
PRELIMINARY
XRT86SH221
60
REV. P1.0.5
SDH-TO-PDH FRAMER/MAPPER WITH INTEGRATED 21-CHANNEL E1 SH LIU
PATH TRACE (J1) MONITOR
The J1 byte of the path overhead is used as a path trace identifier. The path trace identifier is monitored using
the following SDH standard rules:
I
An SDH NE that contains STS PTE shall allow the user to provision, on a per-path basis, the contents of
the STS Path Trace carried in the J1 byte of the STS path overhead originated by the PTE. The
transmitted STS Path Trace string shall be 64 bytes in length.
I
An SDH NE that contains STS PTE shall support a feature that allows the contents of the STS Path
Traces to be provisioned as ASCII characters. In addition, the following apply:
I
The feature shall allow the user to enter a string of up to 62 characters
I
The feature shall place no restriction on the content of the string except that the characters shall be
ASCII printable characters
I
The NE shall automatically pad the string entered by the user to 62 characters using ASCII NULL
characters, and then add <CR> and <LF> characters (i.e., 'OD' and '0A' for a total of 64 characters
I
Each 8 bit ASCII character shall be loaded into one J1 byte.
I
An SDH NE shall support a feature to allow the user to provision the expected ASCII-based path trace
for each STS path that it terminates and for which TIM-P detection has been activated. In addition, the
following apply:
1. The feature shall allow the user to enter a string of up to 62 characters
2. The feature shall place no restriction on the contents of the string, except that
3. The characters shall be ASCII printable characters.
I
STS PTE shall detect a TIM-P defect within 30 seconds (or less) when none of the sampled 64-byte
STS path trace strings match the provisioned expected value.
I
STS PTE shall terminate a TIM-P defect within 30 seconds (or less) when four-fifth (or more) of the
sampled STS path trace strings match the provisioned expected value
I
An SDH NE that is monitoring for changes of the incoming path trace shall detect when a sustained
change in the path trace content occurs. Upon detecting a sustained change, the NE shall send a
message to an OS. The level of the message shall be Not Alarmed, and it shall include both the
previously received path trace, and the new path trace (assuming they are ASCII-based).
I
An SDH NE that is monitoring for a mismatch between the incoming path trace and an expected path
trace for diagnostics purposes shall detect when a sustained mismatch occurs. Upon detecting a
sustained mismatch, the NE shall set an indication for that path and send a message to an OS. The level
of the message shall be Not Alarmed, and it shall include both the expected path trace, and the new
path trace (assuming they are ASCII-based).
I
An SDH that is monitoring the incoming path trace for diagnostic purposes and that has detected a
sustained mismatch shall detect when the incoming path trace matches the expected path trace. Upon
detecting a match, the NE shall clear the indication for that path and send a clear message to the OS (if
the mismatch was reported to an OS).
The SDH standard defines the path trace message length to be a 16 byte message. The message format is
such that the first byte of the message always has a "1" in its most significant bit while the subsequent bytes in
the message all have a "0" in their most significant bits.
The rxspoh_stat block allows software to specify the length of the J1 section trace message. This length could
be 1 or 16 for SDH. The software also specifies whether to look for a <LF> or a starting "1" bit when the
rxspoh_stat block is trying to locate the start of the message. Software also specifies the number (3 or 5) of
consecutive consistent section trace messages that must be observed before it is accepted.
An interrupt is generated when a new section trace message is accepted as valid. The valid section trace
message is compared with an expected section trace message downloaded to memory by software. A J1
mismatch (J0_MIS) flag is raised if the 2 messages are not identical. The rxspoh_stat block also implements a
J1 unstable counter. The J1 unstable counter is incremented for each byte that differs from the previously