Ethernet

• Ethernet is a packet-switched LAN technology introduced by Xerox PARC in the early 1970s. Ethernet was designed to be a shared bus technology where multiple hosts are connected to a shared communication medium. All hosts connected to an Ethernet receive every transmission, making it possible to broadcast a packet to all hosts at the same time.
• Ethernet uses a distributed access control scheme called Carrier Sense Multiple Access with Collision Detect (CSMA/CD). Multiple machines can access an Ethernet at the same time. Each machine senses whether a carrier wave is present to determine whether the network is idle before it sends a packet.
• Only when the network is not busy sending another message can transmission start. Each transmission is limited in duration and there is a minimum idle time between two consecutive transmissions by the same sender.
• In order to achieve an acceptable level of performance and to eliminate any potential bottleneck, there must be some balance between the Ethernet speed and the processor speed. The initial Beowulf prototype cluster in 1994 was built with DX4 processors and 10 Mbit/s Ethernet. The processors were too fast for this kind of Ethernet. In late 1997, a good choice for a cluster system was sixteen 200 MHz P6 processors connected by Fast Ethernet. The network configuration of a high-performance cluster is dependent on the size of the cluster, the relationship between processor speed and network bandwidth and the current price list for each of the components.