glossary

A-bit (active bit)

The bit in the frame relay frame header that indicates the status of the far end user device and the status of the PVC segment in the foreign network.

A-law

An analog to digital encoding scheme used to convert voice samples to an 8-bit data word used in CEPT E1 multiplex equipment. (See also m-law.)

ABR (Available Bit Rate)

ATM connection type for bursty traffic, such as data. Provides closed loop control of service rate that allows connections to use additional bandwidth when available. ABR may be used with ATM Traffic Management 4.0 standards VSVD flow congestion control, or with the proprietary ForeSight flow congestion control. (See also CBR and VBR.)

ACO (Alarm Cut Off)

A switch to turn off the audible alarm outputs from a node while leaving the visual alarm outputs unchanged.

adaptive voice

An optional feature that disables VAD from connections using it whenever there is excess bandwidth available to allow the normal encoded voice to be carried on the packet line. (See also VAD.)

ADPCM (Adaptive Differential Pulse Code Modulation)

A compression method that samples voice 8,000 times per second, and uses the changes between samples as the basis for compression. Increases the capacity of a T1 line from 24 to 48 channels.

ADTF (Allowed Cell Rate Decrease Factor)

Time permitted between sending RM cells before the rate is decreased to ICR.

AIT-E3 (ATM Interworking Trunk E3 Interface Card)

The AIT-E3 backcard provides an E3 interface for the BTM (IGX switch) ATM trunk cards.

AIT-T3 (ATM Interworking Trunk T3 Interface Card)

The AIT-T3 backcard provides a T3 interface for the BTM (IGX switch) ATM.

alternate routing

An automatic rerouting of a failed connection by a node to a new route through the network to maintain service.

AMI (Alternate Mark Inversion)

The line code used for T1 and E1 lines where the "1s" or "marks" on the line alternate between positive polarity and negative polarity.

arbiter

A BPX administration processor that polls each network port to control the data flow in and out of the crosspoint switch matrix.

ARI (Alarm Relay Interface Card)

An alarm interface back card for the IGX switches.

ARM (Alarm Relay Module)

An alarm front card for the IGX switch.

ASM (Alarm/Status Monitor Cards)

An alarm front card and back card set for the BPX switch.

ATM (Asynchronous Transfer Mode)

Data transmission that uses a very flexible method of carrying information, including voice, data, multimedia, and video between devices on a local or wide area network using 53-byte cells on virtual circuits. The 53 byte cell consists of data and a small header. (See also cell relay.)

ATM Edge LSR

A label switching router that is connected to the ATM-LSR cloud through LC-ATM interfaces. The ATM edge LSR adds labels to unlabeled packets and strips labels from labeled packets.

ATM-LSR

An ATM-LSR is a MPLS (Multiprotocol Label Switching) router in which packets are forwarded by switching cells rather than frames, and all packet interfaces are MPLS (Label) Controller-ATM interfaces.
A label switching router with a number of LC-ATM intefaces. The router forwards the cells from these interfaces using labels carried in theVPI and/or VCI field.

ATM Switched Virtual Circuits (SVCs)

A member of the INS product family that uses ATM SVC Server Shelves and software to enhance a Cisco WAN switching network with ATM switched virtual circuits.

ATM SVC Server Shelf

An adjunct processor used in the INS ATM SVC application to enhance traditional Cisco WAN switching networks with ATM switched virtual circuits. The ATM SVC Server Shelf is co-located with and connected to a BPX switch.

auxiliary port

An RS-232 port on the front panel of the SCC card used for connecting a printer or an out-dial modem. This port is a one-way, outgoing port.

B3ZS (Bipolar with Three Zero Suppression)

A protocol for T3 lines that converts a channel word with three consecutive zeros into a code which at the far end is converted back to three zeros.

B8ZS (Bipolar with Eight Zero Suppression)

A T1 line protocol that converts a channel word with eight consecutive zeros into a code which, at the far end, is converted back to eight zeros. Allows 64 Kbps clear channel operation while assuring the ones density required on the T1 line.

bandwidth reservation

A software feature that allows circuits to automatically become active (or "upped") at a specified time and date and downed at some later time and date. For circuits that do not need to be available 100% of the time.

B channel

In ISDN, a full-duplex, 64-kbps channel used to send user data. Also known as the bearer channel. Compare with D channel.

BCC

The switch control card in the BPX is the Broadband Control Card, with a 68040 processor..

BC-E1 (Backcard E1)

E1 interface card used on IGX switches.

BC-E3 (Backcard E3)

E3 interface card used on IGX switches.

BC-J1 (Backcard J1)

J1 interface card used on IGX switches.

BC-SR (Backcard Subrate)

Subrate interface card used onIGX switches.

BC-T1 (Backcard T1)

T1 interface card used on IGX switches.

BC-T3 (Backcard T3)

T3 interface card used on IGX switches.

BC-Y1 (Backcard Y1)

Y1 interface card used on IGX switches.

