OS/400
OS/400 is IBM’s operating system for its AS/400 and AS/ 400e line of business computers. Because OS/400 is closely attuned to the AS/400 hardware design and generally comes as part of the basic package, there is no alternative operating system to compete with it. OS/400 is built to operate with the AS/400 logical partition (LPAR) architecture, in which multiple instances of the operating system can run concurrently in different partitions. Among other uses, LPAR is useful when migrating to a new release. The old production system can keep operating in one partition while a new system is being tested.
As the AS/400 has evolved to meet the latest trends in business and information technology, OS/400 and its related software has added support for:
• Applications written in the Java programming language
• The ability to run Windows 2000/NT applications (when certain other products are installed)
• The Portable Application Solutions Environment (PASE), which supports a subset of the AIX environment so that UNIX applications can be ported and run on the AS/400
• Lotus Domino, which provides groupware and e-mail from Lotus Notes applications or a standard Web browser
oscillator
An oscillator is an electronic device used for the purpose of generating a signal. Oscillators are found in computers, wireless receivers and transmitters, and audio-frequency equipment, particularly music synthesizers. There are many types of oscillator devices, but they all operate according to the same basic principle: an oscillator always employs a sensitive amplifier whose output is fed back to the input in phase. Thus, the signal regenerates and sustains itself. This is known as positive feedback. It is the same process that sometimes causes unwanted "howling" in public-address systems.
The frequency at which an oscillator works is usually determined by a quartz crystal. When a direct current is applied to such a crystal, it vibrates at a frequency that depends on its thickness, and on the manner in which it is cut from the original mineral rock. Some oscillators employ combinations of inductors, resistors, and/or capacitors to determine the frequency. However, the best stability (constancy of frequency) is obtained in oscillators that use quartz crystals.
In a computer, a specialized oscillator, called the clock, serves as a sort of pacemaker for the microprocessor. The clock frequency (or clock speed) is usually specified in megahertz (MHz), and is an important factor in determining the rate at which a computer can perform instructions.
oscilloscope
An oscilloscope is a laboratory instrument commonly used to display and analyze the waveforms of electronic signals. In effect, the device draws a graph of the instantaneous signal voltage as a function of time.
A typical oscilloscope can display alternating current (AC) or pulsating direct current (DC) waveforms having a frequency as low as approximately 1 hertz (Hz) or as high as several megahertz (MHz). High-end oscilloscopes can display signals having frequencies up to several hundred gigahertz (GHz). The display is broken up into so-called horizontal divisions (hor div) and vertical divisions (vert div). Time is displayed from left to right on the horizontal scale. Instantaneous voltage appears on the vertical scale, with positive values going upward and negative values going downward.
The oldest form of oscilloscope, still used in some labs today, is known as the cathode-ray oscilloscope. It produces an image by causing a focused electron beam to travel, or sweep, in patterns across the face of a cathode ray tube (CRT). More modern oscilloscopes electronically replicate the action of the CRT using a liquid crystal display (LCD) similar to those found on notebook computers. The most sophisticated oscilloscopes employ computers to process and display waveforms. These computers can use any type of display, including CRT, LCD, and gas plasma.
In any oscilloscope, the horizontal sweep is measured in seconds per division (s/div), milliseconds per division (ms/ div), microseconds per division (s/div), or nanoseconds per division (ns/div). The vertical deflection is measured in volts per division (V/div), millivolts per division (mV/div), or microvolts per division (mV/div). Virtually all oscilloscopes have adjustable horizontal sweep and vertical deflection settings.
The illustration shows two common waveforms as they might appear when displayed on an oscilloscope screen. The signal on the top is a sine wave; the signal on the bottom is a ramp wave. It is apparent from this display that both signals have the same, or nearly the same, frequency. They also have approximately the same peak-to-peak amplitude. Suppose the horizontal sweep rate in this instance is 1 ms/ div. Then these waves both complete a full cycle every 2 ms, so their frequencies are both approximately 0.5 MHz or 500 kilohertz (kHz). If the vertical deflection is set for, say, 0.5 mV/div, then these waves both have peak-to-peak amplitudes of approximately 2 mV.
