See Secure Phone Lines.
A way of insuring data on a network is protected from unauthorized use. Network security measures can be software-based, where passwords restrict users' access to certain data files or directories. This kind of security is usually implemented by the network operating system. Audit trails are another software-based security measure, where an ongoing journal of what users did what with what files is maintained . Security can also be hardware-based, using the more traditional lock and key.
Also called the Directory Services Database, stores information about user accounts, groups, and access privileges on a Microsoft Windows NT server.
The ability of a switch to blank out the called digits for certain extensions so no called number detail is printed. Senior executives in serious takeover negotiations find this feature useful. There have been instances of people figuring out which company another company is about to buy based on telephone calling records. If you have this information, you can buy the company's stock before the bid is announced and make a lot of money. This feature ” security blanking ” is designed to avoid such occur- rences.
A cabinet, usually on casters, used to store confidential materials under lock and key prior to shredding .
A user identification code required by computer systems to protect information or information resources from unauthorized use.
A six-digit number used to prevent unauthorized or accidental alteration of data programmed into cellular phones. The factory default is 000000.
The asterisks that appear onscreen as you type in your password.
A security equivalence allows one user to have the same rights as another. Use security equivalence when you need to give a user temporary access to the same information or rights as another user. By using a security equivalence, you avoid having to review the whole directory structure and determine which rights need to be assigned in which directories.
Protects a network from invalid accesses . It is one of the management categories defined by the ISO (International Standards Organization).
A Bluetooth term . The module in a Bluetooth device that controls security aspects of communications to other Bluetooth devices.
A class of modem providing secure access.
This is a number that, together with a destination IP address and a security protocol, uniquely identifies a particular security association. When using Internet Key Exchange (IKE) to establish the security associations, the SPI for each security association is a pseudo- randomly derived number. Without IKE, the SPI is specified manually for each security association.
A cylindrically shaped metal finger that holds open the door to a Cash Box until the box is removed for collection.
See Positive Trapping and Negative Trapping.
Smoke Emitting Diode. Diodes not installed properly can become SEDs, which then can become FEDs (Fire Emitting Diodes). See also Diode.
Router in an AppleTalk network that has the network number or cable range built in to its port descriptor. The seed router defines the network number or cable range for other routers in that network segment and responds to configuration queries from nonseed routers on its connected AppleTalk network, allowing those routers to confirm or modify their configurations accordingly . Each AppleTalk network must have at least one seed router.
Software designed to get demand for a product or a new market segment started. Software designed to "seed" a market. Seedware is typically a less-full featured piece of software than the software you're really trying to sell. Seedware typically costs very little. It may even be free. It's also called Feedware.
The time it takes to move a disk drive's read/write head to a given track. Seek time varies depending on where the head starts from and has to go it. Average seek time is a critical measure of the speed of a computer disk drive.
Source Explicit Forwarding. Security feature that allows transmissions only from specified stations to be forwarded by bridges.
Severely Errored Framing. A SONET defect which is the first indication of trouble in detecting valid signal framing patterns. Four consecutive errored framing patterns constitutes an SEF defect. If the SEF defect persists, an LOF defect is instituted, and if the LOF defect persists an LOF alarm is declared. See also LOF.
Severely Errored Framing Seconds. A count of the number of seconds during which at any point the SEF defect was present. See SEF.
64 characters . Use as a method of data communications billing by some overseas phone companies.
An electronically continuous portion of a network, usually consisting of the same wire.
A single ATM link or group of interconnected ATM links of an ATM connection.
Method of classifying a group of people by their purchase behavior, lifestyle and attitudes.
SAR. An ATM term. See SAR.
To access a circuit and use it, or make it busy so that others cannot use it.
A signal used by the calling end of a trunk or line to indicate a request for service.
Selector: A subfield carried in SETUP message part of ATM endpoint address Domain specific Part (DSP) defined by ISO 10589, not used for ATM network routing, used by ATM end systems only.
A name for a Pacific Bell (and possibly other local telephone companies') service which allows you to have calls from selected numbers ring at another number.
What most people call a "block" in a word processed document, Microsoft calls a "selection." If you want to print test you've blocked, tell Windows to print a selection.
Permits incoming calls only from numbers you preselect.
Forewords all calls from a pre-selected list to a specific destination.
Blocks incoming calls from numbers you pre-select.
The ability of the transmitting phone to specify which of several phones on the a line is to receive a message.
Fading in which the components of the received radio signal fluctuate independently.
SILC. A control application available with CCIS that dynamically controls the amount and type of traffic offered to an overloaded or failed system.
A phone can page to individual phone instruments.
A method of ringing only the desired party on a party line.
SR. In the US emergency services telephone network, selective routing is the routing of a 911 call to the appropriate public safety answering point based on the call's Emergency Service Number, i.e., the caller's location.
A method of inband signaling used on private networks to tell switches to switch the call.
Ability of a tuner or receiver to get only a desired station while rejecting other adjacent stations. The higher the figure expressed in decibels (dB), the better the selectivity.
The identifier (octet string) used by an OSI entity to distinguish among multiple SAPs at which it provides services to the layer above.
The intermediate distributing switch in an (very old) step-by-step mechanical switching system. It is directly controlled by the customer dial in its vertical motion and hunts for an idle path in its angular motion.
Your phone system tells you when something is wrong with it by sending you a "message" via the operator console or through one of the data ports on the phone system.
When internal chemical reactions (such as the dying out of chemicals) cause the loss of useful capacity of a cell or battery in storage.
SEEDs. Switches guided by light.
The characteristic of a material whose flame is extinguished after the igniting flame is removed.
Self healing means it fixes itself, which is really a misnomer. It really doesn't fix itself. In telecom, self-healing really means 100% connectivity. The term came into telecom use with the invention of SONET fiber rings. Here's how they work: A phone company lays down several concentric rings of fiber ” typically around a city or an industrial park. You, the customer, buy service from the carrier. If one ring fails, the system knows and instantly your traffic is shunted in a different direction or to a different fiber. "Self-healing" is actually 100% fiber connectivity between business locations and telephone company serving wire centers. "Self-healing" means that SONET rings provide for automatic network backup with 100% redundancy so that if there is a point of failure on your fiber ring, your service continues.
There is another definition. Brian Livingston, author of books on Windows and InfoWorld columnist, says that self healing software upgrades itself by periodically calling a central phone number (via bulletin board) or a Web site and automatically downloading and installing any new components that may have become available since the last product upgrade.
Microsoft uses the term "self healing" to refer to an operating system that crashes less often than a traditional operating system. They mean that when the software encounters bad code, it goes to find the good code and somehow replaces the bad code with good code. Several software programs, like Microsoft's Office 2000 claim to be self-healing.
