Cloud Computing (AD-702 (A)) - Unit 1 Short Notes

How unit 1 is examined

This unit covers the NIST definition and reference architecture, the five characteristics, the three service models, the four deployment models and the benefits; marks sit on characteristics, the NIST architecture, deployment models and service models.

Definition

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Low weight</span>

Definition. <mark>Cloud computing is a model for enabling convenient, on-demand network access to a shared pool of configurable computing resources (networks, servers, storage, applications, services) that can be rapidly provisioned and released with minimal management effort (NIST).</mark>

Key points.

1. The NIST reference architecture is a vendor-neutral model that shows the actors, activities and functions of cloud computing.
2. It has five actors: Consumer (uses the service), Provider (delivers it), Broker (intermediates and combines services), Auditor (independently checks security, privacy and performance) and Carrier (network and telecom link that transports the service).
3. The provider handles service orchestration, cloud management and security across the SaaS, PaaS and IaaS layers.

Diagram. <figure class="ds-fig" style="margin:1.4rem 0;overflow-x:auto"><svg xmlns="http://www.w3.org/2000/svg" id="dsfig-u1-01" viewBox="0 0 424 424" width="424" height="424" role="img" aria-label="NIST architecture. Con = Consumer, Bro = Broker, Pro = Provider, Aud = Auditor, Car = Carrier"><style>#dsfig-u1-01 .e{stroke:#454C5A;stroke-width:1.4;fill:none}#dsfig-u1-01 .e.hi{stroke:#2340B8;stroke-width:2.6}#dsfig-u1-01 .n{fill:#FFFFFF;stroke:#16181D;stroke-width:1.4}#dsfig-u1-01 .n.hi{fill:#E3E9FC;stroke:#2340B8;stroke-width:2.2}#dsfig-u1-01 .n.rb-b{fill:#16181D;stroke:#16181D}#dsfig-u1-01 .n.rb-r{fill:#BD3227;stroke:#BD3227}#dsfig-u1-01 text{font-family:"JetBrains Mono",ui-monospace,Menlo,Consolas,monospace;font-size:13px}#dsfig-u1-01 .t{fill:#16181D;font-weight:500}#dsfig-u1-01 .t.inv{fill:#FFFFFF;font-weight:700}#dsfig-u1-01 .kd{stroke:#16181D;stroke-width:1.2}#dsfig-u1-01 .dot{fill:#16181D}#dsfig-u1-01 .ann{fill:#2340B8;font-size:11px;font-weight:700}#dsfig-u1-01 .lbl{fill:#6F7787;font-family:system-ui,-apple-system,sans-serif;font-size:12px;font-weight:700}#dsfig-u1-01 .ptr{fill:#2340B8;font-size:12px;font-weight:700}#dsfig-u1-01 .ah{fill:#454C5A}#dsfig-u1-01 .ah.hi{fill:#2340B8}#dsfig-u1-01 .wl rect{fill:#FFFFFF;stroke:#DCE0E7}#dsfig-u1-01 .wl .t{font-size:12px;font-weight:700}#dsfig-u1-01 .wl.hi