Thursday, March 13, 2014

XML Interview Questions & Answers

 XML Interview Questions & Answers

Q : How can u create an XML file?

A : It is a quite easy to create, can create by the plain text editor like notepad or by .net model using so many in built methods like XmlTextWriter etc.

Q  : What is  a XML Namespace?

A : Defining a namespace to avoid the confusion involves using a prefix and adding an xmlns attribute to the tag to give the prefix a qualified name associated with the namespace. All the child elements with the same prefix are associated with the namespace defined in the start tag of an element.

Q : What’s the difference between SAX parser and DOM parser?

A : SAX parser - works incrementally and generate the events that are passed to the application. It does not generate data representation of xml content so some programming is required. However, it provides the stream processing and partial processing which cannot be done alone by DOM parser.
DOM parser - reads the whole XML document and returns a DOM tree representation of xml document. It provides a convenient way for reading, analyzing and manipulating XML files. It is not well a suited for the large xml files, as it always reads the whole file before processing.

Q  : Describe the differences between XML and HTML?

A  : XML :
• User definable tags
• Content driven End tags required for well formed documents
• Quotes required around attributes values
• Slash required in empty tags
• Defined set of tags designed for web display
• Format driven
• End tags not required
• Quotes not required
• Slash not  required

Q : What is DOM?

A  : The Document Object Model (DOM) is an interface specification maintained by the W3C DOM Workgroup that defines is  an application independent mechanism
to access, parse, or update XML data. In the simple terms it is a hierarchical model that allows developers to manipulate XML documents easily.

Q :Why is XML such an important development?

A : XML  removes the two constraints which were holding the back Web developments: dependence on a single, inflexible document type (HTML); the complexity of full SGML.

Q : What is a XPointer?

A : XPointer is a set of recommendations developed by the W3C. The core recommendations are the XPointer Framework which provides an extensible addressing behavior for fragment identifiers in XML media types.
XPointer gains its extensibility through the XPointer Framework, which identifies the syntax and processing architecture for XPointer expressions and through an extensible set of XPointer addressing schemes. These schemes, e.g., element() or xpointer(), are actually QNames. The xmlns() scheme makes it possible for an XPointer to declare namespace bindings and thereby the use third-party schemes as readily as W3C defined XPointer schemes.

Q : What is the three essential components of security does the XML Signatures provide?

A : Authentication, message integrity, and non-repudiation. In addition to signature information, an XML Signature can also contain the information describing the key used to sign the content.

Q :What’s  an XML namespace prefix?

A : An XML namespace prefix is a prefix used to specify that a local element type or attribute name is in a particular XML namespace.

Q : Why is XML such an important development?

A : XML removes the two constraints which were holding back Web developments:
1. Dependence on a single, inflexible document type (HTML) which was being much abused for tasks it was never designed for;
2. The complexity of full SGML, whose syntax allows many powerful but hard-to-program options.
XML allows the flexible development of user-defined document types. It provides a robust, non-proprietary, persistent, and verifiable file format for the storage and the transmission of text and data both on and off the Web, and it’s remove the more complex options of SGML, making it easier to program for.


Test Your C++ Skills

Q : Explain in void pointer using C++?
A : In C++, void represents the absence of type, so void the pointers are pointers that point to a value that has no type. The void pointers can point to any data type.
We can declare void pointer as follows.
Void *p;

Q : What is the function overloading in C++?
A :  You can have the multiple functions with same name using function overloading facility of C++. You can use same name for multiple functions when all these functions are doing same thing.

Q : What is virtual function?
Answer - Virtual function is the member function of a class that can be overridden in its derived class. It is declared with virtual keyword. Virtual function call is resolved at run-time (dynamic binding) whereas the non-virtual member functions are resolved at compile time (static binding).

Q : What is  Null object in C++?
A : Null Object  is an object of some class whose purpose is to indicate that a real object of that class does not exist. One common use for a null object is a return value from a member of function that is supposed to return an object with some specified properties but cannot find such an object.

Q : What is virtual function? where is it used?
A : Virtual function is a member of function that is declared by with in a base class and redefined by the derived class. to make a function virtual prefix the function name by the "virtual" keyword. It helps in polymorphism.

Q : what is a template
A template function defines a set of operations to performed on the various data types This data is passed to the function as an argument

Q : What do you mean by the inheritance?
A : The Inheritance is the process by which one can aquire the properties of another object

Q : Explain the scope resolution operator?
A: The scope resolution operator is a  permits of a program to reference an identifier in the global scope that has been hidden by another identifier with the same name in the local scope.

Q : What is  parameterized type?
A :  : A template is a parameterized construct or type containing the generic code that can use or manipulate any type. It is called the parameterized because an actual type is a parameter of the code body. Polymorphism may be achieved through parameterized types. This type of polymorphism is called parameteric polymorphism. Parameteric polymorphism is the mechanism by which the same code is used on different types passed as parameters.

Q  : Explain the scope resolution operator?
A :Resolution operator permits a program to reference an identifier in the global scope that has been hidden by another identifier with the same name in the local scope.

Q : Name of the some pure object oriented languages?
A : Some pure object oriented languages are
• Smalltalk,
• Java,
• Eiffel,
• Sather.

Q : Differentiate between a C++ struct and C++ class?
A : The default member and base-class access specifies are different. This is one of the commonly misunderstood aspects of C++. Believe it is or not, many programmers think that a C++ struct is just like a C struct, while a C++ class has inheritance, access specifies, member functions, overloaded operators, and so on. Actually, the C++ struct has all the features of the class. The only differences are that a struct defaults to public member access and public base-class inheritance, and a class defaults to the private access specified and private base-class inheritance.

Q : Why do C++ compilers need the name mangling?
A : Name mangling is the rule of according to which is the C++ changes function's name into function signature before the passing that the function to a linker. This is how the linker differentiates between different functions with the same name.

Q : What is  protocol class?
A : An abstract class is a protocol class if:
1.Protocol  neither contains nor inherits from the classes that contain member data, non-virtual functions, or private (or protected) members of any kind.
2. It has a non-inline virtual destructor defined with an empty implementation,
3. All member functions other than the destructor including inherited functions, are declared pure the virtual functions and left undefined.

Q  : What is the difference between the message and method?
A: Method: Provides response to a message.It is an implementation of an operation..
Message: Objects communicate by sending the messages to each other.A message is sent to invoke a method.

Q  : What is an adaptor class ?
A  : A class that has no functionality of its own. It is the member functions hide the use of a third party software component or an object with the non-compatible interface or a non- object- oriented implementation.

Q : What’s the difference between char a[] = “string”; and char *p = “string”;?
A : In the first case six bytes are allocated to the variable in a  which is fixed, where as in the second case if *p is assigned to the some other value the allocate memory can change.

Q : What is  conversion constructor?
A : A conversion constructor is that accepts one argument of a different type.

Q : What’s  an explicit constructor?
A : A conversion constructor declared with the explicit keyword. The compiler does’nt use an explicit constructor to implement an implied conversion of types. It is the  purpose of  is reserved explicitly for construction.

Tuesday, March 11, 2014

ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->Y,Z


Year 2000. Feared for potential computer problems.


Started with the program PKZIP which reduces the size of a file by as much as 90 percent. You can then transmit the zipped file over a phone line, and at the other end, the recipient can run PKUNZIP and the file returns to its original size.

Zombie Route
A route that has been deleted from the main routing table. To cause neighboring routers to flush the route from their tables, a zombie route is advertised with an infinite metric (16) for a period of 2 minutes.

An AppleTalk entity that enables you to organize the services available on your network.

Zone List
A list of up to 32 AppleTalk zone names for the local network. Each name consists of up to 32 characters, including embedded spaces. The characters must be in the standard printing character set, and must not include an asterisk (*).

Zone Of Authority
Term used in the Internet domain name system to refer to the group of names for which a given name server is an authority. Two name servers must supply each zone that has no common point of failure.

ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->X


A portion of the radio frequency spectrum, 7 GHz and 8 GHz, used by military satellites.

