Cisco Introduces Overlay Transport Virtualization

Datacenters today are interconnected via any number of different public and private connection mechanisms. Cisco Systems (NASDAQ: CSCO) is now adding another choice to the mix with its new Overlay Transport Virtualization (OTV) technology that enables virtual datacenter migrations using the company’s Nexus 7000 switching gear.

With OTV, Cisco is aiming to make it easier to connect datacenters with a technology that will enable data to flow from one to another regardless of the underlying transport mechanism.

“From a technology point of view, what OTV does is it encapsulates the Ethernet frames or LAN traffic inside an IP packet and then that can be sent across any existing mechanism a datacenter has,” Craig Griffin, Cisco’s director of product management, told

Griffin added that OTV traffic can traverse fiber, MPLS or even conventionally routed IP networks, making datacenter connections a matter of simply issuing some OTV commands.

OTV is an extension of Cisco’s Data Center Interconnect (DCI) technology. Rival networking vendor Juniper Networks (NYSE: JNPR) announced its own version of a datacenter migration technology in 2008.

“Other solutions, MPLS or otherwise, often involve either complexity, time or both,” Craig Huitema, director of marketing at Cisco’s datacenter group, told “What’s cool about OTV is whatever the existing connection model is, OTV can work on top of it so a customer isn’t required to do something overly complicated.”

OTV has a number of potential use cases for datacenter-to-datacenter connectivity. One use case involves virtualization and VMware’s Vmotion technology for migrating virtual servers across physical machines. Vmotion typically migrates virtual servers across physical servers on the same LAN, Griffin noted.

“So if you want to move a virtual server across datacenters you have to have a way of connecting via a LAN extension,” he said. “So with OTV you can now enable that and do long-distance Vmotion.”

With datacenter-to-data center migration, network administrators can enable their networks for disaster recovery as well as the overall load balancing of applications.

Currently the OTV solution requires that datacenters have Cisco Nexus 7000 switches at both ends of the migration. Cisco first introduced the Nexus 7000, powered by the NX-OS operating system, in January 2008. The OTV feature is enabled as a license key on NX-OS for Nexus 7000 users. Cisco plans to make OTV available on other platforms at some point in the future.

Between datacenters and under the Nexus 7000, administrators can have any combination of networking gear.

“Everything in between is essentially transparent,” Griffin said. “You could have a multi-hop router over a server provider IP network and none of the equipment in the middle needs to know that you’re running OTV over it.”

Sean Michael Kerner is a senior editor at, the news service of, the network for technology professionals.

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