Glossary

A card protection scheme that pairs a working card with a protect card of the same type in an adjacent slot. If the working card fails, the traffic from the working card switches to the protect card. When the failure on the working card is resolved, traffic reverts back to the working card if this option is set. This protection scheme is specific to electrical cards.

An electrical-card protection scheme that allows a single card to protect several working cards. When the failure on the working card is resolved, traffic reverts back to the working card.

An optical-card protection scheme that pairs a single working card with a single dedicated protect card.

Points where network devices can access the network.

Bit combination used to describe the portion of an IP address that refers to the network or subnet and the part that refers to the host. Sometimes referred to as mask. See also subnet mask.

Add/drop multiplexer. ADM allows a signal to be added into or dropped from a SONET span.

1. Generally, software that processes queries and returns replies on behalf of an application.

2. In a network management system, a process that resides in all managed devices and reports the values of specified variables to management stations.

Access Identifier. An access code used in TL1 messaging that identifies and addresses specific objects within ONS nodes. These objects include individual pieces of equipment, transport spans, access tributaries, and others.

Alternate Mark Inversion. Line-code format used on T1 circuits that transmits Ones by alternate positive and negative pulses. Zeroes are represented by 01 during each bit cell and ones are represented by 11 or 00, alternately, during each bit cell. AMI requires that the sending device maintain ones density. Ones density is not maintained independently of the data stream. Sometimes called binary-coded alternate mark inversion.

Automatic Protection Switching. SONET switching mechanism that routes traffic from working lines to protect lines if a line card failure or fiber cut occurs.

Autonomous Message Tag. ATAG is used for TL1 message sequencing.

Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3.

Binary 8-zero Substitution. A line-code type, used on T1 circuits, that substitutes a special code whenever 8 consecutive zeros are sent over the link. This code is then interpreted at the remote end of the connection. This technique guarantees Ones density independent of the data stream. Sometimes called bipolar 8-zero substitution.

Part of a network that acts as the primary path for traffic that is most often sourced from, and destined for, other networks.

A synchronous transfer signal that carries different sets of traffic on different spans at the same time.

Bit Error Rate. Ratio of received bits that contain errors.

Bidirectional Line Switched Ring. SONET ring architecture that provides working and protection fibers between nodes. If the working fiber between nodes is cut, traffic is automatically routed onto the protection fiber.

Speed at which bits are transmitted, usually expressed in bits per second.

Building Integrated Timing Supply. A single building master timing supply that minimizes the number of synchronization links entering an office. Sometimes referred to as a Synchronization Supply Unit.

Dense wavelength division multiplexing (DWDM) wavelengths are broken into two distinct bands: red and blue. DWDM cards for the ONS 15454 operate on wavelengths between 1530.33nm and 1542.94nm in the blue band. The blue band is the lower frequency band.

Device that connects and passes packets between two network segments that use the same communications protocol. In general, a bridge will filter, forward, or flood an incoming frame based on the MAC address of that frame.

Data packet that is sent to all nodes on a network. Broadcasts are identified by a broadcast address. Compare with multicast and unicast. See also Broadcast address.

Special address reserved for sending a message to all stations. Generally, a broadcast address is a MAC destination address of all ones.

Undesirable network event in which many broadcasts are sent simultaneously across all network segments. A broadcast storm uses substantial network bandwidth and, typically, causes network time-outs.

Common physical signal path composed of wires or other media across which signals can be sent from one part of a computer to another.

The C2 byte is the signal label byte in the STS path overhead. This byte tells the equipment what the SONET payload envelope contains and how it is constructed.

Basic Unit of ATM switching and multiplexing. Cells contain identifiers that specify the data stream where they belong.

Controlled environment vault. An underground room that houses electronic and/or optical equipment in controlled temperature and humidity.

In Ethernet, the result of two nodes transmitting simultaneously. The frames from each device impact and are damaged when they meet on the physical media.

