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Appendix D
Glossary
Static route
A route that is manually entered into a routing table. Static routes take precedence over routes chosen
by all dynamic routing protocols.
STP
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.
STS-1
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.
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.
Subtending rings
SONET rings that incorporate nodes that are also part of an adjacent SONET ring.
Superuser
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.
T
T1
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.
Tag
Identification information, including a number plus other information.
TDM
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.
Cisco ONS 15454 Installation and Operations Guide
D-12
November 2001
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