A self healing grid is a proposed electrical power infrastructure that would monitor itself through an array of sensors, run simulations to identify potential glitches, and then correct itself to avert problems. See also Self Restorable Rings.
An SCSA definition. The Client and the Server are on the same computer platform. A server with one or more self-hosted applications may be a standalone unit which is not connected to any other system.
Optical rings can be self-restorable. Most vendors are considering the protection mechanisms (OSP and optical channel protection) for adaptation to the ring topology. Any of these mechanisms works under a failure situation. Optical channel subnetwork-connection protection (OCh-SNCP), as its name implies, protects the optical channel, while OMS shared protection ring (OMS-SPRing) protects all of the OMS. OMS-SPRing is the optical equivalent of the multiplex section shared protection ring (MS- SPRing) standardized by ITU-T in G.841. In SONET, this scheme is frequently referred to as a bidirectional line-switched ring. OCh-SNCP, meanwhile, is the optical counterpart to SDH's subnetwork connection protection, also sometimes called unidirectional line-switched ring. See also Self Healing.
The capability of a PBX to run programs at regular intervals to test its own operation and signal when failures have occurred or are about to occur without human intervention.
Selling consists of three steps: Prospecting. Qualifying and Closing.
A telemarketing term. The steps involved in a sale: A clear call objective, identify and reach the decision maker, introduction and call justification, identify needs, present solution/benefits, answer questions or objections, close, confirm the conditions, and congratulate.
A message sent when a file is opened to prevent other users from opening the same file at that time. Its purpose is to preserve the integrity of data (i.e. stop it from being messed with) while you're using it.
An apparatus for visual signaling, such as by the use of flags. The term comes from the Greek "sema," meaning sign or signal, and "phoros," meaning carrying. Semaphores were in common use for message signaling prior to the invention of the telegraph. In fact, the British Admiralty Office on August 5, 1816 officially rejected the idea of the electric telegraph, which had been suggested by Mr. (later Sir) Ronald Edwards. It seems that the Admiralty preferred the semaphore, although it was useless during the night or when it was foggy.
A channel separated from a specific channel by one channel.
A network control technique whereby an operator manually switches a message to a destination according to the address information contained in the message header.
An RFID definition. Similar to active tags, but the battery is used to run the microchip's circuitry but not to communicate with the reader. Some semi- passive tags sleep until they are woken up by a signal from the reader, which conserves battery life. Semi-passive tags cost a dollar or more.
A cable containing a flexible inner core and a relatively inflexible sheathing material, such as a metallic tube but, which can be bent for coiling or spooling and placing in duct or cable run.
Semiconductors are the basic building blocks of telecom and computing. They are made into microprocessors which drive our computers, our PDAs, our communications networks, our phone systems, our watches and our cars . They are called integrated circuits, chips and a thousand other variations. In their basic form, semiconductors are materials that are midway between conductors and insulators; they have a resistance to electricity between a conductor (e.g. a copper wire) and an insulator (e.g. plastic). Hence the word "semi" conductor. Silicon and germanium are the two most commonly- used materials to make semiconductors. The flow of current in a semiconductor can be changed by light or the presence or absence of an electric or magnetic field. Semiconductors will only conduct electricity when a certain threshold voltage has been reached. Because the energy needed to " turn on" a semiconductor can be high, most semiconductors have their conductivity enhanced through a process called doping. Doping consists of adding an impurity that has either a surplus or a shortage of electrons. Semiconductors with impurities that provide a surplus of electrons are called N-type semiconductors. Semiconductors with impurities that have a shortage of electrons are called P- type semiconductors. Together N-type and P-type semiconductors are the basic building blocks of nearly all solid state electronic devices.
Making semiconductor integrated circuits can consist of more than a hundred steps, during which hundreds of copies of an integrated circuit are formed on a single wafer.
Generally , the process involves the creation of eight to 20 patterned layers on and into the substrate, ultimately forming the complete integrated circuit. This layering process creates electrically active regions in and on the semiconductor wafer surface. The first step in semiconductor manufacturing begins with production of a wafer ” a thin, round slice of a semiconductor material, usually silicon. In this process, purified polycrystalline silicon, created from sand, is heated to a molten liquid. A small piece of solid silicon (seed) is placed on the molten liquid, and as the seed is slowly pulled from the melt the liquid cools to form a single crystal ingot. The surface tension between the seed and molten silicon causes a small amount of the liquid to rise with the seed and cool. The crystal ingot is then ground to a uniform diameter and a diamond saw blade cuts the ingot into thin wafers. The wafer is processed through a series of machines, where it is ground smooth and chemically polished to a mirror-like luster. The wafers are then ready to be sent to the wafer fabrication area where they are used as the starting material for manufacturing integrated circuits. The heart of semiconductor manufacturing is the wafer fabrication facility where the integrated circuit is formed in and on the wafer. The fabrication process, which takes place in a clean room, typically takes from 10 to 30 days to complete. Wafers are pre-cleaned using high purity, low particle chemicals (important for high-yield products). The silicon wafers are heated and exposed to ultra -pure oxygen in the diffusion furnaces under carefully controlled conditions forming a silicon dioxide film of uniform thickness on the surface of the wafer. Masking is used to protect one area of the wafer while working on another. This process is referred to as photolithography or photo-masking. A photoresist or light-sensitive film is applied to the wafer, giving it characteristics similar to a piece of photographic paper. A photo aligner aligns the wafer to a mask and then projects an intense light through the mask and through a series of reducing lenses, exposing the photoresist with the mask pattern. Precise alignment of the wafer to the mask prior to exposure is critical. Most alignment tools are fully automatic.
The wafer is then "developed" (the exposed photoresist is removed) and baked to harden the remaining photoresist pattern. It is then exposed to a chemical solution or plasma (gas discharge) so that areas not covered by the hardened photoresist are etched away. The photoresist is removed using additional chemicals or plasma and the wafer is inspected to ensure the image transfer from the mask to the top layer is correct. Atoms with one less electron than silicon (such as boron), or one more electron than silicon (such as phosphorous), are introduced into the area exposed by the etch process to alter the electrical character of the silicon. These areas are called P-type (boron) or N-type (phosphorous) to reflect their conducting characteristics. The thermal oxidation, masking, etching and doping steps are repeated several times until the last "front end" layer is completed (all active devices have been formed). Following completion of the "front end," the individual devices are interconnected using a series of metal depositions and patterning steps of dielectric films (insulators). Current semiconductor fabrication includes as many as three metal layers separated by dielectric layers.