A mechanism for allocating contiguous bandwidth for payload transport. Through the use of concatenation pointers, multiple OC-1s can be linked together to provide contiguous bandwidth through the network, from end to end.

A set of physical or logical contacts that operate together to extend the speech and signal channels in a switching network.

Correlation tag. A unique identifier given to each input command by the TL1 operator. When an ONS 15327 or ONS 15454 system responds to a specific command, it includes the command's CTAG in the reply. This eliminates discrepancies about which response corresponds to which command.

The previous name of the Cisco Transport Controller (CTC).

Cisco Transport Controller. A Java-based program that allows a user to provision and manage ONS 15327s and ONS 15454s using an Internet browser.

Cisco Transport Manager. A Java-based network management tool used to support large networks of Cisco 15000-class equipment.

Data communications channel. Used to transport information about operation, administration, maintenance, and provisioning (OAM&P) over a SONET interface. DCCs can be located in section DCC (SDCC) or line overhead (LDCC).

Separates multiple multiplexed input streams from a common physical signal back into multiple output streams. See also Multiplexing.

Digital signal cross-connect frame. A manual bay or panel where different electrical signals are wired. A DSX permits cross-connections by patch cords and plugs.

Dense Wave Division Multiplexing. A technology that increases the information carrying capacity of existing fiber optic infrastructure by transmitting and receiving data on different light wavelengths. Many of these wavelengths can be combined on a single strand of fiber.

Erbium Doped Fiber Amplifier. A form of fiber optical amplification that transmits a light signal through a section of erbium-doped fiber and amplifies the signal with a laser pump diode. EDFA is used in transmitter booster amplifiers, in-line repeating amplifiers, and in receiver preamplifiers.

Electromagnetic Interference. Interference by electromagnetic signals can reduce data integrity and increase error rates on transmission channels.

The wrapping of data in a particular protocol header.

The part of messaging that varies in composition from one transmittal step to another. It identifies the message originator and potential recipients, documents its past, directs its subsequent movement by the message transfer system (MTS), and characterizes its content.

Express Orderwire. A permanently-connected voice circuit between selected stations for technical control purposes.

An Ethernet data switch. Ethernet switches increase the aggregate LAN bandwidth by allowing simultaneous switching of packets between switch ports. Ethernet switches subdivide previously-shared LAN segments into multiple networks with fewer stations per network.

A timing reference obtained from a source external to the communications system, such as one of the navigation systems. Many external timing references are referenced to Coordinated Universal Time (UTC).

A falling threshold is the counterpart to a rising threshold. When the number of occurrences drops below a falling threshold, this triggers an event to reset the rising threshold. See also rising threshold.

Fiber Distributed Data Interface. LAN standard, defined by ANSI X3T9.5, specifying a 100-Mbps token-passing network using fiber-optic cable, with transmission distances of up to 2 km. FDDI uses a dual-ring architecture to provide redundancy.

Logical grouping of information sent as a data-link layer unit over a transmission medium. Often refers to the header and trailer, used for synchronization and error control that surrounds the user data contained in the unit.

Occurs when the external timing sources have been disabled and the ONS node is receiving timing from its Stratum 3 level internal timing source.

Gigabit Interface Converter. A hot-swappable input/output device that plugs into a Gigabit Ethernet port to link the port with the fiber optic network.

The physical removal and insertion of a card.

High Level Data Link Control. Bit-oriented, synchronous, data-link layer protocol developed by ISO. HDLC specifies a data encapsulation method on synchronous serial links using frame characters and checksums.

Part of IP address used to address an individual host within the network or subnetwork.

The process of replacing a failed component while the rest of the system continues to function normally.

1. Hardware or software device that contains multiple independent but connected modules of network and internetwork equipment. Hubs can be active (where they repeat signals sent through them) or passive (where they do not repeat, but merely split, signals sent through them).

2. In Ethernet and IEEE 802.3, an Ethernet multiport repeater, sometimes called a concentrator.

Used for external sensors such as open doors, temperature sensors, flood sensors, and other environmental conditions.

