Token Circulation Research Articles

Fault tolerant mutual and k-mutual exclusion algorithms for single-hop mobile ad hoc networks

Previous mutual exclusion (MUTEX for short) protocols for mobile ad hoc networks are based on the token circulation technique. They assume that the network is reliable to avoid starvation. Considering that the MUTEX issue is to share a communication channel, we have designed an average-case-analysis protocol for single-hop networks which is based on the fully distributed construction of a random binary tree. Contrarily to other papers, the stations are not identified and their number (n) is unknown. Assuming that time is slotted, our algorithm runs in approximately n/log 2 slots. The derived k-MUTEX protocol runs in n/log k slots.

QoS-Based Remote Control of Networked Control Systems Via Profibus Token Passing Protocol

This paper focuses on a quality-of-service (QoS)-based remote control scheme for networked control systems via the Profibus token passing protocol. Typically, token passing experiences random network delay due to uncertainties in token circulation, but the protocol has in-built upper and lower bounds of network delay. Thus, to ensure the control performance of networked control systems via the Profibus token passing protocol, the network delay should be maintained below the allowable delay level. As the network delay is affected by protocol parameters, such as target rotation time, we present here an algorithm for selection of target rotation time using a genetic algorithm to ensure QoS of control information. We also discuss the performance of the QoS-based remote control scheme under conditions of controlled network delay. To evaluate its feasibility, a networked control system for a feedback control system using a servo motor was implemented on a Profibus-FMS network.

Self-stabilizing dynamic mutual exclusion for mobile ad hoc networks

We propose a self-stabilizing mutual exclusion algorithm for mobile ad hoc networks, in which the composition of processors that want to enter the critical section can change dynamically. Our algorithm is based on dynamic virtual rings formed by circulating tokens. The algorithm always guarantees mutual exclusion and it guarantees different levels of progress under different levels of performance of the token circulation in the presence of mobility and message loss. Rigorous proofs of correctness and performance are given.

Distributed token circulation in mobile ad hoc networks

This paper presents several distributed algorithms that cause a token to continually circulate through all the nodes of a mobile ad hoc network. An important application of such algorithms is to ensure total order of message, delivery in a group communication service. Some of the proposed algorithms are aware of, and adapt to changes in the ad hoc network topology. When using a token circulation algorithm, a round is said to complete when every node has been visited at least once. Criteria for comparing the algorithms include the average time, required to complete a round, number of bytes sent per round, and number of nodes visited per round. Comparison between the proposed algorithms is performed using simulation results obtained from a detailed simulation model (with ns-2 simulator). We also give a rigorous worst-case analysis of the proposed LR algorithm, which gives the best overall performance in the simulation.

Group Mutual Exclusion in Token Rings

The group mutual exclusion (GME) problem was introduced by Joung. The GME solution allows n processes to share m mutually exclusive resources. We present several algorithms to solve the GME problem in token rings. The space requirement and the size of messages of all algorithms are bounded. So, the proposed algorithms solve the problem suggested by Joung, which is to obtain a solution using messages of bounded size. The time and space complexities of the first and second algorithms depend on n and m respectively. The first algorithm is more efficient when n <<m, whereas the second one when m <<n. The cost of the third algorithm is min(n, m). So, it is suitable for any type of network. However, the third solution is obtained with a message size of log(min(n, m)) extra bits. The third algorithm has an additional desirable property. It serves the requests in a first in first out manner. The fourth algorithm improves the bandwidth usage by avoiding the token circulation when no new requests are made for a different session. This property of the fourth algorithm can be incorporated into the other three algorithms.

Self-stabilizing group communication in directed networks

This paper presents the first self-stabilizing group membership service, multicast service, and resource allocation service for directed networks. The first group communication algorithm is based on a token circulation over a virtual ring. The second algorithm is based on construction of distributed spanning trees. In addition, a technique is presented that emulates, in a self-stabilizing fashion, any undirected communication network over strongly connected directed networks, is presented. A resource allocation asynchronous algorithm for strongly connected directed networks is presented.

