Design, implementation, and evaluation of a software-based real-time Ethernet protocol

Abstract

Distributed multimedia applications require p erformance guarantees from the underlying network subsystem. Ethernet has been the dominant local area network architecture in the last decade, and we believe that it will remain popular because of its cost-eectiveness and the availability of higherbandwidth Ethernets. We present the design, implementation and evaluation of a software-based timed-token protocol called RETHER that provides real-time performance guarantees to multimedia applications without requiring any modications to existing Ethernet hardware. RETHER features a hybrid mode of operation to reduce the performance impact on non-real-time network trac, a race-condition-free distributed admission control mechanism, and an ecient token-passing scheme that protects the network against token loss due to node failures or otherwise. To our knowledge, this is the rst software implementation of a real-time protocol over existing Ethernet hardware. Performance m e asurements from experiments on a 10 Mbps Ethernet indicate that up to 60% of the raw bandwidth can be r eserved without deteriorating the performance of non-real-time trac. Additional simulations for high bandwidth networks and faster workstation hardware indicate that the protocol allows reservation of a greater percentage of the available bandwidth.1 Introduction With the growing trend towards distributed multimedia applications, it has become essential for the underlying systems to provide resource guarantees. Applications such a s LAN-based teleconferencing and video-on-demand services require support for real-time data transport from the underlying network to support real-time video playback. LANbased real-time transport also plays a critical role in extending WAN-based teleconferencing systems to the end-user's display, which m a y be connected to the site's WAN interface with a local area network. With the large existing base of Ethernets, it is essential to support such applications on the Ethernet. Our work addresses the problem of providing bandwidth guarantees on an Ethernet-based network.

Hardware Acceleration for Conditional State-Based Communication Scheduling on Real-Time Ethernet

“…We can implement such a framework in two ways: in software and in hardware. Commercially available and research systems [8], [10]- [13], [19]- [22] would allow us to implement it in software on top of it-this has already been done [18] and the driver resides in the network driver of a real-time Linux system using standard Ethernet. This provides good flexibility, because the software can easily be changed and extended to accommodate new features.…”

“…This motivated research to move towards commercial off-the-shelf (COTS) Ethernet components. Approaches using COTS advocate either statistical methods [4]- [7] for traffic shaping and traffic prediction or higher level communication frameworks [8]- [14] on top of the standard Ethernet card with a separate arbitration mechanism. However, running the framework and arbitration control on the workstation can cause a huge computation overhead in the processor [15] and is subject to high jitter.…”

Network-Code Machine: Programmable Real-Time Communication Schedules

“…However, the coding schemes for schedules have been ignored so far. Thus, most related work uses either a table-based structure to describe the schedule or implements a policy for online scheduling (see [18,12,11,24,23]). …”

“…This approach is static, because the system executes one row after the other and there are no variations. Dynamic policy-driven schedules (see for example [24,4] and a survey [13]) utilize an algorithm, which implements the protocol's media-accesscontrol policy and decides dynamically, which node gets which communication slot. The policy can implement any arbitrary schedule with on-the-fly decisions.…”

RTnet: a distributed real-time protocol for broadcast-capable networks

“…The real-time network RETHER [16][17][18], developed at the State University of New York at Stony Brook, is based on Ethernet. It uses a token-based technique to regulate access of all the nodes to the network.…”