Cyclic Reservation Multiple Access Research Articles

Design and Implementation of 100 Gbit/s OTDM Packet-interleaved MAN/LAN for Future Ultrafast Burst-mode Interconnection

In this paper, detailed data frame format and schematic node structure is investigated and designed for 100 Gbit/s OTDM packet-interleaved metropolitan area network and local area network (MAN/LAN) under unidirectional ring-like folded bus architecture with optional statistic multiplexing extension, CoS and flow control extension and multiple data rate access extension. Several kinds of media access control (MAC) methods are introduced to achieve fair and efficient access among upstream and downstream nodes with the consideration of future burst-mode interconnection application. Also, an improved cyclic reservation multiple access method is proposed and validated to provide fair and efficient access at the aspect of node access rate, access delay and access delay variation under unbalanced pareto on-off burst mode traffic model. Finally, several component technologies, such as optical pulses generator and TOAD are presented and analyzed for the implementation of OTDM packet-interleaved MAN/LAN.

A Fast Optimal Non-Continuous Slot Reuse Scheme for CRMA High-Speed Networks

Cyclic-Reservation Multiple-Access (CRMA) is an effective access scheme for high-speed networks. In CRMA, the headend periodically generates reserve commands. If necessary, each station may reserve a number of empty slots in each reserve command. For each reserve command, the headend generates a cycle of length equal to the total number of empty slots which are reserved to serve the reservations. Generally speaking, a longer cycle length means a longer access delay and a lower throughput. Therefore, it is desirable to study how to reduce the cycle length. However, it has been shown that the problem is NP-complete if all the empty slots used by a station in a cycle are required to be consecutive [1]. In this paper, we remove the slot-contiguity constraint and propose a fast, optimal non-continuous slot reuse scheme with low time complexity O(M^2), where M denotes the number of stations. Experimental results demonstrate that our new scheme has much shorter cycle lengths, much higher throughput, and much shorter MAC (Medium Access Control) delay than the original CRMA scheme.

An optimal time slot assignment algorithm for CRMA high-speed networks

Cyclic-Reservation Multiple-Access (CRMA) is an access scheme for high-speed local and metropolitan area networks based on a folded-bus or dual-bus configuration. CRMA provides high throughput and fairness independent of the network speed or distance. In CRMA, the headend generates reserve commands periodically. Each station may reserve a number of empty slots in each reserve command if necessary. Corresponding to every reserve command, the headend generates a cycle of length equal to the total number of slots reserved. Every cycle is used to serve the reservations made on its corresponding reserve command. Generally, a longer cycle length means a longer access delay and a lower throughput. Therefore, it is desirable to have a scheme to make the cycle length as short as possible. In this paper, we will study the problem of reducing the total number of empty slots generated within every cycle as much as possible. However, it has been shown that the problem is NP-complete under the constraint that all the slots used by a station in a cycle are required to be consecutive [1][N.F. Huang, H.I. Liu, G.K. Ma, A cycle compression algorithm for CRMA high-speed networks, IEEE ICC'93, 1993, pp. 1363–1367]. In this paper, we discover that if this slot-contiguity constraint is released, then the problem can be optimally solved in polynomial time. Furthermore, we propose an optimal slot scheduling algorithm with time complexity O ∑ i≔1 M α i 2 where α i is the number of empty slots reserved by Station i in the cycle and M is the number of stations. To evaluate the effectiveness of our algorithm, a large number of computer simulations were performed. We compare our algorithm with the original CRMA in terms of the following three important performance measurements: average cycle length, average throughput, and average medium access control (MAC) delay. Experimental results demonstrate that our algorithm has much shorter cycle lengths, much higher throughput, and much shorter MAC delay. Therefore, our algorithm is very attractive.

A slot reuse scheme for CRMA networks

In the cyclic reservation multiple access (CRMA) scheme, nodes reserve slots in each reserve command. Cycles are then generated in sequence, each of which services the reservations made in the corresponding reserve command. Huang et al. [2,3] proposed a reservation scheme, in which nodes are partitioned into regions and slots can be reused in succeeding regions, to reduce access delays due to long cycles. However, slots cannot be reused by the nodes in the same region, resulting in the waste of available slots and line utilization. We propose a modified scheme to eliminate this disadvantage. As a result, cycles generated are shorter and access delays are smaller.