1. Connection between two systems or devices.

2. In routing terminology, a network connection.

Internet Protocol. Network layer protocol in the TCP/IP stack offering a connectionless internetwork service. IP provides features for addressing, type-of-service specification, fragmentation and reassembly, and security.

32-bit address assigned to host using TCP/IP. An IP address belongs to one of five classes (A, B, C, D, or E) and is written as 4 octets separated by periods (dotted decimal format). Each address consists of a network number, an optional subnetwork number, and a host number.

Object-oriented programming language developed at Sun Microsystems to solve a number of problems in modern programming practice. The Java language is used extensively on the World Wide Web, particularly for applets.

Automatic protection switching bytes. K bytes are located in the SONET line overhead and monitored by equipment for an indication to switch to protection.

Local Area Network. High-speed, low error data network covering a relatively small geographic area. LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited area. Ethernet, FDDI, and Token Ring are widely used LAN technologies.

Liquid Crystal Display. An alphanumeric display using liquid crystal sealed between two pieces of glass. LCDs conserve electricity.

Bridge that performs MAC address learning to reduce traffic on the network. Learning bridges manage a database of MAC addresses and the interfaces associated with each address. See also MAC address learning.

Refers to the segment between two SONET devices in the circuit. The line layer deals with SONET payload transport, and its functions include multiplexing and synchronization. Sometimes called a maintenance span.

A node that derives its clock from the SONET lines.

The difference between the output power and receiver power of an optical signal expressed in dB. Link refers to an optical connection and all of its component parts (optical transmitters, repeaters, receivers, and cables).

The network communications channel is intact.

Test that sends signals then directs them back toward their source from some point along the communications path. Loopback tests are often used to test network interface usability.

Local Orderwire. A communications circuit between a technical control center and selected terminal or repeater locations.

Standardized data-link layer address that is required for every port or device that connects to a LAN. Other devices in the network use these addresses to locate specific ports in the network and to create and update routing tables and data structures. MAC addresses are six bytes long and are controlled by the IEEE. Also known as the hardware address, MAC-layer address, and physical address.

Service that stores the source MAC address of each received packet so that future packets destined for that address can be forwarded only to the bridge interface where that address is located. This scheme helps to minimize traffic on the attached LANs. See also learning bridge and MAC address.

A security level that limits user access to maintenance options only. See also Superuser, Provisioning User, and Retrieve User.

A network node that contains an SNMP agent and resides on a managed network. Managed devices include routers, access servers, switches, bridges, hubs, computer hosts, and printers.

In network management, a network device that can be managed by a network management protocol. Sometimes called an MIB object.

A logical association between one set of values, such as addresses on one network, with quantities or values of another set, such as devices on another network.

Management Information Base. Database of network management information that is used and maintained by a network management protocol such as SNMP or CMIP. The value of a MIB object can be changed or retrieved using SNMP or CMIP commands, usually through a GUI network management system. MIB objects are organized in a tree structure that includes public (standard) and private (proprietary) branches.

Single packets copied by the network and sent to a specific subset of network addresses.

Generates section and line overhead, and converts electrical/optical signals when the electrical/optical card is transmitting.

Scheme that allows multiple logical signals to be transmitted simultaneously across a single physical channel. Compare with Demultiplex.

Network Element. In an Operations Support System (OSS), a single piece of telecommunications equipment used to perform a function or service integral to the underlying network.

Generic term used to describe systems or actions that help maintain, characterize, or troubleshoot a network.

Part of an IP address that specifies the network where the host belongs.

Network Management System. System that executes applications that monitor and control managed devices. NMSs provide the bulk of the processing and memory resources required for network management.

Endpoint of a network connection or a junction common to two or more lines in a network. Nodes can be processors, controllers, or workstations. Nodes, which vary in routing and other functional capabilities, can be interconnected by links, and serve as control points in the network. Node is sometimes used generically to refer to any entity that can access a network. In this manual the term "node" usually refers to an ONS 15327.