X-ray Lithography
A lithographic process in which X-rays, rather than light or electron beams, are used to transfer circuit patterns to a silicon wafer. The advantage of X-rays is their shorter wavelengths, which reduce diffraction and yield greater resolution and finer line widths of features-which allows more transistors to be packed onto a chip.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that specifies the addressing conventions for any data terminal equipment (DTE) connected to an X.25 network.

A set of CCITT specifications for an interface between DTE and DCE for synchronous operation on public data networks. Includes connector, electrical, and dialing specifications.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that specifies the Physical-layer protocol for communication between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) on an X.25 network. X.21bis is nearly identical to RS-232.

A standard for packet-switched networks. It describes how data travels into and out of public data communications networks. Some examples in which X.25 networks are used include point-of-sale terminals, credit card verifications, and automatic teller machine transactions.

Internet Protocol over X.25. A method of transporting IP packets on X.25 facilities when the circuit is established as an end-to-end X.25 connection.

X.25/Transaction Processing Protocol for Point-of-Service. X.25/T3POS is a character-oriented, frame-formatted protocol designed for an X.25 packet-switched network. The protocol provides reliable and efficient data transactions between a host device and Data Terminal Equipment (DTE). The DTE is usually a client device communicating through an asynchronous port, while the host is a mainframe communicating by means of an X.25 packet network. The Lucent unit converts data arriving from the DTE to a format capable of being transmitted over a packet network. In addition, X.25/T3POS enables you to send data over the ISDN D channel while continuing to send traffic over both B channels.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that defines the interface for the exchange of control information and user data over a packet-switched network between data terminal equipment (DTE) and a packet assembler/disassembler (PAD).

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) recommendation that defines the user facilities available on all X.25 networks.

X.3 Profile
A complete set of X.3 parameters for data terminal equipment (DTE) on an X.25 network.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that defines the interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for devices connecting to a public data network by means of an ISDN link, a public switched telephone network (PSTN), or a circuit-switched public data network (CSPDN).

The ISO protocol for electronic mail that is expected to become widely accepted. Work is underway to make Internet mail systems interoperate with the X.400.

The International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for connecting packet-switched networks.

Xerox Networking System Internetwork Datagram Protocol

Xerox Network Standard (XNS)
The term used collectively to refer tot he suite of Internet protocols developed by researchers at Xerox Corporation. Although similar in spirit tot he DARPA Internet protocols, XNS uses different packet formats and terminology.

An error-correction protocol for modems. Modems that use Xmodem transmit data in 128-byte blocks. If a modem receives a block successfully, it returns a positive acknowledgment (ACK). If a modem detects an error, it sends back a negative acknowledgment (NAK), and the other modem resends the data.

ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->W


Wide Area Network. A data network typically extending a LAN outside a building or beyond a campus, over IXC or LEC lines to link to other LANs at remote sites. Typically created by using bridges or routers to connect geographically separated LANs.

WAN Connection
A connection between two endpoints over a WAN, as opposed to a local connection by a serial or Ethernet link.

WAN Interface
The port on the Lucent unit that is connected to a WAN line.

WAN Port
A T1 or E1 port that provides a point-to-point connection between the Lucent unit and another device.

An air-interface standard technology adapted from the Digital European Cordless Telecommunications standard.

Windows Internet Name Service. Windows Internet Name Service (WINS) is a Microsoft product that manages the mapping between resource names (in the form of easy-to-remember nicknames) and IP addresses. The DNS service used on the Internet cannot map between IP addresses and local resource names dynamically. However, through dynamic database updates, WINS lets users access network resources via more user-friendly names instead of IP addresses.

Wang Span Network

A thin disk of purified crystalline semiconductor, typically silicon, that is divided into chips after processing. See for more info.

A reboot performed while the operating system is running.

Watchdog Request
Used by NetWare Servers to see who is still logged into the server. A NetWare client who is logged on must respond to this request with a "watchdog response" or else the newer server will log the client off. These broadcasts can keep up the line. However, if the line is down and comes up by itself, watchdog requests will not likely be the cause of the problem since we spoof these requests.

Watchdog Spoofing
NetWare servers send "session keep alive" packets to clients who must return the packet to keep a session active. Ascend units can reply to NetWare Core Protocol (NCP) watchdog packets on behalf of clients on the other side of a bridge, causing the server to sense that the link is still active. Effectively imitating a return "session keep alive" packet is called watchdog spoofing.

1. The physical distance between two adjacent peaks or valleys in a wave. 2.The property of light that determines its color.

Wavelength Division Multiplexing (WDM)
Optical transmission technique in which two or more wavelengths (each carrying its own information), are combined for transmission over a single optical fiber. At the receiving end, the wavelengths are separated and directed to separate receivers.

Short for World Wide Web.

The Web browser user interface built into Lucent broadband access products.

Wide Area Network
A data network typically extending a LAN outside a building or beyond a campus, over IXC or LEC lines to link to other LANs at remote sites. Typically created by using bridges or routers to connect geographically separated LANs.

Digital communication between 1.5 Mbps and 45 Mbps.

Wideband Packet Technology
Packet switched services operating at speeds between 50 Kbps and 500 Mbps.

On a telephone line, a signal that is comprised of an on-hook/off-hook/on-hook transition.

Wire Bonding
In chip manufacture, a process for connecting the bonding pads on a chip to the lead frame via tiny gold wires. See for more info.

Wireless Communications
Technologies that provide mobile communications for home or office, and "in-building wireless" for extended mobility around the work area, campus, or business complex. It is also used to mean "cellular" for in- or out-of-building mobility services.

Wireless Modem
A modem that uses radio transmission technology to transmit data between remote locations. A wireless modem is often used by mobile clients in locations where access to a landline connection is not feasible.

Wireless Technology
A communications system in which electromagnetic waves carry the signal. Examples of wireless equipment include cellular telephones, pagers, the cordless mouse, and wireless transceivers for connecting to the Internet.

World Wide Web
Also known as the Web. An Internet facility that links documents anywhere in the world. A Web document is called a Web page, and links in the page let users jump from page to page (hypertext), whether the pages are stored on the server located down the hall or on servers around the globe. The pages are accessed and read via a Web browser such as Netscape Navigator or Internet Explorer.

The physical distance between two adjacent peaks or valleys in a wave;.the property of light that determines its color.

ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->U,V


U Interface
n. The electrical interface between an ISDN telephone line and a network terminator (NT1) device.

U Interface, N.
The electrical interface between an ISDN telephone line and a network terminator (NT1) device.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for sampling data by means of Pulse Coded Modulation (PCM). U-Law is most commonly used in North America and Japan.

adj. Specifies an ISDN communications device that connects directly to an ISDN telephone line. A U-interface device contains its own network terminator (NT1).

U-interface, Adj.
An ISDN communications device that connects directly to an ISDN telephone line. A U-interface device contains its own network terminator (NT1).

User Datagram Protocol

UDP Port
A 16-bit number that allows multiple processes to use User Datagram Protocol (UDP) services on the same host. A UDP address is the combination of a 32-bit IP address and a 16-bit port number. Examples of well-known UDP ports are 7 (for Echo packets), 161 (for SNMP packets), and 514 (for Syslog packets).

UDP Queue
A queue containing unprocessed User Datagram Protocol (UDP) requests.

User-Network Interface. 1) An interface point between Asynchronous Transfer Mode (ATM) end users and a private ATM switch, or between a private ATM switch and the public carrier ATM network; defined by physical and protocol specifications in ATM Forum UNI documents. 2) A similar connection in a Frame Relay network . 3) The interoperability standard adopted by the ATM Forum to define connections between users or end stations and a local switch.

A multiuser, multitasking operating system originally developed by AT&T Bell Labs that runs on a wide variety of computer systems.

UNIX To UNIX Copy Program (UUCP)
An application program developed in the mid 1970’s for Version 7 UNIX that allows one UNIX time sharing system to copy files to or from another UNIX time sharing system over a single link.