BDA (Bframe Destination Address)

The address of the slot.port.channel for which the Bframe is destined. This address is part of the Bframe header and is only used across the switch fabric locally in the node.

Bframe

The BPX frame is the 64-byte format for messages used to encapsulate ATM cells which are sent across the switch fabric.

bipolar violations

Presence or absence of extra "1" bits on a T1 transmission facility caused by interference or a failing line repeater. These extra or missing bits interrupts one of the rules for bipolar pairs of a digital transmission line.

BISDN (broadband ISDN)

ITU-T communication standards designed to handle high-bandwidth applications. Compare with ISDN.

BNI (BPX Network Interface Card)

The front card used to network BPX switches together and to connect to AXIS and IGX nodes configured as shelves. Supports T-3, E-3, and OC3 trunks carrying ATM cells.

BPX Switch

The Cisco Broadband Packet Exchange (BPX): A high-speed broadband, high-capacity ATM cell relay network switch from for private and public networks, with trunk and CPU hot standby redundancy.

BPX-LSR

An ATM label switch router consisting of a label switch controller (series 7200 or 7500 router) and a label controlled switch (BPX switch).

BRI (Basic Rate Interface)

ISDN interface composed of two B channels and one D channel for circuit-switched communication of voice, video, and data. Compare with PRI.

bundled connections

Frame relay connections grouping a number of ports into one permanent virtual circuit.

BTM (Broadband Trunk Module)

The BTM provides an ATM trunk interface for the IGX switch. The BTM operates in conjunction with a backcard, AIT-T3, or AIT-E3.

BXM

The Broadband Switch Module (BXM) cards are a series ATM port cards for the BPX switch: BXM-T3/E3, BXM-155, or BXM-622. These can be configured for either trunk or line (service access) modes. These cards and support ATM Traffic Management 4.0, including VSVD congestion flow control. Various port configurations are supported by the BXM card: 8¥DS3, 12¥DS3, 4¥OC-3, 8¥OC-3, 1¥OC-12 or 2¥OC-12. The Monarch chipset's architecture supports up to 64K bi-directional cross-connect legs per BXM card. The BXM has very flexible input and output queueing facilities, a SAR (Segmentation Assembly and Reassembly) capability, and a MIPS 4650 control processor.

CAS (Channel Associated Signalling)

A signalling mode in E1 transmission where the signalling bits for all 30 E1 channels are carried in timeslot 16. Timeslots 1 to 15 and 17 to 31 carry encoded voice bits only.

CBR (Constant Bit Rate)

ATM Connection type for constant bit rate traffic such as voice or synchronized data requiring a low variation in delay. (See also, VBR and ABR.)

CCDV (Compliant Cell Delay Variation)

A parameter utilized in defining ATM Constant Bit Rate service. The amount of delay that is acceptable between ATM cells for them to be accepted as compliant (usable).

CCITT (Consultive Committee for International Telephone and Telegraph)

An international telecommunications advisory committee established under the United Nations to recommend worldwide standards for data and voice communications.

CCS (Common Channel Signalling)

A carrier signalling mode in E1 transmission where signalling bits are not used. CCS typically separates user data from signalling information. A signalling channel is used to provide signalling for all other user data channels in the system.

CDVT (Cell Delay Variation Tolerance)

Controls time scale over which the PCR is policed.

Cell

A unit of data with a fixed number of bytes. For ATM the cell size is 53 bytes.

cell relay

A form of digital communications using fixed length cells consisting of data and a small header. IPX FastPacket was an early implementation of cell relay. The 53 byte ATM cell consists of data and a small header.

CEPT

CEPT is the European Conference of Posts and Telecommunications Administrations. This association is comprised of European Telecommunications service providers that participate in relevant areas of the work of CEN/CENELEC.

CGA (Carrier Group Alarm)

A major alarm condition for a T1 multiplexer or PABX that results in all channels being taken out of service.

channel

The logical end point for a connection.

circuit line

A T1 or E1 line that connects a user device, such as a PABX or channel bank to a switch. Carries customer DS0 voice and data circuits. (See also line.)

Cisco StrataView Plus

A Unix-based workstation and software used as a network management system (NMS) for Cisco WAN switching networks. It is part of the StrataSphere group. Provides a graphical user interface for configuration, maintenance, administration of the network. Collects and displays network statistics.

clear channel capability

When all eight bits of a channel word in the T1 line signal are available for transmitting customer data with no restrictions on content. Also referred to as 64 Kbps clear channel.

Cmax

A frame relay connection parameter that specifies the number of packets allowed in the initial burst of data after which the data bandwidth is reduced to the connection's minimum specified bandwidth.

CLLM

Consolidated Link Layer Management. A protocol used to transmit ForeSight messages across the frame relay NNI port.

CLP (Cell loss priority)

Cell loss Priority. CLP Hi and CLP Lo thresholds are configurable.

