RE: [ippm] comments on draft-ietf-ippm-multimetrics-03.txt

Hi Rüdiger,

Thanks for your comments. 

See my answers inline.

> 
> The spatial result matrix proposed by the authors is a good idea. It may
> additionally be compared against another option:
> 
> current:   R1dT1     R1DT2     R1DT3    ...R1DT
> 
> additional: T0-R1dT1    R1DT2-R1dT1    R1DT3-R1dT2  .....R1DT-R1dTn-1
> R1DT (as an additioinal line)
> 
This looks like a stream of delay variations experienced by the receiver R1: it is an end-to-end metric which looks like "Type-P-One-way-ipdv-Poisson-stream" defined in http://tools.ietf.org/html/rfc3393#section-3.1.

> The second table may help to identify multicast tree sections inducing
> delay variations and constant delay more clearly (T0 = probe sending time,
> all numbers in [ms]).
> 
> R1dT1     R1DT2     R1DT3    R1DT4
> T0+5        T0+7      T0+8     T0+12
> T0+7        T0+9      T0+10    T0+14
> T0+6        T0+8      T0+9     T0+13
> 
> could also be expressed as
> 
> R1dT1-T0    R1DT2-R1dT1    R1DT3-R1dT2   R1DT4-R1dT3   R1DT4
>    5             2              1             4              12
>    7             2              1             4              14
>    6             2              1             4              13
> 
I apologize; I don't see where the multicast sections on the figure above are. 

> Another point to be discussed would be the spatial distribution of packet
> loss. A packet loss close to the source of a multicast tree has a
> different impact than a packet loss close to a receiver. I can't provide a
> good proposal now and I respect that providing a "single" metric may
> collide with the aim of identifying the cause of a problem fast.
> 

The draft defines spatial and multicast metrics. It does not mix these metrics to provide statistics for investigate the performance of a multicast tree. My thinking is that spatial distribution of packet loss in a multicast tree has to be build on the top Type-P-Spatial-Packet-loss-Vector. 

Regards
Emile