for each process and cycle through them. This method is heavily bases on a lot of time consuming to each process. Too short a lot time will fragment the processes, and too long a lot time will increase waiting time for each process to be executed. Choosing right a lot time is the foundation for this method. Multilevel queue scheduling Many queues are used in Multilevel queue scheduling method and each queue has its own scheduling algorithm. Multilevel queue scheduling is more complex compare to other methods, but it provides flexibility for OS to serve different data in complicated situation. Networking In networking, packets are the key foundation for scheduling. There are many different types of packet travelling around network core every day, and they are treated totally different. For example, voice and video packets have higher priority than normal packets. In order to manage and distribute packet effectively, network devices also use input queue to determine which packet will be transmitted first. First in, first out queue (FIFO) In this mode, packets are taken out from the queue in the order that they are coming from the queue. Every packet is treated the same priority. If a large packet A comes before a small packet B, B still has to wait until A is completely served. If a system treats every packet the same, users can experience the delay in transmitting such as: voice packets. Weighted fair queue (WFQ) Weighted fair queue uses the min-max-fair-share algorithm to distribute packets. The min fair-share means the network OS will distribute equally minimum resource for each type of packet. The max fair-share means the network OS will provide more resource for packets that need to transfer large amount of date at that moment, but it will take the resource back after transferring. “Weighted” means the scheduler will assign weight for each type of packet. Base on the weight, it will determine how to put packet into the queue and serve them. Usually, each packet will be weighted based on IP Precedence field from IP header of each packet. Fair allocation = (resource capacity – resource already allocated) / number of packets Priority queue (PQ) Priority queue is divided into 4 sub queues with different priorities. Data in each queue are only served when the higher priority queues are empty. If data come into the empty higher priority queue while the network OS