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 and the processor speeds.
• 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
  • the price for each of the components.