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Abstract:

Distributed multimedia applications require guaranteed quality of service (QOS) from the underlying networks. Most of the QOS research is focused on networks consisting of Layer-3 routers or ATM switches. Relatively little attention is given to the QOS support on existing local area networks, in particular Ethernet, which essentially forms the last mile of the end-to-end network bandwidth guarantee solution. This paper describes the design, implementation, and evaluation of a real-time Fast Ethernet switch called EtheReal that provides bandwidth guarantees to real-time applications running on Ethernet without modification to the hardware and operating system on the host machines. At the heart of the EtheReal switch architecture is a novel real-time connection setup protocol that is completely transparent to the host machine's OS, and thus allows the switch to be deployed in a network of heterogeneous machines running different OS platforms. The only dependency of EtheReal on the hosts is their support for TCP/UDP/IP. In addition, the EtheReal switch uses an Ethernet address swapping technique for real-time packets, similar to ATM to avoid the complexity of maintaining a global connection ID space. Because of the inherent CRC support built into Ethernet hardware, this technique significantly reduces the total processing overhead compared to address swapping at higher network layers. The current EtheReal switch prototype is fully operational, and is built with off-the-shelf PC hardware. It is capable of supporting up to 640 Mbits/sec across 4 ports, and has a per-hop connection establishment overhead of 0.1-0.6 msec and a 10 ��s non-real-time packet latency.

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