Complex Gateway

Refers to interworking of a connection with respect to the IGX nodes. For example, in a Frame Relay to ATM interworking, the Frame Relay data is extracted from FastPackets and transformed to ATM cells with redundant overhead bits discarded.

composite data rate

The sum of the data rates for all circuits transmitting on the same synchronous or frame relay data card.

control port

An RS-232 port on the face plate of a back card for a controller card (BCC, NPC, NPM.) that may used for connecting a control terminal. This port is bi-directional.

COS (Class of Service)

The priority assigned each user connection. Defines which circuits get rerouted first during a network failure.

COS Buffer

A buffer or queue that serves connections with similar QoS requirements. Also called "qbin" (though a qbin is a platform-specific instance, such as a BXM card, of the more general Class of Service Buffer (CoSB).

Class of Service (CoS) Buffer Descriptor Template

A component of a Service Class Template that contains Class of Service Buffer configurations indexed by CoSB number.
A qbin is a platform-specific (BXM in this case) instance of the more general Class of Service Buffer (or CosB).

CLI

There are two separate Command-Line Interfaces on the BPX-LSR: One on the BPX itself and one on the MPLS (Multiprotocol Label Switching) Controller. The Control Point integrate these into a single command line interface.

CommBus

The CommBus is the BPX's internal messaging protocol. The Switch Control Interface (SCI) that is used by PNNI on the Service Expansion Shelf (SES) is based on CommBus messaging accessed through interfaces to the BPX cards.

CoSB

See Class of Service (CoS) Buffer.

courtesy downing

A software feature that is used to conserve network bandwidth by automatically "downing" a voice connection when the signalling status indicates an inactive (on-hook) circuit. The circuit is automatically "upped" when the circuit becomes active.

CRC (Cyclical Redundancy Check)

A method of error checking that detects errors in a block of data. Unlike parity checks, the CRC can detect multiple data errors within the block and thus equipment using a CRC error check can derive a error rate.

crosspoint switch

A two-dimensional data switch type that is arranged in a matrix of all input connections along one axis and all output connections along the other axis. Each input and output line has a switch point where the two axis intersect that can be enabled (switch closed) or disabled (switch open). The central matrix switch providing the switching matrix for traffic routing by the BPX switch.

CSU (Channel Service Unit)

A network protection unit that terminates any T1 span line connected to the carrier's central office, providing receive direction regeneration and maintenance loopback for the 1.544 Mbps signal.

D4-format

A digital signal format with 24 eight-bit channels plus one synchronizing bit per T1 line. Channels are assigned in a straight, numeric sequence.

DACS (Digital Access and Control System)

Equipment, usually found in the telephone company central office, that is used to groom and retime the 24 channels in a DS1 signal. Individual DS0 channels can be cross-connected from one DS1 source and inserted in another DS1 source either with the same or with a different channel number.

DAS Server Shelf

The adjunct processor used in INS Dial-Up Frame Relay applications to provide frame relay dial-up and dial-backup circuits. The DAS Server Shelf is co-located with and connected to an IGX switch.

DCE (Data Communications Equipment)

As defined by the RS-232 standard, any device that transmits or receives information. Usually used with data terminal equipment (DTE, like a computer or network node).

D channel

A message-oriented ISDN signalling channel, typically carried in DS24 of a PRI on T1 facilities or TS16 of a PRI on E1 facilities. Compare to B channel.

DDS (Digital Data Service)

An AT&T dial-up data service offering for 2.4 to 56 Kbps over subscriber loop cable. Requires a Data Service Unit, DSU, at customer premise for interface to the DDS trunk.

Device Code

The first 8 bits of a FastPacket Address.

DFM (Data Frame Multiplexing)

An optional feature that saves data channel bandwidth by analyzing data channel content and suppressing repetitive data patterns.

Dial Access Switching

Another name for the INS Dial-Up Frame Relay application.

Dial-Up Frame Relay

An INS application that uses a DAS Server Shelf and software to enhance Cisco WAN switching networks with frame relay soft permanent virtual circuits (SPVCs) for dial-up dial-backup connections.

DLCI (Data Link Connection Identifier)

A field in a frame relay data packet that identifies the destination for the data.

domain

A grouping of nodes sharing common interests or attributes.

domain name

A unique name consisting of the letter "D" immediately followed by a number (1-8) delineated by a "." (period) from the node name (1-8 characters maximum). Example: D1.alpha.

domain number

A number from 1-8 assigned with the cnfdmn command. The number assigned is part of the domain name.

DPNSS

Digital Private Network Signalling System. A common-channel message-oriented signalling protocol commonly used by private branch exchanges (PBXes). The INS Voice Network Switching application supports DPNSS signalling.

DS0 (Digital Signal 0)

A 64 Kbps channel used to transmit encoded voice and/or data. There are 24 DS0 channels in a circuit T1 (DS1) line. DS0 data is transmitted using one or more DS0 circuits in a T1 or E1 circuit line.

