Page 61 - ITU Journal Future and evolving technologies Volume 2 (2021), Issue 1

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 1

CONTROLLER PLACEMENT OPTIMIZATION FOR SOFTWARE DEFINED WIDE AREA NETWORKS
(SDWAN)

2
Lusani Mamushiane 1,2 , Joyce Mwangama , Albert Lysko 1,2
2
1 Council for Scienti ic and Industrial Research (CSIR), University of Cape Town, South Africa
NOTE: Corresponding author: Lusani Mamushiane, Lravhuanzwo@csir.co.za

Abstract – Software De ined Networking (SDN) has emerged as a promising solution to revolutionize network deployment,
operations and economic growth. This paradigm aims to address management and con iguration complexities in legacy
networks so as to reduce the total cost associated with deploying and running telecommunication infrastructures. At the heart
of SDN is a controller which oversees orchestration of resources. An important problem that must be addressed during the
initial design of an SDN‑based network deployment is to ind the optimal number of controllers and their locations, to achieve
desired operational ef iciency. This problem constitutes competing objectives such as latency, load balancing, and reliability.
We apply Silhouette Analysis, Gap Statistics and the Partition Around Medoids (PAM) algorithms and, unlike previous work,
we add a new method for solving the controller placement problem using an emulation orchestration platform. Our approach
aims to optimize controller‑to‑node latency, alleviate control‑plane signalling overhead and ensure control‑plane resiliency.
Our results for South African national research network (SANReN) reveal that deploying two controllers yields the lowest
latency, reduces control‑plane signalling overhead and guarantees control‑plane resiliency. Our approach can be used by
network operators as a guideline to start integrating SDN or plan a new SDN deployment, by helping them make quick
automatic decisions regarding optimal controller placement.

Keywords – Controller placement, Gap Statistics, Partition Around Medoids, Silhouette, Software De ined Networks,
South African National Research and Education Network

1. INTRODUCTION Software ined Networking (SDN) has emerged
as a promising candidate to revolutionize future
Over the past decade, the use of information and telecommunication landscapes. Contrary to the
communication technology has reached the upper traditional network architecture where the control
bounds of Internet penetration [1]. According to a Cisco and data‑plane of packet processing devices are tightly
White paper [2], Internet usage is anticipated to continue
coupled, SDN presents a paradigm shift in networking by
on an upward trajectory in the foreseeable future. This
decoupling the control‑plane logic from the underlying
strong appetite for Internet access is causing a high
physical infrastructure [5]. The control‑plane is then
demand for bandwidth and putting icant pressure
logically centralized in an external entity called a
on the existing telecommunication infrastructure.
controller and interacts with the physical infrastructure
There is a consensus that the current infrastructure
via its southbound interface. By decoupling the
will not ice to cater for these exploding demands
control logic from the physical hardware, operators
[3]. This is primarily attributed to the rigidity of the can programme new ic engineering policies (such
legacy infrastructure, especially because of vendor as bandwidth management, security, protection and
lock‑in (the use of proprietary silicon hardware) which restoration policies) without worrying about the
les innovation and makes it icult to scale the constraints of closed proprietary hardware and irmware.
network on the ly. As a result of vendor lock‑in, the cost Moreover, the abstraction of lower level functionality
associated with upgrading the infrastructure to cater provided by SDN enables convergence of heterogeneous
for the changing tr ic patterns is very high, meaning hardware thereby fostering a vendor‑neutral ecosystem.
adding new features ad hoc is virtually impossible [4]. In addition to enabling centralized network provisioning
Therefore, network operators desiring new features to and holistic network management, SDN promises
address their market needs end up beholden to a vendor’s its such as security granularity (by providing a
upgrade timelines and costs. To cater for the increase central point of control to holistically and consistently
in Internet demand, the infrastructure has to evolve disseminate security information), savings in operational
from its current monolithic nature to a vendor‑agnostic, costs (by automating network administrative tasks),
programmable, cost‑effective (in terms of deployment savings in capital expenditures (by capitalizing on
(CapEx) and operational costs (OpEx)) and more lexible commodity hardware) and cloud abstraction (which is
infrastructure.
critical to consolidate and facilitate the management of
massive data centers) [6]. According to [7] a huge portion
of operational expenditure is from costs related to the

© International Telecommunication Union, 2021 45