Notes for BSc CSIT

  Thread is different from the task in the following ways:- A t ask  describes a program that may need input files and generate output files as a result of its execution and applications are a collection of tasks. Tasks are submitted for execution, and their Output data is gathered at the conclusion. The way tasks are produced, the sequence in which they are executed, and whether they need data interchange to distinguish the application models that come under the task programming umbrella.  A Task may be used to indicate what you want to perform, and then that Task may be attached to a Thread. Threads are utilized to finish the task by splitting it up into pieces and executing them individually in a distributed system. A  thread  is a fundamental unit of CPU utilization that consists of a program counter, a stack, and a collection of registers. Threads have their program and memory areas. A thread of execution is the shortest series of programmed instructions th...

  HYPERVISOR A hypervisor (also known as a virtual machine monitor, VMM, or virtualizer) is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is called a host machine, and each virtual machine is called a guest machine. The hypervisor presents the guest operating systems with a virtual operating platform and manages the execution of the guest operating systems.  The term hypervisor is a variant of supervisor, a traditional term for the kernel of an operating system: the hypervisor is the supervisor of the supervisors, with hyper- used as a stronger variant of super. A hypervisor is a function that abstracts, or separates, operating systems and applications from the underlying computer hardware. This abstraction enables the underlying host machine hardware to run one or more virtual machines as guests independently, allowing numerous guest VMs to effectively shar...

 Cloud Computing Cloud Computing is the delivery of on-demand IT resources (such as the Internet, database, Server, Big-Data, etc ) implemented on the internet to process, manage and store data. In cloud computing, we can pay for only those resources which we have used. Benefits of Cloud Computing: Data backup and Storage of data Powerful server capabilities Incremental Productivity Cost-effective and Time-saving Agility (Access to a broad range of technology) Elasticity    The differentiating public cloud from the private cloud. Public Cloud :  The cloud services which are exposed to the public and can be used by anyone are called public clouds. The public cloud is owned, managed, and operated by businesses, universities, and government organizations. In the public cloud, data centers are located anywhere on the internet.  P rivate Cloud: The cloud services which are private in the internal network within the organizations and selected users ins...

  CLOUD SERVICE REQUIREMENTS 1. Efficiency/cost reduction By using cloud infrastructure, you don’t have to spend huge amounts of money on purchasing and maintaining equipment. 2. Data security Cloud offers many advanced security features that guarantee that data is securely stored and handled. Cloud storage providers implement baseline protections for their platforms and the data they process, such as authentication, access control, and encryption. 3. Scalability Different companies have different IT needs — a large enterprise of 1000+ employees won’t have the same IT requirements as a start-up. Using the cloud is a great solution because it enables enterprises to efficiently — and quickly — scale up/down according to business demands. 4. Mobility Cloud computing allows mobile access to corporate data via smartphones and devices, which is a great way to ensure that no one is ever left out of the loop. Staff with busy schedules, or who live a long way away from the corporat...

 MapReduce  MapReduce is triggered by the map and reduces operations in functional languages, such as Lisp. This model abstracts computation problems through two functions: map and reduce. All problems formulated in this way can be parallelized automatically. All data processed by MapReduce are in the form of key/value pairs. The execution happens in two phases. In the first phase, a map function is invoked once for each input key/value pair and it can generate output key/value pairs as intermediate results. In the second one, all the intermediate results are merged and grouped by keys. The reduce function is called once for each key with associated values and produces output values as the final results. A map function takes a key/value pair as input and produces a list of key/value pairs as output. The type of output key and value can be different from input key and value: map::(key1,value1) => list(key2,value2) A reduce function takes a key and associated value list as in...

  CLOUD SERVICES Cloud computing service models are divided into three categories: Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS) (SaaS). There are evident distinctions between the three in terms of what they can provide a business in terms of storage and resource sharing, but they may also interact with one another to build a single comprehensive cloud computing platform. 1. IaaS (Infrastructure as Service):  This is the most prevalent cloud computing service architecture since it provides the underlying infrastructure of virtual servers, networks, operating systems, and data storage devices. It provides the flexibility, stability, and scalability that many organizations desire from the cloud while eliminating the need for hardware in the office. This makes it excellent for small and medium-sized businesses seeking a cost-effective IT solution to support business growth. IaaS is a completely outsourced pay-for-use service th...

  Cloud The “cloud” in cloud computing can be defined as the set of hardware, networks, storage, services, and interfaces that combine to deliver aspects of computing as a service. Cloud services include the delivery of software, infrastructure, and storage over the Internet. A cloud service is any service made available to users on demand via the Internet from a cloud computing provider's servers as opposed to being provided from a company's own premises servers explained before, the most common cloud service is that one offers data storage disks and virtual servers, i.e. infrastructure. Examples of Infrastructure-as-a-Service (IaaS) companies are Amazon, Rackspace, and Flexi scale. Cloud computing is the use of computing resources (hardware and software) that are delivered as a service over a network (typically the Internet).  Cloud computing is the on-demand availability of computer system resources, especially data storage (cloud storage) and computing power, without direc...