DS0A

An extension of DS0 that defines the format for assembling various low-speed data circuits (1.2 to 19.6 Kbps) into a single 64 Kbps DS0 channel.

DS1 (Digital Signal 1)

A digital transmission standard that carries 24 individual channels in a bipolar, high-speed line signal at 1.544 Mbps. DS1 signal level is ±3V.

DSI (Digital Speech Interpolation)

An algorithm that analyzes DS0 voice bits for non-speech codes. Suppresses these bits to conserve packet line bandwidth and inserts a code to indicate to the far end that these bits have been removed. Similar to DFM for data channels. Also, referred to as VAD (Voice Activity Detection).

DTE (Data Terminal Equipment)

As defined by the RS-232 standard, any device that generates or utilizes information. (See also, DCE.)

E1

European transmission service at the rate of 2.048 Mbps.

E3

Transmission service at a rate of 34.368 Mbps.

ECN (Explicit Congestion Notification)

A frame relay feature to signal the onset of network congestion to external devices. Sets FECN and BECN bits in frame relay header to indicate forward and backward congestion.

SES

The Service Expansion Shelf is the controller on which the BPX's PNNI implementation runs. It is SPARC-based.

Fast EIA

Same as interleaved EIA. Seven data circuit control leads in each direction are transmitted in alternating bytes with data. For fast control lead response to data being turned on and off but with a sacrifice in packet line bandwidth

FBTC (Frame Based Traffic Control)

An AAL5 frame based traffic control that provides the possibility of discarding the whole frame, not just one compliant cell. This avoids wasting bandwidth by continuing to send the cells in a frame once a cell has been found to be non-compliant.

Feeder

A feeder is a small switch that acts as an extension shelf, typically with lower-bandwidth interfaces, for a larger switch. The larger switch is referred to as the Routing node with the feeder(s) it supports. Collectively, the feeder(s) and routing node form a type of supernode.

FGCRA (Frame Based Generic Cell Rate Algorithm)

An enhancement option to GCRA that allows an entire frame to be discarded if any of its cells are non-compliant, rather than transmitting a partial frame over the network.

flat network

A non-structured network, a network in which there are no junction nodes or domains.

foreign network

An adjacent network that is owned and managed by a different party than the one that owns the local network.

ForeSight

A proprietary optional feature that uses feedback techniques to dynamically allocate extra bandwidth to frame relay and ATM connections when the network bandwidth is available and not used by other connections. (See also VSVD.)

frame forwarding

A software feature allowing point-to-point frame relay type connection for various data applications that do not conform to the Frame Relay Interface Specification.

frame relay connection class

A tag for a frame relay circuit which indicates the class of service to be provided for this connection. Parameters associated with a connection class include minimum information rate guaranteed, peak information rate expected, maximum network delay, and so on.

FRI (Frame Relay Interface Card)

The backcard for an FRM (IGX switch) card. The FRI provides V.35, X.21, T1, or E1 interfaces.

FRM (Frame Relay Module)

An IGX frame relay front card that supports 1-4 data ports, and in single-port mode, operates up to 2.048 Mbps. The card is used in conjunction with FRI-V.35, X.21, T1, or E1 backcards.

FRM-2 (Frame Relay Module)

An IGX frame relay front card that provides an interface to the frame relay Port Concentrator Shelf (PCS). The card is used with the FRI-2-X.21 backcard which connects to the PCS.

Frame Relay Service

A packet interface data transmission protocol used for connecting widely-separated LANs. Characterized by long intervals of no data to be sent interspersed with bursts of large volumes of data; sometimes referred to as "bursty data".

FRTT (Fixed Round Trip Time)

The sum of the fixed and propagation delays from the source to a destination and back.

Full Status Report

A message sent across the NNI indicating the A-bit status of all connections routed across this NNI frame relay port.

gateway

A node configured to handle both T1 and E1 packet and circuit lines for direct interface international circuits.

GCRA (Generic Cell Rate Algorithm)

GCRA is a "continuous leaky-bucket" process that monitors the cell depth in the input queue for each PVC to determine whether to admit a new cell to the network without setting the Cell Loss Priority bit.

global addressing

A frame relay addressing convention that uses the DLCI to identify a specific end device somewhere else in the frame relay network. In a global addressing scheme, the DLCI is a unique number for each port in the network.

grouped connections

Frame relay connections grouping a number of ports onto one permanent virtual circuit. Similar to bundled connections except the grouped connections do not have to be contiguous, nor do they all have to be added simultaneously.

HDB3 (High Density Bipolar Three)

A line interface for E1, similar to B8ZS for T1, which eliminates patterns with eight or more consecutive zeros. Allows for 64 Kbps clear channel operation and still assure the ones density required on the E1 line.

HDP (High Speed Data PAD)

An IGX front card that supports one to four medium speed, synchronous data channels.

