Show understanding of cloud computing

Published by Patrick Mutisya · 14 days ago

Cambridge A-Level Computer Science 9618 – Networks: Cloud Computing

2.1 Networks – The Internet

Objective: Show understanding of cloud computing

Cloud computing is a model for delivering computing resources (hardware, software, storage, and services) over a network, typically the Internet. Resources are provided on‑demand and billed based on usage, allowing users to access powerful capabilities without owning the underlying infrastructure.

Key Characteristics

  • On‑demand self‑service

  • Broad network access (any device with Internet connectivity)

  • Resource pooling (multi‑tenant architecture)

  • Rapid elasticity and scalability

  • Measured service (pay‑as‑you‑go)

Service Models

The three primary service models define the level of control and responsibility shared between the provider and the consumer.

ModelWhat the Provider OffersWhat the Consumer ManagesTypical Use‑Cases
IaaS (Infrastructure as a Service)Virtual machines, storage, networks, hypervisorsOperating system, middleware, runtime, data, applicationsHosting websites, disaster recovery, big‑data processing
PaaS (Platform as a Service)Operating system, middleware, runtime environment, development toolsApplications and dataRapid application development, testing environments
SaaS (Software as a Service)Complete applications delivered over the webOnly user-specific configuration and dataEmail, CRM, office productivity suites

Deployment Models

Deployment models describe how the cloud infrastructure is owned, managed, and accessed.

  1. Public Cloud – Resources are owned by a third‑party provider and shared among many organisations.

  2. Private Cloud – Infrastructure is dedicated to a single organisation, either on‑premises or hosted.

  3. Hybrid Cloud – Combines public and private clouds, allowing data and applications to move between them.

  4. Community Cloud – Shared by several organisations with common concerns (e.g., security, compliance).

Advantages of Cloud Computing

  • Cost reduction – no capital expenditure on hardware.

  • Scalability – resources can be increased or decreased quickly.

  • Accessibility – services available from any location with Internet access.

  • Reliability – providers often offer high availability and redundancy.

  • Focus on core business – IT staff can concentrate on strategic tasks.

Disadvantages / Risks

  • Dependence on Internet connectivity.

  • Potential security and privacy concerns.

  • Limited control over underlying infrastructure.

  • Vendor lock‑in and data portability issues.

  • Variable performance due to shared resources.

Relationship to the Internet

Cloud services are delivered over the Internet using standard protocols (HTTP/HTTPS, TCP/IP). The Internet provides the transport layer that connects end‑users to remote data centres, making cloud computing possible on a global scale.

Example Scenario

A university wants to provide students with a virtual lab environment. Using an IaaS provider, the university can spin up virtual machines with pre‑installed software, scale the number of instances during exam periods, and shut them down afterwards, paying only for the time the resources are used.

Suggested diagram: Layered view of cloud service models (IaaS, PaaS, SaaS) stacked on top of deployment models (Public, Private, Hybrid, Community) with the Internet as the underlying network.

Key Formula (Cost Estimation)

For a simple pay‑as‑you‑go model, the monthly cost can be estimated by:

\$\text{Cost}{\text{month}} = \sum{i=1}^{n} \left( \text{Rate}i \times \text{Usage}i \right)\$

where \$n\$ is the number of resource types (e.g., compute, storage, bandwidth), \$\text{Rate}i\$ is the price per unit, and \$\text{Usage}i\$ is the amount consumed during the month.

Summary

Cloud computing transforms traditional networking by providing flexible, on‑demand resources over the Internet. Understanding the service and deployment models, along with their benefits and challenges, is essential for designing modern networked solutions in the A‑Level curriculum.