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FEATURE OPTICAL TRANSPORT


ROADMs move into the cloud


Reconfigurable optical add drop multiplexers will bring flexibility and efficiency to data centre interconnect transport networks, argues Coriant’s Bill Kautz


virtualised and elastic. Evolving consumer services dominated by on-demand streaming services are now hosted in the cloud. Te growth of mobile broadband and the development of the Internet of Tings continue the transformation. But one thing remains the same: an ever-increasing expectation of quality. At the heart of the cloud are data centres where


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storage and compute resources host services and applications, as well as the networks that interconnect with other data centres and end users. Not only is the need for an ever-increasing amount of bandwidth driving how transport networks between data centres are built, but the dynamic nature of service support in the cloud is also driving the need for a programmable and more flexible transport network to match the inherent flexibility in the storage and virtual compute resources provided by the cloud of data centres. Tis article explores different cloud transport network requirements, especially the use of reconfigurable optical add drop multiplexers (ROADMs) in data centre transport networks, and their role in enable flexible dynamic networking for cloud network deployments.


Cloud transport network needs Te requirements for cloud transport networking mirror what’s needed in cloud data centres as they evolve in terms of scale, flexibility, capability, and applications. Te five key transport networking


requirements are: l


High bandwidth – the need for high bandwidth transport between data centres and end-users continues to grow, driven by applications and the growing number of end users. Tis figure will


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he dramatic transformation of service delivery to the cloud touches business users and consumers alike. Business services in the cloud have become


continue to grow as more machines connect to cloud applications. Depending on the application, there are also additional requirements for low latency and low jitter. Dense wave division multiplexing (DWDM) transport systems are usually deployed for connecting data centres. DWDM and a variety of other networking solutions connect end users to cloud data centres.


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Power efficiency – optical transport systems must efficiently transport large amounts of bandwidth with minimum power consumption. Minimising the number of systems, reducing the number of interfaces, employing low power digital signal processors, and enabling transport signals to remain optical to avoid electrical regenerations, all contribute to reduced power consumption.


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Security – the importance of a secure network has grown as services are now distributed in geographically diverse data centres. Because optical transport networks are inherently optical, there is a built-in measure of security in terms of how difficult it is to snoop or decode information. Additional security measures are required for data plane transmission, network control and management plane, and system access.


Resiliency – transport network resiliency that enables application and connection continuity is very important, especially when considering the large amount of traffic and services


supported by optical transport networks connecting data centres and end users. Geographic path diversity and more mesh interconnections improve the ability of transport networks to quickly recover from path problems. It is important that resiliency is implemented in a way that does not increase power consumption to support more systems or interfaces, but instead uses existing interfaces as much as possible for protection, restoration and disaster recovery. Optical switching is a low-power approach to this requirement.


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Programmability – In addition to dramatically increasing bandwidth requirements, services are becoming more dynamic, generating the need for a greater variety of connectivity options and more flexible and responsive network behaviour. Tis area is still poised to undergo further transformation from today’s mostly rigid networking. Programmable networking can provide the flexibility and scalability necessary to support diverse and customised offerings while being able to dynamically adapt as conditions and requirements change. Use cases include bandwidth on demand, data centre backup, maintenance, and more.


Te nature of the data centre operator also influences cloud transport network requirements and the methods deployed for interconnecting data centres and end users.


Issue 9 • Autumn 2015 FIBRE SYSTEMS 29


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