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To the IETF area directors, MPLS and PWE3 working group chairs, document authors and IETF community,
I've recently started looking at the MPLS-TP drafts and only this past week have had an opportunity to review the OAM requirements draft for MPLS-TP. I realize the IESG has requested Last Call comments for this draft,
and am sensative that these comments would have been better received earlier. That said, these comments are not trivial and should be considered before progressing the draft.
ITU-T SG15 has a history of OAM protocol development for transport technologies. This expertise has led to development of an OAM methodology and definition approach as documented in G.806. Two key characteristics
exist in this document that I don't see being reflected in the OAM requirements draft:
- A requirement for consistancy in OAM approach with other transport technology layers.
This characteristic is necessary to enable existing transport network management systems to easily integrate new transport technologies. It further enables existing Methods and Procedures to be easily adapted for
new technologies. Considering the familiarity that exists with existing transport OAM approaches, deviation should only be considered after receiving significant input from transport network operators. Please be aware that transport network operators typically
participate in the work of the ITU, not the IETF and therefore many are not aware of this work.
- A requirement for OAM interactions between transport technology layers.
This characteristic is key when a network utilizes multiple transport technology layers to carry customer traffic. This is very common in Transport networks. G.806 provides a framework for this interaction. An example
embodiment can be found in G.782 and its definition of OAM interactions between the RS and MS layers, as well as the MS and Path layers. MPLS-TP is not an island of technology -- it runs over other transport layers (e.g. OTN/DWDM, Ethernet layers) and other
transport layers are targeted to run on top of it (e.g. Ethernet over PseduoWire, SONET/SDH over PseudoWire). The OAM mechanisms used in the layers found in Transport networks were developed with G.806 in mind. Interactions between the OAM indications from
lower layers and MPLS-TP as well as between MPLS-TP and higher layers must be handled as described in G.806 when considering the design for MPLS-TP OAM.
The work of IETF and ITU-T has endevored to meet many different requirements for MPLS-TP Networks. Many good results have come from this process. And the process allows for comments like these to be made to avoid key
areas from being overlooked. I appreciate the opportunity to provide them to the IETF community and IESG as the MPLS-TP OAM Requirements document is considered.
Thanks,
Jonathan Sadler
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