[Nfd-dev] On the necessity of the STRAGGLER timer

[Junxiao Shi]

Hi Seweryn

Straggler timer delays transferring Nonces from PIT out-records to DNL, in
order to keep DNL small.

PIT entry is needed for Data measurements, because strategy needs to know
which Interest is being satisfied by the incoming Data (recall that
Interest name is a prefix of Data name and thus may be shorter than the
Data name), and when that Interest was forwarded (so as to calculate RTT).
Neither information is available in NameTree.

Yours, Junxiao

On Wed, Nov 16, 2016 at 3:55 AM, Seweryn Dynerowicz <f80120 at ulusofona.pt>
wrote:

> Dear NDN Developers,
>
> I'm currently investigating how to implement a Long-Lived Interest concept
> into NDN.
> In the process of reading the documentation and code (forwarder.cpp), I
> keep wondering
> about the STRAGGLER timer which makes me question the need for having one.
>
> According to the dev-guide, STRAGGLER serves a double purpose; loop
> detection and data
> measurements.
>
> For LOOP DETECTION, all I see is that STRAGGLER delays the transfer of the
> Nonces from
> the Out-Records to the DeadNonceList (DNL). It seems to me that no
> detection capability
> would be lost if the Nonces were transferred directly to DNL instead of
> starting STRAGGLER.
>
> As for the DATA MEASUREMENTS, I do not see why the PIT entry has to be
> involved in it.
> It seems to me that with a bit of rewriting, the NameTree could be used
> directly for the lookup
> which means that the PIT entry would not be required in the DATA
> MEASUREMENTS aspect. However,
> I might be missing something about the scope and nature of MEASUREMENTS
> foreseen for NDN.
>
>
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