Ethernet as a Lossless Deadlock Free System Area Network

The way conventional Ethernet is used today differs in two aspects from how dedicated system area networks are used. Firstly, dedicated system area networks are lossless and only drop frames when bit errors occur, while conventional Ethernet drop frames whenever congestion occur. Secondly, these networks are either deadlock free or use mechanisms which avoids deadlock situations, while still using all available links. Ethernet avoids deadlocks by using a spanning tree protocol which turns any topology into a tree. A drawback of this approach is that we are left with a lot of unused links and thus wasting resources. In this paper we describe how to obtain a lossless deadlock free network with the best possible performance, while adhering to the current Ethernet standard and using off-the-shelf Ethernet equipment. We achieve this by introducing flow control in all network nodes and by taking control over the routing algorithm. Also, we use TCP to illustrate the effect of flow control on higher layer protocols. Through simulations we verify the following tree improvements. Firstly, the activation of flow control turns Ethernet into a lossless network. Secondly, taking control over the routing algorithm allows us to build any topology without the limitations of the spanning tree protocol. And thirdly, an overall improvement in throughput is achieved by combining these enhancements.