Fast Ethernet: Introduction
Driven by recent advances in computing technology, today's networking applications have grown in speed, power and information processing. However, these new applications are placing so much demand on the underlying network that it is running out of capacity. This is the driving need for greater bandwidth and improved response time. Based on the same CSMA/CD protocols familiar to Ethernet users, 100BASE-T Fast Ethernet offers a natural migration path from traditional Ethernet. With many manufacturers shipping selectable 10/100 Mbps products, you can protect your investment in existing 10 Mbps Ethernet LAN equipment. Also, Fast Ethernet allows you to preserve investments in existing cabling, since the technology is capable of running on Category 3, 4, or 5 cabling.
Fast Ethernet Technology
The 100BASE-T standard consists of five different component specifications. These include the Media Access Control (MAC) layer, the Media Independent Interface (MII), and the three physical layers, (100 BASE-TX, 100BASET4, and 100BASE-FX).
Media Access Control (MAC) Layer
The MAC layer is based on the same CSMA/CD protocol as 10Mbps Ethernet. The only difference is that it runs ten times faster. Fast Ethernet retains all of the robustness of the traditional protocol. Rather than having to learn an entirely different technology, the customer can rely on all the experience gathered over the years while retaining a considerable investment in training, management, and analysis tools.
Media Independent Interface (MII) Layer
The MII is a new specification that defines a standard interface between the MAC layer and any of the three physical layers (100BASE-TX, 100BASE-T4, and 100BASE-FX). It is capable of supporting both 10 Mbps and 100Mbps data rates.
The MII can be implemented internally in a network device to connect the MAC layer directly to the physical layer. This is often the case with adapters (network interface cards or NICs).
The MII can be implemented externally in a network device via a 40-pin connector. Some class I repeaters may be equipped with this connector. With the MII and the proper transceiver, a Class I repeater can be connected to any STP, UTP, or fiber cable device; analagous to the AUI connector in 10 Mbps Ethernet networks.
Back to the KMJ White Paper Page?
Go on the the next section: Physical Layers in Fast Ethernet