These days, typical high-end oscilloscopes are digital devices. They connect to personal computers and use their displays. Although these machines no longer employ scanning electron beams to generate images of waveforms in the manner of the old cathode-ray "scope," the basic principle is the same. Software controls the sweep rate, vertical deflection, and a host of other features which can include:
• Storage of waveforms for future reference and comparison
• Display of several waveforms simultaneously
• Spectral analysis
• Portability
• Battery power option
• Usability with all popular operating platforms
• Zoom-in and zoom-out
• Multi-color displays
OSGi
OSGi (Open Service Gateway Initiative) is an industry plan for a standard way to connect devices such as home appliances and security systems to the Internet. With such a standard, home users could, for example, install a security system and be able to change from one monitoring service to another without having to install a new system of wires and devices. The ”service gateway” would be an application server in a computer that was a gateway between the Internet and a home or small business’s network of device. The OSGi plans to specify the application program interface (API) for programmers to use to allow communication and control between service providers and the devices within the home or small business network. OSGi’s API will be built on the Java programming language. Java programs can generally be run on any computer operating system platform. OSGi is an open standard programming interface. Changes will evolve through the ”Java Community Process.”
OSGi is intended to connect new Jini ”smart appliances,” Bluetooth wireless device groups, as well as TV set-top boxes, cable modems, alarm systems, energy management systems, and other devices to Internet sites that can be used to manage them remotely and interactively. The service gateway (SG) is intended to manage this interconnection with ”zero administration.”
Among some popular device-to-Internet applications are expected to be energy measurement and load management in the home; home security systems that a home owner can monitor and control away from home; continous monitoring of critical care and home-care patients; and predictive failure reporting for home appliances. The OSGi specification will be designed to complement existing residential standards, such as those of LonWorks (see control network), CAL, CEBus, HAVi, and others.
The initial group of companies that formed the initiative were: Alcatel, Cable Wireless, Electricite de France, Enron Communications, Ericcson, IBM, Lucent Technologies, Motorola, NCI, Nortel Networks, Oracle, Philips Electronics, Sun Microsystems, Sybase, and Toshiba.
OSI
OSI (Open Systems Interconnection) is a standard description or ”reference model” for how messages should be transmitted between any two points in a telecommunication network. Its purpose is to guide product implementors so that their products will consistently work with other products. The reference model defines seven layers of functions that take place at each end of a communication. Although OSI is not always strictly adhered to in terms of keeping related functions together in a well-defined layer, many if not most products involved in telecommunication make an attempt to describe themselves in relation to the OSI model. It is also valuable as a single reference view of communication that furnishes everyone a common ground for education and discussion.
Developed by representatives of major computer and telecommunication companies beginning in 1983, OSI was originally intended to be a detailed specification of interfaces. Instead, the committee decided to establish a common reference model for which others could develop detailed interfaces, that in turn could become standards. OSI was officially adopted as an international standard by the International Organization of Standards (ISO). Currently, it is Recommendation X.200 of the ITU-TS. The main idea in OSI is that the process of communication between two end points in a telecommunication network can be divided into layers, with each layer adding its own set of special, related functions. Each communicating user or program is at a computer equipped with these seven layers of function. So, in a given message between users, there will be a flow of data through each layer at one end down through the layers in that computer and, at the other end, when the message arrives, another flow of data up through the layers in the receiving computer and ultimately to the end user or program. The actual programming and hardware that furnishes these seven layers of function is usually a combination of the computer operating system, applications (such as your Web browser), TCP/IP or alternative transport and network protocols, and the software and hardware that enable you to put a signal on one of the lines attached to your computer.
