Hi students, coming to the next topic in the subject cloud computing or service models. So in the previous videos, I explained about the deployment models and the deployment models or the public cloud, private cloud, hybrid cloud and community cloud. And coming to the service models, the service models or the reference models on which the cloud computing is based.
The cloud computing is completely based on these service models. With the help of the service models, they are providing the services to the customers. And these can be categorized into three basic service models, infrastructure as a service, platform as a service, software as a service.
So here are the cloud service models, whatever I said, the software as a service, platform as a service, infrastructure as a service. So software as a service is access and end users. So it is connected to the end users, the end users applications, delivery as a services rather than on premises software.
So here this software as a service consists of packaged software operating systems and application stack server storage networks. Whereas platform as a service is consisting of some application developers, the application developers are going to develop an application by using the platform as a service which is provided by the cloud. Here the application platforms are middleware as a service on which developers can build and deploy custom applications so it consists of some operating systems and application stacks server storage networks and next is the infrastructure as a service so the infrastructure as a service so it is completely consisting of the hardware the server storage networks and network architecture infrastructures so here the computer storages or other id infrastructure as service rather than as a dedicated capability So rather than their own organization infrastructure, the customers are using the services of infrastructure as a service which is provided by the cloud.
Now let us see this IaaS infrastructure as a service. So before going to know about this infrastructure as a service, let us just remember IaaS, PaaS and SaaS. Infrastructure as a service is just acts like a host and whereas platform as a service is to build and software as a service is to consume.
Whatever it is built, it is consumed by the software as a service and it will be delivered to customer. Okay, so IaaS is a host, PaaS is to build and SaaS is to consume. So these three terms should be remembered so that you can clearly understand what exactly these three services are providing the services to the customer.
So it provides an access to fundamental resources such as physical machines, virtual machines and virtual storage etc. So some of the examples for IaaS is Amazon Web Services and GoGrid. And it also offers some of the services like virtual machine disk storage, virtual local area network, load balances, IP addresses, software battles.
Now let us see whatever the IaaS offers all these resources are available to end users via server virtualization. So the resources which is provided by the infrastructure as a service is available to end users. These resources are accessed by the customers as if they are own them.
So when the customers Own these resources they can access. Okay. So this is also on based of their usage only.
Based on the demand of the customer, the customer can own the resources which is provided by the infrastructure as a service. Here the organization use their own platforms and applications with a service provider infrastructure. Now let us see some of the key features of using the infrastructure as a service. Instead of purchasing hardware outright, users pay for IaaS on demand.
So rather than buying their own equipment to perform the operations or to storage by the organization, rather than purchasing their own equipment, they will use the IaaS on demand. So that is that to users pay. So by paying some... amount to the cloud they are using infrastructure as a service on demand who are using the organizations or the customers here the infrastructure is scalable depending on processing and storage needs so scalable means based on the usage you can pay if you are using less you play less if you are using more pay more like that so it is completely uh scalable depending on processing and storage needs and next Let's see the issues that are facing by the infrastructure as a software. So here the first issue is it is completely compatible with the legacy security vulnerability.
So means here infrastructure as a service offers the customers to run legacy softwares. So which provides the infrastructure to expose customers to all of the security vulnerabilities of such legacy software. so the main thing is the the main issue is the here the all the customers has to run legacy software if they are using the platform as a service next is a virtual machine sprawl the virtual machine can become out of date with respect to the security updates so whenever the security updates are there automatically the virtual machines can become out of date so the cloud providers had to provide some service to that automatically update such virtual machines but it is somewhat hard and complex to maintain this mechanism so that is one of the issue and robust of virtual machine isolation so here the ios offers an isolated environment robust means ias infrastructure as a service offers an isolated environment so to individual customers through hypervisors and the next issue is data arrest practice data is practice means suppose whenever the customer using this cloud okay so whenever the customer releases the resources the cloud provider must ensure that next customer to rent the resources does not observe data of previous customer so whenever the customer releases the resources the cloud provider has to take care about that that disk has to be arranged perfectly so these are the issues faced by this Platform as a Service