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FEATURE SDN


Programming the network


Interest in transport software-defined networking has grown over the past year, but Roy Rubenstein finds there are still challenges to be overcome


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arriers are exploring a fundamental change to how they manage and operate their networks.


Distributed routing protocols


that enable connectionless packet-based networking have long been the norm for carrier traffic. Now operators are exploring the idea of a central control instead of sprinkling intelligence across the equipment in their networks. Having a global view promises


operational benefits and more efficient usage of network resources. Soſtware-defined networking (SDN) is at the core of the change – but, for it to be used, it must first be extended to the wide area network (WAN). At its grandest, carriers view


SDN as a way to optimise their complete infrastructure: network, storage, and processing. ‘Te global orchestration of their compute, storage, and networking is the Holy Grail for the network providers,’ says Chris Liou, vice president for network strategy at Infinera. SDN is still in its infancy but the


technology is already proven in the data centre, where SDN enables search-engine and content service providers to cope with the demands of traffic flows created by virtualising servers and storage.


A numbers game


Te biggest data centres can have as many as 100,000 servers running even greater numbers of virtual machines. Te network must cope


18 FIBRE SYSTEMS Issue 1 • Autumn 2013


with workflows moving between servers but also between sites – which partly explains the interest in transport SDN. Te data centre, while vast in


scale, is a more confined environment than the WAN. Equipment in the data centre is limited to a few types only while networking is largely Ethernet. Transport SDN, in contrast, has multiple networking layers, multiple vendors’ equipment, and many networking protocols and domains. ‘Applying SDN technologies on a


complete carrier network is a big challenge,’ says Jörg-Peter Elbers, vice president for advanced


SDN is still in its infancy but the technology is already proven in the data centre


technology at ADVA Optical Networking. Operators are interested in


transport SDN for several reasons. BT points out that operators could already manage networking layers using control plane protocols such as Generalised Multi-Protocol Label Switching (GMPLS). ‘Control plane research has been


around for a long time. We don’t use it; we could, but we don’t,’ says Andrew Lord, head of optical research at BT. ‘We are still sitting with heavy operational expenditure-centric networks, especially optical.’ BT views SDN as a way to reduce operational costs, especially in


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