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 Monday, February 06, 2006

A new ITU-T standard (Recommendation) will allow operators offering Ethernet services to use operations, administration, and maintenance (OAM) mechanisms to facilitate network operation and troubleshooting.

Given that performance management has been cited as a major concern of operators looking at Ethernet as an end-to-end solution, and that OAM features are not standard in Ethernet, it is seen as crucial to provide this facility. Standards-based OAM features that will allow for interoperability between different vendors are seen as a requirement for carriers adopting Ethernet on a wide scale. Experts say that operator deployments may start in 2007.

Ethernet services are becoming popular because they allow carriers to offer considerably improved flexibility to customers through a much simpler and lower cost interface. Ethernet allows users to specify exactly how much bandwidth they want between the 10Mbit/s and 1Gbit/s range currently offered. Further, Ethernet provides reduced operation complexity and improved scalability for carriers.

And as operators look to NGN and the use of the Internet Protocol (IP), Ethernet is seen as the best fit, especially given the rise of such services as IP VPNs, VLANs and dedicated Internet access. Equally this OAM functionality may be deployed in a local area network (LAN).

The ITU-T Recommendation, Y.1731 consented at the recent meeting of Study Group 13, identifies the OAM functions which are needed to allow fault management (fault localization, defect detection, etc.) and performance monitoring (error counts, delay measurement, etc.) in an Ethernet network. With regards to performance monitoring, the Recommendation only addresses point to point connectivity today, says Gilles Joncour, ITU-T Rapporteur for the Recommendation, (multi)point to multipoint will be the next step.

Joncour gives some more detail: Y.1731 also specifies the so called OAM PDUs (protocol data units) which constitute the payload of the Ethernet OAM frames. The content (fields) of the PDUs vary according to the function(s) they correspond to. Y.1731 does not specify the processes associated to the sending, reception and analysis (of the content) of the OAM frames/PDUs. This will be part of another Recommendation (G.8021), from Study Group 15. Y.1731 specifies methods for measuring sample values of parameters identified for monitoring the performance of Ethernet networks. It does not deal with the integration of those values over a period of time and the use of such results, when applicable for defect detection. This will also be done in G.8021.

Recommendation Y.1713 gives user-plane OAM functionality in Ethernet networks. The architectural basis for this Recommendation is the Ethernet specification G.8010. A previous Recommendation Y.1730 served as a prelude to Y.1731 outlining the OAM requirements of operators. Joncour says that Y.1731 was developed in close collaboration with the Institute of Electrical and Electronics Engineers (IEEE) group 802.1. This group is also preparing a standard (802.1ag - Connectivity Fault Management) devoted to Ethernet OAM aspects. IEEE 802.1ag defines a subset of the functions/PDUs described in Y.1731. Regular communications between the two groups ensured alignment of the description of the common features.