 Disaster recovery (DR)   Disaster recovery (DR) is an area of security planning that aims to protect an organization from the effects of significant negative events. DR allows an organization to maintain or quickly resume mission-critical functions following a disaster. A disaster can be anything that puts an organization's operations at risk, from a cyberattack to equipment failures to natural disasters. The goal with DR is for a business to continue operating as close to normal as possible. The disaster recovery process includes planning and testing and may involve a separate physical site for restoring operations. The recovery point objective (RPO) differs from the recovery time objective (RTO):- Recovery point objective (RPO) and recovery time objective (RTO) are two important measurements in disaster recovery and downtime. RPO is the maximum age of files that an organization must recover from backup storage for normal operations to resume after a disaster. The recov...

Data center virtualization  Data center virtualization is the process of designing, developing, and deploying a data center on virtualization and cloud computing technologies. It primarily enables virtualizing physical servers in a data center facility along with storage, networking, and other infrastructure devices and equipment. Data center virtualization usually produces a virtualized, cloud, and collocated virtual/cloud data center. Virtualization, Offering profound changes to the way data centers perform, virtualization makes sense on multiple levels.  The benefits of data center virtualization are as below: 1. Less heat buildup Millions of dollars have gone into the research and design of heat dissipation and control in the data center. But the cold, hard fact is, all of those servers generate heat. The only way around that? Use fewer servers. How do you manage that? Virtualization. Virtualize your servers and you're using less physical hardware. Use less physical hardwa...

Manages Service Providers (MSP)  A managed service provider (MSP) is a company that remotely manages a customer's IT infrastructure and/or end-user systems, typically on a proactive basis and under a subscription model. The MSP business model differs from other types of channel companies, such as value-added resellers (VARs), in numerous ways described below. MSPs charge for their services under a number of different pricing models. Typical approaches include per-device, per-user and all-inclusive pricing. 2nd part In the past, the concept of providing a service involved much more than inventing and designing the service, itself. The appropriate amount and quality of hardware were required for every company to not only build their service but have an adequate amount of space to hold and maintain the hardware for the life of each service, as well. Fortunately, that on-premise era is slowly but surely passing, leaving those rather dated companies still attempting to manage their own ...

 Service-oriented architecture (SOA)   Service-oriented architecture (SOA) is a software development model for distributed application components that incorporates discovery, access control, data mapping, and security features. Service-oriented architecture (SOA) is a software development model for distributed application components that incorporates discovery, access control, data mapping, and security features. The use of services provides major benefits: In contrast to the use of large applications, which tend to be “information silos” that cannot readily exchange information with each other, the use of finer-grained software services gives freer information flow within and between enterprises. Integrating major applications is often expensive. SOA can save integration costs. Organizing internal software as services makes it easier to expose its functionality externally. This leads to increased visibility that can have business value, for example, when a logistics comp...

Intrusion Detection System (IDS)  An Intrusion Detection System (IDS) is a network security technology originally built for detecting vulnerability exploits against a target application or computer. Intrusion Prevention Systems (IPS)extended IDS solutions by adding the ability to block threats in addition to detecting them and has become the dominant deployment option for IDS/IPS technologies. This article will elaborate on the configuration and functions that define the IDS deployment. Active and passive IDS An active Intrusion Detection System (IDS) is also known as Intrusion Detection and Prevention System (IDPS). The intrusion Detection and Prevention System (IDPS) is configured to automatically block suspected attacks without any intervention required by an operator. Intrusion Detection and Prevention System (IDPS) has the advantage of providing real-time corrective action in response to an attack. Network Intrusion detection systems (NIDS) and Host Intrusion detection systems...

 Virtualization is one of the key components of the cloud computing paradigm, especially in infrastructure as a service model where the mentioned technology is essential to provide a large set of computing resources. Some experts even define cloud computing as simple as virtualized hardware and software plus advanced monitoring and resource management technologies. To say it straight and clear, without virtualization, cloud computing would leave the data unstable, uncontrolled, and unsafe. It is an important and probably an inseparable element of cloud computing services. Virtualization allows us to consolidate multiple physical components so that they can be managed in one place. With the help of virtualization, organizations have better visibility and also greater control of their infrastructure making security management simpler for the cloud. It is due to virtualization that cloud computing services are so cost-effective. Moreover, it is also responsible for the simplicity of d...