Minimizing cell delay variation in CRMA/ATM interworking

In wide area, networks, ATM is emerging as the predominant technology which provides flexible transmission and switching mechanism to accommodate a large variety of services. Though ATM can be used for LAN/MANs, at present it does not provide economical solution for LAN/MAN. A simple Cyclic-Reservation Multiple-Access (CRMA) protocol proposed in [1] can be used as a media access protocol for high-speed LAN and MAN on slotted unidirectional bus structure. While there is a need for interconnection of existing LAN/MAN networks, the evolution of new LAN/MAN protocols will depend on how easily and efficiently the protocol can interwork with the ATM. Under the normal CRMA protocol, ATM stations located in the CRMA network will experience large Cell Delay Variation (CDV) due to variable cycle lengths during access within the CRMA network. Also due to the cancellation mechanism incorporated within the CRMA protocol, the CDV increases. The CRMA access mechanism also forms bursts during access. This paper proposes a novel mechanism that minimizes the CDV in CRMA/ATM interworking by embedding fixed length cycles for the ATM traffic in the normal CRMA cycles of variable length. Another novel scheme is used which allocates CRMA slots uniformly to the ATM traffic within the fixed length cycles, thereby smoothing the ATM traffic. The simulation results show that the proposed scheme reduces the CDV and burstiness of ATM traffic to a great extent without significantly affecting the delay performance of the CRMA traffic.

Performance comparison of media access protocols for Gbit/s networks in the local area

The evolution towards future communication systems is strongly influenced by increasing transmission capacities, changing service requirements and the emerging ATM technology. The next generation of high-performance local and metropolitan area networks has to be designed including control schemes which provide high throughput while simultaneously supporting real-time services. The slotted ring architecture enhanced by spatial slot reuse is one potential approach for data transmission and admission control in distributed Gbit/s networks. Various concepts have been proposed for an efficient medium access control which maintains fairness and bounded access delays. By using simulation results, this paper compares the performance of several protocols: ATMRing (ATMR), CRMA-II (Cyclic Reservation Multiple Access) and MetaRing. First, the differences in their basic mechanisms are generally analysed applying saturated traffic scenarios. Then the behaviour in a multi-service environment is discussed, with particular regard to the requirements of universal broadband services. It is shown that all approaches offer efficient bandwidth sharing mechanisms. They overcome the well-known trade-off between high throughput and strong real-time requirements by providing extended bandwidth for user data and suitable end-to-end delays. Their performance, however, is quite sensitive to the actual network conditions and chosen protocol parameters.

Reservation scheme for CRMA high-speed networks

Cyclic-Reservation Multiple-Access (CRMA) is an access scheme for high speed local and metropolitan area networks based on a slotted unidirectional dual-bus structure. In CRMA, the headend generates reserve commands periodically. Each node reserves a number of slots in each reserve command. Finally, the headend generates a sequence of cycles, each of which is used to service the reservations on the corresponding reserve command. The length of each cycle is equal to the total number of slots reserved by the nodes in the corresponding reserve command. Generally, a longer cycle length will have a lower slot utilization and longer access delay. It has been shown that the problem of finding a shortest cycle length is NP-complete 1. In this paper, we propose a new reservation scheme for CRMA high-speed networks to make a shorter cycle length. Simulation results show that compared with the original CRMA reservation scheme, this new scheme does result in a much shorter average cycle length. Further-more, the proposed scheme also obtains better throughput (slot utilization), as well as a lower access delay.