IGX Switch

A multi-service, multi-band ATM cell relay network switch for private and public networks.

Intelligent Network Server (INS)

INS is the broad name for a range of products that enhance traditional Cisco WAN switching networks. These products include Dial-Up Frame Relay, Voice Network Switching, and ATM Switched Virtual Circuits.

interleaved EIA

Same as "Fast EIA".

ISDN (Integrated Services Digital Network)

A service provided by the telephone company or OCC that supports combined customer voice and data connections over the twisted pair subscriber loop. Requires special equipment at the customer premise and a connecting central office switch that is capable of providing ISDN.

IPX Switch

A narrowband cell relay network switch from for private and public networks.

J1

A. multiplexed 24-channel circuit line to a PBX conforming to the Japanese TTC-JJ-20 circuit standard. Similar to E1, it operates at 2.048 Mbps.

junction node

A node handling inter-networking of domains.

junction trunk

A packet line connecting junction nodes.

LC-ATM Interface

A Label Controlled ATM interface is a MPLS (Multiprotocol Label Switching) interface where labels are carried in the VPI/VCI bits of ATM cells, and where VC (virtual circuit) connections are established under the control of MPLS (Multiprotocol Label Switching) control software.

LCN

Each interface card in a BPX has a certain number of Logical Connection Numbers. A Logical Connection Number is used for each cross connect leg through the card in question. "LCN" is often roughly synonymous with "cross connect leg". In VSI temrinology, an LCN is an example of an Other End Reference.

LCON

The logical connection used to represent an individual routing entity.

LDM (Low Speed Data Module)

An IGX data front card that supports up to 8 synchronous or asynchronous data ports. When used with an LDI4/DDS, an LDP can provide 56-Kbps Digital Data Service (DDS) interfaces to the IGX switch.

line

Connects a user device to a service interface, for example, a router to an AUSM card, a data line to a data card, a frame relay line to an FRP or a port concentrator, or a T1 or E1 line to a CDP card.

link

The network connection between two nodes.

LMI (Local Management Interface)

The protocol and procedures for control of frame relay connections. Used for configuration, flow control, and maintenance of these connections.

local addressing

A frame relay addressing convention that uses the DLCI to identify the frame relay port at the interface between the user device and the frame relay network. In local addressing, a particular DLCI is used only at the local FR connection. The DLCI may be reused at any other node in the network.

local alarm

An alarm indicating that the associated T1 line is down due to a local failure of its receive path.

local bus

An utility bus (LB/0 or LB/1) located on the midplane, which provides the electrical connections between various front and back cards. For example, the front and back cards of the Low Speed Data PAD group (LDP and LDI) plug into this utility bus.

Logical Interface

Each physical interface and every virtual trunk endpoint on a platform is represented to the VSI controllers as a different logical interface with partitions, and other VSI configuration. Logical Interface numbers are 32-bit with a format which is, in general, known only to the platform.

logical port

A frame relay circuit consisting of either 1, 6, 24 (T1,) or 31 (E1) contiguous DSO's on a T1 or E1 physical port.

LSR

Label Switching router, which is an MPLS (Multiprotocol Label Switching) router.

major alarm

A local or remote failure that is affecting operation of the network.

MBS (Maximum Burst Size)

Maximum number of cells which may burst at the PCR but still be compliant.

MCR (Minimum Cell Rate)

The minimum cell rate that is supported by an ATM connection for an ABR connection.

MIR (Minimum Information Rate)

The minimum information rate that is supported by a frame relay connection.

minor alarm

A local or remote failure that is not affecting operation of the network, but nonetheless should be investigated.

n+1 redundancy

A redundancy method in which a group of cards share the same standby redundant card.

Network-to-Network Interface (NNI)

The protocol at a frame relay port that serves as a bidirectional interface between a local Cisco WAN switching network and a separate and independent "other" network.

node

An IGX or BPX switch serving as a connection point to the network. At a node, connections from service lines are routed to trunks for transmission to other nodes in the network.

NPM (Network Processor Module)

Micro-processor based system controller front card that contains the software used to operate the IGX switch.

Nrm

Maximum number of cells a source may send for each forward RM cell, that is, an RM cell must be sent for every Nrm-1 data cells.

NTM (Network Trunk Module)

IGX front card that coordinates fastpacket trunk traffic to another node via a number of backcards: T1, E1, Y1, and subrate (RS449, X.21, and V.35).

OC-3

Standard optical transmission facility rate of 155.20 Mbps.

OCC (Other Common Carrier)

In the United States, reference to all the other telecommunications companies providing various transmission services other than AT&T.

packet line

Packet line referred to a line used to carry FastPackets between nodes in a network. The term in these documents is replaced by the more general "trunk" which is defined as a physical link from node to node, node to shelf, or node to network. The trunk may be one that supports 24-byte FastPackets (packet trunk), or one that supports 53 byte ATM cells (cell trunk).

packet switching

A system that breaks data strings into small units (packets), then individually addresses and routes them through the network.

