Adding real-time networking and QoS capabilities to RTLinux-GPL

This paper presents an architecture to build distributed embedded real-time systems in the RTLinux-GPL platform. The architecture (built in a layered fashion) has being built around open source projects ranging from Ethernet drivers to a CORBA environment. The paper focuses on those layers that give support for QoS and real-time networking over Ethernet networks. The main ideas are: to accomplish deterministic access times by using a TDMA protocol over Ethernet and to multiplex different types of traffic in that real-time network, providing different service types (QoS) to each type of traffic without jeopardizing the a priori guarantee of the system´s real-time properties. Traffic types include real-time messages, multimedia streams and conventional TCP/IP traffic. The traffic multiplexing is achieved using a modular packet scheduler based on the principles of differentiated services architecture. The paper describes in detail the design basics and analyzability of both implementations: a TDMA protocol and a traffic multiplexing (QoS) layer