Incrementing STM ID Overview
When configured in SDH framing mode, SONET/SDH interfaces on a Juniper Networks router might not interoperate with some older versions of ADMs or regenerators that require an incrementing STM ID.
Current SDH standards specify a set of 3*n overhead bytes in an STMn that includes the J0 section trace byte. The rest are essentially unused (spare Z0) and contain hexadecimal values (0x01, 0xCC, 0xCC ... 0xCC). The older version of the standard specified that the same set of bytes should contain an incrementing sequence: 1, 2, 3, ..., 3*n. Their use was still unspecified although they might have been used to assist in frame alignment. You can configure an incrementing STM ID to enable your Juniper Networks router to interoperate with older equipment that relies on these bytes for frame alignment.
The STM identifier has a precise definition in the SDH specifications. In ITU-T Recommendation G.707, Network node interface for the synchronous digital hierarchy (SDH) (03/96), Section 188.8.131.52.