On the performance of topologies and access protocols for high-speed LANs and MANs

Abstract The performances of several topologies and access protocols proposed for high-speed local and metropolitan area networks (LANs and MANs) are compared using simulation models. First, FDDI (Fiber Distributed Data Interface), DQDB (Distributed Queue Dual Bus), CRMA (Cyclic Reservation Multiple Access), and CRMA-II (the latest evolution of CRMA) are compared in a uniform traffic scenario. Second, the slot reuse technique is studied for DQDB and CRMA, showing that remarkable gains in performances can be obtained, particularly in the case of non-uniform traffic distributions. Finally, meshed topologies that allow a further exploitation of spatial reuse are considered, focusing on Manhattan Street Networks (MSNs). Numerical results indicate that the massive exploitation of spatial reuse permits significant advantages in terms of user throughput and access delay to be obtained, with a node complexity comparable to that of bus or ring topologies.

CRMA MAC protocol: A simulative analysis

This paper reports on an extended simulation analysis of the Cyclic Reservation Multiple Access (CRMA) Media Access Control (MAC) protocol. The analysis is divided into two parts. In the first part we study CRMA in underload conditions, i.e. when the offered load is lower than the medium capacity. In the second part we study CRMA in overload conditions, i.e. when the offered load is higher than the medium capacity. Our results show that in underload conditions the behaviour of CRMA depends on load distribution and node position, but it is quite predictable and basically fair. In overload conditions the node buffer may be a critical parameter and the network becomes fair only if the buffer size is greater than a threshold. The value of this threshold depends on the workload and on network parameters. Finally, we present a case study to show that CRMA is suitable to service integration.

An Efficient Slot-Reuse Scheme for CRMA High-Speed Networks

Cyclic-Reservation Multiple-Access (CRMA), based on slotted unidirectional dual-bus structure, is an access scheme for high speed local and metropolitan area networks. In CRMA, the headend generates reserve commands periodically. Each node reserves a number of slots which it needs when each reserve command passes by. Finally, the headend generates a sequence of cycles, corresponding to each reserve command, service the reservations commanded by each node. The length of cycle is equal to the total number of slots reserved by the nodes. It is desirable to have some mechanisms to reduce the length of a cycle since slot reuse can reduce the number of slots used to carry the same amount of user information, whereby reducing network congestion. It had been shown that the problem of finding a shortest cycle length is NP-complete [2]. Recently, a reservation scheme based on finding single-level regions (FSR) to make a shorter cycle length had been proposed [3]. That is to say, some of used slots can be reused by downstream nodes and hence the throughput and access delay are improved.In this paper, we propose an efficient slot reuse scheme based on finding multiple-level regions (FMR). As compared with the original CRMA reservation scheme and the one proposed in [3], the new scheme makes the cycle length much shorter. Besides, the resulting throughput (slots utilization) and the access delay are better than those of the other two schemes. We also address the differences and effects on slot-reuse schemes applied in CRMA-II (using destination release), [14] and [15], and FSR/FMR (using cycle compression).

A discrete-time analysis of the cyclic reservation multiple access protocol

In this paper a performance analysis of the CRMA (Cyclic Reservation Multiple Access) medium access protocol, which is proposed as an access mechanism for high-speed LANs and MANs is presented. An approximate computational method is derived to obtain the distribution functions of performance measures of interest like the medium access delay and the packet transfer time. The analysis is done in discrete-time domain using a decomposition approach for the access delay in conjunction with a G/G/1 queue with control-feedback and a M/G/1 queue with server vacation. In the model the reservation-cancelation backpressure mechanism is also taken into account. Numerical results are obtained to investigate the efficiency of the backpressure scheme and the scaling issues of the interreserve interval under various load conditions and system configurations. Furthermore, results addressing performance aspects like the fairness issues, the jitter of maximum access delay and the system behavior under station-wise saturated conditions are also discussed.

Cyclic reservation schemes for efficient operation of multiple-queue single-server systems

We study two new cyclic reservation schemes for the efficient operation of systems consisting of a single server and multiple queues. The schemes are the Globally Gated regime and the Cyclic-Reservation Multiple-Access (CRMA). Both procedures possess mechanisms for prioritizing the queues and lend themselves to a closed-form analysis. The combination of these two properties allows for effective and efficient operation of the systems, for which we provide a thorough delay analysis and derive simple rules for optimal operation.