Design and implementation of a real-time switch for segmented Ethernets

Providing network bandwidth guarantees over an Ethernet requires coordination of the network nodes for traffic prioritization such that real-time data can have deterministic access to the network. We have shown previously how RETHER, a software based token passing protocol can efficiently provide real-time support over a single shared Ethernet segment. This work extends the token passing mechanism into a switched, multi-segment Ethernet environment. This paper describes the detailed design issues, their solutions, and a fully operational switch implementation built into the FreeBSD kernel. By testing the protocol independently and as the underlying network protocol of the Stony Brook Video Server, we have verified that the bandwidth guarantees are successfully provided, with relatively low run-time overhead, for real-time connections crossing multiple Ethernet segments. This paper also provides a comprehensive performance evaluation of the prototype