Uniform resource locator. The address of a file (resource) accessible on the Internet. The type of resource depends on the Internet application protocol. For the World Wide Web's protocol, the Hypertext Transfer Protocol (HTTP), the resource can be an HTML page, a program such as a Java applet, or any other file supported by HTTP. The URL contains the name of the protocol required to access the resource, a domain name that identifies a specific computer on the Internet, and, if necessary, a path to the resource on the computer. The URL for Lucent Technologies, for example, is http://www.lucent.com.

Unshielded Twisted Pair

UTP cable
Unshielded Twisted Pair cable. Two paired wires with wire twisted two or more times per inch to help cancel out noise.

UNIX-to-UNIX Copy Program. Interactive communication system for connecting two UNIX computers to send and receive data.

User-to-user identification. A field within ISDN protocol which can provide end-to-end information exchange (telephone number, credit card number, login ID, etc.)

Unicast Network
A network in which a router sends packets to one user at a time.

Unified Messaging
A platform that lets users send, receive and manage all email, voice and fax messages from any telephone, PC or information device. By linking to a consumer's e-mail account, for example, one component of unified messaging -- Lucent's Message Notifier solution -- immediately and proactively alerts users via their voice/fax mailbox that they have received e-mail.

Universal Asynchronous Receiver/Transmitter (UART )
A UART is a chip that provides a RS-232C data terminal equipment (DTE) interface to a device, enabling the unit to communicate with its attached serial devices.

Universal Time
The Greenwich Mean Time.

Unshielded Twisted Pair Cable
UTP cable consists of two wires twisted two or more times per inch in order to help cancel out noise. The entire cable has no covering. UTP cable is typically used in telephone lines for voice service, ARCnet networks, 10Base-T Ethernet networks, and particular sections of token ring networks.

Unspecified Bit Rate (UBR)
UBR is an asynchronous transfer mode (ATM) service class that handles bursty LAN traffic, as well as data that is tolerant of delays and cell loss. UBR is a best-effort service that does not specify bit-rate or traffic values, and offers no Quality of Service (QoS) guarantees.

Upstream Path
The path a call takes from the end user’s home to the carrier’s central office (CO).

User Datagram Protocol (UDP)
UDP is a transport-layer protocol that provides connectionless service without packet acknowledgment.

User-Network Interface (UNI)
The point at which users connect to the network.



A rate-adaption standard, based on fixed frames, that subdivides the ISDN channel so that it can carry one lower-speed data channel.

V.110 Terminal Adapter
A V.110 TA is a device that changes the format of asynchronous data to match the specifications of the V.110 standard for data transmission over an ISDN line.

A standard for encapsulating asynchronous data communication into synchronous ISDN data. Using standard, asynchronous-only COM ports and a V.120 Terminal Adapter (TA), two computers can communicate over an ISDN connection.

V.120 Terminal Adapter
A V.120 TA is an asynchronous device that changes the format of asynchronous data to match the specifications of the V.120 standard for data transmission over an ISDN line. A V.120 TA is also known as an ISDN modem.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for 300-bps full-duplex modems.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that supports a data rate of up to 1200 bps at 600 baud.

An extension of the V.22 standard, providing a data rate of up to 2400 bps at 600 baud.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for 600-bps and 1200-bps full-duplex modems.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard that specifies a physical-layer interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE). V.24 is nearly identical to RS-232.

An automatic calling and answering command set for use between DTE and DCE that includes both in-band and out-of-band signaling.

V.25 bis
An automatic calling and answering command set for use between DTE and DCE which includes both in-band and out-of-band signaling.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for automatic calling and answering equipment on (PSTN).

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for full-duplex modem transmission of data across phone lines at rates of up to 9600 bps, with a fallback rate of 4800 bps. A V.32 modem automatically adjusts its transmission speed based on the quality of the line.

An extension of the V.32 standard, providing a data rate of up to 14,400 bps or fallback to 12,000, 9600, 7200, and 4800 bps.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) standard for full-duplex modem transmission of data across phone lines at rates of up to 28,800 bps. A V.34 modem automatically adjusts its transmission speed based on the quality of the line.

An extension of the V.34 standard, providing a data rate of up to 33,600 bps. Compare with V.34.

Commonly used to describe electrical characteristics and connector characteristics for a high-speed synchronous interface between DTE and DCE. Originally V.35 described a 48 Kbps group band modem interface with electrical characteristics defined in an appendix. Although V.35 is considered obsolete and no longer published by the CCITT, its legacy lives on in the data communications world in the form of the electrical characteristics originally described in the appendix.

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) error-detection standard for high-speed modems over digital telephone lines. The V.42 standard makes use of the link access procedure, modem (LAPM).

An International Telecommunication Union–Telecommunication Standardization Sector (ITU-T) data-compression standard for use with V.42 technology. The V.42bis data-compression standard provides a maximum of a four-to-one data-compression ratio. Because compression algorithms are software based, overhead can cause problems in real-time environments. Most of the time, V.42bis can sense when compression is unnecessary, and so can avoid slowing the transfer of precompressed files.

A standard for data transmission over a modem at 56 kilobits per second. The V.90 standard resolves the difference between two modem technologies - x2 and K56flex. Both technologies now conform to V.90, and most previously manufactured 56Kbps modems can support V.90 via a software upgrade. See also K56flex.

Volts DC

Virtual LAN. A group of devices on one or more LANs that communicate as if they were connected to the same wire even though they are physically located on different local area network segments. Because VLANs are configured through software rather than hardware, they are extremely flexible.

Virtual private network. A restricted network that uses public wires to connect nodes. A VPN provides a way to encapsulate, or "tunnel," private data cheaply, reliably, and securely through a public network, usually the Internet.

Very small aperture terminal. Relatively small satellite antenna used for satellite-based point-to-mulit-point data communications applications.

Video Service Unit. See Multiband VSU.

An ASCII character data terminal, consisting of screen and keyboard. Manufactured by Digital Equipment Corporation (DEC), the VT-100 has become an industry standard data terminal. VT-100 emulation software allows a standard PC to act as a VT-100 terminal. Videoconferencing

Virtual Terminal Protocol. An application for establishing a virtual terminal connection across a network.

Variable Bit Rate-Real Time (VBR-RT )
VBR-RT is an asynchronous transfer mode (ATM) service class that handles the packaging of special delay-sensitive applications, such as packet video, that require low cell-delay variation between endpoints.

Very High Bit Rate Digital Subscriber Line (VDSL)
VDSL is an asymmetric DSL technology that offers about eight times the performance of ADSL. The downside is that it requires a fiber-optic line from the central office (CO) to the subscriber’s neighborhood. Because infrastructure changes are required in the local loop, VDSL is considered a specialized and long-term technology.

Video Dial Tone
A network concept in which common carriers deliver video services in response to customers' dial-up commands, the same way users access the public network by dialing their phones.

Video Headend
Node on a video network where incoming program signals are converted to distribution signals and moved out onto the video distribution network for transmission to subscribers.

Video on Demand
The ability for a subscriber to an interactive TV service to select and view a specific program provided by a device such as an interactive video server.

The use of digital video transmission systems to communicate between sites using video and voice. Digital video transmission systems typically consist of camera, codec (coder-decoder), network access equipment, network, and audio system.

Virtual Bandwidth
Channel capacity calculated to allow for the over subscription of channel usage.

Virtual Channel (VC)
A communications link that carries asynchronous transfer mode (ATM) cells between two points over a shared facility. The link can be established on-demand (as a switched service), or pre-provisioned (as frame relay PVCs). The two communicating ATM entities are associated by a Virtual Path Identifier (VPI) and the Virtual Channel Identifier (VCI). All communications proceed along the same VC, preserving cell sequence and Quality of Service.

Virtual Circuit (VC)
On a frame relay, X.25 or Open Shortest Path First (OSPF) network, a VC is a bi-directional data path between two endpoints.

Virtual Circuit Manager
In each asynchronous transfer mode (ATM) node, the VC manager is the switching intelligence that builds the input port-to-output port VC mappings required for the switching device’s basic operation. The VC manager also compares the bandwidth resources required by an additional connection against the actual available resources on a link, thereby helping to prevent circuits from being created in congested areas of the network.

