Abstract :
Historically, the provision of priority services in LANs that would allow differentiation between different types of traffic has been patchy and inconsistent. Some LAN technologies offer no prioritisation; others offer between 2 and 8 priority levels. Even where priorities are available, the recommendations as to their use are not very helpful in allowing the needs of modern jitter- and latency-sensitive applications, such as real time voice and video, to be properly supported. Two recently published IEEE LAN standards, IEEE Std 802.1D-1998 and IEEE Std 802.1Q-1998, offer a coherent approach both to the provision of prioritisation capabilities in LAN infrastructures and to the uses to which the range of priorities should be put. Also specified in these standards is sufficient management capability to allow legacy devices to be integrated with devices that offer the new capabilities
