SMAC May 1999 Durkin - 7

sizes. A frame brackets a data packet with the destination address and other routing and error-checking codes. Picture a CSMA/CD frame as a railroad boxcar. The amount of data is the freight. Empty, half-loaded, or chock-full, each boxcar takes up the same amount of space and time on the track. The SMAC protocol is more efficient because it fits the frame to the size of the data packet - no wasted time or space.

CHART B

Percentage of Usable Bandwidth – CSMA/CD vs. SMAC

1 0 Mbps 100 Mbps 1000 Mbps SMAC at 10, 100 CSMA/CD CSMA/CD CSMA/CD and 1000 Mbps

2048

bits per data frame with 200 – 300 nodes

The reason why packet size cannot go lower than the 802.3z specifications is illustrated in Chart B. Quite literally, Gigabit Ethernets can't go the distance.

SMAC - THE NEW DOMINANT PARADIGM

A popular T-shirt in the Silicon Valley reads: "Subvert the Dominant Paradigm." There is no argument that CSMA/CD is the dominant paradigm in computer networking at the medium access control level. It has reigned supreme for almost 25 years. But CSMA/CD has not been able to keep up with the phenomenal growth – and change – in network speeds and bandwidth. Indeed, as shown, CSMA/CD is proving to be more of a liability than an asset to Gigabit Ethernet networks. SMAC technology doesn't fix CSMA/CD. It replaces it. Instead of being a better protocol for managing information-packet collisions, The SMAC protocol so precisely synchronizes packet traffic that there are no collisions.