Masahiko Nakahara

Isochronous scheduling and its application to traffic control

Existing operating systems and communication protocols cannot achieve high quality video data transmission on an Ethernet, because they lack QoS assurance mechanisms for the shared medium. We have developed a kernel called Tactix to investigate new QoS assurance technologies that enable distributed continuous media applications. In this paper we focus on fixed bit rate video data transfer over an Ethernet, and we propose isochronous scheduling and its application to software traffic shaping. Furthermore, we present the results of measuring the service quality achieved by these technologies, which we obtained using ordinary personal computers and a shared mode 100-Mbps Ethernet. These indicate that the technologies enable multiple video streams (up to a total bandwidth of about 60 Mbps) and non-real-time background traffic to coexist on an Ethernet with a very low packet loss ratio and a transmission delay of less than a few milliseconds.

A Micro-kernel for Isochronous Video-Data Transfer

We developed a new micro-kernel (Tactix) that provides isochronous thread scheduling. Isochronous scheduling is designed to achieve cyclic executions of multiple threads with extremely low jitters (less than 1 msec). Furthermore, we made an experimental video-server application on top of Tactix and evaluated its performance and service quality.