er is responsible for QoS enforcement for the cloud services. Service layer. This contains the implementation of the cloud services and controls the software components. This layer is dependent upon the resource layer and its capabilities, which directly influence the QoS (e.g. specified in the SLA). Resource layer. This contains the resources, such as servers (in data centers), switches, and routers for the networking, storage devices, and non-cloud software. Most of today's Internet services are based on the cloud computing paradigm, partic- ularly OTT services. All cloud service types are grouped into a limited number of cloud computing service categories. All such categories are based on the following: Infrastructure as a service (IaaS). It allows the CSCs to use the provided cloud infras- tructure resources, which include processing, storage, or networking. Platform as a service (PaaS). CSP provides to CSC a platform that includes operating systems, execution environment for a given set of programming languages, databases, and web servers. Software as a service (SaaS). CSPs install and manage application software in the cloud, thus reducing the need to run the software on cloud users' own computers or devices. All cloud computing services are using one or more cloud computing categories (IaaS, PaaS, and SaaS). Regarding the network impact on cloud services and their QoS require- ments, there are two main types [2]: Over the top (OTT) cloud services. They are provided over the public Internet network. With network neutrality in force, there is no possibility for differentiation of cloud 6 Services in Fixed and Mobile Ultra-Broadband services from other Internet services regarding network performance. However, CSPs can provide QoS support by proper dimensioning of all four layers: resource layer, service layer, access layer, and user layer. In general, many OTT services utilize cloud services (e.g. SaaS is the most used cloud service category), such as web applications that offer storage, social networking ser