SDH TU pointer

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The TU pointers point to the four multiframes V1, V2, V3, and V4.

Other related questions:
TU pointer adjustment event
Question: Does a TU pointer justification event detected on a lower-order channel of the local station mean pointer justification on the local station? Why? Answer: When the local station detects a TU pointer justification event on a lower-order channel, it does not mean that pointer justification occurs at the local station. Instead, it means that pointer justification occurs at the remote station corresponding to the lower-order channel. Pointer justification occurs during lower-order channel multiplexing into the AU. To be specific, pointer justification occurs in upstream signals. However, pointers are explained in downstream signals, or at the receive end. Therefore, the pointer justification at the local station can be detected only at the remote station. When the local station detects a pointer justification event, the pointer justification occurs at the remote station.

Reasons for pointer justification on an SDH line board
Reasons for pointer justification on an SDH line board: The reason why pointer justification occurs on an SDH line board is that NE clocks are not synchronized. When the rate (frame rate) of VC-4 is higher than that of AU-4, a negative pointer justification occurs. When the rate of VC-4 is lower than that of AU-4, a positive pointer justification occurs.

Definition of SDH bit error performance
Definitions of SDH bit error performance: Background block error (BBE): an errored block not occurring as a part of an SES. Errored second (ES): Errored bit second: interval of 1 second during which a given digital signal is received with one or more errored bits according to G.821. Errored block second: interval of 1 second during which a given digital signal is received with one or more errored blocks according to G0.826. Errored second: errored bit second and errored block second. Severely errored second (SES): Severely errored bit second: interval of 1 second during which a given digital signal is received with an error bit ratio greater than 1 x 10-3 according to G.821 Severely errored block second: interval of 1 second during which 30% or more errored blocks exist or at least one defect exists according to G.826. Unavailable second (UAS): Unavailable second: An unavailable period starts from the first second of 10 consecutive SES events. These 10 seconds are considered as a part of the unavailable seconds. A new available period starts from the first second of 10 consecutive non-SES events. These 10 seconds are considered as a part of the available seconds. Consecutive severely errored second (CSES): Consecutive severely errored second: 2 to 9 consecutive SES events.

OSN 8800 not supporting SDH ASON
SDH ASON is called OCS ASON in OSN 8800.

K-byte pass-through modes in the SDH frame structure
1. Paired-slot pass-through: overhead pass-through between paired slots (Pay attention to the paired relationship between the slots.) 2. Paired-port pass-through: overhead pass-through between paired optical ports on a board 3. In-board pass-through: overhead self-loopback, that is, overhead pass-through between the receive end and transmit end of a board (This mode is rarely used.)

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