As one of the fastest growing wireless access technologies, wireless LANs must evolve to support adequate degrees of service differentiation. Unfortunately, current WLAN standards like IEEE 802.11 Distributed Coordination Function （DCF） lack this ability. Work is in progress to define an enhanced version capable of supporting QoS for multimedia traffic at the MAC layer. In this paper, we aim at gaining insight into three mechanisms to differentiate among traffic categories, i.e., differentiating the minimum contention window size, the Inter-Frame Spacing （IFS）, and the length of the packet payload according to the priority of different traffic categories. We propose an analysis model to compute the throughput and packet transmission delays. In addition, we derive approximations to obtain simpler but more meaningful relationships among different parameters. Comparisons with discrete-event simulation results show that good accuracy of performance evaluation can be achieved by using the proposed analysis model.
基于最长前缀匹配,本文提出了一种新的IP转发表搜索方法。该方法在实现过程中依赖的主要硬件是一片逻辑控制器以及高速的DDRII(Double Date RateⅡ)SDRAM(Synchronous Dynamic Random Access Memory)。依据研究IP地址前缀所得出的规律,将IP地址前缀存储到DDRII中。该搜索方法能够将搜索时间限制在两个DDRII读周期之内,不超过4ns;同时保证转发表更新时间小于512ns。
