The AT&T Standard for ESF
AT&T Publication 54016 (revised 1989) defines the performance-monitoring and
data-link requirements for ESF CSUs. Per the latest revision of Publication 54016
(September 1989), the following performance parameters must be monitored:
•
ESF Error Event—
Any ESF in which an OOF event or CRC-6 error
occurs.
•
Errored Second (ES)—
A second with one or more CRC errors or
Out-of-Frame (OOF) conditions.
•
Severely Errored Second (SES)—
A second with 320 or more CRC
errors or one or more Out-of-Frame (OOF) conditions.
•
Bursty Errored Second (BES)—
A second with more than one but less
than 320 CRC errors.
•
Unavailable Second (UAS)—
A second during which Unavailable
Signal State is in effect. Unavailable Signal State is declared after 10
consecutive seconds of SES; it is cleared after 10 consecutive seconds
which are not SES.
•
Loss of Frame Count (LOFC)—
The number of times Loss of Frame
is declared. Loss of Frame is declared when a device loses sync on the
framing pattern for approximately 2.5 seconds. Loss of Frame is
cleared when a device maintains sync for about 15 milliseconds.
•
Controlled Slips (CS)—
Monitored and reported by devices which
perform controlled timing slips, optional.
ES, BES, SES, and UAS counts are to be kept in 24-hour registers divided into
96 intervals of 15 minutes each. In addition, a running total count of ESF errors
is to be kept. All ESF performance statistics can be requested, transmitted, and
cleared via the data link.
AT&T Publication 54016 defines two loopbacks which can be controlled from
the network. Line loopback (near the CSU’s line interface) is controlled by
in-band codes. Payload Loopback (near the CSU’s DTE interface) is controlled
by data link codes. These loopbacks correspond to Access-T’s LS Line and DS
Line loopbacks, respectively.
Chapter 1
ACST-0351-005
Introduction
June 1996
1-12