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Networking Solution Glossary

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2/4-Wire Analog - 2-wire circuit: A telephone line or trunk that has just one current loop (one pair- most commonly FXS, FXO or E&M). 4-wire circuit: A circuit having two pairs, TX and RX. Provides higher quality signal than two-wire circuit, most commonly E&M. RAD voice interfaces can usually be ordered in any of these formats.

AC/DC - Support for AC (usually 90-240 VAC) and DC (usually -48 VDC).

Address - A coded representation of the origin or destination of data.

Agent - In SNMP, this refers to the managed system.

Alternate Routing - In switching, alternate routing is the choice of the next-best path when the best path is blocked.

Analog- A continuous wave or signal (such as human voice).

Analog Transmission - The transmission of a continuously variable signal, as opposed to a discrete (digital) one.

AR (Access Rate) - The data rate of the user access channel in a Frame Relay network. The speed of the access channel determines how fast (maximum rate) the end user can inject data into a Frame Relay network.

Asynchronous Transmission - A transmission method that sends units of data one character at a time. Characters are preceded by start bits and followed by stop bits, which provide synchronization at the receive terminal. Also called start-stop transmission.

Balanced Line - A circuit in which neither side of the line is grounded. This minimizes crosstalk or noise pickup between pairs in the same cable.

Baud - Unit of signaling speed equivalent to the number of discrete conditions or events per second. If each signal event represents only one bit condition, baud rate equals bps (bits per second).

Bc (Committed Burst Size) - The maximum amount of data (in bits) that the network agrees to transfer during a time interval Tc.

BISDN (Broadband Integrated Services Digital Network) - The next generation of ISDN, which is intended to carry digital data, voice and video. ATM provides the switching fabric and SONET or SDH the physical transport.

Bit- The smallest unit of information in a binary system. Represents either a one or zero ("1" or "0").

Bit Interleaving/Multiplexing - A process used in time division multiplexing where individual bits from different lower speed channel sources are combined (one bit from one channel at a time) into one continuous higher speed bit stream.

Bps (Bits Per Second) - A measure of data transmission rates in serial transmission.

Bridge - A device interconnecting local area networks at the OSI Data Link Layer, filtering and forwarding frames according to media access control (MAC) addresses.

Bus- A transmission path or channel. A bus is typically an electrical connection with one or more conductors, where all attached devices receive all transmissions at the same time.

Byte - A group of bits (normally 8 bits in length).

CC (Continuity check) - A cell used periodically to check whether a connection is idle or has failed. Continuity checking is one of the OAM function types for fault management.

CDV (Cell Delay Variation) - A QoS parameter that measures the difference between the transfer delay of a single cell (CTD) and the expected transfer delay. This parameter is important for time-sensitive virtual circuits such as CBR and VBR-RT.

Cell- In asynchronous transfer mode (ATM), a 53-byte fixed-length data packet.

Channel- A path for electrical transmission between two or more points. Also called a link, line, circuit or facility.

Channel Bank - Equipment that connects multiple voice channels to high speed links by performing voice digitization and time division multiplexing. Voice is converted to a 64 kbps signal (24 channels into 1.544 Mbps in countries offering T1 services, such as the U.S.A.; 30 channels into 2.048 Mbps in countries offering E1 or CEPT services, such as in Europe).

Channelized T1/E1 - T1 or E1 service that is divided into individual 64 kbps channels (or channels that are multiples of 64 kbps such as a 256 kbps channel made from four 64 kbps channels), as opposed to unchannelized service, which uses the entire bandwidth of the T1 (1.544 Mbps) or E1 (2.048 Mbps). Channelized T1 or E1 lines can consist of switched lines with in-band signaling or leased lines.

CIR (Committed Information Rate) - A term used in Frame Relay which defines the information rate the network is committed to provide the user.

Clock- A term for the source(s) of timing signals used in synchronous transmission.

Compression - Any of several techniques which reduce the number of bits required to represent information in data transmission or storage, thereby conserving bandwidth and/or memory.

Configuration Planner - RADview configuration planner makes it possible to configure products in advance, without having to connect to a physical product.

