CLOUD COMPUTING

UNIT – 3

SYLLABUS: Cloud Platform Architecture: Cloud Computing and service Models, Public
Cloud Platforms, Service Oriented Architecture, Programming on Amazon AWS and
Microsoft Azure.

3.1. CLOUD COMPUTING AND SERVICE MODELS:

In recent days, the IT industry has moved from manufacturing to offering more services (service-
oriented). As of now, 80% of the industry is ‘service-industry’. It should be realized that services
are not manufactured/invented from time-to-time; they are only rented and improved as per the
requirements. Clouds aim to utilize the resources of data centers virtually over automated
hardware, databases, user interfaces and apps.
I)Public, Private and Hybrid Clouds: Cloud computing has evolved from the concepts of
clusters, grids and distributed computing. Different resources (hardware, finance, time) are
leveraged (use to maximum advantage) to bring out the maximum HTC. A Cloud Computing
model enables the users to share resources from anywhere at any time through their connected
devices.
Advantages of Cloud Computing: Recall that in Cloud Computing, the programming is
sent to data rather than the reverse, to avoid large data movement, and maximize the bandwidth
utilization. Cloud Computing also reduces the costs incurred by the data centers, and increases
the app flexibility. Cloud Computing consists of a virtual platform with elastic resources and puts
together the hardware, data and software as per demand. Furthermore, the apps utilized and
offered are heterogeneous.
The Basic Architecture of the types of clouds can be seen in Figure 4.1 below.

• Public Clouds: A public cloud is owned by a service provider, built over the Internet and
offered to a user on payment. Ex: Google App Engine (GAE), AWS, MS-Azure, IBM
Blie Cloud and Salesforce-Force.com. All these offer their services for creating and
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 managing VM instances to the users within their own infrastructure.
• Private Clouds: A private cloud is built within the domain of an intranet owned by a
single organization. It is client-owned and managed; its access is granted to a limited
number of clients only. Private clouds offer a flexible and agile private infrastructure
to run workloads within their own domains. Though private cloud offers more control, it
has limited resources only.
• Hybrid Clouds: A hybrid cloud is built with both public and private clouds. Private
clouds can also support a hybrid cloud model by enhancing the local infrastructure with
computing capacity of a public external cloud.

• Data Center Networking Architecture: The core of a cloud is the server cluster and the
cluster nodes are used as compute nodes. The scheduling of user jobs requires that virtual
clusters are to be created for the users and should be granted control over the required
resources. Gateway nodes are used to provide the access points of the concerned service
from the outside world. They can also be used for security control of the entire cloud
platform. It is to be noted that in physical clusters/grids, the workload is static; in clouds,
the workload is dynamic and the cloud should be able to handle any level of workload on
demand.

Data centers and supercomputers also differ in networking requirements, as illustrated in

Figure 4.2. Supercomputers use custom-designed high-bandwidth networks such as fat trees
or 3D torus networks. Data-center networks are mostly IP-based commodity networks, such
as the 10 Gbps Ethernet network, which is optimized for Internet access. Figure 4.2 shows a
multilayer structure for accessing the Internet. The server racks are at the bottom Layer 2,
and they are connected through fast switches (S) as the hardware core. The data center is
connected to the Internet at Layer 3 with many access routers (ARs) and border routers
(BRs).
• Cloud Development Trends: There is a good chance that private clouds will grow in the
future since private clouds are more secure, and adjustable within an organization. Once
they are matured and more scalable, they might be converted into public clouds. In another
angle, hybrid clouds might also grow in the future.

ii) Cloud Ecosystem and Enabling Technologies: The differences between classical
computing and cloud computing can be seen in the table below. In traditional computing, a
user has to buy the hardware, acquire the software, install the system, test the configuration and
execute the app code. The management of the available resources is also a part of this. Finally,
all this process has to be revised for every 1.5 or 2 years since the used methodologies will
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become obsolete.

