There are many different types of middleware. Some focus on specific types of connectivity, others on specific applications, application components and devices; some combine middleware capabilities for a specific development task. Some of the best-known and most commonly-used types of middleware software include: Show
Message-oriented middleware (MOM) enables application components using different messaging protocols to communicate to exchange messages. In addition to translating - or transforming - messages between applications, MOM manages routing of the messages so they always get to the proper components in the in the proper order. Examples of MOM include message queues and message brokers. Remote procedure call (RPC) middleware enables one application to trigger a procedure in another application - running on the same computer or on a different computer or network - as if both were part of the same application on the same computer. Data or database middleware simplifies access to, and interaction with, back-end databases. Typically database middleware is some form of SQL database server. API (application programming interface) middleware provides tools developers can use to create, expose and manage APIs for their applications - so that other developers can connect to them. Some API middleware includes tools for monetizing APIs - enabling other organizations to use them, at cost. Examples of API middleware include API management platforms, API gateways and API developer portals. Object request broker (ORB) middleware acts as broker between a request from one application object or component, and the fulfillment of that request by another object or component on the distributed network. ORBs operate with the Common Object Request Broker Architecture (CORBA), which enables one software component to make a request of another without knowing where other is hosted, or what its UI looks like - the "brokering" handles this information during the exchange. Transactional middleware provides services to support the execution of data transactions across a distributed network. The best-known transactional middleware are transaction processing monitors (TPMs), which ensure that transactions proceed from one step to the next - executing the data exchange, adding/changing/deleting data where needed, etc. - through to completion. Asynchronous data streaming middleware replicates a data stream in an intermediate store, enabling data sharing between multiple applications. Apache Kafka is one of the best-known examples of middleware for real-time data streaming. Device middleware provides a focused set of integration and connectivity capabilities for developing apps for a specific mobile OS. Portal middleware provides tools and resources for integrating content and capabilities from various related applications 'at the glass' - or on a single screen - to create a single, composite application. Robotics middleware simplifies the process of integrating robotic hardware, firmware and software from multiple manufacturers and locations. Enterprise application integration middleware
Until about ten years ago, the most prevalent enteprise application integration middleware was the enterprise service bus (ESB), which served as the integration hub within a service-oriented architecture (SOA). Today iPaaS lets an organization connect applications, data, processes and services across on-premises, private cloud, and public cloud environments - without the work and expense of purchasing, installing, managing, and maintaining the integration middleware (and the hardware it runs on) within its own data center. Platform middleware
First WWW server located at CERN with its original sticker that says: "This machine is a server. DO NOT POWER IT DOWN!!" In computing, a server is a piece of computer hardware or software (computer program) that provides functionality for other programs or devices, called "clients". This architecture is called the client–server model. Servers can provide various functionalities, often called "services", such as sharing data or resources among multiple clients, or performing computation for a client. A single server can serve multiple clients, and a single client can use multiple servers. A client process may run on the same device or may connect over a network to a server on a different device.[1] Typical servers are database servers, file servers, mail servers, print servers, web servers, game servers, and application servers.[2] Client–server systems are usually most frequently implemented by (and often identified with) the request–response model: a client sends a request to the server, which performs some action and sends a response back to the client, typically with a result or acknowledgment. Designating a computer as "server-class hardware" implies that it is specialized for running servers on it. This often implies that it is more powerful and reliable than standard personal computers, but alternatively, large computing clusters may be composed of many relatively simple, replaceable server components. History[edit]The use of the word server in computing comes from queueing theory,[3] where it dates to the mid 20th century, being notably used in Kendall (1953) (along with "service"), the paper that introduced Kendall's notation. In earlier papers, such as the Erlang (1909), more concrete terms such as "[telephone] operators" are used. In computing, "server" dates at least to RFC 5 (1969),[4] one of the earliest documents describing ARPANET (the predecessor of Internet), and is contrasted with "user", distinguishing two types of host: "server-host" and "user-host". The use of "serving" also dates to early documents, such as RFC 4,[5] contrasting "serving-host" with "using-host". The Jargon File defines "server" in the common sense of a process performing service for requests, usually remote, with the 1981 (1.1.0) version reading:
Operation[edit]A network based on the client–server model where multiple individual clients request services and resources from centralized servers Strictly speaking, the term server refers to a computer program or process (running program). Through metonymy, it refers to a device used for (or a device dedicated to) running one or several server programs. On a network, such a device is called a host. In addition to server, the words serve and service (as verb and as noun respectively) are frequently used, though servicer and servant are not.[a] The word service (noun) may refer to either the abstract form of functionality, e.g. Web service. Alternatively, it may refer to a computer program that turns a computer into a server, e.g. Windows service. Originally used as "servers serve users" (and "users use servers"), in the sense of "obey", today one often says that "servers serve data", in the same sense as "give". For instance, web servers "serve [up] web pages to users" or "service their requests". The server is part of the client–server model; in this model, a server serves data for clients. The nature of communication between a client and server is request and response. This is in contrast with peer-to-peer model in which the relationship is on-demand reciprocation. In principle, any computerized process that can be used or called by another process (particularly remotely, particularly to share a resource) is a server, and the calling process or processes is a client. Thus any general-purpose computer connected to a network can host servers. For example, if files on a device are shared by some process, that process is a file server. Similarly, web server software can run on any capable computer, and so a laptop or a personal computer can host a web server. While request–response is the most common client-server design, there are others, such as the publish–subscribe pattern. In the publish-subscribe pattern, clients register with a pub-sub server, subscribing to specified types of messages; this initial registration may be done by request-response. Thereafter, the pub-sub server forwards matching messages to the clients without any further requests: the server pushes messages to the client, rather than the client pulling messages from the server as in request-response.[6] Purpose[edit]The role of a server is to share data as well as to share resources and distribute work. A server computer can serve its own computer programs as well; depending on the scenario, this could be part of a quid pro quo transaction, or simply a technical possibility. The following table shows several scenarios in which a server is used.