After the last metal layer is patterned, a final dielectric layer (passivation) is deposited to protect the circuit from damage and contamination. Openings are etched in this film to allow access to the top layer of metal by electrical probes and wire bonds . An automatic, computer-driven electrical test system then checks the functionality of each chip on the wafer. Chips that do not pass the test are marked with ink for rejection. A diamond saw typically slices the wafer into single chips. The inked chips are discarded, and the remaining chips are visually inspected under a microscope before packaging. The chip is then assembled into a package that provides the contact leads for the chip. A wire-bonding machine then attaches wires, a fraction of the width of a human hair, to the leads of the package. Encapsulated with a plastic coating for protection, the chip is tested again prior to delivery to the customer. Alternatively, the chip is assembled in a ceramic package for certain military applications. Thanks to Intersil of Irvine for description of the manufacturing of a semiconductor IC above.
A laser is really an oscillator, which means an amplifier plus a feedback. In a semiconductor laser, the amplification is provided by the population inversion in the active layer obtained by injecting current in it. There are two basic types of semiconductor lasers ” the Fabry-Perot and DFB lasers. They use different ways to provide the feedback. In a Fabry-Perot (FP), you a have a mirror at each end (usually obtained by cleaving the semiconductor crystal), which reflects part of the light and give the feedback. In a DFB (or Distributed FeedBack) laser, a Bragg grating is incorporated along the active layer, providing a distributed reflection of the light. Often the end facets are anti- reflection coated to avoid the Fabry-Perot effect. The grating is usually made by varying the thickness of one layer in a periodic fashion. This gives a periodic variation of the propagation constant (effective index) of the waveguide . For the right period, you get reflection of the light at a certain wavelength. The main difference between the two types is that DFBs are often single mode (only one wavelength determined by the Bragg grating), while FPs are usually multi-mode (4 to 20 different wavelengths at the same time and determined by the gain curve of the active material and the cavity length). See also Semiconductor.
A connection established via a service order or via network management.
A descriptive term for a data communications protocol that provides little or no assurance that the data gets to the destination device as intended. Send and pray first was applied to Parity Checking, also known as Vertical Redundancy Checking (VRC), which is the very poor error detection mechanism used in asynchronous protocols using the ASCII coding scheme. Parity checking not only is highly uncertain in its ability to detect an error created in transmission, but also provides no mechanism for the receiving device to advise the transmitting device of a detected error in order that it might be corrected by some means. Hence, the term "send and pray"-you just send the data and pray that it gets to the other end correctly. More recently, the term has been applied to voice and data over IP networks. While IP provides a fairly robust mechanism for error detection and correction, it was intended for true data communications applications, which have time to recover from errors created in the process of transmission and switching. Voice and video, however, have no time to recover. The data is presented to the receiving device as it exits the network. Any errored, delayed or corrupted data packets are simple discarded in this stream-oriented communication mode. If you are talking over an IP-based network, therefore, you just send your voice into the phone and pray that it all gets there.
A term for the method by which the misguided amongst us seek to damage our data. These poor, misguided souls embed viruses in programs which we then download. They send them to us, and then prey upon us. This term was coined by Ray Horak, my Contributing Editor.
Equipment in the originating telephone system which outpulses (sends out) the routing digits and the called person's number. Senders are necessary in computerized (stored program control) switches because the switch needs to know all the digits of the numbers you are calling before it chooses and seizes a trunk.
Sendmail is the UNIX software that handles electronic mail. It is the most common form of electronic mail software on the Internet. Sendmail provides back-end message routing and handling for Simple Mail Transfer Protocol-based electronic mail communications.
I have senior moments when I forget something my wife asks me to. those moments could also be called selective hearing loss. The buzz-phrase, "senior moment," is a joke, but it's also serious. We all fear Alzheimer's, a stroke or something that will affect us mentally as we get older.
A call center term. A field in each employee record establishing that employ - ee's seniority for the purpose of automatic schedule assignment. This is typically the employee's hire date (year, month, and day) plus a three-digit "tie breaker."
The input signal level required for a tuner, amplifier, etc., to produce a stated output. The lower the required input, the higher the sensitivity. Measured in mV (microvolts).
The degree to which a radio receiver responds to the wave to which it is tuned .
The process of rerunning a financial study to figure the degrees to which changing the assumptions changes the result of the analysis.
The person in history winning the prize for most in need of sensitivity training is the Roman emperor Commodus (A.D. 180-192) . His accomplishment: He collected all the dwarfs, cripples, and freaks he could find in the city of Rome and had them brought to the Coliseum, where they were forced to fight each other to death with meat cleavers, much to the delight and amusement of the audience.
A device that responds to a physical stimulus and produces an electronic signal. Sensors are increasingly being combined with RFID tags to detect the presence of a stimulus at an identifiable location.
Services involving the remote monitoring of instruments including burglar alarms, fire alarms, meter reading, energy management and load shedding.
An interface device for experiencing virtual reality with the hand. Wired with sensors, it detects changes in finger, hand and arm movements and relays them to the computer, allowing users to manipulate and move things in a virtual environment. See Virtual Reality.
A utility industry term that describes all calls charged to the originating number or collected as coins in a pay telephone.
Extent to which two stereo channels are kept apart. Expressed in decibels, the larger the number, the better the separation and stereo effect.
The use of FDM (Frequency Division Multiplexing) to establish separation of upstream and downstream information channels. FDM is commonly used in cellular telephony and other radio technologies and applications. Channel separation using FDM also sometimes is used in high-speed data transmission systems in order to maintain separation between the primary data stream and other information streams such as POTS and ISDN. For example, it is proposed that FDM channel separation will be used in early versions of VDSL (Very-high-data-rate Digital Subscriber Line). See also FDM and VDSL.
A complex set of accounting procedures developed by the traditional telephone industry. The procedures classify telephone plant as intrastate or interstate, and return revenues from long distance phone calls to local telephone companies to compensate them for the use of local exchange facilities (e.g., switches and local loop cable plant) in the origination and termination of long distance calls. The issue is that long distance is highly profitable, while local service is not. Prior to the breakup of the Bell System, AT&T and the local telephone companies cooperated in this process. AT&T Long Lines calculated the settlement payments for the BOCs (Bell Operating Companies), which then reimbursed the independent (i.e., non-Bell) companies within their states of operation. In 1983, the FCC mandated the creation of NECA (National Exchange Carrier Association), which is charged with administering this process under Subpart G of Part 69 of the FCC's rules and regulations. The settlements pool consists of several elements. Subscribers contribute directly to the pool through the monthly Subscriber Line Charge (SLC), which is capped by the FCC at various levels for all local loops of the same type; that amount appears as a separate line item on your phone bill. (The SLC also is known variously as the Access Charge, CALC, and EUCL.) The IXCs (IntereXchange Carriers) pay into the pool a fixed amount for access trunks and termination facilities between their networks and the LEC networks; this charge is known as the CCL (Carrier Common Line Charge). The IXCs also pay per-connection and per-minute access charges into the pool. All LEC revenues from these sources are submitted to NECA, along with statements of associated costs. NECA then divides the revenues on an average-cost basis, with special consideration for "high-cost" serving areas, which are defined as having service costs in excess of 115% of the national average. In this manner, the LECs are reimbursed for the use of their networks, and "universal service" availability is assured. As deregulation and local competition have begun to alter the telecommunications landscape, the CLECs (Competitive Local Exchange Carriers) have been included in this process, as well. See also Access Charge, CLEC, NECA and Universal Service.
