QoS guarantees for high-speed variable-length packet LANs

To be able to cope with the demand for multimedia traffic, a lot of research has been done on star-based, ring-based, and other shared-medium high-speed multimedia LANs. A lot of this research has been done on dual counter-rotating ring LANs. This is because the use of spatial reuse (removal of packets at their destination) in dual-ring LANs can result in a major increase in ring throughput. In addition, dual-ring LANs are less susceptible to failure. For star LANs, if the central repeater malfunctions, the whole network fails. However, because there is no central node in dual-ring LANs, the network will not fail even if a node malfunctions. The majority of dual-ring LAN research done so far has been concentrated on fixed-length slot LANs. This is because slot LANs are compatible with ATM and B-ISDN technology. In addition, the slot-waiting time, a problem in low-speed LANs, can be ignored. However, the authors think that variable-length packet LANs are more suitable for high-speed LANs than slot LANs. They consider the use of packet LANs in comparison with slot LANs for high-speed dual-ring LANs. In addition, they introduce the idea of semi-global fairness for dual-ring LANs and propose an algorithm for realizing such fairness.