Abstract: With the development of the computer network and communication technology, there are not only some users who need the service of the Internet, but also people who need providing real-time requirements and bandwidth assurance in many network applications. In this way, there are three kinds of primary network businesses：best-effort, real-time and bandwidth assurance businesses. How to realize packet scheduling for multi-service at the same time to achieve the control of Quality of Service become a problem worthying of study. According to the Earliest-Deadline-First algorithm, the improved EDF algorithm which is based on three kinds of primary services regarding the need of network users in the current stage is put forward. In this algorithm, a new bandwidth assurance strategy on time granularity and the schedule process based on three different models are provided. And then, the presented algorithm is simulated in the SIM network simulation environment. The results show that the improved algorithm can reduce the delay of business flows and increase the bandwidth assurance rate. As a whole, the performances of network QoS are improved.

Key words: quality of service, the earliest deadline first, best-effort service, bandwidth assurance, time granularity

摘要： 随着计算机网络和通信技术的发展，在许多网络环境中，除了要上网实现Internet服务外，可能还包括一定数量的实时要求和带宽保证用户，这主要涉及三类主要网络业务：尽力服务、实时和带宽保证业务。如何同时实现多类业务的分组调度来达到QoS控制成为一个值得研究的课题。以最早时限优先（EDF）算法为依据，针对现阶段网络用户的需求，提出了一种基于三类主要网络业务并存的改进EDF调度算法。在这种算法中，提出了基于时间粒度的带宽保证策略，依据三种不同模型对业务流进行调度，并且在SIM网络仿真环境下进行了实验。结果表明改进的调度算法在一定程度上降低了业务流的时延，提高了带宽保证率，总体上来说改善了网络QoS性能。

关键词: 服务质量, 最早时限优先, 尽力服务, 带宽保证, 时间粒度