4. Fast Ethernet was designed to compete with LAN protocols such as FDDI (Fiber Distributed Data Interface) or Fiber Channel. IEEE created Fast Ethernet under the name 802.3u. Fast Ethernet is backward-compatible with Standard Ethernet, but it can transmit data 10 times faster at a rate of 100 Mbps. The topology used by the fast ethernet is shown in the figure.
8. The need for higher data rate resulted in the design of the Gigabit Ethernet (1000 Mbps). The IEEE committee calls the standard 802.3z. All configurations of gigabit Ethernet are point to point. Point-to-point, between two computers or one computer – to –switch. It supports two different modes of operation: full duplex mode and half duplex mode. Full duplex is used when computers are connected by a switch. No collision is there and so CSMA/CD is not used.
9. Figure 4- (a) point to point between two computers (b) point to point between switch and computer
10. Half duplex is used when computers are connected by a hub. Collision in hub is possible and so CSMA/CD is required. The 802.3z committee considered a radius of 25 meters to be unacceptable and added two new features to increase the radius. Carrier Extension tells the hardware to add its own padding bits after the normal frame to extend the frame to 512 bytes. Frame Bursting allows a sender to transmit a concatenated sequence of multiple frames in a single transmission. If the total burst is less than 512 bytes, the hardware pads it again.