This paper is an overview of virtual network embedding strategies within cloud infrastructure backbone networks. We will first of all summarise and define the main principles of cloud computing and its different supplied services. Then, we will describe the cloud infrastructure architecture, named the Totally Virtualized Cloud Infrastructure (TVCI), which makes use of virtualization in all the cloud's equipment (i.e., backbone and data centers). Afterwards, we will describe, analyse, and compare the main virtual network mapping algorithms for cloud infrastructure networks found in existing literature. We will evaluate the above strategies in terms of: i) virtual network request reject rate, ii) embedding cost of virtual network request, iii) embedding revenue of virtual network request and iv) average usage rate of physical resources.