Page 16 - ITU Journal Future and evolving technologies Volume 2 (2021), Issue 6 – Wireless communication systems in beyond 5G era

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 6

First, the vision of outsourcing and centralising comput‐ scalability. In 2020, ONOS started the µONOS project
ing has been the main driver for a paradigm‐shift of in‐ aimed at designing and realising a new generation of
network computing. The so‐called cloud computing orig‐ open‐source SDN controllers. While original SDN con‐
inally started and evolved during the second half of the trollers (either centralised or distributed) have been
21st century, when the computing hardware and the In‐ ’monolithic’ entities, the µONOS controller will be based
ternet grew. However, around 2008, the term cloud com‐ on micro‐services. This important change will permit the
puting became popular, due to the maturity of the tech‐ split of the controller into various subfunctions. Each sub‐
nologies to provide remote access to computing equip‐ function will be responsible for a certain control opera‐
ment in data centres, together with the growth of private tion and/or con iguration and/or management function
entities such as Salesforce.com, Google, and Amazon Web of the SDN network. In µONOS, the so‐called service or‐
Services. Cloud computing means a “[...] method of run‐ chestrator (i.e. Kubernetes) manages each micro‐service,
ning application software and storing related data in cen‐ running in a software container.
tral computer systems and providing customers or other
users access to them through the Internet. [...]” [12]. As it In 2012, NFV was proposed by the industrial commu‐
is possible to guess, this technology created the bridge be‐ nity (i.e. AT&T, BT, CenturyLink, China Mobile, Deutsche
tween big data centres and computing, and wireless cel‐ Telekom, KDDI, NTT, Orange, Telecom Italia, Telefon‐
lular networks. Within cloud computing, it is possible to ica, Telstra and Verizon) with the publication of the
identify a taxonomy of services, which can be grouped white paper [13]. Next, these operators identi ied ETSI
into three main paradigms, according to what is made as the standardization body to undertake the standard‐
available: Infrastructure‐as‐a‐Service (IaaS) for remote ization effort of this paradigm. In NFV, a network
hardware access, Platform‐as‐a‐Service (PaaS) for soft‐ element/function/entity/etc. is no longer hardware‐
ware platform access, and Software‐as‐a‐Service (SaaS) dependent but it is a complete software element, running
for remote software access. on any general‐purpose hardware within the network.
The NFV original architecture consists of three main lay‐
Next, the idea of network virtualisation (and more pre‐ ers [1]:
ciselysoftwarization)waschangingthewaynetworkshad
been intended by then, by transposing any network func‐ • Physical resources, which are “A physical asset for
tion, protocol, operation, etc. from dedicated hardware computation, storage and transport (e.g. switch,
to software, running on general‐purpose hardware. If we router, antenna, etc.)” [14];
generally consider a network, its functions can logically • Virtual resources, that are “An abstraction of physical
be grouped into two planes, the so‐called data (or user) or logical resource, which may have different char‐
and control planes. Around 2010, the original visions of acteristics from the physical or logical resource and
programmable networks and decoupling data and control whose capability may be not bound to the capability
planes became reality via the irst developments of SDN, of the physical or logical resource” [14];
led by the nonpro it consortium Open Network Founda‐
tion (ONF). • Services, which are the virtual network functions,
running in software environments such as virtual
In order to achieve this decoupling, SDN requires three machines, containers, etc. [15]
main entities [1]:
Next, there is a transverse management layer called Man‐
• a centralised SDN controller, which changes the en‐ agement and Orchestration (MANO), which handles the
tries in the low tables of SDN switches according to provisioning of virtual network functions, their con ig‐
either static or dynamic algorithms, in order to man‐ uration, placement, orchestration, and management of
age the paths of packets among end users (comput‐ physical and virtual resources. This layer contains the so‐
ers); called orchestrator.

• SDN switches, that contains the low tables to man‐ After the previous design and standardization efforts,
age the routing of messages from source(s) to desti‐ ETSI started focusing on the uni ication of SDN and NFV in
nation(s); a unique architecture. The outcome was the ETSI MANO
SDN‐NFV architecture, which is depicted in Fig. 3. The
• a control protocol (e.g. Open low), which enables the whole architecture irst consists of four main blocks such
communication between controller and switches, as:
while also analysing and modifying the low tables
within the SDN switches. • the Network Management System (NMS), responsible
for management of the virtual network;
Currently, an Open Network Operating System (ONOS)
is leading the design and implementation of an open‐ • the Network Function Virtualization Infrastructure
source SDN controller. This controller can also be soft‐ (NFVI), the set of resources (physical or virtualized)
warized and outsourced to the cloud, in a centralised or that are used to run and to connect virtual network
distributed manner to improve for example resilience and functions;

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