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

Recent Linux[7] kernel introduced an interrupt mitigation method called NAPI to reduce the overhead of interrupt handling procedures caused by frame arrival and transmission. However, NAPI caused serious delay and jitter in such procedures. On the other hand, many conventional real-time communication mechanisms were implemented independently to the existing network stack, and most of such mechanisms disabled the stack. Therefore, it is difficult to utilize both of real-time communication and IP communication in parallel. This paper proposed a parallel implementation method to realize both of real-time communication and IP communication simultaneously in a single computer unit. This method implement real-time network stack and IP network stack in parallel by using multiple queue functionality in a NIC (network interface card). Also, this method applied the interrupt mitigation method only to the IP stack. Therefore, this method achieved to reduce the overhead of the wide bandwidth of IP traffic, also to keep delay and jitter of real-time traffic enough small. Some experiments were conducted to measure the performance of the proposed method. The RTT (round trip time) delay of real-time communication was kept lower than 100 mu s even in high traffic load of 800 Mbitis with small jitter, while the RTT of IP communication varied between 100 mu s to 20 ms. This paper introduced the design, implementation, and evaluation of the proposed method.