Queuing Models of DATA-ACK Prioritization in TCP

[[abstract]]在數據網路的環境中，不管是有線還是無線的，其品質都與封包的優先權有關。TCP傳送必須要確定接收到ACK，因此，當在傳送時，ACK傳輸的優先權也會影響到網路的延遲時間效能。比較TCP與ACK 之間優先權的變化對網路的品質是有幫助的，因此可以透過排隊理論的網絡模組去找出符合TCP/ACK傳輸模式的排隊模型並加以探討。在排隊理論中可以發現到reservations and polling的排隊模型是最符合TCP/ACK可靠傳送模式。 因此可以透過reservations and polling的公式去做一些修改來推導出TCP/ACK 優先權改變的公式，公式部分則可以分成2部分，第一部分是TCP > ACK 公式(TCP優先權較高)，第二部分是ACK > TCP 的公式(ACK優先權較高)。公式推倒出來比較2者哪一種的延遲是比較小的。因此可以知道RTT(Round Trip Time)較小者的TCP/ACK的效率是比較好，就可以利用該種優先權模式去改進延遲時間及效能。另外，藉由NS2驗證本排隊模型的正確性。[[abstract]]Regardless of wired or wireless comp. networks, Quality of Service (QoS) has much to do with priority. A TCP transmission is confirmed, successfully after the reception of its ACK. Hence, in a TCP session, The priority ACK affects transmission delays. Comparison of the priorities between TCP and ACK is helpful to achieve QoS. We analyze TCP-ACK using queuing models. Among queuing models, the reservation and polling one is suitable and is adopted to analyze the performance of TCP-ACK. We modify the queuing models of reservation and polling by adding the priority without preemption. We have two schemes, TCP > ACK (TCP has higher priority) and ACK > TCP (ACK priority is higher). Two queuing models are compared, and we find that the ACK > TCP scheme provides shorter delay and better QoS. In addition, the model is verified using NS2