glossary

10BaseT

A physical layer communications specification for 10 Mbps, baseband data transmission over a twisted-pair copper wire. Commonly used for Ethernet.

AAL1

ATM Adaptation Layer Type 1

A protocol used to translate higher layer services into the size and format of an ATM cell. AAL1 functions in support of constant bit rate, time-dependent traffic such as voice and video.

AAL5

ATM Adaptation Layer Type 5

A protocol used to translate higher layer services into the size and format of an ATM cell. AAL5 functions, similar to AAL-3/4, in support of variable bit rate, delay-tolerant connection-oriented data traffic requiring minimal sequencing or error detection support.

AIS

Alarm Indication Signal

1) A signal that replaces the normal traffic signal when a maintenance alarm indication has been activated.

2) (ATM) An all ones signal sent down or up stream by a device when it detects an error condition or receives an error condition or receives an error notification from another unit in the transmission path.

AM

Alarm Management

AMI

Alternate Mark Inversion

A line coding technique, in which successive ones (marks) are inverted. It is used to meet the ones density requirements of T1 facilities. AMI supports only one bit per BAUD and imposes sever provisioning constraints. B8ZS is the preferred coding for T1 lines.

APS

Automatic Protection Switching

A method of allowing transmission equipment to automatically recover from failures such as a cable cut.

ASCII

American Standard Code for Information Interchange

Coded character set to be used for the general interchange of information among information-processing systems, communications systems, and associated equipment. The standard code (characters 0 through 127) includes controls codes, upper- and lower-case letters, numerals, punctuation marks, and commonly used symbols.

Async

Asynchronous

A network where transmission system payloads are not synchronized and each network terminal runs on its own clock.

ATM

Asynchronous Transfer Mode

A broadband switching and multiplexing, connection-oriented, high-performance and cost-effective integrated technology for supporting B-ISDN services (e. g., multimedia) under certain QoS guarantees. Since no clock control is necessary, it is called asynchronous. Information is transmitted at very high rates (up to hundreds of Mbps) in fixed-length packets called cells. Traffic streams can be distinguished according to different QoS classes. The ATM Reference Model describes the various functions, services, protocols, and standards encompassed by the ATM technology.

1) High bandwidth, low-delay packet switching and multiplexing technique used to transfer voice, video, images, and character-based data.

2) Method of formatting, multiplexing, cross-connecting, and switching information in 53-byte cells (see below).

3) Transmission method that operates over various physical media including Synchronous Optical Network (SONET), Synchronous Digital Hierarchy (SDH), and digital cross-connect (DCS) systems.

ATM is recently commercialized switching and transmission technology that is one of a general class of packet technologies that relay traffic by way of an address contained within the first five bits of a standard 53-bit-long packet or cell. ATM-based packet transport was specifically developed to allow switching and transmission of mixed voice, data, and video at varying rates. The ATM includes a protocol that specifies how diverse kinds of traffic, mixed voice, data, and video are transformed into standardized packets whose transport can be managed uniformly within the network. The ATM format can be used by many different information systems including LANs.

B3ZS

Binary 3-Zero Substitution

A T1 carrier line coding format used to accommodate ones density requirements for clear channel transmission.

B8ZS

Binary 8-Zero Substitution

A T1 carrier line coding format used to accommodate ones density requirements for clear channel transmission

BERT

Bit Error Rate Test(er)

A data transmission quality measurement. A known pattern of bits is transmitted; errors received are counted to figure the Bit Error Rate (BER). The BER is the ratio of received erroneous bits to total bits received. Usually expressed in a power of 10. Sometimes called Block Error Rate Tester.

BITS

Building Integrated Test

A clock, or a clock with an adjunct, in a building that supplies DS1 and/or composite clock timing reference to all other clocks in that building.

BTU

British thermal unit

A quantity measurement of heat energy.

CAC

Connection Admission Control

Connection Admission Control is defined as the set of actions taken by the network during the call set-up phase (or during call re-negotiation phase) in order to determine whether a connection request can be accepted or should be rejected (or whether a request for re-allocation can be accommodated).

CAS

Channel Associated Signaling

A form of circuit state signaling in which the circuit state is indicated by one or more bits of signaling status sent repetitively and associated with that specific circuit.