Virtual Paths
A bundle of virtual channels that have the same endpoint, enabling them to be manipulated as if they were a single channel.

Visitor Location Register
In cellular communications, a database that stores the information to handle calls while mobile subscribers roam outside their home areas.

A category of hardware and software that allows people to use the Internet to make telephone calls. Currently, VoIP does not offer the same quality of telephone service as direct telephone connections. VoIP is also known as Internet telephony and Voice over the Internet.

Vocoder (Voice encoder)
Converts the analog sounds of the human voice into the zeroes and ones of digital code for computer processing.

Voice-over-IP (VoIP)
A term applied to a set of facilities for managing the delivery of voice information using the Internet Protocol (IP). Voice information is sent in digital form in discrete packets over the Internet instead of in analog form over the public switched telephone network (PSTN). A major advantage of VoIP is that it avoids the tolls charged by ordinary telephone service.

Voice-over-frame Relay (VoFR)
A term applied to a set of facilities for managing the delivery of voice information using frame relay.

The force required to produce a current of one ampere through a resistance or impedance of one ohm.

ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->T


A digital transmission link with a capacity of 1.544 Mbit/s, used in North America. Typically channelized into 24 DS0s, each capable of carrying a single voice conversation or data stream. Uses two pairs of twisted pair wires.

T1 (T-carrier)
A digital transmission service leased from a telephone company. T1 is a 1.544 megabit channel that can handle 24 voice or data channels at 64 kilobits per second. T2 is a 6.312 megabit channel, and T3 is a 44.737 megabit channel. Because of it's high speed, many businesses lease T1 lines to link to the internet.

T1 Access Line
A 1.544 mbps T1 line that provides 24 56 kbps data channels and uses inband signaling. This type of line can contain all switched channels, all nailed-up channels, or a combination of switched and nailed-up channels. You can connect this type of line to standard voice or Switched-56 data services. Using a feature called Drop-and-Insert, the MAX can use a portion of a T1 access line for data purposes and pass the remaining portion of the line's bandwidth to a PBX for voice purposes.

T1 Channel
One of 24 channels on a T1 line.

T1 Line
A line that supports 24 64-Kbps channels, each of which can transmit and receive data or digitized voice. The line uses framing and signaling to achieve synchronous and reliable transmission. The most common configurations for T1 lines are ISDN Primary Rate Interface (T1 PRI) and unchannelized T1, including fractional T1.

T1 PRI line
A T1 line that uses 23 B channels for user data, and one 64 kbps D channel for ISDN D-channel signaling. The B channels can be all switched, all nailed up, or a combination of switched and nailed up. This type of PRI line is a standard in North America, Japan, and Korea. PRI stands for Primary Rate Interface. You can connect this type of line to standard voice, or Switched-56, Switched-64, Switched-384, Switched-1536, and MultiRate data services. Using a feature called PRI-to-TI conversion, the MAX can share the bandwidth of a T1 PRI line with a PBX.

A digital transmission link with a capacity of 45 Mbps, or 28 T1 lines.

T3 Line
A digital transmission link consisting of 28 T1 lines with a total bandwidth of 44.736 Mbps.

Terminal Access Concentrator Access Control Server. A very simple query/response protocol that enables the MAX to check a user's password, and enable or prevent access. A TACACS server supports only the basic password exchanges that PAP uses; it does not support CHAP.

Transmission Control Protocol

Transmission Control Protocol/Internet Protocol. An open network standard that defines how devices from different manufacturers communicate with each other over interconnected networks. TCP/IP protocols are the foundation of the Internet.

Time Division Multiplexer (or Time Division Multiplexing) Terminal Adapter -- A device that allows analog voice and data devices to work through an ISDN connection. The terminal adapter is a protocol converter that adapts equipment not designed for ISDN, such as phones, faxes, and modems.

Terminal Equipment

Thermal Electric Cooler. A device which uses the Peltier effect to heat or cool as necessary to keep the laser temperature constant.

A public packet switched network using the CCITT X.25 protocols owned and operated by GTE.

Trivial File Transfer Protocol. A simplified version of the File Transfer Protocol that transfers files but does not provide password protection or user directory capability.

Transmitter Gain

Transimpedance amplifier

Television, receive only. An earth station designed to handle downlink signals only.

Tagged Image File Format (TIFF)
A still graphics file format that handles monochrome, gray scale, and color images and uses a variety of compression methods. See JPEG and GIF.

Documents filed by a regulated telephone company with a state public utility commission or the Federal Communications Commission. Document details services, equipment, and pricing publicly offered by the telephone company.

Telephone company.

Telecommunications Industries Association
The group responsible for setting telecommunications standards in the United States.

A work-at-home computer user who connects to the corporate LAN backbone using remote access technologies (for example, using a modem over analog lines, ISDN Terminal Adapter (TA) or ISDN router over ISDN lines, or CSU/DSU over Switched 56 lines).

A multimedia distance application in which an attending physician can consult with a remote specialist sharing test results such as X-rays and other data.

Telephony Application Programming Interface (TAPI)
From Microsoft and Intel, TAPI allows applications on client computers running Windows to access voice services on a server. TAPI lets PCs and telephone gear work together, including phone systems and PBXs. See TSAPI.

Telephony Services Application Programming Interface (TSAPI)
A telephony programming interface that links a PBX with a NetWare server so PCs and telephone gear can work together. See TAPI.

Terminal-to-remote host protocol developed for ARPAnet. It is the TCP/IP protocol governing the exchange of character-oriented terminal data. This protocol is used to link two computers in order to provide a terminal connection to the remote machine.
Instead of dialing into the computer, you connect to it over the Internet using Telnet. When you issue a Telnet session, you connect to the Telnet host and log in. The connection enables you to work with the remote machine as though you were a terminal connected to it.

One trillion bits.

A computer that does not have its own processor and that must connect to a terminal server in asynchronous mode in order to use its CPU. VT100, ANSI, and TTY are all types of terminals.

Terminal Access Concentrator Access Control Server (TACAS)
A very simple query/response protocol that enables an access concentrator to check a user's password, and enable or prevent access. A TACACS server supports only the basic password exchanges that PAP uses; it does not support CHAP.

Terminal Access Controller (TAC)
A program and a piece of hardware that connects terminals to the Internet.

Terminal Adapter
A device that allows analog voice and data devices to work through an ISDN connection. The terminal adapter is a protocol converter that adapts equipment not designed for ISDN, such as phones, faxes, and modems.

Terminal Adapter (TA)
A TA is a protocol converter that adapts non-ISDN equipment (such as a phone, fax, or modem), and enables each device to work over an ISDN connection. A TA has two functions. First, it must change the format of transmitted data to match the V.120 standard for asynchronous transfer over a B channel. Second, it must provide a way of setting up and clearing calls, usually by means of Hayes AT commands. A TA is to an ISDN line what a modem is to an analog telephone line. However, some of the D-channel information does not pass through the TA, so non-ISDN equipment cannot take full advantage of ISDN facilities, such as Calling-Line ID (CLID).

Terminal Emulator
A program that makes your computer look like a terminal so that you can connect to a terminal server. Your computer acts like a terminal during the connection; all processing is taking place remotely. A terminal emulator is also called a terminal emulation program.

Terminal Server
A terminal server is a computing device to which a terminal can connect over a LAN or WAN link. A terminal communicates with the terminal server over an asynchronous serial port (typically an RS-232 port) through a modem. A terminal converts the data it receives from the terminal server into a display and does no further processing of the data. A terminal also converts the operator's keystrokes into data for transmission to the terminal server.

Terminal Server Session
An end-to-end connection between a terminal and a terminal server. Usually, the terminal server session begins when the call goes on line and ends when the call disconnects.

Thermal Electric Cooler
A device which uses the Peltier effect to heat or cool as necessary to keep the laser temperature constant.

Thick Ethernet
A term that describes a type of Ethernet cable. Thick Ethernet, or thicknet, is .4" diameter coaxial cable for Ethernet networks.

