[Time] draft-tissa-netmod-oam

Gregory Mirsky <gregory.mirsky@ericsson.com> Mon, 25 August 2014 05:14 UTC

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From: Gregory Mirsky <gregory.mirsky@ericsson.com>
To: "'draft-tissa-netmod-oam@tools.ietf.org'" <draft-tissa-netmod-oam@tools.ietf.org>
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Subject: [Time] draft-tissa-netmod-oam
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Dear Authors, et.al,
please kindly consider my comments and questions to this document:

*         Introduction

o    "... it is a reasonable choice to develop the unified OAM framework based on those (CFM) concepts." I agree that for packet switching connection-oriented networks that are based on G.800 architecture CFM, but more so Y.1731, provides shared concepts. I think that the same cannot be said for connectionless packet switching networks. Thus extending CFM model onto arbitrary networks without consideration whether these are connection-oriented or connectionless is very questionable approach, IMO;

o   "...CFM, it is a reasonable choice to develop the unified OAM framework based on those concepts" IP OAM is not based on Ethernet Service OAM model or principles but, IMO, OAM of overlay networks more closer resemble IP OAM as these networks are connectionless in their architecture;

o   "The YANG model presented in this document is the base model and supports IP Ping and Traceroute." If only these and similar OAM tools, e.g. LSP ping, Loopback/Linktrace, are in scope of the document, then, I believe, the title may say something like "YANG model of on-demand OAM tool to detect and localize Loss of Continuity defect". Referring to ping/traceroute as "generic OAM" comes as stretch too far;

o    "...initiate a performance monitoring session can do so in the same manner regardless of the underlying protocol or technology" I'd point to work of LMAP WG on informational model of performance measurements in large-scale access networks, work of ITU-T's SG15, MEF. Perhaps sentence can be stopped after "... or a Traceroute".

o   "In this document we define the YANG model for Generic OAM" Can you provide definition or reference to the definition of the "Generic OAM"? It is challenging to validate informational model of something that not been sufficiently defined.

*         Section 3

o   "This allows users to traverse between OAM of different technologies at ease through a uniform API set." Usually relationships between OAM layers referred and viewed as OAM interworking. There are several examples of IETF addressing aspects of OAM interworking. I think that interworking includes not only scenarios of nested OAM layers but peering layers and thus is broader than introduced in the document "nested OAM".

o   Figure 1 depicts OAM of both connection-oriented and connectionless networks. What you see common, generic in respective OAM of these networks?

*         Section 4

o   "In IP, the MA can be per IP Subnet ..." As there's no definition of MA in IP, is this the definition or one of examples. Can MA in IP network be other than per IP Subnet?

o   "Under each MA, there can be two or more MEPs (Maintenance End Points)" Firstly, since you adopt MA-centric terminology, MEP stands for Maintenance Association End Point. Secondly, in some OAM models Down and Up MEP being distinguished. Would your model consider that? As there's no definition of MEP for several networks you've listed, e.g. IP, how the YANG model will abstract something that is not defined? And thirdly, how and where MIPs are located in IP OAM?

Thank you for your consideration of my notes and looking forward to the interesting discussion.