Congestion - A state in which the network is overloaded and starts to discard user data (frames, cells or packets).

Control Characters - In communications, any extra transmitted characters used to control or facilitate data transmission (for example, characters associated with polling, framing, synchronization, error checking or message delimiting).

Control Signals - Signals passing between one part of a communications system and another (such as RTS, DTR or DCD), as part of a mechanism for controlling the system.

CRC (Cyclic Redundancy Check) - A data transmission error-detection scheme. A polynomial algorithm is performed on the data, and the resultant checksum is appended at the end of the frame. The receiving equipment performs a similar algorithm.

Crosstalk- An undesirable condition that happens when a communication from one line can be heard on another independent line. This is usually caused by inductive or capacitive coupling, or by an electrical short circuit between lines.

CSMA/CD (Carrier Sense Multiple Access/Collision Detection) - In this protocol, stations listen to the bus and only transmit when the bus is free. If a collision occurs, the packet is retransmitted after a random time-out. CSMA/CD is used in Ethernet.

CSU/DSU (Channel Service Units/Data Service Units) - CSUs and DSUs are usually grouped together. They convert carrier line signals to digital signals.

CTD(Cell Transfer Delay) - A QoS parameter that measures the average time for a cell to be transferred from its source to its destination over a virtual connection (VC). It is the sum of any coding, decoding, segmentation, reassembly, propagation, processing and queuing delays.

CTS (Clear To Send - ) A modem interface control signal from the data communications equipment (DCE) indicating to the data terminal equipment (DTE) that it may begin data transmission.

Current Loop - Method of data transmission. A mark (binary "1") is represented by current on the line, and a space (binary "0") is represented by the absence of current.

Data- Information represented in digital form, including voice, text, facsimile and video.

Data Interface Variety - More than one serial or LAN interface option is available for this product. Please refer to data sheet for product selection. Interfaces available from RAD include: V.35, RS-530, V.36/RS-449, X.21, V.24/RS-232, G.703, HSSI, Ethernet, Fast Ethernet, Token Ring, and FDDI.

Data Link Layer - Layer 2 of the OSI model. The entity which establishes, maintains, and releases data-link connections between elements in a network. Layer 2 is concerned with the transmission of units of information, or frames, and associated error-checking.

dB (Decibel) - A unit used to measure relative increase or decrease in power, voltage or current, using a logarithmic scale.

Digital- The binary ("1/0") output of a computer or terminal. In data communications, an alternating, non-continuous (pulsating) signal.

Drop-and-Insert - A process of adding data (insert) to a T1 data stream, or terminating data (drop) from a T1 data stream to other devices connected to the drop-and-insert equipment.

DS-1 (Digital Signal Level 1) - Framing specification used in transmitting digital signals at 1.544 Mbps on a T1 facility or 2.048 Mbps on an E1 facility.

DS2 Channel - For a T1 line, a 6.312 Mbps channel that consists of four DS1 channels; for an E1 line, an 8.45 Mbps channel that consists of four DS1 channels.

DS3 Channel - A 44.736 Mbps line consisting of seven DS2 channels. A DS3 line is also called a T3 line.

DTR (Data Terminal Ready) - A modem interface control signal sent from the DTE to the modem, usually telling the modem that the DTE is ready to transmit data.

DXI (Data Exchange Interface) - Protocols used between routers and DSUs for SMDS and ATM.

Encapsulation - Encapsulating data is a technique used by layered protocols in which a low level protocol accepts a message from a higher level protocol, then places it in the data portion of the lower-level frame. The logistics of encapsulation require that packets traveling over a physical network contain a sequence of headers.

Enterprise Network - An information infrastructure, often combining private and public facilities, to cover all of the locations operated by a single company or corporate enterprise with a single communications fabric.

Ethernet- A local area network that connects devices like computers, printers and terminals. Ethernet operates over twisted-pair or coaxial cable at speeds of 10 or 100 Mbps.

Fiber - Hair-thin glass structures, usually cylindrical in shape, for transmitting optical signals.

Fiber Optics - A transmission medium consisting of thin glass filaments. Light beams travel through the fiber optic line, carrying large amounts of data over long distances.