Fair circulation of a token

Suppose that a distributed system is modeled by an undirected graph G = (V, E), where V and E, respectively, are the sets of processes and communication links. Israeli and Jalfon (1990) proposed a simple self-stabilizing mutual exclusion algorithm: a token is circulated among the processes (i.e., vertices) and a process can access the critical section only when it holds the token. In order to guarantee equal access chance to all processes, the token circulation needs to be fair in the sense that all processes have the same probability of holding the token. However, the Israeli-Jalfon token circulation scheme does not meet the requirement. This paper proposes a new scheme for making it fair. We evaluate the average of the longest waiting times in terms of the cover time and show an O(deg(G)n/sup 2/) upper bound on the cover time for our scheme, where n and deg(G) are the number of processes and the maximum degree of G, respectively. The same (tight) upper bound is known for the Israeli-Jalfon scheme.

A distributed access control method for wireless LANs in shadowing environments

In recent years, the trend to use wireless LANs to realize mobile or ad hoc network is expanding. Previous proposals for access control methods for wireless LANs included such methods as Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) and polling. However, both methods have problems of transfer efficiency and delay time. Research and development on new access control methods is required to implement high-performance wireless LANs. In this paper, we examine the development of a wireless version of the wired token passing LAN access control method as a new wireless LAN access control method and propose Dynamic Token Passing (DTP) as a wireless token passing LAN access control method that incorporates a token circulation method and a data relay scheme based on a reserved logical ring. The results show that compared to existing methods, such as the IEEE 802.11 protocol, the proposed method exhibits better performance in an environment suffering from transmission path failures caused by blocking objects. A discussion of the optimum configuration for the reserved logical rings shows that if A reserved logical rings are prepared and the optimum reserved logical ring is selected, then a network can continue operation under the condition of A-1 failures. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 84(9): 16–26, 2001

A distributed access control method for wireless LANs in shadowing environments

AbstractIn recent years, the trend to use wireless LANs to realize mobile or ad hoc network is expanding. Previous proposals for access control methods for wireless LANs included such methods as Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) and polling. However, both methods have problems of transfer efficiency and delay time. Research and development on new access control methods is required to implement high‐performance wireless LANs. In this paper, we examine the development of a wireless version of the wired token passing LAN access control method as a new wireless LAN access control method and propose Dynamic Token Passing (DTP) as a wireless token passing LAN access control method that incorporates a token circulation method and a data relay scheme based on a reserved logical ring. The results show that compared to existing methods, such as the IEEE 802.11 protocol, the proposed method exhibits better performance in an environment suffering from transmission path failures caused by blocking objects. A discussion of the optimum configuration for the reserved logical rings shows that if A reserved logical rings are prepared and the optimum reserved logical ring is selected, then a network can continue operation under the condition of A‐1 failures. © 2001 Scripta Technica, Electron Comm Jpn Pt 1, 84(9): 16–26, 2001

SELF-STABILIZING DEPTH-FIRST MULTI-TOKEN CIRCULATION IN TREE NETWORKS

Self stabilization is one of the new paradigms to investigate fault tolerance in distributed algorithm design. The multi-token or the l-exclusion problem is the logical generalization of standard mutual exclusion problem where l processes can enter their critical section at the same time. Self stabilizing single token circulation or the standard mutual exclusion problem has been investigated by a number of authors; recently authors in [16] have proposed a self stabilizing multi-token protocol for the ring networks. We propose a new self stabilizing algorithm (protocol) for depth first circulation of multiple tokens in a tree network. The algorithm uses only bounded integers and the correctness is proved by using induction.

Self-stabilizing depth-first token circulation in arbitrary rooted networks

We present a deterministic distributed depth-first token passing protocol on a rooted network. This protocol uses neither the processor identifiers nor the size of the network, but assumes the existence of a distinguished processor, called the root of the network. The protocol is self-stabilizing, meaning that starting from an arbitrary state (in response to an arbitrary perturbation modifying the memory state), it is guaranteed to reach a state with no more than one token in the network. Our protocol implements a strictly fair token circulation scheme. The proposed protocol has extremely small state requirement - only 3(Δ + 1) states per processor, i.e., O(log Δ) bits per processor, where Δ is the degree of the network. The protocol can be used to implement a strictly fair distributed mutual exclusion in any rooted network. This protocol can also be used to construct a DFS spanning tree.