CBR

Constant Bit Rate

An ATM service category which supports a constant or guaranteed rate to transport services such as video or voice as well as circuit emulation which requires rigorous timing control and performance parameters.

CDV

Cell Delay Variation

CDV is a component of cell transfer delay, induced by buffering and cell scheduling. Peak-to-peak CDV is a QoS delay parameter associated with CBR and VBR services. The peak-to- peak CDV is the ((1-a) quantile of the CTD) minus the fixed CTD that could be experienced by any delivered cell on a connection during the entire connection holding time. The parameter "a" is the probability of a cell arriving late. See CDVT.

CES

Circuit Emulation Service

The ATM Forum circuit emulation service interoperability specification specifies interoperability agreements for supporting Constant Bit Rate (CBR) traffic over ATM networks that comply with the other ATM Forum interoperability agreements. Specifically, this specification supports emulation of existing TDM circuits over ATM networks.

CPE

Customer Premises Equipment

All telecommunication terminal equipment located on the customer's premises, except coin-operated telephones.

End user equipment that resides on the customer's premise which may not be owned by the local exchange carrier.

All telecommunications terminal equipment located on the customer premises, except coin operated telephones.

Usually refers to key systems, private branch exchanges (PBXs), telephones, and computers.

CPS

Cells Per Second

A measure of the throughput of an ATM device as measured in the number of cells it can handle in a one second interval.

Craft

Craft Interface

An interface accessible locally to an equipment for use by the installer.

D4

A type of framing configuration used on T1 lines.

Diagnostic Loopback

DS0

Digital Signal 0

Standard North American telecommunications industry digital signal format with bit rate of 64 kilobits/second. Can transmit a single uncompressed voice conversation.

DS1

Digital Signal 1

Standard North American telecommunications industry digital signal format with bit rate of 1.544 megabits/second. Also referred to as T1.

DS3

Digital Signal 3

Standard North American telecommunications industry digital signal format with bit rate of 44.736 megabits/second. Also referred to as T3.

DSX-1

Digital Signal Cross-Connect Level 1

A DSX that crossconnects circuits at the DS1 rate.

EMI

Electromagnetic Interference

Interference, generally at radio frequencies, that is generated inside systems as contrasted to radio-frequency interference coming from sources outside a system.

ESF

Extended Superframe Format

A transmission structure consisting of 24 DS1 frames. The frame overhead bit positions are shared between an extended superframe frame alignment signal, a CRC, and a data link.

Ethernet

A local area network technology used for connecting computers, printers, workstations, terminals, etc. within the same building. Operates over twisted wire or coaxial cable at speeds up to 100 megabits per second. The most popular LAN technology.

FDL

Facilities Data Link

A 4 Kbps channel, carried within a T1 link, used for managing the circuit.

FDOS

First Day of Service

FERF

Far End Reporting Failure

Same as RDI.

FTP

File Transfer Protocol

An IETF protocol used for transferring files over an IP-based network.

G.703

ITU-T Recommendation G.703, "Physical/Electrical Characteristics of Hierarchical Digital Interfaces" provides specifications for various high speed interfaces including E1 & E3.

G.704

ITU-T Recommendation G.704, "Synchronous Frame Structures Used at Primary and Secondary Hierarchy Levels."

GMT

Greenwich Mean Time

Mean solar time at the meridian of Greenwich. Also known as Greenwich civil time, universal time, Z time, Zulu time.

GR-63-CORE

Bellcore specification covering safety and environmental issues. A part of NEBS.

GR-1089-CORE

Bellcore spec for EMI & surge protection.

HEC

Header Error Control

Using the fifth octet in the ATM cell header, ATM equipment may check for an error and corrects the contents of the header. The check character is calculated using a CRC algorithm allowing a single bit error in the header to be corrected or multiple errors to be detected.

IETF

Internet Engineering Task Force

One of two technical working bodies of the Internet Activities Board. It meets three times per year to set the technical standards that run the Internet. The primary developer of new TCP/IP standards for the Internet.

