m if a fiber-optic medium is employed and to 316 m for 1 Gbps. At 1000 Mbps the developers turned to frame bursting. In this burst mode the MAC is allowed to send a short burst of frames equal to approximately 5.4 maximum-length frames without having to relinquish control of the medium. The transmitting MAC station fills each interframe interval with extension bits SO that other stations on the network will see that the network is busy and will not attempt transmission until the burst is complete. 11.6 LAN ACCESS PROTOCOLS If the length of the first frame is less than the minimum of 520 octets, an extension field is added to maintain the frame at minimum length. Subsequent frames in a frame-burst sequence do not need extension fields, and a burst may continue as long as the burst limit has not been reached. The burst mode is not used in the 10-Mbps and 100-Mbps transmission rates. Another improvement measure that was optional was to adopt a full-duplex transmis- sion capability over point-to-point links. In Ref. 12, it has been pointed out that full-duplex operation is much simpler than half-duplex because it involved no media contention, no collisions, no need to schedule retransmissions, and no need for extension bits on the end of short frames. It effectively doubles the bit rate capacity of the link allowing full-rate, simultaneous, two-way transmission. Flow control must also be incorporated on an Ethernet full-duplex link. On a point- to-point link we might typically find on one end of the link perhaps a file server and on the other side a network switch port. Suppose the receiving node encounters congestion. It will request the sending node to stop transmitting frames by sending a "pause frame" which is valid for a short time period. VLAN2 tagging is another important option available to the IT/system engineer.5 A VLAN tagged frame is a basic data frame that has had a 4-octet VLAN header inserted between the SA and length/type fields. It consists of two adjacent fields and indicates that the frame is a VLA