*2.6.5 Cloud-native architecture is the foundation of 5G innovation*

Through persistent effort and determination, Telecom operators are implementing a digital transformation to create a better digital world. To provide enterprises and individuals with a real time, on demand, all online experience requires an end-to-end (E2E) coordinated architecture featuring agile, automatic, and intelligent operation during each phase. The comprehensive cloud adaptation of networks, operation systems, and services is a prerequisite for this muchanticipated digital transformation.

In existing networks, operators have gradually used SDN and NFV to implement ICT network hardware virtualization, but retain a conventional operational model and software architecture. 5G networks require continuous innovation through cloud adoption to customize network functions and enable on-demand network definition and implementation and automatic O&M.

Physical networks are constructed based on DCs to pool hardware resources (including part of RAN and core network devices), which maximizes resource utilization.

The "All Cloud" strategy is an illuminated exploration into hardware resource pools, distributed software architecture, and automatic deployment. Operators transform networks using a network architecture based on data center (DC) in which all functions and service applications are running on the cloud DC, referred to as a Cloud-Native architecture.

In the 5G era, a single network infrastructure can meet diversified service requirements. Cloud-Native E2E network architecture has the following attributes:


### **3. Cloud computing for business continuity**

Business continuity is a set of processes that includes all activities that a business must perform to mitigate the impact of service outage. BC entails preparing for, responding to, and recovering from a system outage that adversely affects business operations. It describes the processes and procedures a service provider establishes to ensure that essential functions can continue during and after a disaster. Business

#### *Network Function Virtualization over Cloud-Cloud Computing as Business Continuity Solution DOI: http://dx.doi.org/10.5772/intechopen.97369*

continuity prevents interruption of mission-critical services, and reestablishes the impacted services as swiftly and smoothly as possible by using an automated process. BC involves proactive measures, such as business impact analysis, risk assessment, building resilient IT infrastructure, deploying data protection solutions (backup and replication). It also involves reactive countermeasures, such as disaster recovery, to be invoked in the event of a service failure. Disaster recovery (DR) is the coordinated process of restoring IT infrastructure, including data that is required to support ongoing cloud services, after a natural or human-induced disaster occurs. The basic underlying concept of DR is to have a secondary data center or site (DR site) and at a pre-planned level of operational readiness when an outage happens at the primary data center.

Cloud service availability refers to the ability of a cloud service to perform its agreed function according to business requirements and customer expectations during its operation. Cloud service providers need to design and build their infrastructure to maximize the availability of the service, while minimizing the impact of an outage on consumers. Cloud service availability depends primarily on the reliability of the cloud infrastructure (compute, storage, and network) components, business applications that are used to create cloud services, and the availability of data. The time between two outages, whether scheduled or unscheduled, is commonly referred as uptime, because the service is available during this time. Conversely, the time elapsed during an outage (from the moment a service becomes unavailable to the moment it is restored) is referred to as downtime. A simple mathematical expression of service availability is based on the agreed service time and the downtime.

$$\text{Service availability } (\%) = \frac{\text{Agreeed service time} - \text{Downtime}}{\text{Agreeed service time}} \tag{1}$$

Agreed service time is the period where the service is supposed to be available. For example, if a service is offered to a consumer from 9 am to 5 pm Monday to Friday, then the agreed service time would be 8 x 5 = 40 hours per week. If this service suffered 2 hours of downtime during that week, it would have an availability of 95%.

In a cloud environment, a service provider publishes the availability of a service in the SLA. For example, if the service is agreed to be available for 99.999 percent (also referred to as five 9 s availability) then the allowable service downtime per year is approximately 5 minutes. Therefore, it is important for the service provider to identify the causes of service failure, and analyze its impact to the business.

#### **3.1 Causes of cloud service unavailability**

This section listed some of the key causes of service unavailability. Data center failure is not the only cause of service failure. Poor application design or resource configuration errors can also lead to service outage. For example, if the web portal is down for some reason, then the services are inaccessible to the consumers, which leads to service unavailability. Even unavailability of data due to several factors (data corruption and human error) also leads to service unavailability. A cloud service might also cease to function due to an outage of the dependent services. Perhaps even more impactful on the availability are the outages that are required as a part of the normal course of doing business. The IT department is routinely required to take on activities such as refreshing the data center infrastructure, migration, running routine maintenance or even relocating to a new data center. Any of these activities can have its own significant and negative impact on service availability.

In general, the outages can be broadly categorized into planned and unplanned outages. Planned outages may include installation and maintenance of new hardware, software upgrades or patches, performing application and data restores, facility operations (renovation and construction), and migration. Unplanned outages include failure caused by human errors, database corruption, failure of physical and virtual components, and natural or human-made disasters.