Pertaining to wire and cable, a layer of insulating material such as textile , paper, etc. placed between a conductor and its insulation, between a cable jacket and the components it covers or between various components of a multi-conductor cable. It can be utilized to improve stripping qualities and/or flexibility, or can offer additional mechanical or electrical protection to the components it separates.
Secure Electronic Payment Protocol. An open specification for secure bank card transactions over the Internet, SEPP was developed jointly by IBM, Netscape, GTE, CyberCash and MasterCard. An embodiment of the iKP protocol, which uses public-key cryptography, SEPP is intended for HTTP (HyperText Transfer Protocol) transactions and is adapted to bank card payments in the general context of Electronic Commerce. SEPP messages are transmitted as MIME (Multipurpose Internet Mail Extensions) attachments, and are based on common syntax standards. See also Electronic Commerce, iKP, MIME and Public Key.
Signaling End Point Translator, part of Signaling System 7. See Signaling System 7.
Structured English QUEry Language. The forerunner of SQL (Structured Query Language. See SQL.
A call center term. A pattern of days on and days off as defined in either a schedule preference or shift definition.
Sequencing is the process of dividing a data message into smaller pieces for transmission, where each piece has its own sequence number for reassembly of the complete message at the destination end. Sequencing is thus also the process of properly ordering the receipt of packet data at their destination, regardless of the time they have taken to travel the X.25 network. It's similar to packetizing. See Packet.
All GPS (Global Positioning System) receivers must receive information from at least four satellites to calculate accurately where they (and thus you) are. Sequencing receivers use a single channel and move it from one satellite to the next to gather this data. They usually have less circuitry so they're cheaper and they consume less power than receivers which work on four satellites simultaneously . Unfortunately the sequencing can interrupt positioning and can limit their overall accuracy.
Pertaining to events occurring in a specific time or code order.
The need to read data ” one record after another in sequence ” before getting to the information you want. Magnetic tape, for example, requires you to read the entire tape up to where your information is. This is because the computer cannot tell where on the tape your information is because records on tape files are often of variable length. Most Random Access files, usually kept on a disk drive, require records to be of a fixed length, such as 80 characters per record. Then when you seek record 23, the computer seeks character 1840 in the file (23 x 80), and takes the next 80 characters as the record you want. Using the analogy of music recorded on records and magnetic tape, a phonograph record needle has the capability of random access because the needle can be set down in the spaces between cuts on the record. With mag tape, you must fast forward past all the music you don't want before you get to the music you want to hear. Also, if the computer tape drive is fast forwarding, it cannot count characters to find the record, and must read in the data you don't want (and throw it away), before it gets to the data you need. Random access is much faster than sequential access.
A device that has at least one output channel and one or more input channels, all characterized by discrete states, such that the state of each output channel is determined by the previous states of the input channels.
SPX. Novell's implementation of SPP for its NetWare local area network operating system.
Serializer/Deserializer as in Serializer/Deserializer Framer Level 5 (SFI-5) is a standard electrical interface for 40-gigabit per second transponders and framer devices that promise to drive down communications cost even further. The SFI-5 Implementation Agreement was approved by the Optical Internetworking Forum in June, 2002.
One after another. One event after another. Serial comes from the word "series" ” which is classically defined as a group or a number of related or similar things, events, etc., arranged or occurring in temporal, spatial, or other order or succession. In telecom, there are basically two types of data transmission ” serial and parallel. Serial is one stream of data, one bit following the previous bit. Parallel is the same stream of data, but broken into several streams running simultaneously. The reason to go parallel is that several streams will often be faster than one stream. See Parallel Transmission and Serial Transmission.
Serial acquirers are people who buy things and buy more things and more. Sometimes they buy companies. Sometimes they buy material goods. Usually both. Their major characteristic is they can't stop. Some of the most colorful people in the recent history of telecommunications were serial acquirers ” for example, Dennis Kozlowski of Tyco, Bernie Ebbers of WorldCom, Gary Winnick of Global Crossing and John Rigas of Adelphia.
Serial ATA is a faster, better version of ATA (Advanced Technology Attachment). It is serial interface that boosts the performance of low-cost NAS (Network Attached) storage appliances.
Serial Bus was the original name for Intel's standard for a type of very local, local area network that would be used for connecting peripherals to the motherboard of a PC. There'd be one plug on the back of the PC into which you'd daisy chain various peripherals, including a mouse, a keyboard, speakers , printers, a microphone and a telephone. The idea of serial bus is to clear away all the clutter on the back of the PC. In March of 1995 when the first technical specs were released, serial bus' name was changed to Universal Serial Bus (I don't know why). See USB.
Telephone system feature set up by the attendant when an incoming calling party wishes to speak with more than one person internally. When the first party hangs up, the call automatically moves to the second person the outside party wants to speak with. When that person hangs up, then the call automatically goes to the third person, etc.
Networks (local and long distance) use the RS-232 serial communications standard to send information to serial printers, remote workstations, remote routers, and asynchronous communication servers. The RS-232 standard uses several parameters that must match on both systems for information to be transferred. These parameters include baud rate, character length, parity, stop bit, and XON/XOFF.
Baud rate is the signal modulation rate, or the speed at which a signal changes. Since most modems or serial printers attached to personal computers send only one bit per signaling event, baud can be thought of as bits per second. However, higher-speed modems may transfer several bits per signal change. Typical baud rates are 300, 1200, 2400, 4800, 9600 and 19,200. The higher the number, the greater the number of signal changes and, therefore, the faster the transmission.
Character length specifies the number of bits used to form a character. The standard ASCII character set (including letters , numbers, and punctuation) consists of 128 characters and requires a character length of 7 bits for transmissions. Extended character sets (containing line drawings or the foreign characters used in IBM's extended character set) contain an additional 128 characters and require a character lengths of 8 bits. Parity error checking can only be used with character lengths of 7 bits.