Full Duplex - Circuit in telecommunications with channels for both sending and receiving.

Gateway- Gateways are points of entrance and exit from a communications network. Viewed as a physical entity, a gateway is that node that translates between two otherwise incompatible networks or network segments. Gateways perform code and protocol conversion to facilitate traffic between data highways of differing architecture.

Glare- A signal the switch sends when you attempt to place an outgoing call and answer an incoming call simultaneously.

GUI (Graphical User Interface) - Pronounced "gooey," this software interface is based on pictorial representations and menus of operations and files. Opposite of command line interface.

Hybrid Circuit - A transformer arrangement that permits the transmitted and received signals to be separated and then put back together. Used to connect a 2-wire line to a 4-wire line.

Internet Address - Also known as an IP address. This is a 32-bit hardware-independent address assigned to hosts using the TCP/IP protocol suite.

Inverse Multiplexing - A method in which the inverse multiplexer slices the data stream into equal portions and transmits each portion over an available circuit. The receiving end adjusts for network-induced delay and reassembles the data packets into their proper order. Therefore, an inverse multiplexer allows lower speed channels across a network to be combined into a single, higher speed data stream.

IP (Internet Protocol) - A networking protocol for providing a connectionless service to the higher transport protocol. It is responsible for discovering and maintaining topology information and for routing packets across homogeneous networks. Combined with TCP, it is commonly known as the TCP/IP platform.

IP Address - An address that uniquely identifies each host on a network or Internet.

LAN (Local Area Network) - A network that interconnects devices over a geographically small area, typically in one building or part of a building. The most popular LAN type is Ethernet, a 10 Mbps standard that works with 10BaseT, 10Base2, or 10Base5 cables.

Leased Line - A permanent telephone connection between two points that is rented for exclusive use from a telecommunications common carrier. In contrast to a normal dial-up connection, a leased line is always active. Typically, the highest speed data connections require a leased line connection. For example, a T1 channel is a type of leased line that provides a maximum transmission speed of 1.544 Mbps.

LMI (Local Management Interface) - An ITU-T defined interface to provide an ATM or Frame Relay end system user with network management information.

MAC (Media Access Control) - A protocol that defines the way workstations gain access to transmission media, most widely used in reference to LANs. For IEEE LANs, the MAC layer is the lower sublayer of the data link layer protocol

MAN (Metropolitan Area Network) - A network that provides regional connectivity within a metropolitan area (such as a city). MANs are wider than LANs, but more local than LANs

Modem (Modulator-Demodulator)- A device used to convert serial digital data from a transmitting DTE to a signal suitable for transmission over extended distances. It also reconverts the transmitted signal to serial digital data for acceptance by a receiving DTE

NDIS (Network Driver Interface Specification) - A standard interface specification for PC network adapter cards developed by Microsoft to separate the communications protocol from the PC networking hardware. The driver is able to run multiple protocol stacks concurrently

Network - (1) An interconnected group of nodes. (2) A series of points, nodes, or stations connected by communications channels; the collection of equipment through which connections are made between data stations

Network Layer - A layer in the OSI reference model. The network layer provides address resolution and routing protocols. Address resolution enables the network layer to determine a unique network address for a node. Routing protocols allow data to flow between networks and reach their proper destination. Examples of network layer protocols are Address Resolution Protocol (ARP), Datagram Delivery Protocol (DDP), Internet Control Message Protocol (ICMP), Interior Gateway Protocol (IGP), Internet Protocol (IP), Internetwork Packet Exchange (IPX) and Packet Layer Protocol (PLP).

Node - A point of interconnection to a network

NT1 (Network Terminator Type 1) - An ISDN BRI line terminating device at the subscriber's location that provides line maintenance access, timing and echo cancellation. NT1s may be built into other pieces of equipment or stand alone

Outpulse - Sequence of addressing information, automatically generated and dialed. The RAD VoIP and VoFR gateways (MP-2100H and MAXcess) use voice switching to reach the terminating gateway and then DTMF outpulsing to complete the final leg of a voice call

Packet- An ordered group of data and control signals trthrough a network, as a subset of a larger message

Protocol- A formal set of conventions governing the formatting and relative timing of message exchange between two communicating systems

PVP (Permanent Virtual Path) - A set of permanent virtual channels (PVCs) that exists between two cross points

Register- A storage device capable of receiving and holding a number of digits

Repeater - A device which automatically amplifies, restores or reshapes signals to compensate for distortion and/or attenuation prior to retransmission

RMON- The Remote Monitoring MIB, which allows a network monitoring device to be configured and read from remote locations

Router- An interconnection device that connects 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.