On the other hand, Cloud Computing follows a pay-as-you-go model [1]. Hence the cost is
reduced significantly – a user doesn’t buy any resources but rents them as per his requirements.
All S/W and H/W resources are leased by the user from the cloud resource providers. This is
advantageous for small and middle business firms which require limited amount of resources
only. Finally, Cloud Computing also saves power.

a) Cloud Design Objectives:

• Shifting computing from desktops to data centers : Computer processing, storage, and
software delivery is shifted away from desktops and local servers and toward data centers
over the Internet.
• Service provisioning and cloud economics: Providers supply cloud services by signing
SLAs with consumers and end users. The services must be efficient in terms of
computing, storage, and power consumption. Pricing is based on a pay-as-you-go policy.
• Scalability in performance (as the no. of users increases) : performance The cloud
platforms and software and infrastructure services must be able to scale in performance
as the number of users increases
• Data privacy protection Can you trust data centers to handle your private data and
records? This concern must be addressed to make clouds successful as trusted services.
• High quality of cloud services The QoS of cloud computing must be standardized to
make clouds interoperable among multiple providers.
• New standards and interfaces This refers to solving the data lock-in problem associated
with data centers or cloud providers. Universally accepted APIs and access protocols are
needed to provide high portability and flexibility of virtualized applications.

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b) Cost Model:

The above Figure 4.3a shows the additional costs on top of fixed capital investments in
traditional computing. In Cloud Computing, only pay-as-per-use is applied, and user-jobs are
outsourced to data centers. To use a cloud, one has no need to buy hardware resources; he can
utilize them as per the demands of the work and release the same after the job is completed.

c) Cloud Ecosystems: With the emergence of Internet clouds, an ‘ecosystem’ (a complex

inter- connected systems network) has evolved. This consists of users, providers and
technologies. All this is based mainly on the open source Cloud Computing tools that let
organizations build their own IaaS. Private and hybrid clouds are also used. Ex: Amazon
EC2.

An ecosystem for private clouds was suggested by scientists as depicted in Figure 4.4.

In the above suggested 4 levels, at the user end, a flexible platform is required by the

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customers. At the cloud management level, the virtualization resources are provided by the
concerned cloud manager to offer the IaaS. At the VI management level, the manager
allocates the VMs to the available multiple clusters. Finally, at the VM management level, the
VM managers handle VMs installed on the individual host machines.

d) Increase of Private Clouds: Private clouds influence the infrastructure and services that are
utilized by an organization. Private and public clouds handle the workloads dynamically but
public clouds handle them without communication dependency. On the other hand, private
clouds can balance workloads to exploit the infrastructure effectively to obtain HP. The
major advantage of private clouds is less security problems and public clouds need less
investment.

iii)Infrastructure-as-a-Service (IaaS): A model for different services is shown in Figure 4.5,

as shown below. The required service is performed by the rented cloud infrastructure. On this
environment, the user can deploy and run his apps. Note that user doesn’t have any control
over the cloud infrastructure but can choose his OS, storage, apps and network components.
Ex: Amazon EC2.

iv) platform-as-a-service (PaaS) and Software-as-a-Service (SaaS)

• Platform-as-a-Service (PaaS): To develop, deploy and manage apps with provisioned
resources, an able platform is needed by the users. Such a platform includes OS and
runtime library support. Different PaaS offered in the current market and other details
are highlighted in the Table 4.2 below:
It should be noted that platform cloud is an integrated system consisting of both S/W and
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 H/W. The user doesn’t manage the cloud infrastructure but chooses the platform that is
best suited to his choice of apps. The model also encourages third parties to provide
software management, integration and service monitoring solutions.
• Software as a Service (SaaS): This is about a browser-initiated app s/w over thousands
of cloud customers. Services & tools offered by PaaS are utilized in construction and
deployment of apps and management of their resources. The customer needs no
investment and the provider can keep the costs low. Customer data is also stored in a
cloud and is accessible through different other services. Ex: Gmail, Google docs,
Salesforce.com etc.
• Mashup of Cloud Services: Public clouds are more used these days but private clouds
are not far behind. To utilize the resources up to the maximum level and deploy/remove
the apps as per requirement, we may need to mix-up the different parts of each service
to bring out a chain of connected activities. Ex: Google Maps, Twitter, Amazon
ecommerce, YouTube etc.

