Cisco ONS 15454 Troubleshooting and Maintenance Guide, Release 3.1
Appendix B, Glossary

Table Of Contents


1:1 protection
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.
1+1 protection
A card protection scheme that pairs a single working card with a single dedicated protect card. A term specific to optical cards.
1:N protection
A 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. A term specific to electrical cards.

Access drop
Points where network devices can access the network.
Address mask
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 the ONS 15454. 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 in case a line card failure or fiber cut occurs.
Autonomous Message Tag. ATAG is used for TL1 message sequencing.

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.
Bit Error Rate. Ratio of received bits that contain errors.
Bit rate
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.
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.
Blue band
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 will be sent to all nodes on a network. Broadcasts are identified by a broadcast address. Compare with multicast and unicast. See also Broadcast address.
Broadcast address
Special address reserved for sending a message to all stations. Generally, a broadcast address is a MAC destination address of all ones.
Broadcast storm
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.

C2 byte
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.
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 the 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.
Cisco Transport Controller. A Java-based graphical user interface (GUI) that allows operations, administration, maintenenance, and provisioning (OAM&P) of the ONS 15454 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. DCC can be located in section DCC (SDCC) or line overhead (LDCC.)
To separate 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 type of fiber optical amplifier 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.
Electrical Interface Assemblies. Provides connection points for the ONS 15454 and DS-1, DS-3, or EC-1 units.
Electromagnetic Interference. Interference by electromagnetic signals that can cause reduced data integrity and increased error rates on transmission channels.
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.
Ethernet switch
An Ethernet data switch. Ethernet switches provide the capability to 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.
External timing reference
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).

Falling threshold
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.
Free run synchronization mode
Occurs when the external timing sources have been disabled and the ONS 15454 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.

Hard reset
The physical removal and insertion of a card. A card pull.
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.
Host number
Part of IP address used to address an individual host within the network or subnetwork.
Hot swap
The process of replacing a failed component while the rest of the system continues to function normally.

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

K bytes
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.
Line layer
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.
Line timing mode
A node that derives its clock from the SONET lines.
Link budget
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).
Link integrity
The network communications channel is intact.
Loopback test
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.

MAC address
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.
Maintenance user
A security level that limits user access to maintenance options only. See also Superuser, Provisioning User, and Retrieve User.
Managed device
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.
Managed object
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.
Multiplex payload
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, a single piece of telecommunications equipment used to perform a function or service integral to the underlying network.
Network number
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 15454.

Operations, Administration, Maintenance, and Provisioning. Provides the facilities and personnel required to manage a network.
Optical amplifier
A device that amplifies an optical signal without converting the signal from optical to electrical and back again to optical energy.
Optical receiver
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.
Output contacts (alarms)
Triggers that drive visual or audible devices such as bells and lights. Output contacts can control other devices such as generators, heaters, and fans.

Passive devices
Components that do not require external power to manipulate or react to electronic output. Passive devices include capacitors, resisters, and coils.
Path layer
The segment between the originating equipment and the terminating equipment. This path segment may encompass several consecutive line segments or segments between two SONET devices.
Portion of a cell, frame, or packet that contains upper-layer information (data).
Packet internet grouper. ICMP echo message and its reply. Often used in IP networks to test the reachability of 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.
Priority queuing
Routing feature that divides data packets into two queues: one low-priority and one high-priority.
Provisioning user
A security level that allows the user to access only provisioning and maintenance options in CTC. See also Superuser, Maintenance user, and Retrieve user.

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

Red band
DWDM wavelengths are broken into two distinct bands: red and blue. The red band is the higher frequency band. The red band DWDM cards for the ONS 15454 operate on wavelengths between 1547.72nm and 1560.61nm.
Retrieve user
A security level that allows the user to retrieve and view CTC information but not set or modify parameters. See also Superuser, Maintenance user, and Provisioning user.
Revertive switching
A process that sends electrical interfaces back to the original working card after the card comes back online.
Rising threshold
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.

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 15454 network nodes use the same date and time reference. The server synchronizes alarm timing during power outages or software upgrades.
Soft reset
A soft reset reloads the operating system, application software, etc., and reboots the card. It does not initialize the ONS 15454 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.
Spanning tree
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.
Sync 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.
Static route
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 uses the spanning-tree algorithm to enable a learning bridge to dynamically work around loops in a network topology by creating a spanning tree. 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.
Subnet mask
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.
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.
Subtending rings
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.

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 15454) 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.
Optional devices of a DWDM system providing the conversion of one optical wavelength to a precision narrow band wavelength.
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.
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.

Virtual fiber
A fiber that carries signals at different rates and uses the same fiber optic cable.
Virtual ring
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
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.
VT layer
The VT layer or electrical layer occurs when the SONET signal is broken down into an electrical signal.