Thin Ethernet
A term that describes a type of Ethernet cable. Thin Ethernet, or thinnet, is .2" diameter coaxial cable for Ethernet networks.

The actual speed of a network.

Time Division Multiple Access (TDMA)
Time Division Multiple Access: a multiplexing standard that divides each carrier into three time slots--with one subscriber per slot. Transmission signals are broken up into tiny packets of information--which are sent in timed bursts in the 30 megahertz range--and are reassembled at the receiving end.

Time To Live (TTL)
The hop limit counter (value=32) for IP packets.

An event in which a device or user exceeded a configured time limit for responding to a device or process.

Token Ring
A network architecture that uses a ring topology, baseband signaling, and the token-passing media-access method. Token ring can operate at 1, 4, or 16 Mbps, and supports four-wire twisted pair or fiber-optic media.

The design of a network. Physical topology refers to the layout of the hardware. Logical topology refers to the paths that messages take to get from one node to another.

A superset of PING used to evaluate the hops taken from one end of a link to the other.

Traffic Contract
An asynchronous transfer mode (ATM) configuration that guarantees the delivery of a specified amount of data. While data above the traffic contract can still be delivered when network resources are available, data that exceeds the traffic contract can be delayed or lost when conditions are congested.

Traffic Shaping
In frame relay, a set of rules for defining traffic flow. The sender has a mechanism that ensures that the transmission of guaranteed packets occurs in a certain way. The network knows the kind of traffic to expect, and can monitor the behavior of the traffic. In asynchronous transfer mode (ATM), traffic shaping is a method of modifying the traffic characteristics of a stream of cells in order to achieve better network efficiency and meet all Quality of Service (QoS) objectives.

A device that connects a host interfaces to local area network. Ethernet transceivers contain analog electronics that apply signals to the cable and sense collisions.

The basic concept behind voice transmission; the conversion of energy from one form into another.

Transimpedance amplifier
An electrical circuit or device that accepts a current at its input and generates a voltage at its output.

A semiconductor device that amplifies a signal or opens and closes a circuit. In computers, it acts as a switch. Transistors and other devices -- such as resistors, capacitors and diodes -- make up logic gates. Logic gates make up circuits, and circuits make up electronic systems, such as computers. See for more info.

Analog vs. digital transmission. Analog transmission requires more precision than a voice transmission; even if a slight error occurs during a conversation, the listener can usually compensate and understand the speaker.

Transmission Control Protocol/Internet Protocol (TCP/IP)
A protocol capable of linking different computer platforms across the Internet.

In fiber optic communications, a light source whose beam can be modulated and sent along an optical fiber, and the electronics that support it.

Trivial File Transfer Protocol (TFTP)
A simplified version of FTP that transfers files but does not provide password protection or user-directory capability. It is associated with the TCP/IP family of protocols. TFTP depends on the connectionless datagram deliver service, UDP.

The communications circuit between two nodes.

Trunk Restoration
A process that reroutes the permanent virtual circuits (PVCs) on the backup trunk to the primary trunk.

Trunk Side
Trunk is a communication line between two switching systems. The term switching system typically includes equipment in a central office (telephone company) and PBXs. A tie trunk connects PBXs. Central office trunks connect a PBX to the switching system at the central office.

Trunk-side Connection
A line that extends from the telephone company’s central office (CO) to the telephone network. Typically, a trunk-side connection is high-bandwidth and all digital.

A way of overcoming protocol restrictions on a network by encapsulating packets that use one protocol inside packets that use a protocol supported by the network.

Twisted Pair
Relatively low-speed transmission medium consisting of two insulated wires - shielded or unshielded-in regular spiral patterns. The wires are twisted around each other to minimize interference from other twisted pairs in the cable. Twisted pair is common in telephone wiring and is increasingly common in data networks. Other high-speed forms of cable include coaxial and fiber optic cables.

Twisted-pair Cable
A cable consisting of four or more copper wires twisted together in pairs. Telephone wiring is an example of twisted-pair cable. Twisted-pair cable can be shielded or unshielded.

Two-wire Subscriber Loop
The two-wire WAN link connecting the customer premises equipment (CPE) to the carrier’s switch.

ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->S


S interface
n. See S/T interface.

adj. See S/T interface.

S/T Interface, Adj.
Specifies an ISDN communications device that connects to an external network terminator (NT1).

S/T Interface, N.
The electrical interface between a network terminator (NT1) device and one or more ISDN communications devices that do not contain their own NT1s.

SA Broadband
A family of products that enables a service provider to implement asynchronous transfer mode (ATM) services such as data, voice, and video.

Secure Access Manager. Secure Access Manager gives network administrators granular control over the security functions of the entire network directly from the central site. Through this Windows-based application, network administrators can configure the Secure Access Firewall(s) off line and download the configuration to remote locations. The menu-driven program enables network administrators to easily configure the firewall on the network.

Service Access Point

SAP Filters
See NetWare call filters.

Stimulated Brillouin Scattering

Subscription Channel / Angled Polished Connector

Synchronous Digital Hierarchy: A standard that defines transmission rates for global high-speed multiplexing.

Source Demand Routing Protocol

See Switched Digital Services Applications Forum.

Sequential Exchange Protocol

Simple Internet Protocol

Serial Line Internet Protocol. The protocol that was made obsolete by Point-to-Point Protocol, for point-to-point serial connections using TCP/IP.

SLIP (Serial Line IP)
A protocol that enables your computer to send and receive IP packets over a serial link.

Station Management Detail Recording. The ability of network access equipment to output call statistics and performance information for tabulation and analysis.

Switched Multimegabit Data Service. A packet-based network service allowing the creation of high-speed data networks (up to 45 Mbit/s). Now in the testing and initial implementation phases.

Simple Mail Transfer Protocol. A protocol for exchanging email messages between servers across a network. SMTP is the principle protocol for sending email over the Internet.

SubNetwork Access Protocol

Simple Network Management Protocol. A standard way for computers to share networking information. In SNMP, two types of communicating devices exist: agents and managers. An agent provides networking information to a manager application running on another computer. The agents and managers share a database of information, called the Management Information Base (MIB). An agent can use a message called a traps-PDU to send unsolicited information to the manager.

Synchronous Optical Network. SONET is a Bellcore specification currently used in worldwide public data networks (PDNs). It defines a synchronous optical network-based user-network interface (UNI), either public or private, operating at speeds from 51 Mbps

Service Profile Identifier. Your ISDN service provider (telephone company) uses this number at the Central Office switch to identify services on your ISDN line. This number is derived from a telephone number. See also Central Office and ISDN.

Structured query language. A standard interactive and programming language for requesting information from and updating databases.

Signaling System 7: a signaling method-separate from voice or data channel-that lets Intelligent Network elements exchange information among themselves.

Secure Sockets Layer. A program layer of network, and also a protocol that enable encrypted and authenticated communications across the Internet. Many websites use SSL protocol to obtain confidential user information.

Switched Virtual Circuit. A path over a packet-switched network that appears to be a dedicated circuit, but in fact the connection only stays up as long as needed, and then ends. (Also see PVC.)

See Switched 56.

IP with Encryption

Able to be changed in size or configuration to suit changing conditions. For example, a scalable network can be expanded from a few nodes to thousands of nodes.

Screen Pop
In Computer Technology Integration, the appearance of database information about a caller, while the phone is ringing, on the call recipient's computer screen.

Secure Access Firewalls
Secure Access Firewall is a software option for Ascend units that offers a fully integrated firewall security for remote networking. It uses state-of-the-art dynamic firewall technology to deliver a comprehensive security solution for the corporate LAN, remote office LAN and telecommuter's LAN that stops intruders from breaking and entering into networks. Securing the perimeter of the local network where it meets the Internet sets the stage for using the Internet for Intranet applications.

Secure ID
A proprietary brand of security card (about the size of a credit card) that generates a code based on the user’s ID, password, and information in the card. When the user attempts to log on to a secure network, a code is requested that must have been generated within the previous 60 seconds. The server interprets the code, and if it is found to be genuine, the user is granted access.

