Grid technologies are emerging as the next generation of distributed computing, allowing the aggregation of resources that are geographically distributed across different locations. The network remains an important requirement for any Grid application, as entities involved in a Grid system (such as users, services, and data) need to communicate with each other over a network. The performance of the network must therefore be considered when carrying out tasks such as scheduling, migration or monitoring of jobs. Network buffers management policies affect the network performance, as they can lead to poor latencies (if buffers become too large), but also leading to a lot of packet droppings and low utilization of links, when trying to??keep a low buffer size. Therefore, network buffers management policies should be considered when simulating a real Grid system. In this paper, we introduce network buffers management policies into the Grid Sim simulation toolkit.Our framework allows new policies to be implemented easily, thus enabling researchers to create more realistic network models. Fields which will harness our work are scheduling, or QoS provision. We present a comprehensive description of the overall design and a use case scenario demonstrating the conditions of links varied over time.