Abstract
The placement of controllers in Software Defined Networks (SDN) plays a vital role in the network's overall performance. This is mainly measured in terms of the overall average latency between the switches and their responsible controller. For an Internet Service Provider (ISP), optimally placing contrailers for their large topology can minimise the overall average latency within the bounds of operational expenses.Whilst various studies have investigated the placement of controllers, non-realistic assumptions are factored in to reach their near-optimal solution. Some examples would be ignoring worst-case latency for outliers, placing controllers on unowned or non-hostable locations, assuming lossless mediums, and using an inaccurate distance calculator.
The study initially aims to negate these assumptions to form a more realistic environment to consider optimal placements. This study uses the Vincenty distance algorithm, evidencing better placements with lower average latency even with a slight variation in accuracy. Furthermore, transit site latency and realistic optical fibre induced latency are analysed.
The study then proposes an adapted Partition Around Medoids (PAM) algorithm considering outliers with node and link weights for placing the required number of controllers at ISP owned locations. Placement simulations are conducted using real ISP topology data sets. The results show lower total average latency placements when compared to other studies using different forms of clustering algorithms. A case study is presented offering a comparison on the effect of using realistic attributes when deciding the number of controllers required for the size of the network.
Secondly, the study investigates the effect of virtualising controllers to offer resiliency in the event of a failure. The simulations show that up to three instances can be hosted with minimal latency costs. Based on this, a resiliency-aware placement algorithm is proposed, factoring in the worst-case latency and total overall average latency. Compared to similar studies, the results show that fewer locations are needed to host backup controllers, thus minimising the overall cost. The study also offers ISPs with alternative placement options at minimal latency costs.
| Date of Award | 2022 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Jackie Riley (Supervisor) |