rect{fill:#2340B8;stroke:#2340B8}#dsfig-u1-01 .wl.hi .t{fill:#FFFFFF}html.dark #dsfig-u1-01 .e{stroke:#B1B7C3}html.dark #dsfig-u1-01 .e.hi{stroke:#8FA3FF}html.dark #dsfig-u1-01 .n{fill:#161920;stroke:#E6E8ED}html.dark #dsfig-u1-01 .n.hi{fill:#1E2748;stroke:#8FA3FF}html.dark #dsfig-u1-01 .n.rb-b{fill:#E6E8ED;stroke:#E6E8ED}html.dark #dsfig-u1-01 .n.rb-r{fill:#FF7E71;stroke:#FF7E71}html.dark #dsfig-u1-01 .t{fill:#E6E8ED}html.dark #dsfig-u1-01 .t.inv{fill:#0F1115}html.dark #dsfig-u1-01 .kd{stroke:#E6E8ED}html.dark #dsfig-u1-01 .dot{fill:#E6E8ED}html.dark #dsfig-u1-01 .ann{fill:#8FA3FF}html.dark #dsfig-u1-01 .lbl{fill:#858D9C}html.dark #dsfig-u1-01 .ptr{fill:#8FA3FF}html.dark #dsfig-u1-01 .ah{fill:#B1B7C3}html.dark #dsfig-u1-01 .ah.hi{fill:#8FA3FF}html.dark #dsfig-u1-01 .wl rect{fill:#161920;stroke:#2A2E37}html.dark #dsfig-u1-01 .wl.hi rect{fill:#8FA3FF;stroke:#8FA3FF}html.dark #dsfig-u1-01 .wl.hi .t{fill:#0F1115}</style><defs><marker id="ah1" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path class="ah" d="M0,1 L9,5 L0,9 z"/></marker><marker id="ahh1" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path class="ah hi" d="M0,1 L9,5 L0,9 z"/></marker></defs><path class="e" d="M54.8,197.2 L197.2,54.8" marker-end="url(#ah1)" marker-start="url(#ah1)"/><path class="e" d="M212,61 L212,191" marker-end="url(#ah1)" marker-start="url(#ah1)"/><path class="e" d="M61,212 L191,212" marker-end="url(#ah1)" marker-start="url(#ah1)"/><path class="e" d="M212,233 L212,363" marker-end="url(#ah1)" marker-start="url(#ah1)"/><path class="e" d="M53.4,225.4 L197.2,369.2" marker-end="url(#ah1)"/><path class="e" d="M233,212 L363,212" marker-end="url(#ah1)" marker-start="url(#ah1)"/><path class="e" d="M61,212 L363,212" marker-end="url(#ah1)" marker-start="url(#ah1)"/><circle class="n" cx="40" cy="212" r="18"/><text class="t" x="40" y="212" dy=".35em" text-anchor="middle">Con</text><circle class="n" cx="212" cy="40" r="18"/><text class="t" x="212" y="40" dy=".35em" text-anchor="middle">Bro</text><circle class="n" cx="212" cy="212" r="18"/><text class="t" x="212" y="212" dy=".35em" text-anchor="middle">Pro</text><circle class="n" cx="212" cy="384" r="18"/><text class="t" x="212" y="384" dy=".35em" text-anchor="middle">Aud</text><circle class="n" cx="384" cy="212" r="18"/><text class="t" x="384" y="212" dy=".35em" text-anchor="middle">Car</text></svg><figcaption style="font-size:.82em;opacity:.72;margin-top:.45rem">NIST architecture. Con = Consumer, Bro = Broker, Pro = Provider, Aud = Auditor, Car = Carrier</figcaption></figure>