II) PUBLIC CLOUD PLATFORMS: Cloud services are provided as per demand by different
companies. It can be seen in Figure 4.19 that there are 5 levels of cloud players.

The app providers at the SaaS level are used mainly by the individual users. Most business
organizations are serviced by IaaS and PaaS providers. IaaS provides compute, storage, and
communication resources to both app providers and organizational users. The cloud
environment is defined by PaaS providers. Note that PaaS provides support both IaaS services
and organizational users directly.
Cloud services depend upon machine virtualization, SOA, grid infrastructure management and
power efficiency. The provider service charges are much lower than the cost incurred by the
users when replacing damaged servers. The Table 4.5 shows a summary of the profiles of the
major service providers.

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PKI=> Public Key Infrastructure; VPN=> Virtual Private Network

a. Google App Engine (GAE): The Google platform is based on its search engine
expertise and is applicable to many other areas (Ex: MapReduce). The Google Cloud
Infrastructure consists of several apps like Gmail, Google Docs, and Google Earth and
can support multiple no. of users simultaneously to raise the bar for HA (high
availability). Other technology achievements of Google include Google File System
(GFS) [like HDFS], MapReduce, BigTable, and Chubby (A Distributed Lock Service).
GAE enables users to run their apps on a large number of data centers associated with
Google’s search engine operations. The GAE architecture can be seen in Figure 4.20 [1]
below:

The building blocks of Google’s Cloud Computing app include GFS for storing large amounts
of data, the MapReduce programming framework for developers, Chubby for distributed lock
services and BigTable as a storage service for accessing structural data.
GAE runs the user program on Google’s infrastructure where the user need not worry about

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 storage or maintenance of data in the servers. It is a combination of several software
components but the frontend is same as ASP (Active Server Pages), J2EE and JSP.

Functional Modules of GAE:

• Datastore offers OO, distributed and structured data storage services based on
BigTable techniques. This secures data management operations.
• Application Runtime Environment: It is a platform for scalable web programming
and execution. (Supports the languages of Java and Python)
• Software Development Kit: It is used for local app development and test runs of the
new apps.
• Administration Console: Used for easy management of user app development cycles
instead of physical resource management.
• Web Service Infrastructure provides special interfaces to guarantee flexible use and
management of storage and network resources.

The well-known GAE apps are the search engine, docs, earth and Gmail. Users linked with one
app can interact and interface with other apps through the resources of GAE (synchronise and
one login for all services).

b. Amazon Web Services (AWS): Amazon applies the IaaS model in providing its
services. The Figure 4.21 [1] below shows the architecture of AWS:

EC2 provides the virtualized platforms to host the VMs where the cloud app can run.
S3 (Simple Storage Service) provides the OO storage service for the users.
EBS (Elastic Block Service) provides the block storage interface which can be used to support
traditional apps.
SQS (Simple Queue Service) ensures a reliable message service between two processes.
Amazon offers a RDS (relational database service) with a messaging interface. The AWS
offerings are given below in Table 4.6

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 c. MS-Azure: The overall architecture of MS cloud platform, built on its own data
centers, is shown in Figure 4.22. It is divided into 3 major component platforms as it
can be seen. Apps are installed on VMs and Azure platform itself is built on Windows
OS.

• Live Service: Through this, the users can apply MS live apps and data across multiple
machines concurrently.
• .NET Service: This package supports app development on local hosts and execution on cloud
machines.
• SQL Azure: Users can visit and utilized the relational database associated with a SQL server
in the cloud.
• SharePoint Service: A scalable platform to develop special business apps.
• Dynamic CRM Service: This provides a business platform for the developers to manage the
CRM apps in financing, marketing, sales and promotions.