Parity is a method of checking for errors in transmitted data. You can set parity to odd or even, or not use parity at all. When the character length is set to 8, parity checking cannot be done because there are no "spare" bits in the byte. When the character length is 7, the eighth bit in each byte is set to 0 or 1 so that the sum of bits (Os and 1s) in the byte is odd or even (according to the parity setting). When each character is received, its parity is checked again. If it is incorrect (because a bit was changed during transmission), the communications software determines that a transmission error has occurred and can request that the data be retransmitted.
Stop bit is a special signal that indicates the end of that character. Today's modems are fast enough that the stop bit is always set to one Slower modems used to require two stop bits.
XON/XOFF is one of many methods used to prevent the sending system from transmitting data faster than the receiving system can accept the information. See also EIA/TIA-232-E, RS-232-C and serial data transmission.
Serial data transmission is the most common method of sending data from one DTE to another. Data is sent out in a stream, one bit at a time over one channel. When a computer is instructed to send data to another DTE, the data within the computer must pass through a serial interface to exit as serial data. Then it passes through ports, cables, and connectors that link the various devices. The boundaries (physical, functional, and electrical) shared by these devices are called interfaces. See serial communications.
Digital information that is transmitted in serial form. Often used informally to refer to serial digital television signals.
The " lowest common denominator" of data communications. A mechanism for changing the parallel arrangement of data within computers to the serial (one bit after the other) form used on data transmission lines and vice versa. At least one serial interface is usually provided on all computers for the connection of a terminal, a modem or a printer. Sometimes also called a serial port. See EIA/TIA-232-E, RS-232-C, Serial Interface Card and the Appendix.
A printed circuit card which drops into one of the expansion slots of your computer and changes the parallel internal communications of your computer into the one-bit-at-time serial transmission for sending information to your modem or to a serial printer.
Memory medium to which access is in a set sequence and not at random.
An input/output port (plug) that transmits data out one bit at a time, as opposed to the parallel port which transmits data out eight bits, or one byte at a time. Most personal computers (PCs) have at least one serial and one parallel port. In a typical configuration, the serial port is used for a modem while the parallel port is used for a printer. For a diagram of a typical 25-pin RS-232-C serial port, see the Appendix at the back of this book.
Method of data processing in which only one bit is handled at a time.
Sending pulses one after another rather than several at the same time (parallel). When transmitting data over a telephone line there is only one set of wires. Therefore, the only logical way to transmit it is to send the data in serial mode. It is possible to use eight different frequencies to transmit a character all at once (parallel), but these modems are ridiculously expensive. See Parallel, Parallel Port and Serial Port.
To change from parallel-by-byte to serial-by-bit.
A connection of electrical apparatus or circuits in which all of the current passes through each of the devices in succession or on after another. See also Parallel.
An AT&T private line long distance tariff created in the 1970s and designed expressly to reduce MCI's chances of selling any private lines and thus of surviving. It was thrown out by the FCC and the tariff figured in MCI's and the Federal Government's antitrust against AT&T.
In a series circuit, the electric current has only one path to follow. All of the electric current flows through all the components of the circuit. To calculate the resistance of a series circuit add up the resistance of each of the components in the circuit. In contrast, see parallel circuits.
A connection of electrical apparatus or circuits in which all of the current passes through each of the devices in succession or on after another. See also Parallel.
A bugging device. It is a radio transmitter which is installed in series with one wire of the telephone circuit. Normally a parasite (i.e. takes power from the phone line). Transmits both sides of the conversation. It transmits only when the phone is off-hook. See also Series.
A type of shield used in coaxial cable systems, a serve shield, or spiral shield, is simply wound around the inner conductor. See also Coaxial Cable.
Hardware definition of server: A server is a shared computer on the local area network that can be as simple as a regular PC set aside to handle print requests to a single printer. Or, more usually, it is the fastest and brawniest PC around. It may be used as a repository and distributor of oodles of data. It may also be the gatekeeper controlling access to voice mail, electronic-mail, facsimile services. At one stage, a local area network had only one server. These days networks have multiple servers. Servers these days have multiple brains , large arrays of big disk drives (often in redundant arrays) and other powerful features. New powerful servers are called superservers. A $35,000 superserver today can match the performance of a $2 million mainframe of ten years ago. Then again, according to Peter Lewis of the New York Times, the lowliest client today has more computing power than was available to the entire Allied Army in World War II. See Downsizing for some of the benefits of running servers as against mainframes.
Software definition of server: A server is a program which provides some service to other (client) programs. The connection between a client program and the server program is traditionally by message passing, often over a local area or wide area network, and uses some protocol to encode the client's requests and the server's responses. Any given program may be capable of acting as both a client and a server, perhaps switching its role based on the nature of the connection. The terms "client" and "server" simply refer to the role that the software program performs during a specific connection. Similarly, any given server may function as an origin server, a proxy server, a gateway server, or a tunnel, modifying its behavior based on the specific nature of a given request from a client.
A SCSA term. A communications protocol that allows a call processing application running on one computer to control SCSA hardware residing in another computer.
Little servers designed for small businesses or workgroups without supervision by a central IT department. See Server.
A Windows NT application that can create objects for linking or embedding into other documents.
A unique digital identification that forms the basis of a Web server's SSL security features. Server certificates are obtained from a mutually trusted, third-party organization, and provide a way for users to authenticate the identity of a Web site.
A group of server computers that are networked together both physically and with software, in order to provide cluster features such as fault tolerance or load balancing. See also Fault Tolerance and Load Balancing.
An ISP/web hoster service in which a client places their server on the Internet at an ISP's office for a monthly fee. In return, the server is, theoretically, always connected via multiple redundant high speed connections to the Internet. See also Web Hosting.
Imagine a room stuffed with PCs, ranged in racks along walls, ranged in racks in lines like a library's back room. The PCs are really servers ” powerful PCs containing databases and other information they are dispensing to the thousands of PCs dialing into them from afar. A server farm may be owned by one company and used by one company, or it may be owned by one company and each of the machines leased to other companies. I first heard the term when MCI described a room it had in a place called Pentagon City. There it had hundreds of servers each of which it leased to other companies who used those servers as their Web sites.
SMB. The protocol developed by Microsoft, Intel, and IBM that defines a series of commands used to pass information between network computers. The redirector packages SMB requests into a network control block (NBC) structure that can be sent over the network to a remote device. The network provider listens for SMB messages destined for it and removes the data portion of the SMB request so that it can be processed by a local device. In short, SMB is basically a protocol to provide access to server-based files and print queues. SMB operates above the session layer, and usually works over a network using a NetBIOS application program interface. SMB is similar in nature to a remote procedure call (RPC) that is specialized for file systems.
