This Recommendation specifies the rates and formats for use in metro transport network (MTN) digital layer networks: the MTN path (MTNP) layer and the MTN section (MTNS) layer, which support the transport of distributed radio access network (D-RAN) and centralized radio access network (C-RAN) traffic. It includes the following elements:

– frame structures;

– functionality of the overhead;

– formats for mapping client signals (CSs).

The MTNP layer provides flexible connections that carry client data and path operations, administration, and maintenance (OAM) in 64 bit/66 bit (64B/66B) blocks that are conformant to the encoding rules in clause 82 of [IEEE 802.3]. OAM functions include connectivity verification (CV), performance monitoring, path status and delay measurement (DM). Overhead to support MTNP layer protection is also supported.

The MTNS layer operates over 50GBASE-R, 100GBASE-R, 200GBASE-R or 400GBASE-R server layers. The MTNS frame format is specified in a way that maximizes reuse of [OIF FLEXE IA] implementation logic, including support for bonding homogenous groups of 50GBASE-R, 100GBASE-R, 200GBASE-R, 400GBASE-R interfaces. The MTNS layer uses 64B/66B blocks that are conformant to the encoding rules in clause 82 of [IEEE 802.3], which allow the MTNS layer to be transported transparently over the lower layers of the Ethernet protocol stack.

Functions and process flows associated with the interfaces specified lie outside the scope of this Recommendation.