ILMI

Integrated Local Management Interface

An ATM Forum-defined component of the Network Management System (NMS) based on SNMP that can provide configuration, performance, and fault management information for circuits between ATM components (DTEs, switches). It operates over a reserved VBR-nrt virtual circuit between the IME in a DTE and the IME in an ATM access switch or between the IMEs in two ATM switches.

I/O

Input/Output

Pertaining to all equipment and activity that transfers information into and out of a computer.

IP

Internet Protocol

A connectionless protocol that operates at the network layer (layer 3) of the OSI model.

Originally developed by the Department of Defense to support interworking of dissimilar computers across a network. Provides connectionless, datagram-based network layer (layer 3) functions across heterogeneous networks and networking technologies. This protocol works in conjunction with TCP and UDP and often identified together as TCP/IP or UDP/IP. IP does not provide error reporting back to the source when routing or other anomalies occur; the ICMP protocol does.

IWF

Interworking Functions

LED

Light Emitting Diode

A semiconductor diode that converts electric energy efficiently into spontaneous and non-coherent electromagnetic radiation at visible and near-infrared wavelengths by electroluminescence at a forward-based pn junction.

LOF

Loss of Frame

A condition at the receiver or a maintenance signal transmitted in the PHY overhead indicating that the receiving equipment has lost frame delineation. This is used to monitor the performance of the PHY layer.

LOP

Loss of Pointer

A condition at the receiver or a maintenance signal transmitted in the PHY overhead indicating that the receiving equipment has lost frame delineation. This is used to monitor the performance of the PHY layer.

LOS

Loss of Signal

A condition at the receiver or a maintenance signal transmitted in the PHY overhead indicating that the receiving equipment has lost the received signal. This is used to monitor the performance of the PHY layer.

Mbit/s

Megabits per second

One million bits of information per second.

NE

Network Element

A system that supports at least NEFs and may also support Operation System Functions/Mediation Functions. An ATM NE may be realized as either a standalone device or a geographically distributed system. It cannot be further decomposed into managed elements in the context of a given management function.

NEBS

Network Equipment Building Standard

Extensive set of performance, quality, environmental and safety requirements developed by Bellcore. NEBS compliance is often required by telecommunications service providers such as RBOCs and Interexchange Carriers for equipment installed in their switching facilities.

NRT

Non-Real Time

Nx DS0

A communications channel composed of n DS0 subchannels, where n can range from 1 to 24.

OAM

Operations, Administration, and Maintenance

Typically a group of network management functions that provide network fault indication, performance information, and data and diagnosis functions.

Operations and Maintenance

A set of administrative and supervisory actions regarding network performance monitoring, failure detection, and system diagnosis and protection.

OC3

Optical Carrier Level 3

An optical fiber line carrying 155.52 Mbps. It is the equivalent of three OC1 facilities and the fundamental transmission rate for SONET. OC3 is the equivalent of STM-1.

OOF

Out of Frame

Refer to Loss of Frame.

PCR

Peak Cell Rate

The Peak Cell Rate, in cells/sec, is the cell rate which the source may never exceed.

PM

Performance Monitoring

PNNI

Private Network-Network Interface

A routing information protocol that enables extremely scalable, full function, dynamic multi-vendor ATM switches to be integrated in the same network.

PVC

Permanent Virtual Circuit

A permanent association between two DTEs established by configuration. A PVC uses a fixed logical channel to maintain a permanent association between the DTEs.

Permanent (or Provisional) Virtual Connection

A virtual connection (VPCC/VCC) provisioned for indefinite use in an ATM network and established by the network management system (NMS).

QoS

Quality of Service

The capability of a network to define and negotiate levels of performance, reliability and predictability between the user and the provider. QoS usually provides a guaranteed amount of bandwidth, or a never-to-exceed latency, or a combination of the two.

RDI

Remote Defect Indication

RJ11

Registered Jack 11

A four conductor modular jack. It is the most common modular jack in the world.

RS232

A standard developed by the Electronic Industries Association that governs the interface between data processing and data communications equipment. It is widely used to connect microcomputers to peripheral devices.

SDH

Synchronous Digital Hierarchy

The ITU-TSS International standard for transmitting information over optical fiber.

Based partly on SONET, an ITU standard for the interworking of ANSI and ITU transmission technologies.

