On Soft Real-Time Guarantees on Ethernet

Abstract

The medium access protocol of Ethernet, CSMA/CD, has an inherent limitation in providing real-time guarantees. Since Ethernet is the most commonly-used local area network (LAN) technology due to its low cost, high bandwidth and robustness, it is very important to overcome this problem so that Ethernet can be used as a network for soft real-time applications like multimedia. An adaptive traffic smoother (ATS) was proposed as a kernel-level software solution that provides soft real-time guarantees on Ethernet.

This paper addresses the reconfigurability, scalability and portability of ATS. First, a mechanism to read and adjust several user-specific parameters of ATS is discussed, and metrics or parameters to indicate the achievement of the user-required Quality-of-Service (QoS) are developed since these parameters are indirectly related to the user-specific QoS. Our experimental evaluation validates the feasibility of enhancing the reconfigurability and portability of ATS. Second, ATS is extended to a switched Ethernet which is commonly used for scalability. Our solution employs an ATS for each port of the switch for real-time packet delivery guarantees. Finally, a prototype of the user-level ATS is implemented and evaluated to enhance the portability of ATS. The performance of this user-level ATS is shown to be comparable to that of the kernel-level implementation, while enhancing both the reconfigurability and portability of real-time Ethernet solutions.

This work reported in this paper was supported in part by DARPA under the US AFRL contracts F30602-01-02-0527.