Cloud computing is on-demand access to a shared pool of computing resources. It is an all-inclusive solution in which all computing resources are provided rapidly to users as demand dictates. The use of the word \"Cloud\" makes reference to the two essential concepts, namely, abstraction and virtualization. Cloud computing, which can be seen as an evolution of Grid computing, has taken many features of Grid computing itself. For cloud service reservation, the consumer and service provider need to establish the service level agreements through negotiation.