Alcatel-Lucent Converging Optical, IP Transport

As Internet traffic continues to grow, how should carrier networks expand to keep up with demand?

One solution is to continue to roll out more routers and move to 100 Gigabit Ethernet (GbE). Another solution is to get better efficiency out of both the optical and IP networks that service providers use already. That’s the latest effort undertake by networking vendor Alcatel-Lucent.

Most carriers have a mix of optical and IP networks and, according to Alcatel-Lucent (NYSE: ALU), there are many inefficiencies along the transport path.

As a result, the company is proposing a new strategy for further converging the optical backhaul networks and the IP networks that carriers use. According to Alcatel-Lucent, a converged approach can save carriers money and provide them with more optimized use of their entire network.

Houman Moderres, IP marketing director at Alcatel-Lucent, explained that in modern carrier networks, there is an IP domain consisting of edge and core routers, managed by an IP network management platform.

There is also an underlying, separately managed optical transport infrastructure: This includes Reconfigurable Optical Add-Drop Multiplexer (ROADM) and Dense Wavelength Division Multiplexing, or DWDM technology, along with optical cross-connects that interconnect and carry the traffic.

“Much of the traffic ends up going to a small number of destinations in today’s Internet model, to a peering point or a video head end or a datacenter,” Moderres told “So there is a significant amount of inefficiency in the unnecessary processing that happens in transit traffic through core routers.”

As an analogy, Moderres said the current IP/Optical carrier network topology operates as though it were a train en route to a destination — but which is slowed because it stops at every station. The more optimal route would be to just take an express train.

“That’s the type of efficiency that would be enabled if there were closer collaboration between the IP and optical domains in a transport network,” Moderres said. “Traffic doesn’t need to zigzag across core routers. On a selective basis, service providers can have optimized paths.”

“That would reduce the number of optical electrical conversions, reduce the power that is used and the ports that are required on core routers where they aren’t adding value to the traffic that is traversing,” he said.

Consequently, Alcatel-Lucent is proposing increased collaboration and visibility into both the IP and optical transport domains. Part of that is being done through control and data plane integration, so that the optical network managers will have IP visibility — and vice versa.

“We can’t keep building networks the same way we have and expect them to scale,” Moderres said. “Having an inefficient transport infrastructure where the optics and IP aren’t closely integrated … will be a relic and we’re now taking the first step in breaking down the barriers and enabling new levels of integration.”

Moderres noted that the convergence of IP and optical involves what he referred to as “grooming” options that optimize traffic flows. One such option is the IP over DWDM (IPoDWDM) approach that router vendors like Cisco (NASDAQ: CSCO) and Juniper Networks (NASDAQ: JNPR) are already deploying.

IPoDWDM is an approach that Moderres referred to as “lambda-level” grooming — that is, at the wavelength level — and is also a capability that Alcatel-Lucent already offers. He explained that what it involves is colored wavelength interfaces that are directly integrated by the core routers.

“Our view is that we see IPoDWDM as part of the solution, but whereas it optimizes transport efficiency for some service mixes in some networks, it is not by itself sufficient,” Moderres said.

As a result, Alcatel-Lucent is now aiming to offer grooming at a deeper port level so traffic coming in can be assessed and optimized.

“Basically what it means is much high utilization within the transport infrastructure and much less wasted bandwidth,” Moderres said.

Part of the port-level grooming is based on technology that Alcatel-Lucent is now deploying while a sub-port level of grooming is set to be available in 2010. At the sub-port level, Alcatel-Lucent will be leveraging the ODU-Flex specification, which will be finalized in 2010.

Moderres explained that optical data units (ODU) are the logical containers within the optical transport infrastructure. ODU will be expanded with the ODU-Flex standard to go beyond the limitation of fixed SONET/SDH containers, and be variable in size.

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