Cabletron Systems HSIM-W87, Руководство пользователя

Страница: 51 / 56

HSIM-W87 User’s Guide C-1
APPENDIX C
WAN TERMS AND ACRONYMS
This appendix provides definitions for WAN terms and acronyms.
AIS —
Alarm Indication Signal, The DS3 AIS is framed with “stuck
stuffing”. This implies that it has a valid M-subframe alignment bits,
M-frame alignment bits, and P bits. The information bits are set to a
1010... sequence, starting with a one (1) after each M-subframe alignment
bit., M-frame alignment bit, X bit, P bit, and C bit. The C bits are all set to
zero giving what is called “stuck stuffing”. The X bits are set to one. The
DS3 AIS defect is declared after DS3 AIS is present in contiguous
M-frames for a time equal to or greater than T, where
0.2 ms<=T<=100 ms. The DS3 AIS defect is terminated after AIS is
absent in contiguous M-frames for a time equal to or greater than T.
AMI —
Alternate Mark Inversion, line coding used with both E-1 and T1.
A digital 1 is encoded as a “mark” (pulse) and a 0 is encoded as a “space.”
The marks alternate polarity.
ANSI — American National Standards Institute, the US member of the
ISO.
Bearer (B) Channel —
A 64 Kbps channel used with BRI and PRI
ISDN services.
BPV —
Bipolar Violation, the occurrence of two successive pulses of the
same polarity in a bipolar signal.
B3ZS — Bipolar with 3 Zero Substitution, an AMI line code with the
substitution of a unique code to replace occurrences of three consecutive
zero signal elements.
B8ZS —
Binary 8-Zero Substitution, line coding utilized with ESF
(Expanded Super Frame) using a bipolar DS1 signal. Insures the ones
density requirement for digital T-carrier facilities in the public network,
while allowing 64 Kbps clear data per channel. This encoding method is
not supported by some Telcos.
BER —
Bit Error Ratio, errored bits over total bits, should be <10–7 for
transmission lines.