Re: [ippm] Next version of the duplicate draft

[Henk Uijterwaal <[e-mail]>]

Hi all,

>> so what if there is no information, such as with pure TCP ACKs?
>  > I wonder - since IPPM is doing metrics for IP - if we can define
>  > duplication only in terms of the IP header fields?
> 
> Well, if there is nothing to distinguish two packets that were
> intentionally sent over a packet that has been replicated along
> the way, then one cannot use this metric.  For active measurements
> between two hosts, this won't be an issues as one generates his own
> packets and can  easily put something in to make them unique.
> For other metrics, we haven't defined the packet format or how to
> do this either.
> 
> If one wants to apply the metric for other cases (say, passive monitoring
> of TCP sequences), then one will have to find something in the packets
> to distinguish two packets from one packet sent twice.  I'm open to
> suggestions here.

This discussion seems to have stopped here.

The text says that active measurement systems MUST NOT send packets with
identical information fields, in order to avoid that all packets are
declared duplicates.   That is sufficient to use this metric in this
case.  The metric will also work for passive methods where one is sure
that each packet is different.  The metric won't work for cases where
multiple identical packets are intentionally sent.

In order to move forward:

a) We accept this (and add text to make this clear to everybody).

b) We don't accept this.  In that case, one will have to find something
    to distinguish two packets from one packet sent twice.

My preference is for the former, but I like to hear other opinions.  I'm
afraid that if we don't accept this and don't come up with good suggestions
to distinguish packets, we'll never end up with a duplication metric.


Henk

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Henk Uijterwaal                           Email: henk.uijterwaal(at)ripe.net
RIPE Network Coordination Centre          http://www.amsterdamned.org/~henk
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