Future PON Data Centre Networks

Significant research efforts have been devoted over the last decade to design efficient data centre networks. However, major concerns are still raised about the power consumption of data centres and its impact on global warming in the first place and on the electricity bill of data centres in the second place. Passive Optical Network (PON) technology with its proven performance in residential access networks can provide energy efficient, high capacity, low cost, scalable, and highly elastic solutions to support connectivity inside modern data centres.
Here, we focus on introducing PONs in the architecture of data centres to resolve many issues in current data centre designs such as high cost and high power consumption resulting from the large number of access and aggregation switches needed to interconnect hundreds of thousands of servers. PONs can also overcome the problems of switch oversubscription and unbalanced traffic in data centres where PON architectures and protocols have historically been optimised to deal with these problems and handle bursty traffic efficiently.
In this thesis, five novel PON data centre designs are proposed and compared to facilitate intra and inter rack communications. In addition to maximising the use of only passive optical devices, other challenges have to be addressed by these designs including off-loading the inter-rack traffic from the Optical Line Terminal (OLT) switch to avoid undesired power consumption and delays, facilitating multi-path routing, and reducing or eliminating the need for expensive tuneable lasers. The Scalability of the
proposed architectures in terms of efficiently accommodating hundreds of thousands of servers is discussed. CAPEX and energy consumption of the proposed architectures are also investigated and savings compared to conventional architectures, such as the Fat-Tree and BCube, are demonstrated. The Routing and Wavelength Assignment (RWA) in intra and inter rack communication and the resource provisioning needed to cater for different applications that can be hosted in data centre are optimised using Mixed Integer Linear Programming (MILP) models to minimise the PON designs power consumption. Furthermore, real-time energy-efficient routing and resource provisioning algorithms are developed. In addition to optimising the power consumption, delay is also considered for the delay sensitive applications that can be hosted in the proposed data centre architectures. To further reduce power consumption and overcome issues related to link oversubscription and multi-path routing, Software Defined Network (SDN) based design is proposed.