PORTLAND, Ore.There was a time when a dredge snagging an undersea optical cable or an earthquake popping a fiber's connector would bring down the whole network. But no more. Carriers are increasingly turning to mesh topologies to route data and voice between nodes, allowing for self-healing connections that automatically reconfigure around broken, blocked or overloaded paths by "hopping" alternate node-to-node routes to the desired destination.
With all the buzz about wireless mesh networks, you might have thought that optical networks were still point-to-point or rings, but nothing could be further from the truth. Optical networks worldwide are quickly moving to mesh topologies.
"Mesh networks are the future. And at the metropolitan level, mesh networks are also making fast progress," said Ronald Kline, research director for optical networks at Ovum (Boston). "Eventually, mesh networks will be ubiquitous--from metro to regional to continental, intercontinental and global, they all will use the mesh topology."
Like routing intercontinental airline flights either around or over the pole, fully connected global mesh networks can route traffic as congestion and failures allow, providing nearly 100 percent network availability, as well as fail-safe security.
Ciena Corp. (Linthicum, Md.), AT&T, Verizon Business, Internet 2 newbie Tata Teleservices (India) and more than 30 other carriers and service providers are switching from antiquated, point-to-point or ring networks to mesh topologies that provide fail-safe connections Ciena describes as "survivable."
"The biggest benefit from our mesh network topology is that we form survivable connections that still work even after multiple simultaneous failures," said James Zik, senior product marketing manager for Ciena's optical transport products.
"Many of our customers use five-degree nodes that have five fiber-optic connections between them, instead of a ring or just one eastbound and one westbound connection, so that users don't lose connectivity even when there are multiple failures," Zik said.
Mesh for optical fiber networks employs all the same tricks as ad hoc wireless networks to ensure connectivity, including the ability to add new nodes arbitrarily, with the workload automatically distributing itself to make optimal use of new routing possibilities.
However, mesh topologies for optical fiber networks do not have to deal with the mobility of wireless nodes, thus providing even better survivability over wireless networks.
Ciena claims the biggest global market share to date, but success is also being pursued by other equipment providers. They include Sycamore Networks Inc. (Chelmsford, Mass.), which connects Sprint's backbone optical mesh, and metropolitan mesh network providers such as Alcatel-Lucent (Paris).
"Ciena is by far the largest provider of mesh optical-backbone networks, and ours are the most mature, using over 9 million lines of code we have developed over the last seven years. But we are not alone anymore. The advantage of mesh networks is forcing our competitors to start offering similar systems," said Zik.
Ciena's mesh network is operated by what the company calls an intelligent control plane. Carriers merely unplug their optical fibers from their current switch and replug into Ciena's CoreDirector Multiservice Switch. The intelligent control plane then redeploys core backbone optical fibers as multidegree nodes and operates them as one large network with shared resources--anywhere from metropolitan to regional, continental, undersea intercontinental or complete global networks, connecting domains in Europe, Asia and Africa to domains in the Americas.
"Our software automatically reroutes traffic on alternative paths whenever there is a failure, within millisecond time frames," said Zik. "We also increase the network availability by a factor of 10, while we simultaneously reduce the operational costs, because all the rerouting around trouble spots is completely automated.
"To configure a network, Ciena's point-and-click software interface enables a network operator to merely click on a starting point, then click on an endpoint, choose the service and the amount of bandwidth required, and activate the connection, after which the mesh takes over to ensure survivable connections, even in the presence of multiple failures," Zik explained. "You don't have to go to the separate network nodes to configure them--that is all completely automated."
Ciena's largest deployment is AT&T's global mesh, but its most recent global mesh is being built for Verizon Business.
Ciena currently connects three CoreDirectors in the United States to four CoreDirectors in Europe. Six undersea fiber-optic cables provide fail-safe connectivity across the Atlantic, with an extra layer of protection in Europe, where one centrally located CoreDirector is connected to all the others there. Now, even if multiple undersea cables are damaged, the network survives. Ciena also claims that Verizon's resultant network availability was also improved to six nines (99.9999 percent).