Parallel Implementation of Real-Time Communication and IP Communication by using Multiple Ring Buffers

Abstract

In this paper, an Ethernet device using two ring buffers was implemented in order to achieve a parallel realization of a real-time communication and an IP communication. Using a conventional device driver, it is difficult to realize such a parallel realization. This is because the non real-time frames (IP frames) are processed using a NAPI mechanism, which introduces large delay and variation. Therefore, processing flows of the real-time frames (RT frames) must be separated from that of IP frames. A proposed mechanism was implemented by modifying the existing open source device driver to realize the flow separation mentioned above. By the modifications of the device driver, the RT frames and the IP frames can be distinguished and managed in the different ring buffers. RT frames are sent to a real-time frame ring buffer and they are processed immediately by using a hardware interrupt. IP frames are processed regularly by the conventional Linux network stack. By implementing them, the proposed device driver achieved 100µs or lower RTT (Round Trip Time) with a real-time communication in parallel with 500Mbit/s or wider bandwidth of IP traffic load. This paper shows the design, the implementation, and the evaluation of the priority processing device driver.