Re: [Lime-oam-model] Design Team report

"Adrian Farrel" <adrian@olddog.co.uk> Sat, 21 March 2015 09:27 UTC

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From: "Adrian Farrel" <adrian@olddog.co.uk>
To: "'Tom Taylor'" <tom.taylor.stds@gmail.com>, "'Qin Wu'" <bill.wu@huawei.com>, "'Gregory Mirsky'" <gregory.mirsky@ericsson.com>, "'Ronald Bonica'" <rbonica@juniper.net>, <lime-oam-model@ietf.org>
References: <CO1PR05MB4422C6491A3B7179F229574AE130@CO1PR05MB442.namprd05.prod.outlook.com> <B8F9A780D330094D99AF023C5877DABA846E1E86@nkgeml501-mbs.china.huawei.com> <7347100B5761DC41A166AC17F22DF1121B92F482@eusaamb103.ericsson.se> <B8F9A780D330094D99AF023C5877DABA84702B17@nkgeml501-mbs.china.huawei.com> <7347100B5761DC41A166AC17F22DF1121B92F643@eusaamb103.ericsson.se> <B8F9A780D330094D99AF023C5877DABA84704C4C@nkgeml501-mbs.china.huawei.com> <7347100B5761DC41A166AC17F22DF1121B92FA5F@eusaamb103.ericsson.se> <B8F9A780D330094D99AF023C5877DABA847066E3@nkgeml501-mbs.china.huawei.com> <7347100B5761DC41A166AC17F22DF1121B930603@eusaamb103.ericsson.se> <BLUPR05MB433DD2E1CBEDF363CB13884AE010@BLUPR05MB433.namprd05.prod.outlook.com> <B8F9A780D330094D99AF023C5877DABA8470BE79@nkgeml501-mbs.china.huawei.com> <7347100B5761DC41A166AC17F22DF1121B9349F2@eusaamb103.ericsson.se> <550B2FEF.1030402@gmail.com> <B8F9A780D330094D99AF023C5877DABA8470D37B@nkgeml501-mbs.china.huawei.com> <550C13BD.60209@! gmail.com>
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Date: Sat, 21 Mar 2015 09:27:37 -0000
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Cc: "'Deepak Kumar \(dekumar\)'" <dekumar@cisco.com>
Subject: Re: [Lime-oam-model] Design Team report
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Hi Tom, all,

Tom said 

> I guess RFC7276 is wrong, then.

And i find that a little bit unhelpful.
Since he was replying to Qin:

> > Based on RFC7276,IP OAM is not primarily used for performance measurement.
> > RFC7276 Table 4 summarizes the OAM functions that are supported in each of
> > the OAM toolsets.
> > Toolset support one or several of these OAM functions including CC, CV, path
> > discovery, performance measurement, other function.
> > Take IP OAM as example, CC can be supported by IP Ping Toolset using Echo
> > request/reply messages and path discovery can be supported
> > By IP Traceroute toolset using Traceroute.

...I assume that Tom asserts that at least one of these items captured from 7276
is wrong.

Let's look at them one at a time:

"IP OAM is not primarily used for performance measurement"
This statement is not found in section 4.1 (on IP ping) but may be deduced from
that section.
Furthermore the development of OWAMP and TWAMP lead one to deduce that IP ping
was not suitable or performance monitoring.

"RFC7276 Table 4 summarizes the OAM functions that are supported in each of the
OAM toolsets."
I think that fact is beyond dispute.

"Toolset support one or several of these OAM functions including CC, CV, path
discovery, performance measurement, other function."
I think the definition of "toolset" speaks for itself.

"Take IP OAM as example, CC can be supported by IP Ping Toolset using Echo
request/reply messages"
Section 4.1 has:
   As defined in [NetTerms], it is a program
   used to test reachability of destinations by sending them an ICMP
   Echo request and waiting for a reply.
I'm not asserting that RFC1208 is the only document that can describe IP ping,
but it has been unquestioned for a while. 
Section 4.1 goes on:
   The ICMP Echo request/reply exchange in Ping is used as a Continuity
   Check function for the Internet Protocol.  The originator transmits
   an ICMP Echo request packet, and the receiver replies with an Echo
   reply.  ICMP Ping is defined in two variants: [ICMPv4] is used for
   IPv4, and [ICMPv6] is used for IPv6.
2.7 defines CC as:
      Continuity Checks are used to verify that a destination is
      reachable, and are typically sent proactively, though they can be
      invoked on-demand as well.
So the statement looks good.

"and path discovery can be supported by IP Traceroute toolset using Traceroute."
I think that is self-evident!


So what is the issue?

Going back a bit I see Tom said:

>>> Obviously, ping and traceroute are the prime IP-level working tools. But I
>>> wouldn't call ping a matter of Connectivity Check except in the grossest
sense. 

I wonder whether there is confusion about CC and LM.
CC means "is the destination reachable?" It is binary over a relatively short
period.
LM means "how many of my packets get through?" It is qualitative over a longer
period.

So perhaps the debate is about the definition of CC, not about what tools can be
applied to CC or whether 7276 is right in its description of the tools.

I do not think that it will be helpful to debate the definition of some pretty
well established terms related to OAM. If you want to define your own terms,
that will be fine (then others can map them to the existing terms), but trying
to change the meaning of terms that are in use will cause indigestion.

Thanks,
Adrian