At an intermediate NE I, the near-end information in the direction from NE A to NE Z
represents the performance of the unidirectional trail segment from NE A to NE I,
while the far-end information represents the performance of the unidirectional trail
from NE Z to NE A. The near-end information in the direction from NE Z to NE A
represents the performance of the unidirectional trail segment from NE Z to NE I,
while the far-end information represents the performance of the unidirectional trail
from NE A to NE Z.
At either end of the trail (NE A or NE Z) the combination of near-end and far-end
information represents the performance of the two directions of the trail. At an
intermediate NE I, the combination of far-end information in the trail signal from NE
A to NE Z and far-end information in the trail signal from NE Z to NE A presents the
performance of the two directions of the trail.
SDH performance monitoring
SDH performance monitoring is based on the evaluation of block errors, where the
block size depends on the transmission layer. At the Regenerator Section (RS) layer, a
block is equivalent in size to an SDH frame. Therefore, the number of bits in an RS
block is dependent on the signal rate. One or more errored bits in the RS parity byte
(B1 byte in the RSOH) constitutes a single RS block error. At the Multiplex Section
(MS) layer, the number of bits in a block is always 801. The BIP comparison is
performed on a per-bit basis. Therefore, a single bit error in the MS parity bytes (three
B2 bytes in the MSOH) constitutes a single MS block error. At the higher order path
layer, a block is equivalent in size to an SDH path. Therefore, the number of bits in a
VC-n block is dependent on the signal rate. One or more errored bits in the parity byte
of the higher order path (B3 byte in the VC-n POH) constitutes a single VC-n block
error. Concerning the Remote Error Indication (REI), the same approach as used for
SONET performance monitoring is also used for SDH performance monitoring.
STM-64 Overhead Access: M0, M1 source (MS-REI)
Source direction:
In every STM-64 MS termination point the Remote Error Information (REI) is written
in the M0 and M1 byte (9,6,1). The REI bytes shall be set to convey the count of
interleaved bit blocks that have been detected in error by the BIP-1536 (in the range of
[0, 1536]). M0 bit 1 is most significant bit and M1 bit 8 is least significant bit. If
interworking with old equipment supporting the single byte REI in M1, the value
conveyed is truncated at 255 and inserted in M1. Usage is in conformance with ITU-T
Rec. G.707 and ETSI ETS 300417.″
STM-64 Overhead Access: M0, M1 sink (MS-REI)
Sink direction:
In every STM-64 MS termination point the received REI is interpreted. If the REI of a
received frame is unequal to zero, the corresponding number of errored blocks can be
counted for far-end performance monitoring purposes. Usage is in conformance with
Performance monitoring
Introduction
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365-312-807R7.2
Issue 4, May 2007
Alcatel-Lucent - Proprietary
See notice on first page
10-5
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