Carrier Access Access Bank II SNMP - Manual (Page 126)

Remote Mode: Remote T1 Line or Payload Loopbacks
9/24/01 12-5
12.7 Remote Mode: Remote T1 Line or Payload Loopbacks
In Remote mode, if the T1 line is ANSI T1.403 ESF formatted and Network Loopback detect and ESF
ANSI detect both has been enabled, the two types of loopback codes the Access Bank II - SNMP can
be configured to detect are Remote T1 Line and Remote Payload Loopback. The default setting in
Remote mode is Remote T1 Line Loopback.
12.8 ANSI T1.403 Remote T1 LLB
In a Remote T1 Line Loopback, upon receipt of a bit-oriented loopup command message consisting
of 0000111011111111 repeated at least 10 times toward the Access Bank II - SNMP in the Facility
Data Link (FDL), data recovered off the T1 line is transmitted back onto that T1 span specified with
no changes in bit sequence integrity, framing format or removal of BPVs. The Access Bank II -
SNMP should maintain the Remote LLB when it receives a loopback retention signal of
0010101011111111 sent continuously from the far-end. The loopback retention code word should be
present in the returned T1 signal. The Remote T1 LLB is released upon receipt of the bit-oriented
command message consisting of 0011100011111111, repeated at least 10 time in the FDL toward the
Access Bank II - SNMP. See ANSI T1.403-1995, Section 9.3.2.2-3 and Table 4.
12.8.1 ANSI T1.403 Remote Payload Loopback
In a Remote Payload loopback, upon receipt of a bit-oriented loopup command message consisting of
0001010011111111 repeated at least 10 times toward the Access Bank II - SNMP in the FDL, the
payload of the received T1 signal (192 information bits of a DS1 frame) is returned with no changes
in bit sequence integrity and newly generated ESF framing. The T1 Framer will correct the BPVs in
the 192 bits of payload data and re-transmit the data. The FPS framing pattern, CRC-6 calculation,
and the FDL bits are not looped back, but are instead, reinserted by the Framer. The remote PLB is
released upon receipt of the bit-oriented command message consisting of 0011001011111111,
repeated at least 10 times in the FDL.
12.9 Illustrations of Loops and Self-Tests
The following illustrations show how the loop-back tests and self-tests work. See the descriptions
above for more information about specific tests.
Figure 12-1 shows how to read the illustrations that follow.