ITU has standardized a new technology optimizing the metro transport network to support IMT-2020/5G with carrier-class Ethernet. The new transport technology targets the transport of traffic from distributed and centralized radio access networks, providing the full range of operations, administration, and management (OAM) capabilities required by carriers.
ITU G.8312 “Interfaces for the metro transport network” adapts IEEE 802.3 Ethernet technology and OIF Flexible Ethernet (FlexE) implementation logic to the requirements of carrier-class transport networks. The OAM capabilities provided by ITU G.8312 include connection verification, performance monitoring, path status, and delay measurement.
5G transport standardization is led by ITU-T Study Group 15 (Transport, access and home).
The ITU G.8312 interfaces and accompanying ITU G.8310 architecture for the metro transport network build on the success of ITU standards for carrier-class Ethernet, standards that brought carrier-class management and control capabilities to Ethernet technology to support Ethernet’s emergence as the preferred ‘onramp’ to the information superhighways provided by Optical Transport Network (OTN) technology.
The development of ITU G.8312 and G.8310 received more than 200 technical contributions over a two-year development cycle, “what is probably record number of contributions on a single topic in such a short space of time,” says Steve Gorshe, Microchip Technology, Rapporteur for the responsible working group (Q11/15).
ITU G.8312 defines a new Section layer adapted from FlexE and a new Path layer based on carrying the Ethernet 66B-encoded block streams. ITU G.8312 makes substantial use of existing technology, creating commonality with other portions of the network as well as associated network management systems. “The technology is especially well suited to carriers using Ethernet technology in their radio access networks in need of the capabilities of a carrier-grade transport network,” says Gorshe.
A key extension to OTN technology in ITU G.709.4 “OTU25 and OTU50 short-reach interfaces” is another ITU standard designed to support 5G transport also developed by the Q11/15 working group.
ITU G.709.4 defines nominally 25 and 50 Gbit/s OTN interfaces optimized for carrying Ethernet 25GBASE-R and 50GBASE-R client signals.
“These are the rates becoming popular in 5G radio access networks,” says Gorshe. “The ITU G.709.4 interfaces make it much easier for carriers to continue to base their radio access networks on OTN technology.”
An informative appendix to ITU G.709.4 also defines lower-rate OTN interfaces that operate at the same rates as Ethernet 25GBASE-R and 50GBASE-R signals, enabling the use of these OTN interfaces for applications where a network operator desires direct reuse of Ethernet optical modules.
More ITU guidance on 5G transport at https://www.itu.int/en/myitu/News/2021/03/15/12/36/New-ITU-standards-optimize-transport-networks-support-for-5G
