| Summary: | 碩士 === 國立中央大學 === 資訊及電子工程研究所 === 81 === The data transmission rate of DQDB is in the range from DS3
to SONET speeds ( 44 Mbps to 155 Mbps ). Due to the
increased ratio of propagation delay to cell transmission
time, the information that a station received about the
current state of DQDB network could be out of date in such a
high speed environment. This fact results in the position
dependent characteristics of the network and is the main
reason that unfair throughput and access delay appears,
especially when the state of network is overloaded to cause
unpredictable behavior. Though Bandwidth Balancing Machine (
BWBM ) is enabled in the IEEE 802.6 DQDB and the fairness of
throughput may be reached, but the unfairness of access delay
still exists, especially under overloaded condition. In this
thesis we propose an efficient modification of REQ Queue
Machine ( RQM ) with an access protection protocol. The
modified RQM scheme eliminates longer access delay for the
stations near the end of bus. The utilization of modified
protection scheme prevents the stubborn unfairness for the
stations close to the head of bus. Simulation results show
that our proposal can reach the fairness of both throughput
and access delay in overloaded DQDB.
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