- Cisco ONS 15454 Manual

D-2
Cisco ONS 15454 Installation and Operations Guide
November 2001
Appendix D Glossary
AID
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.
AMI
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.
APS
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.
ATAG
Autonomous Message Tag. ATAG is used for TL1 message sequencing.
B
B8ZS
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.
BER
Bit Error Rate. Ratio of received bits that contain errors.
Bit rate
Speed at which bits are transmitted, usually expressed in bits per second.
BITS
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.
BLSR
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.