Asked: [7 marks] (Dec 2024) Define NIST cloud computing reference architecture.

Characteristics

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Medium weight</span>

Definition. <mark>NIST lists five essential characteristics: on-demand self-service, broad network access, resource pooling, rapid elasticity and measured service.</mark>

Key points.

1. On-demand self-service means a consumer provisions computing capacity such as server time or storage automatically, without human interaction with the provider.
2. Broad network access means capabilities are available over the network and used through standard mechanisms from phones, tablets and laptops.
3. Resource pooling means the provider serves many consumers from one pool using a multi-tenant model, and resources are dynamically assigned and reassigned by demand.
4. Rapid elasticity means capabilities scale out and in quickly, often automatically, and appear unlimited to the consumer.
5. Measured service means usage is metered and monitored, so it is controlled, reported and billed on a pay-per-use basis.
6. On-demand functionality is provided by automated provisioning through a web portal or API, backed by virtualised pools and metering; example: launching an AWS EC2 instance in minutes and paying per hour.

Answer frame. Open with the NIST definition of cloud computing; list the five characteristics and develop points 1-5 in order with one example each; for the on-demand question define self-service, then develop point 6 (portal or API, automation, pay-per-use, broad access); close with one line that these five make cloud different from traditional hosting.

Pitfall: Do not confuse elasticity (scaling with demand) with resource pooling (sharing among tenants).

Asked: [7 marks] (Dec 2024) What are the characteristics of cloud computing? Asked: [7 marks] (Dec 2024) What is on-demand functionality? How is it provided in cloud computing?

Components

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>A cloud has three main components: clients, the datacenter and distributed servers.</mark>

Key points.

1. Clients are the devices, such as laptops, mobiles and thin clients, that users employ to reach cloud services through a browser or app.
2. The datacenter is the collection of servers, storage and networking where applications and data are hosted, often as virtual machines.
3. Distributed servers are placed at different locations, giving fault tolerance, speed and redundancy if one site fails.

Software as a Service

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>SaaS delivers a complete application over the internet, which the consumer uses through a browser without managing any underlying infrastructure.</mark>

Key points.

1. The provider manages application, data, servers and storage; the user only configures and uses the software.
2. It is billed as a subscription and is accessible from any device.
3. Examples are Salesforce, Gmail and Google Docs.
4. The limit is that the user has almost no control over features or the underlying system.

Platform as a Service

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>PaaS gives developers a ready platform (runtime, middleware, database and tools) to build, test and deploy applications without managing servers.</mark>

Key points.

1. The provider manages OS, servers and runtime; the developer controls only the application and its data.
2. It speeds development and scales automatically with load.
3. Examples are Google App Engine, Microsoft Azure App Service and Heroku.
4. The limit is vendor lock-in to the provider's languages and tools.

Infrastructure as Service

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>IaaS provides virtualised computing resources (virtual machines, storage and networks) on demand, over the internet, on a pay-as-you-go basis.</mark>

Key points.

1. The provider manages hardware and virtualisation; the consumer installs and controls the OS, middleware and applications.
2. It gives the highest control and flexibility of the three models.
3. Examples are AWS EC2, Google Compute Engine and Azure Virtual Machines.
4. It suits variable workloads, testing and disaster recovery without buying hardware.

Service models and scalability.

Flexibility: IaaS gives a free choice of stack, PaaS speeds development and SaaS removes all setup, so each user picks the level of control needed. Scalability: all three give on-demand resources, elastic auto-scaling and pay-as-you-go billing, so capacity follows load.

Asked: [7 marks] (Jun 2025) How do cloud service models (IaaS, PaaS and SaaS) contribute to the flexibility and scalability of cloud computing?

Public clouds

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>A public cloud is owned and operated by a third-party provider and offered to the general public over the internet.</mark>

Key points.

1. Resources are shared among many tenants, with no upfront capital cost and pay-per-use billing.
2. It scales almost without limit and needs no maintenance by the user.
3. Examples are AWS, Microsoft Azure and Google Cloud.
4. Security and control are weaker than in a private cloud.

Private clouds

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>A private cloud is operated for a single organisation, hosted on-premise or by a third party.</mark>

Key points.

1. It gives the highest security, control and compliance.
2. Cost is high because the organisation buys and maintains the infrastructure.
3. Scalability is limited to the capacity owned.
4. Examples are a bank or a government's internal cloud, or OpenStack-based enterprise clouds.

Community clouds

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>A community cloud is shared by several organisations with common concerns (mission, security or compliance) and managed by them or a third party.</mark>

Key points.

1. Cost is split among members, so it is cheaper than private and more secure than public.
2. Examples are a cloud shared by government departments, hospitals or universities for research.
3. Limits are less capacity than public and shared governance.

Hybrid clouds

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Low weight</span>

Definition. <mark>A hybrid cloud combines two or more distinct clouds (private, community or public) that stay separate but are bound by technology allowing data and application portability.</mark>

Key points.

