a multivendor environment. Ideally, it should accept interface modules from earlier products so POPs can be expanded at a minimum cost.

Beyond the POP, the WAN edge switch must work with existing CPE. In addition to basic interface and protocol compatibility, it should support routing protocols and congestion management techniques, cooperating with CPE to optimize both bandwidth use and QOS.

Finally, the WAN edge switch should share a network management system with core switches and CPE. Consolidated network management means reduced operational complexity and lower life-cycle costs.

With a unified view of edge switches and premises gear, service providers more easily can support managed services that include customer-located equipment.

Breakthroughs required To fulfill its promise, the WAN edge switch must incorporate a complete selection of interfaces and protocols. A successful implementation, therefore, begins with an extensive library of proven network technology and know-how. It also calls for significant innovation in at least two areas.

First, a universal chassis is needed. The same enclosure and backplane must accommodate interface speeds up to OC-48c/STM-16 and grow gracefully from a few ports to hundreds or thousands of ports. The chassis should include a complete set of high availability features including Sonet/SDH automatic protection switching, redundant power supplies, hot redundancy of common components and 1-for-N backup of interface modules.

Second, the WAN edge switch requires a breakthrough in internal interconnect design. To scale from DS-0 to OC-48c/STM-16, the next generation switch needs a switching architecture that can scale cost-effectively at all performance levels and configurations.