A ring-based media access control protocol and architecture, Fast Ring, which combines the best features of the token ring and contention ring, is proposed. For this protocol, a free token circulates on the ring when ...
详细信息
A ring-based media access control protocol and architecture, Fast Ring, which combines the best features of the token ring and contention ring, is proposed. For this protocol, a free token circulates on the ring when the ring is idle. A ready station can transmit either by capturing the token or sensing the ring idle. the protocol works in such a way that the ready node which captures the free token, before or while transmitting, is able to continue transmission. All the other contending nodes have to stop their transmissions and then send the abort signal when they receive the upstream transmission. After its transmission, the successful station puts a free token on the ring and the protocol enters the token mode. It behaves like the token ring protocol until the ring becomes idle again when all the ready nodes complete their transmissions. Comparison of the performance of Fast Ring withthose of contention ring, token ring, and carrier-sense multiaccess with collision detection protocols shows that the Fast Ring outperforms all these local area network protocols over the whole throughput range at all transmission rates.< >
A new integrated demand-assignment multiple-access (DAMA) method for multiple-bus local networks (MBLNs) is proposed and evaluated. the performance of this method is shown to be superior to independent token-passing a...
详细信息
A new integrated demand-assignment multiple-access (DAMA) method for multiple-bus local networks (MBLNs) is proposed and evaluated. the performance of this method is shown to be superior to independent token-passing as well as to previously proposed integrated access schemes. V-STIA, a virtual token-passing extension of a modified explicit token-passing scheme called single-token integrated access (STIA), delivers the best overall performance at medium to heavy loads while achieving good light-load performance without collision detection. Consequently, V-STIA makes the fewest possible demands on interface capabilities for DAMA support in MBLNs. Additionally, V-STIA implementation does not require simultaneous transmit capability for correct operation and greatly reduces design complexity. Performance advantages of MBLNs over an equivalent bandwidth single-bus DAMA system are established.< >
A replicated directory management algorithm is presented that supports full location-transparency by allowing migration and reconfiguration at the granularity of individual names. Initially, all names in a directory (...
详细信息
A replicated directory management algorithm is presented that supports full location-transparency by allowing migration and reconfiguration at the granularity of individual names. Initially, all names in a directory (including names not yet in use) are controlled by the same set of sites, but control over any individual name (or range of names) can be migrated, e.g. to the set of sites that control the data object associated withthe name. the method is based on a directory replication algorithm of J.J. Bloch et al. (1987), incorporating two extensions: (1) allowing control over individual names in a directory to migrate independently; and (2) allowing the definition of relationships among names, such that if control over a given name migrates, then those names that depend on it are automatically migrated as well. Finally, it is stated that the major cost of the algorithm, compared to simpler approaches that do not provide the same degree of location transparency, is the additional complexity and difficulty of obtaining a consistent view of the entire directory.< >
Analytical models are presented that use Petri nets for fault-tolerant schemes used in distributed systems. these models are used in the quantitative evaluation and selection of good fault-tolerant schemes for specifi...
详细信息
Analytical models are presented that use Petri nets for fault-tolerant schemes used in distributed systems. these models are used in the quantitative evaluation and selection of good fault-tolerant schemes for specific system configurations. Several different fault-tolerant schemes that can be modeled using Petri nets are discussed in detail. these schemes include rollback recovery with checkpointing, recovery blocks, N-version programming, and conversations. After a brief review of Petri net models, extension of the Petri net models to incorporate fault-tolerant schemes is considered. A methodology for evaluating a fault-tolerant scheme for a specific system configuration and the steps involved in building a Petri net model of a fault-tolerant system are described. the subnet primitives involved in building these models are identified and an algorithm for building the models automatically is described. Examples illustrating this extended Petri net model are discussed and numerical results are presented to show the applicability of the models.< >
A technique is described for constructing a fault-tolerant global clock in a point-to-point distributed system with an arbitrary topology, which constitutes a wide-area network. It is assumed that the network is const...
详细信息
A technique is described for constructing a fault-tolerant global clock in a point-to-point distributed system with an arbitrary topology, which constitutes a wide-area network. It is assumed that the network is constructed of optical links with very high transmission rates. the approach used is to generate a global clock from the ensemble of the local transmission clocks, and not to synchronize these high-speed clocks directly. the steady-state algorithm which generates the global system clock is executed in hardware by the network interface of each node. As a result, it is possible to estimate accurately intermodal delays and thereby to achieve a much tighter synchronization than with other methods. the basic synchronization time step is proportional to the error or uncertainty in the measurement of the end-to-end network delay rather than to the actual value of the end-to-end network delay. Node and network models are presented, and the synchronization condition is defined. the synchronization algorithm, its bound, and its correctness proof are presented. A procedure is described for detecting and isolating a faulty component, while maintaining the integrity of the global clock.< >
A replication control protocol utilizing dynamic voting is presented for ensuring database correctness so that the system behaves like a one-copy database to the users. the protocol dynamically adjusts vote assignment...
详细信息
A replication control protocol utilizing dynamic voting is presented for ensuring database correctness so that the system behaves like a one-copy database to the users. the protocol dynamically adjusts vote assignment of data items in response to failures and recoveries, thus maintaining higher data availability than static voting schemes in the event of network partitioning. Unlike existing dynamic voting schemes, it supports inexpensive read operations which access one copy, rather than all copies, of each data item read. Since read operations outnumber write operations in most applications, this protocol enjoys better performance. Withthis protocol, transactions run in one of three modes: normal mode, missing-partition mode, or pseudo-normal mode. Because a partition number and a last current copy cardinality are associated with each copy, read operations only require one copy of a data item when run in the normal mode.< >
A technique is presented by which a centralized service facility in a distributed system can honor client requests in the global order in which those requests were made. Unlike traditional approaches to this problem, ...
详细信息
A technique is presented by which a centralized service facility in a distributed system can honor client requests in the global order in which those requests were made. Unlike traditional approaches to this problem, the server provides immediate service to its clients. Immediate service requires that, upon receipt of a request which is the oldest unserved message, the server must grant the service immediately. No additional message passing may be used by the server in order to serve that request. the approach requires that certain information be appended to every message in the system. this piggybacked information allows the server to infer the order in which service should be granted to arriving request messages. Increased message length is thus explicitly traded for fewer messages and faster response to requests at the server. that overhead is proportional to the number of processors in the system. In time-critical distributed applications immediate service offers a means by which service response time can be substantially reduced. It is argued that, under certain reasonable assumptions about the network and process behavior, immediate service can outperform the logical timestamp approach for very large systems (and certainly for small systems).< >
thii paper describes the design of a distributed information system for full text retrieval Tbc system is similar in functionality to STAIRS and is being developed on a network of .PC9;s interconnected by PC Networ...
详细信息
the Fineparticle Group at Laurentian University is currently exploring the ergonomic structure and task allocation of a distributedcomputing system for evaluating fineparticles collected in routine monitoring of air ...
详细信息
the Fineparticle Group at Laurentian University is currently exploring the ergonomic structure and task allocation of a distributedcomputing system for evaluating fineparticles collected in routine monitoring of air pollution problems and industrial hygiene samples. In this presentation the characterization of asbestos fibers and silica fineparticles by the distributing computing system is presented.
this paper describes Aspects of distributed Computer Systems by Harold Lorin. the book was published by John Wiley and Sons in 1980. "Aspects" undertakes to discuss issues in the design and the management of...
详细信息
暂无评论