1. Sensitive data and core systems stay in the private cloud, while the public cloud handles peaks ("cloud bursting").
2. Example: an online retailer keeps customer records privately and rents public capacity in a festive sale.
3. It balances cost, security and scalability but is complex to manage.

Comparison of deployment models.

Asked: [7 marks] (Dec 2024) Explain hybrid and community cloud with examples. Asked: [7 marks] (Jun 2025) Compare and contrast different cloud deployment models: Public, Private, Hybrid and Community clouds.

Advantages of Cloud computing

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>Cloud computing lets users rent resources on demand instead of owning them, giving lower cost, scalability and access from anywhere.</mark>

Key points.

1. There is no upfront hardware cost, and pay-per-use turns capital expense into operating expense.
2. Resources scale up and down quickly with demand.
3. Data and services are accessible from anywhere on any device, with high availability and backup.
4. Social networking: Facebook, Twitter and LinkedIn use cloud storage and scaling to hold billions of photos and posts, serve peak traffic, run analytics and stay available worldwide.

Asked: [7 marks] (Dec 2024) Briefly explain the applications of cloud computing in the field of social networking.

Comparing cloud providers with traditional IT service providers

<span style="display:inline-block;padding:.16em .6em;border:1.5px solid currentColor;border-radius:999px;font-size:.68em;font-weight:700;letter-spacing:.06em;text-transform:uppercase;opacity:.75">Not asked since 2022</span>

Definition. <mark>Cloud providers rent shared, elastic resources on pay-per-use terms, whereas traditional IT providers supply fixed, dedicated hardware and software under long contracts.</mark>

Key points.

1. Cloud has no upfront cost; traditional IT needs heavy capital investment.
2. Cloud provisions in minutes; traditional IT takes weeks.
3. Cloud scales elastically; traditional capacity is fixed.
4. Traditional IT gives more physical control, while cloud shifts maintenance to the provider.

Last-minute revision

• Cloud computing (NIST): on-demand network access to a shared pool of configurable resources, minimal management effort.
• Five characteristics: on-demand self-service, broad network access, resource pooling, rapid elasticity, measured service.
• NIST actors: Consumer, Provider, Broker, Auditor, Carrier.
• Service models: IaaS (EC2), PaaS (App Engine), SaaS (Salesforce).
• Control falls and abstraction rises from IaaS to PaaS to SaaS.
• Deployment models: public, private, community, hybrid.
• Public is cheapest and most scalable; private is the most secure.
• Community is shared by organisations with common concerns.
• Hybrid uses cloud bursting to public cloud.
• Cloud converts capital expense into operating expense.

Memory hooks

• On-demand, Broad, Pool, Elastic, Measured: "OBPEM".
• NIST actors: "CPB-AC", Consumer, Provider, Broker, Auditor, Carrier.
• Service stack: I-P-S means Infrastructure, Platform, Software, with control falling.
• Deployment: "Pu-Pr-Co-Hy", from widest to narrowest access.

Coverage checklist

• Definition: NIST definition and reference architecture (Dec 2024).
• Characteristics: characteristics; on-demand functionality (Dec 2024).
• Components: clients, datacenter, distributed servers.
• Software as a Service: SaaS (Jun 2025 model question).
• Platform as a Service: PaaS (Jun 2025 model question).
• Infrastructure as Service: IaaS and service-model table (Jun 2025).
• Public clouds: public cloud (Jun 2025 comparison).
• Private clouds: private cloud (Jun 2025 comparison).
• Community clouds: community cloud (Dec 2024, Jun 2025).
• Hybrid clouds: hybrid cloud and deployment comparison (Dec 2024, Jun 2025).
• Advantages of Cloud computing: benefits; social networking (Dec 2024).
• Comparing cloud providers with traditional IT service providers: comparison points.