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Quick Reference Guide to 100-Mbps Media Systems

9.1 Which Fast Ethernet?

This guide describes the 802.3 Ethernet system, and the 100BASE-T Fast Ethernet segments which are part of that system. However, you should know that there are two LAN standards that can carry Ethernet frames at 100-Mbps.

When the IEEE standardization committee met to begin work on a faster Ethernet system, two approaches were presented. One approach was to speed up the original Ethernet system to 100-Mbps, keeping the original CSMA/CD medium access control mechanism. This approach is called 100BASE-T Fast Ethernet.

Another approach presented to the committee was to create an entirely new medium access control mechanism, one based on hubs that controlled access to the medium using a "demand priority" mechanism. This new access control system transports standard Ethernet frames, but it does it with a new medium access control mechanism. This system was further extended to allow it to transport token ring frames as well. As a result, this approach is now called 100VG-AnyLAN.

The IEEE decided to create standards for both approaches. The 100BASE-T Fast Ethernet standard described here is part of the original 802.3 standard. The 100VG-AnyLAN system is standardized under a new number: IEEE 802.12.

Quick Reference Guide to 100-Mbps Media Systems - 09 SEP 95
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