150-359-100-01, Revision 01
Appendix D - Glossary
HXU-359 List 1
October 27, 2000
59
RFI
Remote Failure Indication — A failure is a defect that persists
beyond the maximum time allocated to the transmission
system protection mechanisms. The RFI is sent to the far end
and will initiate a protection switch if this function has been
enabled.
Section
The span between two SONET network elements capable of
accessing, generating, and processing only SONET section
overhead. This is the lowest layer of the SONET protocol stack
with overhead.
SEF
Severely Errored Frame
SES
Severely Errored Seconds
SONET
Synchronous Optical Network — A standard for optical
transport that defines optical carrier levels and their electrically
equivalent synchronous transport signals (STSs). Provides
significant configuration flexibility and bandwidth availability
over older telecommunications systems. SONET defines a
technology for carrying many signals of different capacities
through a synchronous, flexible, optical hierarchy. This is
accomplished by means of a byte-interleaved multiplexing
scheme.
SPE
Synchronous Payload Envelope — The SONET frame format
used to transport payload and STS path overhead. A SONET
structure that carries the payload (service) in a SONET frame
or virtual tributary. The STS SPE may begin anywhere in the
frame’s payload envelope. The VT SPE may begin anywhere in
a floating mode VT, but it begins at a fixed location in a
locked-mode VT.
SPLB
Special Loopback.
STS-1
Synchronous Transport Signal, Level 1 — The basic SONET
building block signal transmitted at 51.84 Mb/s data rate.
STS-N
Synchronous Transport Signal, Level N — The signal obtained
by multiplexing integer multiples (N) of STS-1 signals
together.
TAO
Terminal Access Option.
TL1
Transaction Language 1.
Transport
The STS-1 interface.
TSA
Time Slot Assignment
UAS
Unavailable Seconds
UL
Underwriters Laboratories