Almost the entire structure of the Internet is based upon a client–server model. High-level root nameservers, DNS, and routers direct the traffic on the internet. There are millions of servers connected to the Internet, running continuously throughout the world[9] and virtually every action taken by an ordinary Internet user requires one or more interactions with one or more servers. There are exceptions that do not use dedicated servers; for example, peer-to-peer file sharing and some implementations of telephony (e.g. pre-Microsoft Skype). Hardware[edit]A rack-mountable server with the top cover removed to reveal internal components Hardware requirement for servers vary widely, depending on the server's purpose and its software. Servers are more often than not, more powerful and expensive than the clients that connect to them. Since servers are usually accessed over a network, many run unattended without a computer monitor or input device, audio hardware and USB interfaces. Many servers do not have a graphical user interface (GUI). They are configured and managed remotely. Remote management can be conducted via various methods including Microsoft Management Console (MMC), PowerShell, SSH and browser-based out-of-band management systems such as Dell's iDRAC or HP's iLo. Large servers[edit]Large traditional single servers would need to be run for long periods without interruption. Availability would have to be very high, making hardware reliability and durability extremely important. Mission-critical enterprise servers would be very fault tolerant and use specialized hardware with low failure rates in order to maximize uptime. Uninterruptible power supplies might be incorporated to guard against power failure. Servers typically include hardware redundancy such as dual power supplies, RAID disk systems, and ECC memory,[10] along with extensive pre-boot memory testing and verification. Critical components might be hot swappable, allowing technicians to replace them on the running server without shutting it down, and to guard against overheating, servers might have more powerful fans or use water cooling. They will often be able to be configured, powered up and down, or rebooted remotely, using out-of-band management, typically based on IPMI. Server casings are usually flat and wide, and designed to be rack-mounted, either on 19-inch racks or on Open Racks. These types of servers are often housed in dedicated data centers. These will normally have very stable power and Internet and increased security. Noise is also less of a concern, but power consumption and heat output can be a serious issue. Server rooms are equipped with air conditioning devices. Clusters[edit]A server farm or server cluster is a collection of computer servers maintained by an organization to supply server functionality far beyond the capability of a single device. Modern data centers are now often built of very large clusters of much simpler servers,[11] and there is a collaborative effort, Open Compute Project around this concept. Appliances[edit]A class of small specialist servers called network appliances are generally at the low end of the scale, often being smaller than common desktop computers. Mobile[edit]A mobile server has a portable form factor, e.g. a laptop.[12] In contrast to large data centers or rack servers, the mobile server is designed for on-the-road or ad hoc deployment into emergency, disaster or temporary environments where traditional servers are not feasible due to their power requirements, size, and deployment time.[13] The main beneficiaries of so-called "server on the go" technology include network managers, software or database developers, training centers, military personnel, law enforcement, forensics, emergency relief groups, and service organizations.[14] To facilitate portability, features such as the keyboard, display, battery (uninterruptible power supply, to provide power redundancy in case of failure), and mouse are all integrated into the chassis. Operating systems[edit]Sun's Cobalt Qube 3; a computer server appliance (2002); running Cobalt Linux (a customized version of Red Hat Linux, using the 2.2 Linux kernel), complete with the Apache web server. On the Internet the dominant operating systems among servers are UNIX-like open-source distributions, such as those based on Linux and FreeBSD,[15] with Windows Server also having a significant share. Proprietary operating systems such as z/OS and macOS Server are also deployed, but in much smaller numbers. Specialist server-oriented operating systems have traditionally had features such as:
In practice, today many desktop and server operating systems share similar code bases, differing mostly in configuration. Energy consumption[edit]In 2010, data centers (servers, cooling, and other electrical infrastructure) were responsible for 1.1-1.5% of electrical energy consumption worldwide and 1.7-2.2% in the United States.[17] One estimate is that total energy consumption for information and communications technology saves more than 5 times its carbon footprint[18] in the rest of the economy by increasing efficiency. Global energy consumption is increasing due to the increasing demand of data and bandwidth. Natural Resources Defense Council (NRDC) states that data centers used 91 billion kilowatt hours (kWh) electrical energy in 2013 which accounts to 3% of global electricity usage. Environmental groups have placed focus on the carbon emissions of data centers as it accounts to 200 million metric tons of carbon dioxide in a year. See also[edit]
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References[edit]
Further reading[edit]Wikimedia Commons has media related to Servers.
Which term refers to a system or application that acts as a go between for clients requests for network services content filter proxy server application container router?A proxy server is a go‑between or intermediary server that forwards requests for content from multiple clients to different servers across the Internet.
Which term refers to a system or application that acts as a go between?Proxy server: "An Internet server that acts as a “go-between” for a computer on a local network (secure system) and the open Web.
Which term refers to the step between the account having access and the account being removed from the system?Which term refers to the step between the account having access and the account being removed from the system? Account disablement.
Which term refers to the matching of a user to an account through previously shared credentials quizlet?The best algorithms are always public algorithms that have been published for peer review by other cryptographic and mathematical experts. True. Which term refers to the matching of a user to an account through previously shared credentials? Authentication.
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