[ippm] Estimating IP layer capacity in draft-morton-ippm-capacity-metric-method

[Nieminen Klaus <[e-mail]>]

Hi,

I have one question on how much this metric restricts the measurement setup and e.g. can WebTransport be used in the measurement? As I understand this, if we are running the measurement at the application layer, we can measure application layer (e.g. HTTP/3) payload. This again means that we can only estimate the IP layer capacity as we do not have full information about the header sizes or potential retransmissions. I think we can estimate this with a certain error margin, but I was not sure if this is fine according to the metric.

I have not studied this much further, but started to think this question when I read the part 5.3.  Metric Definitions that talks a case where the packet size is known and of fixed size, but is this really the case? Should there be more flexibility to also be able to estimate the IP layer capacity from the application layer measurement results? I think this should be clarified.

And if we think this should be possible, at least I think it would be useful to add how this estimation can be done to the metric itself as the  target is to harmonize the specified metric and this is not specified, it may lead discrepancies between implementations. 

Any thoughts on this?

Best, Klaus