@fibresystemsmag | www.fibre-systems.com


FEATURE SDN


EXTENDING OPENFLOW FOR TRANSPORT SDN


The Open Networking Foundation (ONF), founded in 2011, is tasked with commercialising the OpenFlow specification for controlling switches that began life as an academic exercise. The ONF has since set up


the Optical Transport Working Group to define the OpenFlow extensions needed to control the optical layer, to create a multi-layer control plane. ‘OpenFlow, as it is now, is


very packet-focused – Layer 3 and Layer 2,’ says Lyndon Ong, chair of the Optical Transport Working Group. ‘It was always a natural, technical extension to look at controlling Layer 1 and Layer 0.’ The Working Group


delivers set work each quarter. The first quarter’s work concentrated on use cases and now under development is an architectural information model that includes the OpenFlow extensions. Three use-cases have


been chosen. An enterprise owning both the network and the data centre is the first. The second is network virtualisation, where a carrier provides connectivity for third-party data centres. Such networking must be allocated alongside existing services, requiring partitioning of resources across multiple users. The final use-case is not service-related, but addresses the broader topic


of packet/optical integration. The Working Group is


pursuing two approaches for the transport extensions: the direct and abstract models. Using a direct model, the


SDN controller talks to each network element, controlling its forwarding behaviour and port characteristics. The abstract model controller, in contrast, may talk to a network element, or an intermediate controller or ‘mediation’. ‘This presents an interface as if you are talking to a bunch of network elements,’ says Ong. ‘But in fact it [mediation] is doing filtering and translation of the requests coming down


[from the SDN controller].’ The direct model


interests certain ONF members due to its potential to reduce the cost of networking equipment by moving much of the software from each element to the controller. Factors favouring the


abstract model include its suitability to use-case 2 where a client can partition resources and has some, but not complete, visibility into the network. Equally, the abstract model limits how much the SDN controller is exposed to the underlying network’s details. Coriant has tackled this


issue with its Intelligent Optical Control solution. The vendor has added a


form of mediation – software that sits below the SDN controller – that provides planning and routing smarts across the transport network. ‘It can leverage the full


performance of the WDM network because it knows all the planning rules,’ says Uwe Fischer, CTO at Coriant. ‘It does multi-layer optimisation across the transport layers.’ Coriant has added intelligence this way since it believes there are transport network- specific aspects that cannot be generalised easily. The ONF Working Group


expects its final model and extensions to support the direct and abstract models. Meanwhile, the work is to be completed by April 2014.


terms of soſtware development. Te standard’s open philosophy also promises to fulfil a longstanding desire to avoid being locked into a specific vendor and being able ‘to buy from whomever we want to’, says Lord. Other reasons for operator and


content provider interest in transport SDN include the prospect of a broader optimisation of the network resulting from having a centralised view. Hans-Martin Foisel of Deutsche


Telekom, and chair of the Optical Internetworking Forum’s (OIF) Carrier Working Group, highlights this broader optimisation as a major attraction. He also stresses SDN’s ability to simplify operators’ operational support systems (OSS), and the efficiencies resulting from SDN’s separation of the network’s layers. According to a recent study by


Infonetics Research, almost all the major operators are evaluating SDN or plan to do so within the next three years. Te market research company surveyed 21 leading incumbent, competitive, and


independent wireless operators, and found that 86 per cent are confident they will deploy SDN. ‘Perhaps the most exciting benefit


of SDN for carriers is that it allows them to reinsert themselves in the world of IT instead of having the world of IT happen to them,’ says Richard Brandon, chief marketing officer at Intune Networks.


SDN’s role


SDN segments the network into three planes: management/ applications; control; and data. SDN centralises the information for control, implemented using an SDN controller. Te approach gives the carrier a better perspective on resources across the different networking layers. Te three-layer SDN model is


defined by the Optical Networking Foundation (ONF), which is focused on networking and developing the OpenFlow specification. OpenFlow is one approach by which the middle layer soſtware communicates with the physical or virtual network. ‘With OpenFlow you can


2 1 PLUG PUSH ridgemount.com ridgemount 01869 277233 technologies @ridgemounttech Issue 1 • Autumn 2013 FIBRE SYSTEMS 19 PLAY


HOME ADVANTAGE VENTURI®


Rapid connectivity FTTH solutions


3


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36