Operations, Administration, Maintenance, and Provisioning. Provides the facilities and personnel required to manage a network.

Optical Carrier. Series of physical protocols (OC-1, OC-2, OC-3, and so forth), defined for SONET optical signal transmissions. OC signal levels put Synchronous Transport Signal (STS) frames onto fiber-optic lines at a variety of speeds.

A device that amplifies an optical signal without converting the signal from optical to electrical and back again to optical energy.

An opto-electric circuit that detects incoming lightwave signals and converts them to the appropriate signal for processing by the receiving device.

Equipment that establishes voice contact between a central office and carrier repeater locations.

Used to drive visual or audible devices such as bells and lights. Output contacts can control other devices such as generators, heaters, and fans.

Logical grouping of information that includes a header containing control information and (usually) user data. Packets are most often used to refer to network-layer units of data. The terms datagram, frame, message, and segment are also used to describe logical information groupings.

Components that do not require external power to manipulate or react to electronic output. Passive devices include capacitors, resisters, and coils.

The segment between the originating equipment and the terminating equipment. This path segment can encompass several consecutive line segments or segments between two SONET devices.

Portion of a cell, frame, or packet that contains upper-layer information (data).

Pulse Code Modulation. Transmission of analog information in digital form through sampling and encoding with a fixed number of bits.

Packet internet grouper. ICMP echo message and its reply. Often used in IP networks to test the connection to a network device.

Path-protected mesh network. PPMN extends the protection scheme of a unidirectional path switched ring (UPSR) beyond the basic ring configuration to the meshed architecture of several interconnecting rings.

Routing feature that divides data packets into two queues: one low-priority and one high-priority.

A CTC security level that allows the user to perform provisioning and maintenance options only. See also Superuser, Maintenance user, and Retrieve user.

In routing, a backlog of packets waiting to be forwarded over a router interface.

A CTC security level that allows the user to retrieve and view information but not set or modify parameters. See also Superuser, Maintenance user, and Provisioning user.

A process that sends electrical interfaces back to the original working card after the card comes back online.

The number of occurrences (collisions) that must be exceeded to trigger an event.

Remote Network Monitoring. Allows network operators to monitor the health of the network with a Network Management System (NMS). RMON watches several variables, such as Ethernet collisions, and triggers an event when a variable crosses a threshold in the specified time interval.

Network layer device that uses one or more metrics to determine the optimal path that network traffic should use. Routers forward packets from one network to another based on network-layer information.

The ability of SONET rings to provide automatic network backup with 100% redundancy so if a point of failure occurs on the fiber ring, the service continues.

Errors in the SONET signal exceed the threshold for normal operations but are less than the threshold for signal failure.

Errors in the SONET signal exceed the threshold defined for failure.

Simple Network Management Protocol. Network management protocol used almost exclusively in TCP/IP networks. SNMP monitors and controls network devices and manages configurations, statistics collection, performance, and security.

Simple Network Time Protocol. Using an SNTP server ensures that all ONS network nodes use the same date and time reference. The server synchronizes alarm timing during power outages or software upgrades.

A soft reset reloads the operating system, application software, etc., and reboots the card. It does not initialize the ONS 15327 ASIC hardware.

Synchronous Optical Network. High-speed synchronous network specification developed by Telcordia Technologies, Inc. and designed to run on optical fiber. STS-1 is the basic building block of SONET. Approved as an international standard in 1988.

Loop-free subset of a network topology. See also STA and STP.

Synchronous Payload Envelope. A SONET term describing the envelope that carries the user data or payload.

Synchronous Status Messaging. A SONET protocol that communicates information about the quality of the timing source using the S1 byte of the line overhead.

Spanning-Tree Algorithm. An algorithm used by the spanning tree protocol to create a spanning tree. See also Spanning tree and STP.

Alarms that are currently active.

A route that is manually entered into a routing table. Static routes take precedence over routes chosen by all dynamic routing protocols.