Server mirroring means you have two servers on your networks and each exactly what the other is doing simultaneously. It's a backup method. In Novell's NetWare, server mirroring requires two similarly configured NetWare servers. They should be evenly matched in terms of CPU speed, memory, and storage capacity. The servers are not required to be identical in terms of microprocessors type (386/486), microprocessor revision level, or clock speed. However, identical servers are recommended for NetWare SFT III 3.11. If the two servers are unequal in terms of performance, then SFT III performs at the speed of the slower server. The NetWare servers must be directly connected by a mirrored server link. SFT III servers can reside on different network segments, as long as they share a dedicated mirrored server link.
An individual computer in a server cluster.
An SCSA definition. Operating System running on the SCSA Server.
A process that hosts COM components. A COM component can be loaded into a surrogate server process, either on the client computer (local) or on another computer (remote). It can also be loaded into a client application process (in-process).
Server push is a Internet term. With server push, the Web server sends data to display on the browser display, but leaves the connection open. At some point, the server sends additional data for the browser to display. Server push is used for displaying multimedia information on the browser.
When you have too many people trying to get on your web site and they're having trouble getting on, it's called server queuing. I don't think this is a particularly profound definition.
A COM object that is created with Microsoft Server Scriptlet technology.
SES. A second during which the bit error rate over a digital circuit is greater than a specific limit. During a severely errored second, transmission performance is significantly degraded. The specific definition of SES depends on the circuit involved, e.g. T-1, T-3, OC-3 and OC-48.
Servers are typically ruggedized, industrial-strength PCs, i.e. they have several fans, perhaps two power supplies , perhaps two disk drives, perhaps several central processors. They are designed to work 24 hours a day, seven days a week without breaking down. They are designed to give the reliability of demanded of a business telephone system. See also Server.
SACs (also called Special Area Codes) are 3-digit codes in the Numbering Plan Area (N00) format that are used as the first three digits of a 10-digit address, and that are assigned for special network uses in North America. Whereas NPA codes are normally used for identifying specific geographical areas, certain SACs have been allocated in the NANP (North American Numbering Plan) to identify generic services or provide access capability. Currently only four SACs have been assigned and are in use: 600, 700, 800, and 900. There are two general categories of NPAs:
Geographic NPA ” Associated with a defined geographic area; all telephone numbers bearing such an NPA are associated with services provided within that geographic area.
Non-Geographic NPA ”Associated with a specialized telecommunications service, which may be provided across multiple geographic NPA areas; for example 800, 900, 700, 500 and 888. Also known as an area code. See also SAC.
A protocol developed by Novell so that devices attached to a network could advertise their functionality. For instance, a file server and print server advertise different functions. An SNMP agent can also advertiser itself using SAP's. All of the Compaq manageable repeaters and switches except the 50xx switches support SAP broadcasts.
This definition courtesy Steve Gladstone, author of the book, "Testing Computer Telephony Systems." These are major bugs that significantly impact the reliability or the functionality of computer telephony systems. Comprehensive testing must uncover all service affecting problems with the goal that no computer telephony system should be installed at a live customer installation without an acceptable workaround for the service affecting problem. The goal for transition of a product from one phase to the next is that no service affecting bugs remain , and that the bug rate for new bugs be at or approaching zero.
A list of equipment billed to customer by type, quantity, monthly charge, location and billing dates.
Another term for a LATA, according to some Bell operating companies.
The more common usage is the geographic area served by a supplier. The area in which the supplier, theoretically, stands ready to provide his service. The service area of New York Telephone (now called Bell Atlantic) is most (not all) of New York State.
Service availability is what the United States Government calls its intentional degradation of GPS (Global Positioning Satellite system). The government degrades the signals in case of war or other emergencies. It does this in order to prevent enemies from taking advantages of the system. When GPS signals are degraded, they can significantly change the accuracy of position readings from GPS devices.
The boundary existing between a computing domain and a switching domain as it is established via their interconnected service boundaries over some underlying interconnection medium.
A data processing center that does work for others. There are many ways of bringing work to a service bureau, including mailing it and transmitting it over phone lines. If it comes over phone lines, the service is likely to be called "time sharing."
The amount you pay each month to receive cellular service. This amount is fixed, and you pay the same fee each month regardless of how much or how little you use your cellular phone. It usually ranges from about $10 to $65 per month, depending on the carrier's tariffs and the particular plan of service you select. In addition you pay air time. Service Charge doesn't usually include any air time.
A listing of all the telephone equipment installed as part of a specific telephone system. Usually provided by the vendor or maintenance organization.
A 3-digit code in general use by customers to reach telephone company service, for example, 411 (Directory Assistance), 611 (Repair Service), 811 (Business Office) and 911 (Emergency Service).
SCP. The local versions of the national SMS/800 number database. SCPs contain the intelligence to screen the full ten digits of an 800 number and route calls to the appropriate, customer-designated long distance carrier. Bellcore defines SCP as the network system in the Advanced Intelligent Network Release 1 architecture that contains SLEE (Service Logic Execution Environment) functionality and communicates with AIN Release 1 Switching Systems in processing AIN Release 1 calls.
The set of activities that must be performed to create a new service to be offered to subscribers and the associated service-specific operations capabilities to support the new service. Definition from Bellcore in reference to its concept of the Advanced Intelligent Network.
SCE. A telephone company AIN term. The surroundings, including organizational structure and computing and communications resources, in which creation of new services takes place. See Service Creation.
What the computer telephony industry calls an applications generator, the telephone industry calls a service creation tool. It is a software tool that, in response to your input, writes code a computer can understand. In simple terms, it is software that writes software. Service creation tools have three major benefits:
They save time. You can write software faster.
They are perfect for quickly demonstrating an application.
They can often be used by non-programmers. See also Application Generator.
When you work a delay with a service provider ” a telephone or data carrier, you need to create certain definitions of service so that you can figure penalties if such levels of service are not maintained. For example, we might define service deficiency as being a service outage lasting for more than ten seconds. We might define Repeated Service Deficiency as a service deficiency that occurs at least four times in any given 30 day period. and we might define Chronic Service Deficiency as a service deficiency that occurs more than ten times in any given 30 day period. Of course, how these terms are defined will depend on the SLA ” Service Level Agreement ” which you sign with your carrier.
Displays a specific service being presently in effect.
The point at which network communications lines (telephone company lines) enter a building.
A primary or secondary service function.
The information uniquely identifying an NS/EP telecommunications service to the service vendor and/or service user. NS/EP (National Security and Emergency Preparedness) is federal government telecommunications services that are used to maintain a state of readiness or to respond to and manage any event or crisis (local, national, or international) that causes or could cause injury or harm to the population, damage to or loss of property, or degrade or threaten the national security or emergency preparedness of the United States. See also NS/EP Telecommunications.