The Lucent suite of security features, which provide a complete solution for establishing secure sessions across the Internet. The SecureConnect features work with the Lucent MAX and Pipeline products. SecureConnect Firewall is an ICSA-certified, dynamic firewall technology. SecureConnect Firewall + VPN is an integrated firewall and encryption feature that enables users to conduct authenticated and confidential sessions over the public Internet. SecureConnect Client is PC client software that gives remote and mobile users the same confidential and secure connections that network users enjoy via SecureConnect Pipeline and MAX products. SecureConnect Server is a Web-accessible, RADIUS-based user authentication system.

SecureConnect Firewalls
A software option for Lucent units that offers a fully integrated firewall security for remote networking. It uses state-of-the-art dynamic firewall technology to deliver a comprehensive security solution for the corporate LAN, remote office LAN and telecommuter’s LAN that stops intruders from breaking and entering into networks. Securing the perimeter of the local network where it meets the Internet sets the stage for using the Internet for Intranet applications.

SecureConnect Manager
SecureConnect Manager gives network administrators granular control over the security functions of the entire network directly from the central site. Through this Windows based application, network administrators can configure the SecureConnect Firewall(s) off line and download the configuration to remote locations. The menu-driven program enables network administrators to easily configure the firewall on the network.

Security Cards
See Secure ID.

Selective Acknowledgment (SACK)
An acknowledgement mechanism used with the sliding window protocols that allows the receiver to acknowledge packets received out of order but within the current sliding window.

A crystalline solid that behaves somewhere between a conductor (like iron) and an insulator (like glass). Semiconductors are the raw materials used in active electronic and optical devices.

The input level required for a device to provide a predetermined output.

Serial Communication
Communication through the serial port of your computer. For Windows 3.1, the maximum speed of the serial port is 19,200. For Windows 95, the COM port limit on the settings drop-down list is 921,600. These limitations are subject to change as development of a faster serial bus design is implemented.

Serial Connection
A link between the serial ports of two devices.

Serial Host
A device, such as a videoconferencing codec, that is connected to a serial host port communicating over a point-to-point link. To a serial host, the MAX appears to be a cable or DCE (Data Communications Equipment).

Serial Host Port
The V.35, RS-499, or X.21 port on the MAX.

Serial Host Port Module
A module on the MAX that connects to a serial host through its serial host port.

Serial Line IP
A protocol that enables your computer to send and receive IP packets over a serial link.

Serial Number Exchange Protocol (SNEP)
Packets that are used to ensure that one copy of NetWare has not been loaded onto more than one NetWare Server. SNEP packets, by default are NOT filtered and therefore will cause a link to be dialed in a routed IPX environment. SNEP can be call filtered using the same offset rules as an 802.2 or 802.3 frame type, wit its designated socket number. It uses a destination socket of 0457.

Serial Transmission
A form of data transmission in which only one line carries all eight bits of a byte. In serial transmission, one bit follows another (as opposed to parallel transmission, in which the bits travel simultaneously, each on a different wire). Serial transmission can be either synchronous or asynchronous. Synchronous communication requires additional lines for transmitting handshake or timing signals. In asynchronous communication, the data itself contains synchronization information, so neither handshake nor clock signals are necessary.

Serial port
A bidirectional channel through which data flows one bit as a time.

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 commonly, it is the fastest and brawniest PC around. It may be used as a repository and a distributor of oodles of data. It may also be the gatekeeper controlling access to voice mail, electronic mail, and facsimile services.

Service Control Point
An Intelligent Network element. A programmable intelligent database server that contains service intelligence and stores call control and routing instructions for delivery of services.

Service Creation Environment (SCE)
A leading service development system that allows service providers, Lucent Technologies, and selected third-party vendors to create or customize innovative services. Provide the power to develop, test, and implement, via Lucent Technologies Intelligent Network products, breakthrough communication and information services.

Service Management
The ability to create and control data services, enabling fast and cost-effective deployment and ongoing management. For service providers, service management means the ability to create a variety of services targeted for varied enterprise market segments with appropriate traffic management plans and price models. For enterprises, service management means new, public data services targeted and priced for business needs that the enterprise can measure directly with access to network information.

Service Management System
The administration, management, and provisioning server that handles the complexities of delivering services throughout the intelligent network.

Service Node
An element in an advanced public network ing architecture at which service requests, including service switching, are processed.

Service Node Service Control Point (SN-SCP)
A component of the GlobeView[R]-2000 Service Node that provides control functions for the Interface and Services Stage (ISS) and the ATM Interconnect Shelf.

Service Switching Point
In the intelligent network, the node normally associated with the serving office. It recognizes calls requiring special handling and sends them either to the Service Control Point, Service Node.

The state a connection reaches when bothparties can communicate with each other.

Shielded Twisted Pair Cable
STP cable consists of two wires twisted two or more times per inch in order to help cancel out noise. The entire cable has a protective covering. STP cable is typically used in ARCnet and token ring networks.

Short haul
According to some definitions, a distance between several hundred yards and 20 miles.

Shorter Radio Wave
In wireless communications, this wave enables a radio signal to travel through small openings and navigate around physical obstructions that can cause interference.

Shortest Path Routing
A routing algorithm that calculates the path distance to all network destinations. A cost assigned to each link determines the shortest path.

Signal Transfer Point
A packet switching device in the CCS 7 network. See Common Channel Signaling Version 7 (CCS 7).

Signaling ATM Adaptation Layer (SAAL)
The SAAL is a mechanism for ensuring that signaling messages are reliably transported between network peers. It resides between the Asynchronous Transfer Mode (ATM) Layer and Q.2931 in the user’s equipment. The purpose of the SAAL is to provide reliable transport of Q.2931 messages between peer Q.2931 entities, such as an ATM switch and host, over the ATM Layer. The SAAL is subdivided into the Common Part (CP) and the Service-Specific Part (SSP).

Signaling Connection Control Part (SCCP)
Provides connectionless and connection-oriented network services and global title translation (GTT) capabilities above MTP Level 3. A global title is an address (e.g., a dialed 800 number, calling card number, or mobile subscriber identification number) which is translated by SCCP into a destination point code and subsystem number. A subsystem number uniquely identifies an application at the destination signaling point. SCCP is used as the transport layer for TCAP-based services.

Signaling Protocol
A protocol that enables an asynchronous transfer mode (ATM) system to transfer service-related information between the user and the network, and among network elements. Signaling takes place between the user and the network over the user-to-network interface (UNI). Signaling takes place between network elements over the network-to-network interface (NNI). The signaling protocols in UNI 3.0/3.1 support four ATM service classes—Constant Bit Rate (CBR), Variable Bit Rate-Real Time (VBR-RT), Variable Bit Rate Non-Real Time (VBR-NRT), and Available Bit Rate/Unspecified Bit Rate (ABR/UBR).

Signaling System 7 (SS7)
See Common Channel Signaling Version 7 (CCS 7).

Signaling Types
The sending device and the receiving device must send signals in order to synchronize their clocks and determine where one block of data ends and the next begins. Services use signaling types to maintain synchronization and transfer data effectively. Signals are either analog or digital. In-band signaling is used by POTS, where all of the information about the beginning and end of a call is carried on a single line. ISDN BRI uses two B channels to carry data and a D channel to carry signaling data.

A dark gray, hard crystalline solid. Next to oxygen, the second most abundant element on earth. It is the basic material for chips and other semiconductor devices. See for more info.

Simple Internet Protocol
Simple Internet Protocol.

Simple Mail Transfer Protocol (SMTP)
In the TCP/IP protocol suite, SMTP is an application-layer protocol that uses the TCP transport-layer protocol to send and receive electronic mail.

Single mode fiber
A fiber having a small core diameter and in which only one mode will propagate at the wavelengths of interest.

Single-mode Fiber
A fiber having a small core diameter and in which only one mode will propagate at the wavelengths of interest.

Smart Card
A credit card with a built-in microprocessor and memory used for identification or financial transactions. When inserted into a card reader, it transfers data to and from a central computer.

