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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

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