Cisco ONS 15327 User Documentation page 526

Glossary
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 if a line
card failure or fiber cut occurs.
ATAG
Autonomous Message Tag. ATAG is used for TL1 message sequencing.
ATM
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.
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.
Backbone
Part of a network that acts as the primary path for traffic that is most often sourced from, and destined for, other networks.
Bandwidth reuse
A synchronous transfer signal that carries different sets of traffic on different spans at the same time.
BER
Bit Error Rate. Ratio of received bits that contain errors.
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.
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.
Cisco ONS 15327 User Documentation, R3.3
GL-2
June 2002