OSI divides telecommunication into seven layers. The layers are in two groups. The upper four layers are used whenever a message passes from or to a user. The lower three layers (up to the network layer) are used when any message passes through the host computer. Messages intended for this computer pass to the upper layers. Messages destined for some other host are not passed up to the upper layers but are forwarded to another host. The seven layers are:
Layer 7: The Application layer…This is the layer at which communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. (This layer is not the application itself, although some applications may perform application layer functions.)
Layer 6: The Presentation layer…This is a layer, usually part of an operating system, that converts incoming and outgoing data from one presentation format to another (for example, from a text stream into a popup window with the newly arrived text). Sometimes called the syntax layer. Layer 5: The Session layer…This layer sets up, coordinates, and terminates conversations, exchanges, and dialogs between the applications at each end. It deals with session and connection coordination.
Layer 4: The Transport layer…This layer manages the end-to-end control (for example, determining whether all packets have arrived) and error-checking. It ensures complete data transfer.
Layer 3: The Network layer…This layer handles the routing of the data (sending it in the right direction to the right destination on outgoing transmissions and receiving incoming transmissions at the packet level). The network layer does routing and forwarding.
Layer 2: The Data-Link layer…This layer provides synchronization for the physical level and does bit-stuffing for strings of 1′s in excess of 5. It furnishes transmission protocol knowledge and management.
Layer 1: The Physical layer…This layer conveys the bit stream through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier.
OSPF
OSPF (Open Shortest Path First) is a router protocol used within larger autonomous system networks in preference to the Routing Information Protocol (RIP), an older routing protocol that is installed in many of today’s corporate networks. Like RIP, OSPF is designated by the Internet Engineering Task Force (IETF) as one of several Interior Gateway Protocols (IGPs).
Using OSPF, a host that obtains a change to a routing table or detects a change in the network immediately multicasts the information to all other hosts in the network so that all will have the same routing table information. Unlike the RIP in which the entire routing table is sent, the host using OSPF sends only the part that has changed. With RIP, the routing table is sent to a neighbor host every 30 seconds. OSPF multicasts the updated information only when a change has taken place.
Rather than simply counting the number of hops, OSPF bases its path descriptions on ”link states” that take into account additional network information. OSPF also lets the user assign cost metrics to a given host router so that some paths are given preference. OSPF supports a variable network subnet mask so that a network can be subdivided. RIP is supported within OSPF for router-to-end station communication. Since many networks using RIP are already in use, router manufacturers tend to include RIP support within a router designed primarily for OSPF.
out of the box
1) ”Out of the box” is an expression that describes nonconformal, creative thinking. The term is used as an adverb to describe the thinking or as an adjective to describe the ideas. Although the origin of the term is unknown to us, it would seem to suggest that we tend to carry around an existing and conventional structure of thought that it is hard to escape. One also thinks of the expression ”boxed-in,” or having reduced choices. In the fast-paced world of information technology, employers often say they are looking for someone who ”thinks out of the box.” Older, related but really different terms include blue sky, far out, and off the wall. A variation is ”outside the box.”
As you might expect, the term ”in the box” is sometimes used to describe conformal thinking. For example, in a recent magazine article about MP3 and music pirating, a manager of some music groups is quoted as saying of major label recording companies who have been slow to adapt to the Internet, ”They’re always thinking inside of the box.”
2) ”Out of the box” is also used as a synonym for ”off the shelf,” meaning a ready-made software, hardware, or combination package that meets a need that would otherwise require an ad hoc development effort.
out-of-band signaling
Out-of-band signaling is telecommunication signaling (exchange of information in order to control a telephone call) that is done on a channel that is dedicated for the purpose and separate from the channels used for the telephone call. Out-of-band signaling is used in Signaling System 7 (SS7), the latest standard for the signaling that controls the world’s phone calls.
output feedback
Output feedback (OFB) is a mode of operation for a block cipher. It has some similarities to the ciphertext feedback mode in that it permits encryption of differing block sizes, but has the key difference that the output of the encryption block function is the feedback (instead of the ciphertext). The XOR (exclusive OR) value of each plaintext block is created independently of both the plaintext and ciphertext. It is this mode that is used when there can be no tolerance for error propagation, as there are no chaining dependencies.
