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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