PAD (Packet Assembler/Disassembler)

A device that converts a serial data stream into discrete packets in the transmit direction and converts the received packets back into a serial data stream. Adds header information in the transmit packet to allow it to be routed to the proper destination.

partially-interleaved EIA

One control lead in each direction, generally RTS-CTS, is transmitted in same byte as seven data bits. For fast control lead response to data being turned on and off.

PBX (private branch exchange)

Digital or analog telephone switchboard, classified as customer premise equipment (CPE), used to connect private and public telephone networks.

PCM (Pulse Code Modulation)

The system for transmitting telephone signals digitally. Voice is sampled 8000 times per second and converted to an 8-bit digital word.

PCR (Peak Cell Rate)

The maximum rate for an ATM connection at which cells are allowed into the network.

PCS (Port Concentrator Shelf)

The PCS is an external shelf that expands the capacity of the FRP card. The PCS is sued with the FRM-2 (IGX switch) card to 44 frame relay connections. The PCS connects to the FRI-2.X.21 backcard.

PIR (Peak Information Rate)

The peak level in bits per second allowed for a frame relay connection.

PLCP (Physical Layer Convergence Protocol)

A protocol defined for use with Switched Megabit Data Service. Used on DS3 ATM trunks in the BPX switch.

PLPP (Physical Layer Protocol Processor)

A custom VLSI processor used in the T3 ATM port interface of the BPX BNI card to handle the coding and decoding of the PLCP bit structure. Functions handled by the PLPP include header check sequence generation and checking, DS3 framing, and optional payload scrambling/descrambling.

plesiochronous network

A network where there is more than one source of network timing. The multiples sources must be operating at the same frequency but are not phase locked (synchronous) with each other.

PNNI

Private Network-to-Network Interface controller software that runs on the SES hardware platform. The term PNNI controller and SES may be used interchangeably.

Port

Refers to a signal connection on a data back card that interfaces to a customer circuit or data device. The number of ports on a card ranges from 1 to 8 depending on the particular card type.

"Port" is synonymous with "Interface."

The VSI makes no distinction between trunk ports and end-point ports.

PRI (Primary Rate Interface)

An ISDN interface to primary rate access. Primary rate access consists of a single D channel for signalling and 23 (T1) or 30 (E1) B (bearer) channels for user data. A PRI is typically carried on T1 or E1 facilities.

privilege level

A level between 1 and 6 that is assigned to each command. Each operator is assigned a privilege level by the system administrator. The operator may only access and execute commands equal to or lower than his or her own privilege level. Level 1 is the highest and level 6 is the lowest.

PVCs

Permanent Virtual Connections (circuits). Connections that are assigned but not connected until data is sent, thereby not using bandwidth when idle.

QQ.921/Q.931

ITU-T specifications for the ISDN use network interface (UNI) data link layer.

QSIG

A common-channel message-oriented signalling protocol, defined by the European Telecommunications Standard Institute (ETSI), commonly used by private branch exchanges (PBXes). The INS Dynamic Network Switching application supports QSIG signalling to the Cisco WAN switching network.

queue

A buffer that is used to temporarily hold data while it waits to be transmitted to the network or to the user.

RRIF (Rate increase factor)

Controls the amount by which the cell transmission rate may increase upon receipt of an RM cell.

RDF (Rate decrease factor)

Controls the amount by which the cell transmission rate may decrease upon receipt of an RM cell.

red alarm

Another name for local alarm as the local alarm lamp on most digital transmission equipment is red in color.

remote alarm

An alarm indicating that the associated T1 line is down due to a receive line failure on another node. (See also yellow alarm.)

RPS (repetitive pattern suppression)

Also called data frame multiplexing (DFM). An option for data circuits where repeating strings of data are replaced on the packet line by a single occurrence of the data string and a code that indicates to the far end how may repetitions of the string was being transmitted. Used to conserve network bandwidth.

robbed bit signaling

A type of signaling used on T1 lines where the signaling bits for each channel are substituted for the least significant voice bit in each channel word during frames 6 and 12.

Routing Node

In tiered networks terminology, a routing node is a larger switch to which one or more feeders is attached. Collectively, the feeder(s) and routing node form a type of supernode.

RS-232

A physical and electrical interface standard for a low-speed, unbalanced, serial, data interface adopted by the EIA committee on data communications. Generally used for data circuits operating at data rates below 56 Kbps.

RS-422/423

Another EIA standard electrical interface for serial data circuits operating at higher data rates than RS232. RS422 is a balanced interface; RS423 is unbalanced. Uses RS-449 for the physical interface (connector).

RS-449

The physical interface for the RS422 and R423 electrical interfaces. Contains the Processor Controller Card and the PCC utility bus, and provides system timing and control via the system bus.

SSAR (Segmentation and Reassembly)

The process of breaking a dataframe containing data from a number of virtual paths or circuits apart so that the individual paths/circuits can be switched by reassembling the data into a new frame with a different sequence.

