Just how fast the Internet is growing continues to be hotly contested. One thing is certain, though. For the major Internet backbone providers, the traffic growth on key routes is beginning to outpace the capabilities of traditional routers.

In the past, carriers upgraded to higher Sonet speeds every two years or so. The number of ports on core routers remained the same, but the data rates that those ports could support went from OC-12 to OC-48, and then to OC-192. After that, things changed.

Service providers do not envision upgrading to OC-768 any time soon. That kind of transmission equipment hasn't been developed because dense wave division multiplexing (DWDM) largely negated that need. Instead, service providers are beginning to look for core routers with a larger number of OC-192 ports.

Traditional core routers don't have enough of the highest-speed ports, so the largest network operators have begun to connect multiple routers together in their core points of presence (POPs). The problem with that is that it wastes a lot of ports (Figure 1). Those ports cost $150,000 or so apiece - and when they're used to connect to another core router within the same POP, that investment doesn't generate any revenue.

A crop of new products - mostly from startups, but increasingly, from dominant vendors (Figure 2) - are poised to address this need. And despite the downturn, this is one category that continues to receive substantial development dollars.

"Three-hundred million dollars went into the startups just this year," says Richard Norman, chief technology officer and president of one such startup, Hyperchip. "That's in addition to what Juniper and Cisco are spending."

Most of the larger Internet backbone network operators say that they expect to issue RFPs for core routers late this year or early next.

When asked what their most important criteria will be, operators are virtually unanimous. Bill Leighton, vice president of development for AT&T Laboratories, seems to be speaking on behalf of an entire industry when he says, "The two biggest capabilities to us are scalability and reliability."

Although that may sound like a platitude, it's a far cry from what formerly was the primary driver behind core Internet purchase decisions. When keeping up with traffic growth was the key challenge, operators were in no position to sweat the details.

Today, though, operators are realizing that that attitude may be what has caused the Internet backbone business to be an under-performer in terms of profitability.

Figure 1: POP build-out with one-way routing Low density routing ... consumed 'talking to itself'

"The [return on investment] on these networks must be greater than for T-bills, and that isn't the case now," says Faizel Lakhani, vice president of product and strategic marketing for Caspian, a startup, still operating in stealth mode, that is developing a high-capacity core router.

Operators now acknowledge that they must improve the overall economics of their IP networks. Router density and scalability play into that by reducing non-revenue generating ports. Some players suggest that the new high-density routers could have an even greater impact by eliminating or reducing the need for aggregation routers.

Reliability also affects router economics by potentially reducing operating expenses. Ultimately, some developers say, a more reliable router also could generate capital savings by eliminating the need for redundant network elements.

Maxed-out routers TeleChoice analyst Liza Henderson divides high-capacity core routers into two subcategories: terabit routers that have higher port densities on a single chassis, and terabit-plus routers that can expand ever further by connecting multiple chassis together.

Some question the need for multiple chassis. "What Juniper and Cisco do is to build a product to hit a broad market. A single chassis will be OK for most operators," says Mark Seery, RHK's program director for switching and routing. "A multi-chassis product can only hit a narrow market."

Seery points out that although Juniper has indicated that it plans to eventually support a multi-chassis design with its recently announced T640 model, company executives claim that customers have not yet asked them to commercialize the multi-chassis version. Seery adds that if silicon development continues to progress, that could minimize the need for a multi-chassis design.

Others say that those who downplay the need for a terabit-plus product are not looking at the issue in the right way.

Figure 2: Core router market share

"If you scale an individual POP beyond the capacity of a single router, it's very obvious," says Hyperchip's Norman. "Others have the problem, but instead of 20 routers in a room trying to be one big router, the problem is spread out so they don't realize it."

Norman argues that a high-capacity core router could pave the way for a new network architecture that would reduce the number of hops that data must make as it travels across the Internet. Currently, most networks have at least three tiers of routers. These include edge routers, to which customers connect; aggregation routers that combine multiple lower-speed connections from edge routers onto a smaller number of higher-speed connections; and core routers, which take traffic in from aggregation routers and send it to other core routers (and vice versa). Considering that traffic must pass through each type of router on its way in and out of the core, its easy to see how the hops can quickly add up.

Currently, Norman says, the average packet goes through 10 routers within the US. "That means you're tying up 10 router ports," he says. "That could drop by a factor of five or six. It won't happen overnight, but we can evolve toward that by putting in a regional super core with five to 10 fully meshed routers around the country. That reduces hops to three or four."

Avici advocates a similar approach. "You can get rid of the aggregation layer if you accommodate the feature set associated with it and provide OC-3 to OC-192 connections on a single platform," says Esmeralda Swartz, Avici director of marketing. Avici recently added a new feature set to its core router to support aggregation-layer functionality such as peering and security.