Software traffic management architecture for multimedia flows over a real-time microkernel

Traffic management schemes such as Connection Admission Control (CAC), poli cing, and traffic shaping are important to provide multimedia communication s with better Quality of Service (QoS). In the conventional model, admissio n control and policing are done at intermediate nodes, and traffic shaping is done at the edge of a network. However, QoS of communications should be defined between tasks or threads rather than between hosts. Therefore traff ic management inside a host is as important as that in networks. We propose software-based traffic management architecture over a real-time microkerne l. The architecture focuses on the interface between a network driver and u ser threads calling the driver. We categorized services of communication th reads into three classes: Real-Time at Guaranteed Rate (RT-GR), Real-Time a t Available Rate (RT-AR), and Rest-Effort (BE). Our architecture is designe d for an environment containing a mixture of these services. In the archite cture, a sender periodic thread of RT-GR or RT-AR is executed such that the sending rate matches a user-specified rate. The network driver monitors th e per-how rate of injected data and discards the data if the injected rate exceeds the user-specified rate. To avoid the continuous discarding of data , the sending thread can adjust its sending rate by periodically looking at logged data concerning the rate. RT-AR service can achieve more than the s pecified rate when bandwidth is available. The scheme of software traffic m anagement is effective in attaining higher throughput not only for full-dup lex Ethernet but also for ATM because the difference of rate between hardwa re and software is reduced. In this paper, we describe the design and imple mentation of the software-based traffic management architecture on Real-Tim e Mach. The results of performance evaluations demonstrate that our traffic management scheme performs well for full-duplex Ethernet.