Routing - The process of selecting the most efficient circuit path for a message

SLIP (Serial Link Internet Protocol) - An Internet protocol for host dial- up connection. SLIP frames are encapsulated IP datagrams in which SLIP adds just a few bytes of control data.

SNA (Systems Network Architecture)- IBM's layered communications protocol architecture.

SNMP (Simple Network Management Protocol) - The Internet standard protocol for managing nodes on an IP network.

SONET (Synchronous Optical Network) - A standard for using optical media as the physical transport for high speed long haul networks. SONET basic speeds start at 51.84 Mbps and go up to 2.5 Gbps.

Space- In telecommunications, the absence of a signal. Equivalent to a binary 0.

Synchronous Transmission - Transmission in which data bits are sent at a fixed rate, with the transmitter and receiver synchronized.

T1 - A digital transmission link with a capacity of 1.544 Mbps 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.

T3 - A digital transmission link with a capacity of 45 Mbps, or 28 T1 lines.

TCP/IP (Transmission Control Protocol/Internet Protocol) - A protocol platform, known also as the Internet protocol suite, that combines both TCP and IP. Widely used applications, such as Telnet, FTP and SMTP, interface to TCP/IP.

Telnet- The virtual terminal protocol in the Internet suite of protocols. It lets users on one host access another host and work as terminal users of that remote host. 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.

TFTP (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.

Throughput- The amount of information transferred through the network between two users in a given period, usually measured in the number of packets per second (pps).

Traffic Management - Set of actions and operations performed by the network to guarantee the operability of the network exercised in the form of traffic control and flow control. ATM traffic management includes the following: CAC, FRM, NRM, Priority Control (PC), Traffic Shaping (TS) and UPC, the goal of which is to maintain the required QoS.

UBR (Undefined Bit Rate) - An economical best-effort class of service.

UDP (User Datagram Protocol) - A connectionless transport protocol without any guarantee of packet sequence or delivery. It functions directly on top of IP.

UNI (User Network Interface) - The interface, defined as a set of protocols and traffic characteristics, between the CPE and the Frame Relay or ATM network.

VC (Virtual Connection) - A connection established between end users, where packets are forwarded along the same path and bandwidth is not permanently allocated until it is used.

VPN (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.

WAN (Wide Area Network)- A network that typically spans nationwide distances and usually utilizes public telephone networks.


n. noun(n): a word in a sentence that is an object, person or place, for example apartment, music, cat, Anthony, Paris:adj. adjective(n): a word that tells us more about a noun, for example big, green,

beautiful: 'Tara has beautiful hair.'v. verb(n): the 'action' word in a sentence, for example to speak, to work: 'You speak English.' Irregular verb forms are shown in square brackets [ ].

adv. adverb(n): a word that tells us more about a verb, for example quietly, softly, quickly: 'Ram walks quickly.'



Take a fun and remember!

Nothing is as easy as it looks.

Everything takes longer than you think.

Anything that can go wrong will go wrong.

If there is a possibility of several things going wrong, the one that will cause the most damage will be the one to go wrong. Corollary: If there is a worse time for something to go wrong, it will happen then.

If anything simply cannot go wrong, it will anyway.

If you perceive that there are four possible ways in which a procedure can go wrong, and circumvent these, then a fifth way, unprepared for, will promptly develop.

Left to themselves, things tend to go from bad to worse.

If everything seems to be going well, you have obviously overlooked something.

Nature always sides with the hidden flaw.

It is impossible to make anything foolproof because fools are so ingenious.

Whenever you set out to do something, something else must be done first.

Every solution breeds new problems.

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