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40G: The Fastest Connection You Can Get?

The fastest connection an enterprise could get was the venerable T1, with its 1.54Mbps transmission speeds. Those days are long since gone, as faster speeds available over SONET based optical carrier (OC) and Ethernet networking technologies.

The fastest for many carriers and enterprises is OC-192 and on the Ethernet side it's 10GbE, both of which provide 10Gbps (10G) of networking connectivity.

But there is another speed. At the top end of the network connectivity food chain are 40G optical technologies, such as OC-768. Ethernet doesn't yet have an official 40GbE standard, though one is in the works as is one that will scale to 100GbE.

With the promise of even faster speeds, why would an enterprise push 40G at this point when it's future is largely uncertain? It depends on who's answering the question.

Networking heavyweights Cisco and Juniper claim to have a number of customers for 40G already. Cisco has announced 40G deals with Comcast, Yahoo BB (Japan-based broadband), and Deutche Telecom's T-Com unit. Juniper meanwhile has announced its own 40G deals with NTT, CERNET and MCI.

"Demand for OC-768 is growing dramatically," Stephen Liu, manager of service provider technical marketing at Cisco told InternetNews.com. "The proliferation of consumer broadband growth, along with the advent of IP video, has begun to exhaust what once was excess fiber in carriers."

The challenge

Ramping up to 40G speeds over existing optical networks and fiber faces a number of challenges and barriers, among which include technical issues with the optical wavelengths over which 40G networks can traverse.

According to Helen Xenos, senior marketing manager for Optical at Nortel Networks, OC-768 is primarily transported using 40G Time Division Multiplexing (TDM) .

Xenos said to attain four times the bandwidth, the signal in a 40Gbps TDM solution has four times the baud rate with four times less light entering the receiver. The result is that a 40G TDM may end up with only 25 percent of the reach of a 10G solution.

The solution is to do OC-768 transmission over Dense Wavelength Division Multiplexing (DWDM), which is equivalent to 10G transmissions. Nortel has such a solution in the works, while Cisco and Juniper have their own approaches to dealing with the distance issue.

Transporting OC-768 over "long-haul" inter points of presence (POP) connections -- hundreds or thousands of miles -- is a concern, because there is likely to be non-40G-capable infrastructure along the long-haul route.

Juniper's solution is to bind four OC-192 (10G) connections into what Alan Sardella, the company's senior product marketing manager, referred to as a virtual OC-768 connection. In this setup, he said, data is transported over four OC-192 interfaces, which are then combined into a single traffic stream on the router.

Another challenge for 40G comes from Ethernet. The IEEE has a high-speed group working on 40GbE and 100 GbE.

"The new standards are roughly two years out," Cisco's Liu said. "With the current velocity and acceleration we are seeing with 40Gbps, there will be plenty of deployments on OC-768 by then."

That said, Cisco will still support high-speed Ethernet when available, for the places where it is applicable. Liu argued that the work done in the IEEE for 40GbE is focused on server applications and short-distance interconnections. On the other hand, Liu expects that OC-768 will continue to be the standard for 40Gbps long-haul, regional and metro network applications.

Juniper's Sardella also still sees demand in OC-768 for the foreseeable future.

"Even when/if a 100G standard is ratified, this certainly doesn't mean the end of 40G interfaces," he said.

"Service providers need a range of interface speeds to meet the demands of many different network and service types and deployment scenario. This is why even on our largest T-series routers, Juniper offers interface speeds all the way down to DS3."

About that outlook

While there are still a few years until a 40G challenger emerges, there is another issue that may be holding deployment back: cost.

Dell'Oro Group optical analyst Jason Suey said the deployment of 40G has been limited to select parts of networks where a service provider can utilize the high capacity that 40G provides.

"Since the price of 40G is still over four times the cost of 10G, I don't anticipate rapid widespread adoption of 40G anytime soon," Suey told InternetNews.com. "The sweet spot of when you may see acceleration in volumes of 40G is two-and-a-half times the price of 10G."

That sweet spot might be here soon, according to at least one network vendor.

"Bandwidth growth is driving 40G as it provides lower total price per bit for transport," Alcatel-Lucent spokesperson Dick Muldoon told InternetNews.com. "Our analysis shows that the price for 40G vs. 10G has reached the prove-in range over the last year."

Whether 40G connectivity every truly becomes pervasive or not has yet to be determined. Similarly it's not yet clear which vendor from a technology or deployment point of view will be the big winner in the 40G bandwidth sweepstakes.

"There seems to be a lot of vendors chasing a very small market, since live deployment of 40G has been limited to a handful of service providers," Dell'Oro's Suey said.

"As more vendors bring their 40G solutions to the market, the jury is still out in determining who will be more successful. I would tend to think that vendors that are currently selling 10G to tier-one service providers may have a slight advantage since the relationship has already been established."