The European standard for high-speed data communications over fiber-optic media. The transmission rates range from 155.52 Mbps to 2.5 Gbps.

SF

SuperFrame

A DS1 framing format in which 24 DS0 timeslots plus a coded framing bit are organized into a frame which is repeated 12 times to form the superframe.

SNAP

Subnetwork Access Protocol

A version of the IEEE local area network logical link control frame similar to the more traditional data link level transmission frame that allows use of nonstandard higher-level protocols. SNAP is an Internet protocol that operates between a network entity in the end system and specifies a standard method of encapsulating IP datagrams and ARP messages on IEEE networks.

A protocol that allows IP traffic to be delivered or routed through a subnetwork. SNAP frames are encapsulated IP diagrams where a header and trailer (used by the underlying subnetwork) are attached.

SNMP

Signaling Network Management Protocol

The most common method by which network management applications can query a management agent using a supported Management Information Base.

An IETF-defined standard for exchanging management information between network management systems and network components. It is implemented in SNMP-based management systems and in SNMP Agents (code) managed network components.

SONET

Synchronous Optical Network

An ANSI-defined standard for high-speed and high-quality optical transmission. It has been recognized as the North American standard for SDH.

The electronics and network architecture which enable transmission of voice, video, and data (multimedia) at very high speeds. This self-healing ring network offers advantages over older linear networks in that a cut line or equipment failure can be overcome by rerouting calls within the network. If the line is cut, the traffic is simply reversed and sent to its destination around the other side of the ring.

SRTS

Synchronous Residual Time Stamp

A clock recovery technique in which difference signals between source timing and a network reference timing signal are transmitted to allow reconstruction of the source timing at the destination.

SVC

Switched Virtual Circuit

A connection established via signaling. The user defines the endpoints when the call is initiated.

T1

Transmission Level 1

A Transmission system used to support DS1. It supports a transmission rate of 1.544 Mbps using AMI encoding. T1 is usually implemented over 4-wire metallic facilities and was originally used for transmission between central offices within the core network. It was later tarrifed as a service offering for connecting PBXs and constructing private networks. It has also been used extensively for connecting Remote Access Nodes to the core network. The use of AMI places severe restrictions on the deployment of T1. AMI cannot operate on facilities with bridged taps and requires repeaters 3,000 feet from the CO and every 6,000 feet afterward. It also occupies a spectrum from 0 to 1,544,000 Hz (1.5 MHz bandwidth) with a signal peak at 750 kHz and so corrupts the cable spectrum that only a single T1 line can be placed in a 50 pair cable bundle and a cable bundle containing a T1 line cannot be placed adjacent to another cable bundle. The use of T1 within the core network has been almost totally superseded by fiber cable and HDSL is replacing T1 for DLC use. Various xDSL technologies are vying to replace it's use in the subscriber loop.

Telnet

Telnet is the Internet standard protocol for remote terminal connection service. It is defined in RFC 854 and extended with options by many other RFCs.

Trunk

1) Group of circuits that carry call traffic in and out of the switch.

2) Circuit or channel connecting two exchanges or two switching devices.

3) Circuit capable of being switched at both ends.

UNI

User-Network Interface

An interface point between 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 per ATM Forum UNI documents. The standard adopted by the ATM Forum to define connections between users or end stations and a local switch.

VBR

Variable Bit Rate

An ATM Forum defined service category which supports variable bit rate data traffic with average and peak traffic parameters.

VCC

Virtual Channel Connection

A concatenation of VCLs that extends between the points where the ATM service users access the ATM layer. The points at which the ATM cell payload is passed to, or received from, the users of the ATM Layer (i.e., a higher layer or ATM-entity) for processing signify the endpoints of a VCC. VCCs are unidirectional.

VCI

Virtual Channel Identifier

A unique numerical tag as defined by a 16 bit field in the ATM cell header that identifies a virtual channel, over which the cell is to travel.

Vdc

Volts direct current

VPI

Virtual Path Identifier

An eight bit field in the ATM cell header which indicates the virtual path over which the cell should be routed.

VT-100

Virtual Terminal-100

A low-speed, asynchronous terminal manufactured by DEC. It has become a generic term for any such device.