Cloud computing is an emergent paradigm that allows to customers to rent infrastructure, platforms and software as a service. With resource sharing and reuse through virtualization technology, cloud environments become even more effective and flexible. Nevertheless, networking within virtualized cloud still presents some challenges in performance and resource allocation. In this paper, we propose to integrate an SLA-based Dynamic Bandwidth Allocator (DBA) in a vitualized cloud environment. DBA manages bandwidth allocation efficiently through allocating bandwidth according to the application requirements and the established agreement. It also adjusts the allocated bandwidth dynamically upon change and reduces physical resources usage by dropping packets in the virtual machines rather than the driver domain. Through experimental evaluation we showed the efficacy of the proposed algorithm and the agreements respect.