Optimality and Self-Stabilization in Rooted Tree Networks

In this paper, we consider arbitrary tree networks where every processor, except one, called the root, executes the same program. We show that, to design a depth-first token circulation protocol in such networks, it is necessary to have at least configurations, where n is the number of processors in the network and Δi is the degree of processor pi. We then propose a depth-first token circulation algorithm which matches the above minimal number of configurations. We show that the proposed algorithm is self-stabilizing, i.e., the system eventually recovers itself to a legitimate state after any perturbation modifying the state of the processors. Hence, the proposed algorithm is optimal in terms of the number of configurations and no extra cost is involved in making it stabilizing.

OPTIMALITY AND SELF-STABILIZATION IN ROOTED TREE NETWORKS

In this paper, we consider arbitrary tree networks where every processor, except one, called the root, executes the same program. We show that, to design a depth-first token circulation protocol in such networks, it is necessary to have at least [Formula: see text] configurations, where n is the number of processors in the network and Δi is the degree of processor pi. We then propose a depth-first token circulation algorithm which matches the above minimal number of configurations. We show that the proposed algorithm is self-stabilizing, i.e., the system eventually recovers itself to a legitimate state after any perturbation modifying the state of the processors. Hence, the proposed algorithm is optimal in terms of the number of configurations and no extra cost is involved in making it stabilizing.

OPTIMALITY AND SELF-STABILIZATION IN ROOTED TREE NETWORKS

In this paper, we consider arbitrary tree networks where every processor, except one, called the root, executes the same program. We show that, to design a depth-first token circulation protocol in such networks, it is necessary to have at least [Formula: see text] configurations, where n is the number of processors in the network and Δi is the degree of processor pi. We then propose a depth-first token circulation algorithm which matches the above minimal number of configurations. We show that the proposed algorithm is self-stabilizing, i.e., the system eventually recovers itself to a legitimate state after any perturbation modifying the state of the processors. Hence, the proposed algorithm is optimal in terms of the number of configurations and no extra cost is involved in making it stabilizing.

Self-stabilizing token circulation in uniform networks

A self-stabilizing protocol for token circulation in a connected, uniform network of nodes with prime size is proposed. A network of nodes is said to be uniform if all nodes are logically equivalent and identically programmed. The protocol has the ability to handle any arbitrary initial state in which more than one token or no token at all exist in the network and makes the network eventually have one and only one token fairly circulating among the nodes of the network. The protocol is deterministic, its self-stabilization property is proven under the assumption of a serial and fair scheduler.

A new structural induction theorem for rings of temporal Petri nets

Presents a new structural induction theorem for rings consisting of identical components that are modeled using a Petri net and a temporal logic formula. The theorem gives a condition in terms of the behavior of the rings of sizes k/spl minus/1 and k, k/spl ges/5, under which all rings of size k/spl minus/1 or greater exhibit similar behavior. Using the example of demand-driven token circulation, we show how the theorem can be applied to formally infer the correctness of a ring of any large size from that of a ring having fewer components. >

Self-stabilizing depth-first token circulation on networks

This paper proposes a self-stabilizing protocol which circulates a token on a connected network in nondeterministic depth-first-search order, rooted at a special node. Starting with any initial state in which the network may have no token at all or more than one token, the protocol eventually makes the system stabilize in states having exactly one circulating token. With a slight modification to the protocol - by removing nondeterminism in the search - a depth-first-search tree on the network can be constructed. The proposed protocol runs on systems that allow parallel operations.

Throughput analysis of a timer controlled token passing protocol under heavy load

An analysis is presented of the throughput performance of some recently proposed token-passing local area network (LAN) protocols under a heavy load assumption. The IEEE 802.4 token bus standard which uses a cycle-dependent timing mechanism to control station access to the channel, is studied. It is shown that the cycle-dependent timing mechanism limits the token circulation times properly. Moreover, priority among different access classes is being implemented. Analytic results for computations of throughputs and cycle lengths are derived. These results provide insights into the cycle-dependent timing mechanism and also guidelines for design. Using the results derived, examples concerning the throughput behavior under different heavy load configurations, the sensitivity to parameters, system optimization with delay and bandwidth constraints, and comparison with the other integrated access schemes are studied. >