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Suzuki–Kasami Algorithm
The Suzuki–Kasami algorithm is a token-based algorithm for achieving mutual exclusion in distributed systems. The process holding the token is the only process able to enter its critical section. This is a modification to Ricart–Agrawala algorithm The Ricart–Agrawala algorithm is an algorithm for mutual exclusion on a distributed system. This algorithm is an extension and optimization of Lamport's Distributed Mutual Exclusion Algorithm, by removing the need for release messages. It was d ...Ricart, Glenn, and Ashok K. Agrawala.An optimal algorithm for mutual exclusion in computer networks" Communications of the ACM 24.1 (1981): 9-17. in which a REQUEST and REPLY message are used for attaining the critical section, but in this algorithm, a method was introduced in which a seniority vise and also by handing over the critical section to other node by sending a single PRIVILEGE message to other node. So, the node which has the privilege it can use the critical section and if i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Access Token
In computer systems, an access token contains the security credentials for a login session and identifies the user, the user's groups, the user's privileges, and, in some cases, a particular application. In some instances, one may be asked to enter an access token (e.g. 40 random characters) rather than the usual password (it therefore should be kept secret just like a password). Overview An ''access token'' is an object encapsulating the security identity of a process or thread. A token is used to make security decisions and to store tamper-proof information about some system entity. While a token is generally used to represent only security information, it is capable of holding additional free-form data that can be attached while the token is being created. Tokens can be duplicated without special privilege, for example to create a new token with lower levels of access rights to restrict the access of a launched application. An access token is used by Windows when a process or th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Algorithm
In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specifications for performing calculations and data processing. More advanced algorithms can use Conditional (computer programming), conditionals to divert the code execution through various routes (referred to as automated decision-making) and deduce valid inferences (referred to as automated reasoning). In contrast, a Heuristic (computer science), heuristic is an approach to solving problems without well-defined correct or optimal results.David A. Grossman, Ophir Frieder, ''Information Retrieval: Algorithms and Heuristics'', 2nd edition, 2004, For example, although social media recommender systems are commonly called "algorithms", they actually rely on heuristics as there is no truly "correct" recommendation. As an e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mutual Exclusion
In computer science, mutual exclusion is a property of concurrency control, which is instituted for the purpose of preventing race conditions. It is the requirement that one thread of execution never enters a critical section while a concurrent thread of execution is already accessing said critical section, which refers to an interval of time during which a thread of execution accesses a shared resource or shared memory. The shared resource is a data object, which two or more concurrent threads are trying to modify (where two concurrent read operations are permitted but, no two concurrent write operations or one read and one write are permitted, since it leads to data inconsistency). Mutual exclusion algorithms ensure that if a process is already performing write operation on a data object ritical sectionno other process/thread is allowed to access/modify the same object until the first process has finished writing upon the data object ritical sectionand released the obj ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed Systems
Distributed computing is a field of computer science that studies distributed systems, defined as computer systems whose inter-communicating components are located on different computer network, networked computers. The components of a distributed system communicate and coordinate their actions by message passing, passing messages to one another in order to achieve a common goal. Three significant challenges of distributed systems are: maintaining Concurrency (computer science), concurrency of components, overcoming the clock synchronization, lack of a global clock, and managing the independent failure of components. When a component of one system fails, the entire system does not fail. Examples of distributed systems vary from service-oriented architecture, SOA-based systems to microservices to massively multiplayer online games to peer-to-peer, peer-to-peer applications. Distributed systems cost significantly more than monolithic architectures, primarily due to increased needs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Critical Section
In concurrent programming, concurrent accesses to shared resources can lead to unexpected or erroneous behavior. Thus, the parts of the program where the shared resource is accessed need to be protected in ways that avoid the concurrent access. One way to do so is known as a critical section or critical region. This protected section cannot be entered by more than one process or thread at a time; others are suspended until the first leaves the critical section. Typically, the critical section accesses a shared resource, such as a data structure, peripheral device, or network connection, that would not operate correctly in the context of multiple concurrent accesses. Need for critical sections Different code or processes may consist of the same variable or other resources that must be read or written but whose results depend on the order in which the actions occur. For example, if a variable is to be read by process A, and process B must write to the variable at the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ricart–Agrawala Algorithm
The Ricart–Agrawala algorithm is an algorithm for mutual exclusion on a distributed system. This algorithm is an extension and optimization of Lamport's Distributed Mutual Exclusion Algorithm, by removing the need for release messages. It was developed by computer scientists Glenn Ricart and Ashok Agrawala. Algorithm Terminology * A ''site'' is any computing device which runs the Ricart-Agrawala Algorithm * The ''requesting site'' is the site which is requesting to enter the critical section. * The ''receiving site'' is every other site which is receiving a request from the requesting site. Algorithm Requesting Site * Sends a message to all sites. This message includes the site's name, and the current timestamp of the system according to its logical clock (''which is assumed to be synchronized with the other sites'') Receiving Site * Upon reception of a request message, immediately sending a timestamped ''reply'' message if and only if: :* the receiving process is not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Node (networking)
In Computer network, networking, a node (, ‘knot’) is either a redistribution point or a communication endpoint within telecommunication networks. A physical network node is an electronic device that is attached to a network, and is capable of creating, receiving, or transmitting information over a communication channel. In data communication, a physical network node may either be data communication equipment (such as a modem, Network hub, hub, Network bridge, bridge or Network switch, switch) or data terminal equipment (such as a digital telephone handset, a printer or a host computer). A Passivity (engineering), passive distribution point such as a distribution frame or patch panel is not a node. Computer networks In data communication, a physical network node may either be data communication equipment (DCE) such as a modem, Network hub, hub, Network bridge, bridge or Network switch, switch; or data terminal equipment (DTE) such as a digital telephone handset, a printe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lamport Timestamps
The Lamport timestamp algorithm is a simple logical clock algorithm used to determine the order of events in a distributed computer system. As different nodes or processes will typically not be perfectly synchronized, this algorithm is used to provide a partial ordering of events with minimal overhead, and conceptually provide a starting point for the more advanced vector clock method. The algorithm is named after its creator, Leslie Lamport. Distributed algorithms such as resource synchronization often depend on some method of ordering events to function. For example, consider a system with two processes and a disk. The processes send messages to each other, and also send messages to the disk requesting access. The disk grants access in the order the messages were ''received''. For example process A sends a message to the disk requesting write access, and then sends a read instruction message to process B. Process B receives the message, and as a result sends its own read reques ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
