Cloud computing is a term used to describe a paradigm for delivery of computing services to users on a pay-as-you-go basis. In this paradigm, users utilize the Internet and remote data centres to run applications and store data.[1].The cloud technology allows more efficient computing by removing most of the upfront costs of setting up an IT infrastructure. It allows organizations to expand or reduce their computing facilities[1].Cloud computing delivers infrastructure, platform, and software that are made available as subscription-based services in a pay-as-you-go model to consumers.
These services are referred to as Infrastructure as a Service (IaaS), Platform as a Service (PaaS), and Software as a Service (SaaS) in industries. The adoption of cloud computing spans across industry, governments, [2]{3}. Data centres are crucial to provide the large volumes of compute and storage resources needed by today’s Internet businesses including web search, content distribution and social networking[2][3] Clouds aim to power the next-generation data centres as the enabling platform for dynamic and flexible application provisioning[1].
Based on the trends toward migrating both mission-critical and performance-sensitive workloads to the cloud deployment model and the convergence of mobile, social, and analytics workloads on the cloud, we see a shift of the value proposition of cloud computing from cost reduction to simultaneous agility and optimization.[4] . To achieve cost efficiencies and on demand scaling, cloud data centres are highly multiplexed shared environments, with VMs and tasks from multiple tenants coexisting in the same cluster virtualized and managed as virtual machines[4] .MUILT SERVICE NETWORK THE Typical example of MUILT Service INFRASTRUCTURE is Data center network(DCN). The data center is home to the computational power, storage, and applications necessary to support an enterprise business. The data center infrastructure is central to the IT architecture, from which all content is sourced or passes through. Proper planning of the data center infrastructure design is critical, and performance, resiliency, and scalability need to be carefully considered.Another important aspect of the data center design is flexibility in quickly deploying and supporting new services, The data center network design is based on a proven layered approach, the Basic Layered Design for data center is , composing the DCN Typical DCN architecture is made up by a three-tier topology, which consists of edge, aggregate, and core switches on each layer .[7] Cloud Datacentre is an pool of unlimited resources (RAM, memory, storage), with which to replicate a physical data centre into a virtual environment, adding as many products (firewall, load balancer, VPN, VLAN, etc.) or solutions (SAP Hana, Oracle, D & R) as you need. With your Cloud Datacentre you can create, modify, re-distribute and manage your virtual data centre in an agile and simple way, and control or manage it through a powerful web control panel in real time.Host servers in a cloud data centre are interconnected through network links and switches Host servers within a rack are connected to one or more edge switches, i.e., Top-of-Rack (ToR) switches, and edge switches are connected to upper-tier aggregate switches. Each of the aggregate switches connects to multiple core switches of the top tier.[7]SOFTWARE DEFINE NETWORK In traditional ways of networking when we talk about switches, routers they are generally linked with the network functionality. It was supposedly the job of a network administrator to manually setup a device whenever a new device had to be setup in the network. This specific activity of adding and configuring devices lead to various errors and usually took too much of time. In traditional ways of routing, each router had to be configured separately in the network by the network administrator . This is because control plane and data plane were in the same entity which typically can be a router, switch, etc [6] . This is a tedious and time-consuming task. Also, adding and deleting devices often lead to mistakes and errors. Imagine if there are thousands of routers or switches to be setup in a network, the time to set it up will be large and in most cases a lot of manpower will be needed. This lead to the arrival of software defined networks.SDN is a new way of centrally managing network switches with ability of fine-grained traffic management. SDN enables network elements to be dynamically programmable and controllable through a central controller. This is made possible in SDN by moving the data forwarding plane away from the data control plane. [7]TO conquer the weaknesses of legacy network in the cloud data center, software-defined networking (SDN) is implementing in cloud data centers for idea in the DCN. In software defined networks, the control plane and data plane are decoupled from each other. This decoupling enables the network administrator to manage the dumb switches from a central controller. The controller is often centrally placed and is connected to multiple switches in the forwarding plane[6] SDN gives a single controller to oversee the whole network at the central controller and progressively change that occurs in the network. The network controller can change the flow of network which is very much fitted for the dynamic idea of the cloud service. Google is cloud service provider that already implemented SDN technology in their data center to increase the scalability and manageability. Controllers in SDN can oversee the entire network and thus efficiently perform dynamic bandwidth allocation per flow, faster recovery, and traffic consolidation, all of which can be exploited to improve QoS and energy efficiency[7]