 A service-oriented architecture is essentially a collection of services. These services communicate with each other. The communication can involve either simple data passing or it could involve two or more services coordinating some activity. The reality in IT enterprises is that infrastructure is heterogeneous across operating systems, applications, system software, and application infrastructure. Some existing applications are used to run current business processes, so starting from scratch to build new infrastructure isn't an option. Enterprises should quickly respond to business changes with agility; leverage existing investments in applications and application infrastructure to address newer business requirements; support new channels of interactions with customers, partners, and suppliers; and feature an architecture that supports organic business. SOA with its loosely coupled nature allows enterprises to plug in new services or upgrade existing services in a granular fashio...

 Infrastructure as a Service (IaaS) is one of the three fundamental service models of cloud computing alongside Platform as a Service (PaaS) and Software as a Service (SaaS). Infrastructure as a Service is a provision model in which an organization outsources the equipment used to support operations, including storage, hardware, servers, and networking components.  The service provider owns the equipment and is responsible for housing, running, and maintaining it. The client typically pays on a per-use basis. Clients are able to self-provision this infrastructure, using a Web-based graphical user interface that serves as an IT operations management console for the overall environment. API access to the infrastructure may also be offered as an option. IaaS is usually seen to provide a standardized virtual server. The consumer takes responsibility for the configuration and operations of the guest Operating System (OS), software, and Database (DB). Compute capabilities (such as p...

  Service-oriented architecture (SOA)  Service-oriented architecture (SOA) references a set of principles and methodologies applied by software engineers to design and develop software in the form of interoperable services. Services are usually built in the form of components that can be reused for different purposes than originally intended. For this reason, the interfaces are often defined in a practical manner, allowing use across varying applications and multiple platforms. The principal characteristics of SOA are described in more detail here: SOA is black-box component architecture. The black box lets you reuse existing business applications; it simply adds a fairly simple adapter to them. You don’t need to know every detail of what’s inside each component; SOA hides the complexity whenever possible. SOA components are loosely coupled. Software components are loosely coupled if they’re designed to interact in a standardized way that minimizes dependencies. One loosely co...

Amazon Elastic Compute Cloud (Amazon EC2)  Amazon Elastic Compute Cloud (Amazon EC2) is an Amazon Web Service (AWS) you can use to access servers, software, and storage resources across the Internet in a self-service manner. It provides scalable, pay-as-you-go compute capacity. It is said to be elastic since it is scalable in both directions along the client as well as the service provider.  Amazon EC2 provides the following features: Virtual computing environments, known as instances Preconfigured templates for your instances, known as Amazon Machine Images (AMIs), that package the bits you need for your server (including the operating system and additional software) Various configurations of CPU, memory, storage, and networking capacity for your instances, known as instance types  Secure login information for your instances using key pairs (AWS stores the public key, and you store the private key in a secure place) Storage volumes for temporary data that are deleted whe...

  Platform as a Service PaaS, or Platform as a Service, is simply a cloud basis where you can create, test, and organize various apps for your organization. Implementing PaaS streamlines the company's software development process.  Paas's virtual runtime environment provides a conducive environment for creating and testing applications. The full set of resources available in the form of servers, storage, and networking can be managed by the organization or a platform provider.  PaaS services such as Google App Engine and AWS Elastic Beanstalk are  common examples.  PaaS is also subscription-based, giving you various pricing options based on your business's needs. PaaS provides - Applications Deployment - Configuring application components - Provisioning and configuring supporting technologies The Essential Characteristics of PaaS 1. Runtime Framework This is the “software stack” aspect of PaaS, and perhaps the aspect that comes first to mind for most people. The...

Virtualization  Virtualization is the "creation of a virtual (rather than actual) version of something, such as a server, a desktop, a storage device, an operating system or network resources". In other words, Virtualization is a technique, which allows sharing a single physical instance of a resource or an application among multiple customers and organizations. It does by assigning a logical name to physical storage and providing a pointer to that physical resource when demanded. The role of Virtualization in a Cloud Environment 1. Protection from System Failures Technology is always at risk of crashing down at the wrong time. Businesses can tolerate a few glitches, but if your developer is working on an important application that needs to be finished immediately, the last thing you could wish for is a system crash. To counter this risk, virtualization lets you open the same work on another device. Store all your backup data through virtualization on cloud services or virtua...

 Platform as a service (PaaS) Platform as a service (PaaS) is a category of cloud computing services that provide a computing platform and a solution stack as a service. Along with software as a service (SaaS) and infrastructure as a service (IaaS), it is a service model of cloud computing. PaaS offerings facilitate the deployment of applications without the cost and complexity of buying and managing the underlying hardware and software and provisioning hosting capabilities. Technically, a PaaS is an Application Platform comprised of an operating system, middleware, and other software that allows applications to run on the cloud with much of the management, security, scaling, and other stack-related headaches abstracted away. This allows you to focus on two things: customers and developing your application. Let the PaaS deal with system administration details like setting up servers or VMs, installing libraries or frameworks, configuring testing tools, etc. Platform as a Service al...