We present a new protocol called distributed queueing over a broadcast channel (DQBC). It is a distributed protocol that has the potential to support a large number of users with different performance requirements in the medium access control layer. There is a separate reservation channel from the transmission channel and information is carried over time slots. DQBC presents a solution which requires only two reservation slots of one bit long per time slot. Under Poisson traffic conditions, DQBC has bounded delay up to input rates of 0.9. Under bursty traffic, DQBC has a delay performance comparable to the round-robin protocol.

The topology update mechanism is a key element in a link-state routing algorithm, providing information on which all routing decisions are based. Topology update schemes are essential for coping with link/node failures and recoveries, increasing load levels, and the addition and deletion of links/nodes. The effectiveness of topology update mechanisms for ATM networks for connection oriented services is studied through simulation. We concentrate on link failures, and the rerouting that takes place after a failure. The proposed topology update scheme informs all network nodes of the status of the links/nodes and the flow levels on each link for each connection priority. We define a performance metric that measures the level of control message activity in the network. We compare the proposed scheme with one that does not provide flow level information, but only informs the routing entity at which link an establishing connection was blocked or preempted. The efficiency of the proposed scheme is shown to be much better than the alternative as measured by the defined performance metric.

A new protocol, fair distributed queue (FDQ), suitable for very high-speed metropolitan-area networks (MANs), is presented. FDQ is a slotted system implemented on a unidirectional fiber bus. It has similarities to distributed queue dual bus (DQDB), the IEEE 802.6 Standard for MANs, including the bus topology and same nodal hardware. Like DQDB, FDQ achieves full throughput efficiency independent of the bus length, the transmission speed, and the number of nodes. Unlike DQDB, FDQ allocates equal bandwidth under heavy load to all active users in a time period less than or equal to the round-trip propagation delay without wasting bandwidth. Its delay characteristics are studied via simulation and compared to DQDB. FDQ has lower average delays under Poisson load than DQDB with or without the bandwidth balancing (BWB) mechanism. Two distinct implementations of priority levels are given and their characteristics are discussed. It is shown that FDQ's delay and throughput characteristics are little affected with increasing distances or transmission rates. Thus, FDQ possesses excellent scalability properties which allow its total length to extend over 100 km and transmission rate well above 1 Gb/s.

Fair distributed queue (FDQ) is a high speed metropolitan area network proposed by Kabatepe (1992). FDQ has fair throughput, and delay characteristics and is a highly scalable protocol in that its performance is little affected by growing networks sizes, and/or transmission speeds. While FDQ allocates equal bandwidth to all active nodes, the authors focus on dividing the capacity arbitrarily among the active nodes. Under heavy load, this would result in nodes achieving throughput rates equal to their allocated bandwidths. Under normal load conditions, they aim to provide equal quality of service to the nodes in terms of message delay, if their arrival rates turn out to be equal to their allocated bandwidths. They present the bandwidth allocation FDQ (BA-FDQ) protocol which achieves this objective subject to propagation delays. The delay characteristics of BA-FDQ are compared via simulation with FDQ, DQDB and DQDB with BWB under symmetric load (an important special case in the absence of known arrival rates). They also consider arbitrary bandwidth allocations and study the delay characteristics of BA-FDQ by simulation. The studies show that BA-FDQ makes the mean message delays of individual nodes close to each other as intended for transmissions on one of the buses.>

A new protocol, fair distributed queue (FDQ), suitable for very high speed metropolitan area networks (MANs), is presented. FDQ is a slotted system implemented on a unidirectional fiber bus. It has similarities to the distributed queue dual bus (DQDB) protocol. FDQ achieves full throughput efficiency independent of the bus length, the transmission speed, and the number of nodes. FDQ allocates equal bandwidth under heavy load to all active users in a time period less than or equal to the round-trip propagation delay without wasting bandwidth. Its delay characteristics were studied via simulation and compared to DQDB. FDQ has lower average delays under a Poisson load than the DQDB protocol with or without the bandwidth balancing mechanism. The implementation of priority levels and detailed timing structure of the protocol are also described. It was shown that FDQ's delay and throughput characteristics were only slightly affected by increasing distances or the number of nodes.>

The distributed queue dual bus (DQDB) standard is studied under heavy load conditions. The DQDB protocol for asynchronous traffic is reviewed. The network model and analysis are presented when there are two active nodes. Analytic expressions are derived for the steady-state nodal throughputs and the average value of the request counters of inactive nodes. The three-station case is considered by providing an accurate approximation for the situation when the third node is in between the two initially active nodes. Simulation results are given for comparison. The effect of the position of a node was studied via simulation in the three-station case. The case when one of the active nodes becomes inactive in a network with three initially active nodes is analyzed. The state the network assumes is studied in terms of nodal throughputs after one of the nodes turns off, and the impact on the request counters of the inactive nodes are investigated.>