III) SERVICE-ORIENTED ARCHITECTURE: SOA is concerned about how to design a

software system that makes use of services or apps through their interfaces. These apps are
distributed over the networks. The World Wide Web Consortium (W3C) defines SOA as a form
of distributed architecture characterized by:
• Logical View: The SOA is an abstracted, logical view of actual programs, DBs etc.
defined in terms of the operations it carries out. The service is formally defined in terms of
messages exchanged between providers and requests.
• Message Orientation
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• Description Orientation
i. Services and Web Services: In an SOA concept, the s/w capabilities are delivered &
consumed through loosely coupled and reusable services using messages. ‘Web
Service’ is a self-contained modular application designed to be used by other apps
across the web. This can be seen in Figure 5.2.

WSDL => Web Services Description Language

UDDI => Universal Description, Discovery and
Integration SOAP => Simple Object Access Protocol

SOAP: This provides a standard packaging structure for transmission of XML documents over
various IPs. (HTTP, SMTP, FTP). A SOAP message consists of an envelope (root element),
which itself contains a header. It also had a body that carries the payload of the message.
WSDL: It describes the interface and a set of operations supported by a web service in a
standard format.
UDDI: This provides a global registry for advertising and discovery of web services by
searching for names, identifiers, categories.
Since SOAP can combine the strengths of XML and HTTP, it is useful for heterogeneous
distributed computing environments like grids and clouds
ii. Enterprise Multitier Architecture: This is a kind of client/server architecture
application processing and data management are logically separate processes. As seen
below in Figure 5.4, it is a three-tier information system where each layer has its own
important responsibilities.

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Presentation Layer: Presents information to external entities and allows them to interact with
the system by submitting operations and getting responses.
Application Logic (Middleware): These consist of programs that implement actual operations
requested by the client. The middle tier can also be used for user authentication and granting of
resources, thus removing some load from the servers.
Resource Management Layer (Data Layer): It deals with the data sources of an information
system.

iii. OGSA Grid: Open Grid Services Architecture is intended to

• Facilitate the usage of resources across heterogeneous environments
• Deliver best QoS
• Define open interfaces between diverse resources
• Develop inter-operable standards
OGSA architecture falls into seven broad areas, as shown in Figure 5.5.
Infrastructure Services, Execution Management Services, Data Management Services,
Resource Management Services, Security Services, Security Services, Information Services and
Self- management Services (automation).

These services are summarized as follows:

• Infrastructure Services Refer to a set of common functionalities, such as naming,
typically required by higher level services.
• Execution Management Services Concerned with issues such as starting and
managing tasks, including placement, provisioning, and life-cycle management. Tasks
may range from simple jobs to complex workflows or composite services.
• Data Management Services Provide functionality to move data to where it is needed,
maintain replicated copies, run queries and updates, and transform data into new
formats. These services must handle issues such as data consistency, persistency, and
integrity. An OGSA data service is a web service that implements one or more of the
base data interfaces to enable access to, and management of, data resources in a
distributed environment. The three base interfaces, Data Access, Data Factory, and Data
Management, define basic operations for representing, accessing, creating, and
managing data.
• Resource Management Services Provide management capabilities for grid resources:
management of the resources themselves, management of the resources as grid
components, and management of the OGSA infrastructure.
• Security Services Facilitate the enforcement of security-related policies within a
(virtual) organization, and supports safe resource sharing. Authentication, authorization,
and integrity assurance are essential functionalities provided by these services.
• Information Services Provide efficient production of, and access to, information about
the grid and its constituent resources. The term “information” refers to dynamic data or
events used for status monitoring; relatively static data used for discovery; and any data
that is logged.
• Self-Management Services Support service-level attainment for a set of services (or
resources),with as much automation as possible, to reduce the costs and complexity of
managing the system. These services are essential in addressing the increasing
complexity of owning and operating an IT infrastructure

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