The finite set of BAF (Bellcore Automatic Message Accounting Format) structures and modules needed to record usage of Advanced Intelligent Network (AIN) Release 1 services. The set is said to be robust because it will be designed to record future AIN Release 1 services that have not yet been identified. Definition from Bellcore in reference to its concept of the Advanced Intelligent Network. See also AIN and BAF.
Service Interface Jack The SIJ is generally considered to be the demarcation jack for DS- 1 based services in Canada. It does not necessarily imply being a "smart jack" although quite often this is the case.
A Frame Relay/ATM term. Service interworking is a means of connecting frame relay networks over an ATM backbone. The frame relay PVC (Permanent Virtual Circuit) connects to the ATM PVC through an ATM switch which accomplishes frame relay-to-ATM protocol conversion at the point of entry; at the point of exit from the ATM network, the process is reversed . This is in contrast to Network Interworking, which makes use of a tunneling protocol to provide what essentially is a cut-through path through the ATM network. Service interworking is defined in the FRF.8 specification from the Frame Relay Forum and is recognized by the ATM Forum. See Network Interworking.
SIC. This is a charge to a client by a carrier for the initiation of a new telecom service such as the installation of a new T-1 line or a Frame Relay PVC.
Usually expressed as a percentage of a statistical goal. For example, if your goal is an average speed of answer of 100 seconds or less, and 80% of your calls are answered in 100 seconds or less, then your service level is 80%.
SLA. An agreement between a user and a service provider, defining the nature of the service provided and establishing a set of metrics (fancy word for measurements) to be used to measure the level of service provided measured against the agreed level of service. Such service levels might include provisioning (when the service is meant to be up and running), average availability, restoration times for out- ages, availability, average and maximum periods of outage, average and maximum response times, latency, delivery rates (e.g. average and minimum throughput). The SLA also typically establishes trouble-reporting procedures, escalation procedures, penalties for not meeting the level of service demanded ” typically refunds to the users. An example: in May of 1998, GTE announced a new SLA that promises its "Internet Advantage dedicated Internet access customers will get a minimum packet loss guarantee from GTE. If Internet Advantage customers experience more than a 10% packet loss during any ten minute interval, they will be credited with one day of service." UUNET Technologies has a SLA that says if its network in unavailable for one, you, the user, are credited with one full day of service.
Typical SLAs include statements about
Time to identify the cause of a customer related malfunction.
Time to repair a customer related malfunction.
Service provisioning time.
Quality of service targets.
SLM. A suite of software tools which provide both the end user organization and the service provider a means of managing the committed service levels defined in a Service Level Agreement (SLA). SLM includes monitoring and gathering performance data, analyzing that data against committed performance levels, taking the appropriate actions to resolve discrepancies between committed and actual performance levels, and trending and reporting. SLM is a tough proposition, especially across a wide range of complex technologies (i.e., Frame Relay and ATM) in a multi-site enterprise. The SLM system must be flexible enough to reflect the service dimensions and performance metrics defined in the SLA. See also Service Level Agreement.
An exchange line associated with multiple data station installations to provide monitoring and testing of both customer and Telco data equipment.
SLEE. A functional group residing in an SCP (Service Control Point) or Adjunct that contains the Service Logic and Control, Information Management, AMA (Automatic Message Accounting) and Operations FEs (Functional Entity). This composite set of capabilities, which includes FC routines, provides a functionally consistent interface to SLPs (Service Logic Program) independent of the underlying operating system. Definition from Bellcore in reference to its concept of the Advanced Intelligent Network.
SMS. An operations support system used to facilitate the provisioning and administration of service data required by the SCP. Use of this term does not imply any specific technology platform. See SMS.
Measurements of the actual grade of service provided to our subscribers.
The functionality needed to gather subscriber Advanced Intelligent Network Release 1 business needs; provide answers, AIN Release 1 service/feature descriptions, prerequisite non AIN services, availability and costs; reserve AIN Release 1 resources (e.g. 800 number and 900 number); identify required network resources; and identify available AIN Release 1 services/features by wire center. Definition from Bellcore in reference to its concept of the Advanced Intelligent Network.
See ATM Edge Switch.
If you're the phone company, service objectives are a statement of the quality of service that is to be provided to the customer; for example, no more than 1.5 percent of customers should have to wait more than three seconds for dial tone during the average busy hour or, the busy- hour blocking on a last choice trunk group not exceed 1 percent. According to my friends in the phone industry, service objectives are the criteria used when engineering quantities of switching equipment. Certain basic principles must be kept in mind:
The service must be of high quality.
Rates for telephone service must be reasonable.
When costs of operating the telephone business are subtracted from revenues produced by reasonable rates, enough profit must remain to attract new capital needed to meet increasing demands for service.
If you're designing phone systems, service objectives define the functional and performance goals for how your system will work and what will be experienced by the system's users and other systems. For example, a switch might have a service objective of providing dialtone to all users in less than two seconds. Or, of answering all incoming calls within ten seconds. Or, a VRU may have a service objective of responding to all user DTMF inputs in less than one second. When we buy or design systems, we often have many service objectives, rarely just one.
A generic word used by telephone companies to check the quality of the service they're providing. Some of it is done automatically with machinery. Some of it is done by senior operators who listen in on the conversations of other operators dealing with their subscribers. In short, the senior operators "observe" the service the junior operators are providing.
As a feature of some telephone systems, the Service Observation (SOB) command provides the capability to automatically record data about completed calls, incomplete calls and abnormal calls for the purpose of qualitative supervision of call traffic conditions.
A Telephone Company definition. The official form on which desired customer services are recorded for processing, e.g., new connects, changes, disconnects, etc.
SOI. A Verizon definition. The description of an end user's request for telephone service as represented by several Verizon North end user contact systems. The SOI contains end user information such as billing information, service needs, desired listing, etc.
A euphemism for a software bug fix. Also called a Service Release, Service Pack or a Second Edition, or a software release with a number that differs from the previous one because it includes a numbers after the decimal point.
The time during which the telephone company furnishes a circuit.
A telephone company term. All business days of a month (approximately 22 days). It is recommended that the period established for measuring dial tone speed and incoming matching loss coincide as closely as possible with the Service Observing Month.
The points on the customer's premises where such channels or facilities are terminated in switching equipment used for communications with phones or customer-provided equipment located on the premises.
A telephone company AIN term. The ability of an end user to retain the same geographic or non-geographic telephone number (NANP numbers) as he/she changes from one type of service to another. The INC Number Portability Workshop agreed that NANP numbers (e.g., 800, 500, 555, 950) should not be service portable for applications outside of their respective industry approved service definitions or guidelines, should those definitions or guidelines exist.
