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SDN Enables Routerless Network

Sep 12, 2013
Sue Kim - gu
Sue Kim - gu About the author

John Dunne of Intune Networks discusses the Routerless Network, using OpenFlow-enabled SDN to do what everyone said couldn’t be done.

Among the many cited manifestations of Software-Defined Networking (SDN), the Routerless Network perhaps generates the most quizzical reactions. A Routerless Network is a network of MAN or WAN dimensions that interconnects data centres without any requirement for routing tables, routing decisions, or convergence of distributed routing information. All packet-forwarding smarts will be delivered from a centralised controller to populate forwarding tables at the edge of the MAN – as if the Metro Network were a simple, single switched LAN. Imagine a Metro-area Ethernet that is not just an Ethernet service but an actual Ethernet. This is only possible if ALL routes are available with direct optical connectivity in the first place, obviating the need for a routing decision. A full mesh of optical paths is presented as the holy grail of packet forwarding, replacing routing decisions with load balancing decisions, and this holy grail has finally been reached, using open-source, multi-vendor combinations of technologies to deliver a Routerless Network.

Up to now, the cost of building a full mesh of optical links between all outward-facing ports in several data centres has made this choice virtually impossible. However, Intune has invented a means to virtualise the full mesh of optical paths so that they are all available, but not permanently "on." This is the first physical change proposed in the optical layer of the network since the invention of fiber optics 40 years ago. Intune uses the fiber to build a packet-forwarding fabric that uses bursts or sub wavelengths to create and pull down optical paths in response to packet queues at a rate of microseconds, tuning commodity lasers at a rate of nanoseconds to achieve this. One of your favorite professors told us a few years ago that it couldn't be done.

Intune recently demonstrated how servers with OVS installed can be operated by hypervisor technology to move virtual machines across the Metro Network in an automated fashion. The packet-forwarding fabric is non-blocking because all paths are available and are scheduled using a distributed scheduling algorithm that is fully asynchronous. There is no requirement for a synchronised clock to allocate time slots, as this would be impractical to operate simultaneously across different wavelengths. And not only is there no routing, but since all paths are available as single hops only, there are no loops possible and thus no need for Spanning Tree, as it is a single switch when operated alone.

The applicability in private cloud solutions is vast. This type of SDN-powered solution, using OpenFlow® to control devices at the edge, can dramatically reduce the cost of building a distributed cloud service for Fortune 1000 enterprises. The cost of complex routing software is removed completely. Simplicity (of both operation and management) is the key to reducing the costs. Another huge benefit is the security of an all-optical connectivity service, where eavesdropper access to higher-layer frames and datagrams is no longer possible. All packet forwarding and processing occurs in smaller, cheaper white-label devices at the edge.

Routerless Networking has captivated the banking and airline industries, which have signed up for real-life participation in end-to-end examples to deliver cloud and IT services. All Open Networking Foundation (ONF) members are invited to join the innovators and eyewitnesses. "They said it couldn't be done." But with the combination of radically fast wavelength tuning, the OpenFlow® protocol, and SDN control, it has.

- John Dunne, Intune Networks

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Sue Kim - gu