Spanning Tree Protocol. Bridge protocol that creates a spanning tree to enable a learning bridge to work dynamically around loops in a network topology. See also Spanning tree, STA, and Learning bridge.

Synchronous Transport Signal 1. Basic building block signal of SONET, operating at 51.84 Mbps for transmission over OC-1 fiber. Faster SONET rates are defined as STS-n, where n is a multiple of 51.84 Mbps. See also SONET.

32-bit address mask used in IP to indicate the bits of an IP address that are used for the subnet address. Sometimes referred to simply as mask. See also IP address mask and IP address.

A technique used to maximize the number of networks available within a range (class) of addresses. See also Subnetwork.

In IP networks, a network confined to a particular subnet address. Subnetworks are networks segmented by a network administrator in order to provide a multilevel, hierarchical routing structure while shielding the subnetwork from the addressing complexity of attached networks. Sometimes called a subnet.

SONET rings that incorporate nodes that are also part of an adjacent SONET ring.

A security level that can perform all of the functions of the other security levels as well as set names, passwords, and security levels for other users. A superuser is usually the network element administrator. See also Retrieve user, Maintenance user, and Provisioning user.

Network device that filters, forwards, and floods frames based on the destination address of each frame.

T1 transmits DS-1-formatted data at 1.544 Mbps through the telephone-switching network using AMI or B8ZS coding. See also AMI, B8ZS, and DS-1.

Identification information, including a number plus other information.

Time Division Multiplexing. Allocates bandwidth on a single wire for information from multiple channels based on preassigned time slots. Bandwidth is allocated to each channel regardless of whether the station has data to transmit.

Telcordia Technologies, Inc., formerly named Bellcore. Eighty percent of the U.S. telecommunications network depends on software invented, developed, implemented, or maintained by Telcordia.

Target Identifier. Identifies the particular network element (in this case, the ONS 15327) where each TL1 command is directed. The TID is a unique name given to each system at installation.

Transparent LAN Service. Provides private network service across a SONET backbone.

Message sent by an SNMP agent to an NMS (CTM), console, or terminal to indicate the occurrence of a significant event, such as an exceeded threshold.

The lower-rate signal directed into a multiplexer for combination (multiplexing) with other low- rate signals to form an aggregate higher rate level.

Network traffic travels across this physical and logical connection between two switches. A backbone is composed of a number of trunks. See also Backbone.

Architecture that is designed to provide the services necessary to implement any standard point-to-point encapsulation scheme. See also encapsulation.

The communication of a single source to a single destination.

Cards that are not included in a protection scheme. An unprotected card failure or a signal error results in lost data.

Unidirectional Path Switched Ring. Path-switched SONET rings that employ redundant, fiber- optic transmission facilities in a pair configuration. One fiber transmits in one direction and the backup fiber transmits in the other. If the primary ring fails, the backup takes over.

Set of frequencies used to send data from a subscriber to the headend.

Coordinated Universal Time. Time zone at zero degrees longitude.

Converts each fiber into multiple fibers to allow signals that are carried at different rates use the same fiber-optic cable.

Entity in a source-route bridging (SRB) network that logically connects two or more physical rings together either locally or remotely. The concept of virtual rings can be expanded across router boundaries.

Virtual wires route external alarms to one or more alarm collection centers across the SONET transport network.

Virtual LAN. Group of devices located on a number of different LAN segments that are configured (using management software) to communicate as if they were attached to the same wire. Because VLANs are based on logical instead of physical connections, they are extremely flexible.

Virtual Private Network. Enables IP traffic to travel securely over a public TCP/IP network by encrypting all traffic from one network to another. A VPN uses "tunneling" to encrypt all information at the IP level. (See also Tunneling.)

Virtual Tributary. A structure designed for the transport and switching of sub-DS3 payloads.

The VT layer or electrical layer occurs when the SONET signal is broken down into an electrical signal.

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Glossary