In the broadest sense, a service provider is any company which provides service to anyone else. That means a service provider could be a phone company in the form of either a LEC (Local Exchange Carrier) or IXC (IntereXchange Carrier). It could be an ASP (Application Service Provider). It could be an ISP (Internet Service Provider). A service provider is thus any company which doesn't itself consume all of the service it sells.
A Windows Telephony Applications standard which lies between Windows Telephony and the network. It defines how the network ” anything from POTS (Plain Old Telephone Service) to T-1, from a key system to a PBX ” interfaces to Windows Telephony, which in turn talks to the Applications Programming Interface, which talks to the Windows telephony applications software. See also Windows Telephony.
An SCSA computer telephony definition. An addressable entity providing application and administrative support to the client environment by responding to client requests and maintaining the operational integrity of the server.
See SPI. See Windows Telephony.
An SCSA definition. The message information required by, and provided by, the service provider to perform its functions in the environment in which it is installed. Contrast with SCSA Message Protocol Interface. See Service Provider.
SPNI. An identifier for the service provider operating a particular CDPD network.
A telephone company AIN term. The ability of an end user to retain the same geographic or non-geographic telephone number (NANP numbers) as he/she change form one service provider to another.
What the computer industry calls a network manager, the telephone industry calls a service provisioning tool. It is a complex piece of software that allows telephone companies to contact their various switches and sundry computers dispersed over a wide geographic area, to log onto those machines and to upload, download and organize those machines so they are able to make different, new, updated software services for the telephone industry's customers. Telephone companies use various networks to get into their remote switches. Those networks might vary from dial-up to ISDN to packet switched networks to T-1. The better service provisioning tools allow one technician in one place to update and test multiple central offices and computers simultaneously.
A call center term. A measure of how well staffing matches workload, expressed often as average delay (in answering a call).
The equipment needed to terminate the channel and connect to the phone apparatus or customer terminal.
STM. The platform functionality for detecting overloads associated with a specific service and for sending service-specific control messages to the appropriate entities. STM is the SLEE (Service Logic Execution Environment) functionality for detecting overloads associated with a specific service and for sending Automatic Code Gap messages to the appropriate entities. The SN&M (Service Negotiation and Management) OA (Operations Application) also provides STM (Service Traffic Management)-related capabilities.
Service type and level pair. For example, the service tuple data- band - width=45 Mbps consists of the service type data-bandwidth and the service level 45 Mbps.
SSP. A telephone company AIN term. A switching system, including its remotes, that identifies calls associated with intelligent network services and initiates dialogues with the SCPs in which the logic for the services resides. See SSP.
How easy a system is to configure, service, maintain and repair.
SMS. Administers 800 Data Base Service numbers on a national basis. Customer records for 800 Service are entered into the SCP through this system. See Eighthundred Service.
SN. A network system in the AIN architecture containing functions that enable flexible information interactions between an end user and the network.
An AT&T term for the immediate provision of almost any network service through universal ports, whenever required by a user; as opposed to provision via an expensive, time consuming, inflexible service order process.
A serving area interface is part of a phone company's outside plant. It is a fancy name for a box on a pole, a box attached to a wall or a box in the ground that connects the phone company's feeder or subfeeder cables (those coming from the central office) to the drop wires or buried service wires that connect to the customer's premises. It's also called a cross-wire box. See also Feeder Plant and Drop Wire.
The general term used to refer to either a riser or a satellite closet; Satellite Cabinet; Satellite Closet.
A cellular radio term. The CDPD network entity that operates the Mobile Serving Function. The serving MD-IS communicates with and is the peer endpoint for the MDLP connection to the M-ES.
An office of AT&T or its Connecting or Concurring Carriers, from which interstate communications services are furnished.
The term for the phone number that serves the location, referring to the phone number and terminating wire as one unit. Usually applies to a POTS number.
The wire center from which service is provided to the customer.
An applet that runs on a server. The term usually refers to a Java applet that runs within a Web server Web server environment. This is analogous to a Java applet that runs within a Web browser browser environment. Java servlets are becoming increasingly popular as an alternative to CGI programs. The biggest difference between the two is that a Java applet is persistent. This means that once it is started, it stays in memory and can fulfill multiple requests. In contrast, a CGI program disappears once it has fulfilled a request. The persistence of Java applets makes them faster because there's no wasted time in setting up and tearing down the process.
Short for servomechanism. Devices which constantly detect a variable, and adjust a mechanism to respond to changes. A servo might monitor optical signal strength bouncing back from a disc's surface, and adjust the position of the head to compensate.
Satellite Earth Stations.
Severely Errored Second. A second in which a severe number of errors are detected over a digital circuit. Each error comprises a code violation (CV), such as a bipolar violation. The specific definition of SES depends on the type of circuit involved, e.g. T-1, T-3, OC-3 and OC-48. See also CV and ES.
Source End Station: An ATM termination point, which is the source of ATM messages of a connection, and is used as a reference point for ABR services. See DES.
Secure European System for Applications in a Multivendor Environment. Developed by the ECMA (European Computer Manufacturers Association), it is intended for very large networks of disparate origin.
A set of transmitters and receivers, and the data streams that flow between them. In other words, an active communication, measured from beginning to end, between devices or applications over a network. Often used in reference to terminal-to-mainframe connections. Also a data conversation between two devices, say, a dumb terminal and a mainframe. It may be possible to have more than one session going between two devices simultaneously.
As defined under the Orange Book, a recorded segment of a compact disc which may contain one or more tracks of any type (data or audio). The session is a purely logical concept; when a multisession disc is mounted in a multisession CD-ROM player, what the user will see is one large session encompassing all the data on the disc.
Logically ordered list of sessions based on priority of the sessions. All the sessions in the session group should be configured to connect the same physical machines.
A digital key that is created by the client, encrypted, and sent to the server. This key is used to encrypt data sent by the client. See also Certificate, Digital Signature and Key Pair.
The fifth layer ” the network processing layer ” in the OSI Reference Model, which sets up the conditions whereby individual nodes on the network can communicate or send data to each other. The session layer is responsible for binding and unbinding logical links between users. It manages , maintains and controls the dialogue between the users of the service. The session layer's many functions include network gateway communications.
The data area at the beginning of a recordable compact disc that is left blank for the disc's table of contents. The session lead-in uses up 6750 blocks of space. See Track.
The data area at the end of a session which indicates that the end of the data has been reached. When a session is closed, information about its content is written into the disc's Table of Contents, and the lead-out and the pre-gap are written to prepare the disc for a subsequent session. The lead-out and the pre-gap together take up 4650 two-kilobyte blocks (nine megabytes). See Track.