SCM (System Clock Module)

An IGX backcard that works in conjunction with the NPM. The SCM provides a centralized clock generation function and provides serial and LAN port interfaces.

SCR (Sustainable Cell Rate)

Rate above which incoming cells are either tagged or discarded.

SDP (Synchronous Data PAD)

SDI (Synchronous Data Interface)

The back card for the HDM (IGX switch) cards. The SDI is available with V.24, X.21, and V.35 interfaces.

Service Class (aka Service Type)

A concept for grouping connections that share a common set of traffic characteristics and QoS requirements. The terms "service class" and "service type" are sometimes used interchangeably. In this release, there are some major service categories, such as VbrRt, VbrNRt, CBR, Abr, and Ubr, and under these major service categories are service types such as VbrRt1, VbrRt2, VbrRt3, and VbrNRt1, VbrNrt2, and so on. Sometimes the terms service class and service type are used interchangeably.

Service Class database

The collection of data items that support the service class template concept, and implemented on a per-VI basis on the BXM. These items include a copy of the specific Service Class Template selected for a VI, as well as additional data as required.

Service Class Template (SCT)

A set of data structures that map VSI service types to sets of pre-configured VC and Qbin parameters. Consists of two sub-components—a VC Descriptor Template and a Class of Service Buffer descriptor template.

Simple Gateway

Refers to FastPacket to ATM interworking with respect to the IGX node. In the simple gateway mode, FastPackets are encapsulated in their entirety into cells. Compare with complex gateway.

SIU (Serial Interface Unit)

A set of circuits common to all BPX cards used for transmitting and receiving via the crosspoint switch.

Soft PVC

A PVC in the INS Dial-Up Frame Relay application that is dormant in the networks database until it is activated by a call into the network by a user.

spanning tree

An network topology in which there is only one path available between any two sources in a frame relay multicast group. Spanning trees are required to prevent frames broadcast from a single source to multiple receptors from circulating endlessly around the network a result of frame relay circuits not having properly closed loops.

speech detection

Determining the presence or absence of speech for Digital Speech Interpolation. Performed in either the CDP card.

split clock

A data clocking configuration where the timing for the transmit data is obtained from one source (such as a user device) and the timing for the receive data is obtained from another source (such as a switch).

Status Enquiry

A message transmitted by a FR NNI port requesting an updated status from the attached foreign network. This message is used as a heartbeat to detect when a port has failed.

StrataBus

On the BPX switch, contains crosspoint wiring used to carry ATM trunk data between both the network interface and service interface modules and the crosspoint switch as well as providing control, clock, and communications.

subrate data

Multiple low-speed data circuits carried in a single DS0 timeslot.

superrate data

Single high-speed data circuit carried in multiple DS0 timeslots.

SCR (Sustained Cell Rate)

Long term limit on the rate a connection can sustain.

SVC (switched virtual circuit)

A virtual circuit that is dynamically established on demand and torn down when transmission is complete. SVS do not need to reserve any network resources when they are not in use. Called a switched virtual connection in ATM terminology. Compare with PVC.

T1

The standard US. multiplexed 24-channel voice/data digital span line. Operates at a data rate of 1.544 Mbps.

T3

Transmission service at DS3 rate of 44.736 Mbps.

TBE (Transient Buffer Exposure)

The negotiated number of cells that the network would prefer to limit the source to send during the start-up period.

TDM (time division multiplexing)

The process of combining several communication channels by dividing a channel into time increments and assigning each channel to a timeslot.

timestamp

A field in certain FastPacket formats that indicates the amount of time the packet has spent waiting in queues during the transmission between its source and destination nodes. Used to control the delay experienced by the packet.

Trm

An upper bound on the time between RM cells for an active source, i.e., RM cell must be sent at least once every Trm msec.

trunk

A physical link between two nodes. The trunk may be one that supports 24-byte FastPackets (packet trunk), or one that supports 53 byte ATM cells (cell trunk.)

trunk conditioning

A set of signalling and information bits that indicate a DS1 line failure.

trunk queues

The buffers in packet line cards (NTC, TXR) where the various FastPackets are queued up for transmission over the packet line(s). The buffers attempt to prioritize each packet so it experiences minimum delay.

m-law

An analog to digital encoding scheme used to convert voice samples to an 8-bit data word used in D3/D4 T1 multiplex equipment.

UBR

Unspecified Bit Rate.

UNI (User to Network Interface)

The user to network interface, used for ATM connection to CPE. Compare with NNI.

UPC (Usage Parameter Control)

A general procedure for controlling the rate of user data applied to an ATM network. There are a number of different algorithms for performing UPC. See also GCRA.

USART (Universal Synchronous/Asynchronous Receiver Transmitter)

A single-chip device used in certain applications that allows microprocessors to communicate with input/output (I/O) devices.