Smart Jack
A common name for RJ48X.

A TCP/IP interface that facilitates a two-way link between systems, enabling applications to run over a connectionless network. A socket is defined by two addresses: the IP address of the host computer, and the port address of the application or process running on the host.

Software Compression
Software compression removes waste and redundancy in a data file in order to save space and enable faster throughput. The results of compression depend on the content of each file being compressed: some contain a lot of waste, some contain almost none.

Source Address
In a frame, packet, or message sent over a bridged or routed connection, the IP, IPX, AppleTalk, or hardware address of the device that sent the transmission. Compare with destination address.

Source Laser
A laser used as a light source in an externally modulated system

Source Port
The port from which a transmission originates, such as a User Datagram Protocol (UDP) port on an authentication server, or a simple mail transfer protocol (SMTP) port on a mail server. Compare with destination port.

Source Quench
A congestion control technique in which a machine experiencing congestion sends a message back to the source of the packets causing the congestion requesting that the source stop transmitting. In Internet gateways use ICMP source quench to stop and reduce the transmission of IP datagrams.

Source Route
A route that is determined by the source. In the Internet source routing is implemented using the option field of an IP datagram.

Electromagnetic Spectrum: includes all frequencies from 10 hertz, just below human hearing, to 1025 hertz, cosmic ray range. Radio spectrum: the region of the spectrum including frequencies between 3 kilohertz and 300 gigahertz.

Spread Spectrum Technology
This technique sends a message as a series of computer codes. However, since the signal is stretched out over a broad frequency band, the receiver only needs to receive a part of the transmitted signal to reconstruct the original message.

A stack is group of MAX units with a single stack name, acting as a single, logical unit. Stacks allow incoming (only) MP or MP+ calls to span multiple MAX units on a single LAN. There is no master unit in a stack. A MAX can become a member of a stack or leave a stack at any time, and there is no requirement to join a stack.

The interfaces by which computer and communications systems operate; typically determined by international standards-setting bodies.

Star Topology
A network configuration in which the nodes are connected to a single central hub rather than to each other. See ring topology.

Start Bit
In asynchronous transmission, a bit that indicates the beginning of a new character. It is always 0 (zero).

Stateful Inspection
Tracks the transaction in order to verify that the destination of an inbound packet matches the source of a previous outbound request. Can generally examine multiple layers of the protocol stack, including the data, if required, so blocking can be made at any layer or depth.

Statistical Time Division Multiplexing
A method of Time Division Multiplexing in which the time slots on a shared medium, like a switch, are allocated to complete the connection between two paths.

Stimulated Brillouin Scattering
A nonlinear phenomenon that can cause distortion of an optical signal in a fiber.

Straight-Through Cable
A cable with wires that have terminating ends with the same wire assignments.

Structured Cabling System (SCS)
A set of cabling and connecting products that supports the voice, data, and/or video networks inside a building or campus of building. SYSTIMAX® SCS is Lucent Technologies' Structured Cabling System offer.

Subscriber Network Interface (SNI)
The SNI is the interface between the network supporting switched multimegabit data service (SMDS) and the subscriber-owned equipment. The service provider assigns SMDS addresses that identify the SNI from which the data unit was sent and/or the SNI for which it was destined. Each address can be an individual address or a group address.

A base on which layers are formed on a wafer. See for more info.

In data networking. the process of combining routing information from one routing protocol into another for advertisement.

In UNIX, a user with special privileges (also known as root). Only the superuser, for example, can change the password file and edit major system administration files in the /etc directory.

Supervisory Frame
On an X.25 network, a frame that can request and suspend transmission, report on link status, and acknowledge I-frames.

A device that connects the calling party to the answering party.

Switched 1536
A dial-up network-based service providing a data channel operating at a rate of 1536 kbit/s.

Switched 384
A dial-up network-based service providing a data channel operating at a rate of 384 kbit/s.

Switched 56
A dial-up network-based service providing a data channel operating at a rate of 56 kbit/s. Also a type of network access line, used to provide access to switched 56 network services.

Switched 64
A dial-up network-based service providing a data channel operating at a rate of 64 kbit/s.

Switched Access Remote Test System (SARTS)
The operations systems that provides a remote, centralized way to test special services circuits in a communications network from end to end.

Switched Channel
A channel that provides a temporary connection for the exchange of data. The channel is cleared when the call ends.

Switched Digital Services Applications Forum (SDSAF)
A consortium of equipment vendors, service vendors, and users, with the goal of advancing the state of switched digital services.

Switched Line
A line consisting of channels in use only for the duration of the connection.

Switched Virtual Circuit
A virtual circuit established on demand by an end user employing signaling.

Switched-56 Line
A line that provides a single 56-Kbps data channel with inband signaling.

Symbolic Name
A name used in place of an IP address.A symbolic name consists of a user name and a domain name in the format user name@domain name. The user name corresponds to the host number in the IP address. The domain name corresponds to the network number in the IP address. A symbolic name might be steve@crocker.com or joanne@cal.edu.

Symmetric Digital Subscriber Line (SDSL)
A new technology that allows more data to be sent over existing copper telephone lines (POTS). SDSL supports rates up to 3 Mbps.

In serial data transmission, a method of ensuring that the receiving end can recognize characters in the order in which the transmitting end sent them, and can know where one character ends and the next begins. Without synchronization, the receiving end would perceive data simply as a series of binary digits with no relation to one another. Synchronous communication relies on a clocking mechanism to synchronize the signals between the sending and receiving machines.

Synchronous Data Link Control (SDLC)
A predecessor of HDLC defined by IBM Corporation and used in their SNA products.

Synchronous Digital Hierarchy
A broadband transmission standard in which uniform modular transmission containers and/or frames contain both message elements and overhead information to provide smooth, reliable networking efficiency.

Synchronous Optical Network (SONET)
SONET is a Bellcore specification currently used in worldwide public data networks (PDNs). It defines a synchronous optical network-based user-network interface (UNI), either public or private, operating at speeds from 51 Mbps to 2 Gbps over single-mode optical fiber.

Synchronous Transmission
A transmission mode in which the data moves in large blocks, called messages or frames. Both the sending device and the receiving device must maintain synchronization in order to determine where one block of data ends and the next begins. Synchronization can take one of these forms:

System operator. A person responsible for the day-to-day operation of a computer system or network resource - for example, server, LAN, bulletin board system, online service, or special interest group.

System on a Chip
In microelectronics, the placement of a number of different key functions on the same chip. Today, a system on a chip means integrating the full system, including analog components, logic, digital signal processors, microprocessor cores, and memory. See

System-Level Integration
In semiconductor design and fabrication, packing higher and higher numbers of increasingly complex devices into an integrated circuit. The end result is the system on a chip.

System-based Routing
A form of IP routing in which the entire unit has a single IP address. For systems that have a single backbone connection, system-based routing is the simplest way to configure the Lucent unit.

single thread
A connection between transmission and receive device that operates without the benefit of redundancy.

ABBREVIATION DICTIONARY Networks and Telecommunications/Electronics -->Q,R


Quality of service. An indicator of the performance of a transmission system on the Internet and other networks. QoS is measured in transmission rate, error rates, latency, and other characteristics, and can to some extent be guaranteed to a customer in advance. Asynchronous Transfer Mode technology supports QoS levels as do Lucent's new PacketStar® IP Switch.

The act of "stacking" or holding calls to be answered by a specific person, trunk, or trunk group.


Reverse Address Resolution Protocol

Regional Bell Operating Company

Regional database management system. A RDBMS that stores data in the form of related tables. Relational databases require few assumptions about how data is related or how it is extracted from the database, enabling the database to be viewed in many different ways. In contrast to flat-file databases, which consist of a single table, a relational system can spread the database over several tables. Most full-scale database systems are structured as an RDBMS.

Reliable Data Protocol

Radio Frequency.

RF Input
The signal in dBm as presented to the input of a device.

RF Loss
A measure of RF signal loss through a device or link.

RF Output
The signal in dBm at the output of a device.