Like the ciphertext feedback mode, it uses an initialization vector (IV). Changing the IV in the same plaintext block results in different ciphertext.
In terms of error correction, output feedback can tolerate ciphertext bit errors, but is incapable of self-synchronization after losing ciphertext bits, as it disturbs the synchronization of the aligning keystream. A problem with output feedback is that the plaintext can be easily altered but using a digital signature scheme can overcome this problem.
outsourcing
Outsourcing is an arrangement in which one company provides services for another company that could also be or usually have been provided in-house. Outsourcing is a trend that is becoming more common in information technology and other industries for services that have usually been regarded as intrinsic to managing a business. In some cases, the entire information management of a company is outsourced, including planning and business analysis as well as the installation, management, and servicing of the network and workstations. Outsourcing can range from the large contract in which a company like IBM manages IT services for a company like Xerox to the practice of hiring contractors and temporary office workers on an individual basis.
overclocking
Overclocking is resetting your computer so that the microprocessor runs faster than the manufacturer-specified speed (for example, setting an Intel 166 MHz (megahertz) microprocessor to run at 200 Mhz). Somewhat surprisingly, this is possible. However, it’s more likely to work with an Intel microprocessor than with those of other manufacturers because, according to Tom’s Hardware Guide, Intel labels the speed of its microprocessors more conservatively. Factors that favor your ability to successfully ”upgrade by resetting” include (in addition to having an Intel microprocessor): having a well-designed motherboard with a fast enough bus and having a fan or other cooling device that will keep your system cool enough.
The procedure for ”overclocking” depends on your combination of factors. The first and most commonly applicable step is to reset your computer’s bus speed. The microprocessor is often able to adjust successfully to a slightly higher bus speed. Resetting the bus speed may require resetting jumpers inside your computer. In newer systems with SoftMenu BIOS, the bus speed can be set through your system setup interface.
packet
A packet is the unit of data that is routed between an origin and a destination on the Internet or any other packet-switched network. When any file (e-mail message, HTML file, Graphics Interchange Format file, Uniform Resource Locator request, and so forth) is sent from one place to another on the Internet, the Transmission Control Protocol (TCP) layer of TCP/IP divides the file into "chunks" of an efficient size for routing. Each of these packets is separately numbered and includes the Internet address of the destination. The individual packets for a given file may travel different routes through the Internet. When they have all arrived, they are reassembled into the original file (by the TCP layer at the receiving end).
A packet-switching scheme is an efficient way to handle transmissions on a connectionless network such as the Internet. An alternative scheme, circuit-switched, is used for networks allocated for voice connections. In circuit-switching, lines in the network are shared among many users as with packet-switching, but each connection requires the dedication of a particular path for the duration of the connection.
"Packet" and "datagram" are similar in meaning. A protocol similar to TCP, the User Datagram Protocol(UDP) uses the term datagram.
Packet monkey
On the Internet, a packet monkey is someone (see cracker, hacker, and script kiddy) who intentionally inundates a Web site or network with data packets, resulting in a denial-of-service situation for users of the attacked site or network. Packet monkeys typically use tools created and made available on the Internet by hackers. According to one writer’s distinction, a packet monkey, unlike a script kiddy, leaves no clues as to who is making the exploit, making the identity of a packet monkey more difficult to trace. In addition, a denial-of-service attack can be launched on a wider scale than attacks performed by script kiddies, making them more difficult to investigate. Hackers look down on packet monkeys and often describe them as "bottom feeders." Because a packet monkey uses tools created by others, the packet monkey has little understanding of the harm that may be caused. Typically, packet monkey exploits are random and without any purpose other than the thrill of making an effect.
