Re: [ippm] I-D ACTION:draft-ietf-ippm-multimetrics-04.txt

["Geib, Ruediger" <Ruediger.Geib at t-systems.com>]

Emile,

I just noticed that the 04 version includes text on "Spatial Segments metrics definitions", which in the case of delay follows my proposal. I appreciate that.

The section on "A Definition of a sample of Packet Loss of a segment of the path" correctly includes an 

o  a value of Lk of 2 means that Bk.a has a value of 1 (not observed)
   and that Bk.b have a value of 0 (observed);

The discussion qualifies this as

o  A value of Lk of 2 (1,0) corresponds to a mistake in the ordering
   of Ha and Hb over the path coming either from the configuration
   (asumption on the path) or from the processing of the vectors: bad
   scrutening of the path ordering information, or some other mistake
   in the measure or the reporting.  It is not in the scope of this
   document to go in further details which are mostly implementation
   dependent.  This value MUST not be used to compute packet lost
   statistics.

After talking with Nicolai Leymann (having multicast expertise) I learned that after a rerouting event, a passive monitor along a path may indeed no longer be in it, if the new route is around (also a replication point may change). That means, a value of Lk of 2 can result from a usual re-routing event, it is not an anomaly. In that case, the results should be considered.

I think all metric definitions should respect this case.

I've only searched for the wird "reroute" in the current version and found it once. Sgould my comment be discussed already, I apologize for not having read that section.

Regards


Ruediger

 

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