User to Network Interface (UNI)

The protocol at a frame relay port that passes information between the network and the user device attached to the port.

V.21

A CCITT interface standard often used for data transmission over modems.

V.35

A data communications interface standard adopted by the CCITT. Often used for data circuits operating at 56 Kbps and above.

VAD (Voice Activity Detection)

Used to statistically compress voice by not sending packets in the absence of speech.

VBR (Variable Bit Rate)

Connection type for variable bit rate traffic such as bursty data. Compare with CBR and ABR.

VC

ATM and Frame Relay traffic is carried in Virtual Channels which are set up between adjacent ATM or Frame Relay switches before data transmission occurs. An ATM link between switches may support up to 2²⁸ different VCs, although a small number of VCs is reserved for special purposes.

VCI

Each VC within a specific Virtual Path on a link has a unique Virtual Channel Identifier, which is a 16-bit number .

VC Descriptor Template

A component of a Service Class Template which contains platform-specific VC configurations that are indexed primarily by service type. Together with a Class of Service Buffer (CoSB) descriptor template, it defines a Service Class Template (SCT).

VC_Q

Frame relay buffer allocation parameter that specifies the maximum queue size reserved in the FRP card for the FR connection.

virtual circuit

A circuit that acts like it is an individual transmission path but is actually shared with other circuits over a single transmission path. Compare with PVCs.

Virtual Trunks

A Virtual Trunks is a Virtual Path Connection which appears to VSI masters as ordinary trunk (except that the trunk supports 64k VCs at most). In a VSI platform, a virtual trunk endpoint has its own logical interface.

VNS

The adjunct processor used in the INS Voice Network Switching application. The VNS is co-located with and connected to an IGX switch.

Voice Network Switching

An INS application used to provide voice or data switched virtual circuits over a Cisco WAN switching network for PBXes using either QSIG or DPNSS signalling.

VP, VPC, VPI

A Virtual Path is a bundle of 2¹⁶ Virtual Connections with the same Virtual Path Identifier, that is, the first 12 bits of the VPCI. Most ATM switches can switch VPs using only a single cross-connect (instead of up to 2¹⁶ ). An end-to-end sequence of VPs cross-connected at the intermediate switches is a Virtual Path Connection.

VPCI

Each VC on a link has a unique Virtual Path and Channel Identifier, which is a 28-bit number. The VPCI consists of a 12-bit VPI concatenated with a 16-bit VCI.

VSI

Virtual Switch Interface: this is a proposed common control interface to all Cisco MSSBU switches. It embodies both connection management and switch configuration discovery capabilities.

VSI 2

Virtual Switch Interface, Protocol Version 2: this is revision 2 of a proposed common control interface to all MSSBU switches. It embodies both connection management and switch configuration discovery capabilities.

VSI Controller

A controller, such as a PNNI SVC Controller, Portable AutoRoute or Label Switch Controller, which controls a switch using the VSI.

VSI Master

A VSI master process implementing the master side of the VSI protocol in a VSI controller. Sometimes the whole VSI controller might be referred to as a "VSI Master", but this is not strictly correct.

1) A device that controls a VSI switch, for example, a VSI Label Switch Controller.

2) A process implementing the master side of the VSI protocol.

VSI Slave

1) A switch (in the "Single Slave model") or a port card (in the "Multiple Slave Model") that implements the VSI.

2) A process implementing the slave side of the VSI protocol.

VS/VD (Virtual Source/Virtual Destination)

ATM Forum Traffic Management 4.0 method of providing congestion flow control for ABR connection types. Resource Management (RM) cells are used to convey management information between sources and destinations.

vt (virtual terminal)

An control terminal that is the active control terminal at one node but is physically attached to another node.

WAN (Wide Area Network)

A network of transmission circuits generally spanning a large region or territory for transmission of voice and data between widespread end users. An IGX/BPX network is an example of a WAN.

X.21

A CCITT standard for data interfaces transmitting at rates up to approximately 2 Mbps.

X.25

A commonly-used standard that defines the protocol for low-speed data packet networks.

XON/XOFF

A simple communications protocol for controlling the flow of data from one device to another. An XON sent from a receiving device indicates it is ready to accept data and the transmitting device may begin to output data. An XOFF from the receiving device indicates that it can no longer store any more data and the transmitting device should temporarily cease transmitting.

YY-cable(s)

A short adapter cable forming an electrical branch (thus the term Y) for connecting a single customer data or trunk connection to two identical back cards to provide hardware redundancy on the IGX switch.

Y-cable redundancy

A redundancy type used in the switch when a 1:1 card redundancy is implemented using a split or Y-cable for the data connection between the user device and the primary and standby interface card.

Y1

A digital trunk conforming to the Japanese "Y" circuit standard, for use as a packet line. Similar to T1, it operates at 1.544 Mbps.

yellow alarm

Another name for remote alarm as the remote alarm lamp on digital transmission equipment is always yellow in color.