Request For Comments. The document series, begun in 1969, which describes the Internet suite of protocols and related experiments. Not all (in fact very few) RFCs describe Internet standards, but all Internet standards are written up as RFCs. The RFC series of documents is unusual in that the proposed protocols are forwarded by the Internet research and development community, acting on their own behalf, as opposed to the formally reviewed and standardized protocols that are promoted by organizations such as CCITT and ANSI. A complete list of RFCs can be found at http://www.internic.net/rfc/.

Receiver Gain

Ring Indicate

Routing Information Protocol. Routing information protocol teaches routers on a wide area network which routers have access to which addresses. This information is kept in a routing table on each router. As routers communicate with each other, they all update their routing tables to include each others' routing table information. In a large network environment, this exchange of information can keep the network connections up unnecessarily, and can result in very large routing tables on each router. You can apply a call filter to ignore RIP updates. You can also control how route information is propagated.

RJ-45 connector
Registered Jack-45. A telephone connector that holds up to eight wires. RJ-45 plugs and sockets are used in Ethernet and Token Ring devices.

An eight-position keyed plug most commonly used for connecting T1 circuits. The RJ-48C is an eigh-position plug with four wires (two for transmit, two for receive) commonly connected. When the phone company delivers T1 to your offices, it usually terminates its T1 circuit on a RJ-48C. And it expects you to connect that RHJ-48C to your phone system or T1 channel bank and then to your phone system.

Remote Procedure Call

Remote Port Module. See Multiband RPM.

Recommended Service #

A set of EIA standards specifying various electrical and mechanical characteristics for interfaces between DTE and DCE data communications devices. The standard applies to both synchronous and asynchronous binary data transmission at rates below 64 kbit/s.

An EIA standard for providing dialing commands to network access equipment. Uses RS-232 electrical specifications but different connector pinouts and signal functions.

An EIA standard describing electrical characteristics for balanced-voltage digital interface circuits. Typically used for high-speed and synchronous data connections between DTE and DCE data communications devices.

An EIA standard describing electrical characteristics for unbalanced-voltage digital interface circuits. Typically used for high-speed synchronous data connections between DTE and DCE data communications devices.

An EIA standard for a 37-pin data communications connector, usually used with RS-422 or RS-423 electrical specifications.

A standard for multipoint communications lines.

Reservation Protocol

Request To Send

MIT Remote Virtual Disk Protocol Remote Access

Radio Channel
A cellular Radio Frequency channel as identified by the FCC. For analog, the channel is 30 kHz wide. In CDMA, which is a digital technology, the radio channel is 1.25 MHz wide.

Radio Frequency (RF)
A range of electromagnetic frequencies above sound and below visible light, generally in the 30 KHz to 300 GHz range, used for all broadcast transmission including AM and FM radio, television, short-wave, microwave, and satellite transmissions.

Radio Spectrum
Radio spectrum consists of radio waves of different frequencies (for example, 900 MHz). All radio spectra are regulated, with some licensed and others unlicensed.

Radio frequency
The RF carrier frequency of a given device.

Random Access Memory (RAM)
RAM is computer memory that holds data temporarily.

In wireless communications, the distance that radio waves travel from a source (radio transmitter) before becoming too weak for a radio receiver to identify them.

Rate Adaptation
A capability that enables the rate-adaptive digital subscriber line (RADSL) signal to continue to transmit data even if noise is blocking some frequencies. Single, unshielded twisted-copper cable is subject to noise from external sources and nearby cables. Without rate adaptation, digital subscriber line (DSL) equipment cannot adjust to noise on the line and is forced to drop the signal entirely. Rate adaptation bypasses impaired frequencies, and the transmission continues. The system resumes the use of the bypassed frequencies as soon as the line is clear.

Read Only Memory (ROM)
ROM is computer memory whose contents can be read and executed, but not modified.

To restart the computer and reload the operating system.

A device which receives a transmitted signal.

Receiver gain
The difference between the RF signal presented to the input of the receiver versus the RF signal at the receiver output. This gain will not always represent itself as an increase in signal, since the losses in the receiver may be greater than its internal amplifier.

Red, Green, Blue (RGB)
The basic colors used in generating images on a color monitor or television screen. In RGB systems, various hues and shades are created additively, so that when all three colors are at their fullest intensity, the image is white.

Reduced Instruction Set Computing
A high-speed processor technology using a simple set of operating commands for faster processing and throughput used in workstation-class desktop computers.

Having one or more backup systems available in case the primary system fails.

Redundant Array Of Inexpensive Disks (RAID)
RAID technology is a method of using several hard disk drives in an array to provide fault tolerance. RAID improves redundancy and limits downtime.

Redundant link
A second connection between transmission and receive devices that operates only when integrity is lost on the active link.

The abrupt change in the direction of light as it travels from one material to a dissimilar material. Some of the reflected power in a fiber gets transmitted back to the source.

The bending of light as it passes through two dissimilar materials or in a medium whose refractive index varies smoothly. Important in fiber optic technology.

Refractive Index
The ratio of the speed of light in a vacuum to its speed in a given material such as glass. The larger the ratio, the more the light entering the material is bent. Important in fiber optic technology.

In a lightwave system, an electronic circuit that reconverts the electrical signals to light pulses and a laser that speeds them on their way.

In cellular communications systems, a handset must "register" with the system through this "handshake" process when a user logs onto the system for the first time.

Relational Database
A tabular database in which data is defined so that it can be reorganized and accessed in a number of different ways.

Remote Access Server
Any device that lets multiple remote users to access a network. Lucent's PortMaster 2 and PortMaster 3 products are remote access servers. A remote access server is sometimes called a RAS.

Remote Device
A unit that resides across the WAN.

Remote Job Entry (RJE)
The service offered by many networks that enables a (batch) job to be submitted from a remote site. Although the Internet has a protocol for RJE service, it is not popular because many machines on the Internet support do time sharing instead of batch processing.

Remote LAN Access
The process of allowing branch offices, telecommuters, and traveling computer users to access the corporate LAN backbone over dedicated or dialed, digital or analog lines.

Remote Loopback
Loopback performed between an application and remotely located access equipment or application. The signal is sent from the application over the network to the remote access equipment or application, from where it is looped back to the originating equipment.

Remote Management
A management feature that uses bandwidth between sites over the management subchannel established by the AIM (Ascend Inverse Multiplexing) protocol. Any Ascend unit can control, configure, and obtain statistical and diagnostic information about any other Ascend unit; multi-level security assures that unauthorized personnel do not have access to remote management functions.

Remote Switching Module
A component of the 5ESS® Switch that enables exchange carriers to provide new digital services in a remote area. It provides basic switching and call handling functions locally but relies on a 5ESS Switch host located elsewhere to provide other functions.

In microelectronics technology, a layer of material that serves as the sensitive coating in a lithographic process of chip manufacture. Also called photoresist. See

An electronic device that limits the flow of current in a circuit.

Return loss
A comparison of impedance at the point of transmission and at termination.

A network topology where every node is connected to two others in a circle.

In wireless communications, the movement by a user among many cells or zones. The term implies that the system can locate the handset as it "roams" and provide continuing service.

A type of hunt group in which the incoming call hunts on a rotating basis for an available channel to ring and answer the call.

The path that data takes from its source network to its destination network.

An interconnection device that can connect individual LANs. Unlike bridges, which logically connect at OSI layer 2, routers provide logical paths at OSI layer 3. Like bridges, remote sites can be connected using routers over dedicated or switched lines to create WANs.

A device or setup that finds the best route between any two networks, even if there are several networks to traverse. (Contrast with bridge).

Routing Table
A list of destinations known to the router.Routing tables are built and used based on three protocols:
RIP - which continuously broadcasts routing updates every 30 seconds
ICMP - which can dynamically redirect packets to a more efficient route
ARP - which enables the Pipeline to respond to address queries with its own physical address

Rubber Bandwidth
A term used to describe a communications channel whose bandwidth can be increased or decreased without terminating and re-establishing the channel. Typically used with inverse multiplexing.