<div dir="ltr">Dear Klaus,<div class="gmail_extra"><br><div class="gmail_quote">On 17 November 2016 at 19:02, Klaus Schneider <span dir="ltr"><<a href="mailto:klaus@cs.arizona.edu" target="_blank">klaus@cs.arizona.edu</a>></span> wrote:<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
A more strict loop detection scheme is to keep the PIT in-records around after the initial Interest was satisfied, as done by the straggler timer.<br></blockquote><div><br></div><div>I don't think that keeping the IN-Records will allow you to detect more loops than only keeping the OUT-Records Nonces. That scheme would not be able to detect the forwarding loops described by Marc in his first comment, namely if the Nonce of the INT a node A sent out gets aggregated under another INT at some node B upstream (or node B changes the Nonce) which THEN loops back. Node A will not be able to relate that INT to any it has previously received (IN-Record) or sent (OUT-Record).</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
The fundamental problem is that routers have limited memory, so you have to remove the information about previously seen Interests at some point. Any loop that takes longer than the router's ability to remember previous Interests/nonces cannot be detected that way.<br>
<br>
The "Dead Nonce List" is really only a performance optimization: Only store nonces, not the whole PIT entry + only store some nonces which seem more likely to loop (the ones in out-records). This saves some memory, but doesn't solve the fundamental problem that you would need unlimited memory for perfect loop detection.</blockquote><div><br></div><div>I'm not questioning the function that the Dead Nonce List fulfills. My original question was why delay the insertion of Nonces from OUT-Records to the DNL by means of the STRAGGLER timer but I guess that because the OUT-Records are kept in the PIT entry for data measurements it makes sense to wait that much before transferring only the Nonces in DNL before deleting the PIT entry.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="m_2906015701292414148m_-1272626692082122843h5"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
I was describing what I understand is the RTT that can be computed under<br>
the existing implementation. My original concern here is about how to do<br>
Data measurements without the need to keep the OUT-Records longer in the<br>
PIT entry. The solution to that should make it easy to implement<br>
whatever measurements to whichever granularity someone desires. I think<br>
I have a good solution to this but I need to think it through (short<br>
answer; put it entirely in the strategy and add a callback to it in the<br>
beginning of the onIncomingData pipeline).<br>
</blockquote>
<br></div></div>
How is it possible to do an RTT measurement without the out-record?<br>
Let's say you send out two Interests and Face A and Face B. The Data returns on Face A and you remove the whole PIT entry.<br>
Now that second Data returns on Face B. How could you know its RTT? You just deleted the information about when you sent that Interest.<br>
Of course, you can store this information inside the strategy and then implement what you want in onUnsolicitedData(). But what's the benefit compared to just using the out-records?<br></blockquote></div><div><br></div><div class="m_2906015701292414148m_-1272626692082122843gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div><font face="monospace, monospace">I'm still thinking about this... I don't see yet what measuring the RTT in NDN means.</font></div><div><span style="font-family:monospace,monospace"><br><br>Best regards,<br><br></span></div><div dir="ltr"><span style="font-family:monospace,monospace">S.<br><br></span><div><span style="font-family:monospace,monospace">+-----------------------------</span><span style="font-family:monospace,monospace"><wbr>-----------------+</span></div><div><span style="font-family:monospace,monospace">| Dynerowicz Seweryn |</span></div><div><span style="font-family:monospace,monospace">| PostDoc Researcher |<br></span></div><div><span style="font-family:monospace,monospace">| SITI, COPELABS, Building U |<br></span></div><div><span style="font-family:monospace,monospace">| Universidade Lusófona |<br></span></div><div><span style="font-family:monospace,monospace">| Campo Grande, 388, 1749-024 Lisboa, Portugal |</span></div><span style="font-family:monospace,monospace">+-----------------------------</span><span style="font-family:monospace,monospace"><wbr>-----------------+</span><div><span style="font-family:monospace,monospace"><br></span></div><div><span style="font-family:monospace,monospace">I hate the empty set; he's so full of himself.</span></div><div><span style="font-family:monospace,monospace"><br>"Judge a man by his questions rather than his answers",<br>Pierre-Marc Gaston, Duc de Lévis<br></span>
<span style="font-family:monospace,monospace"><br>"Ignorance more frequently begets confidence than does knowledge.",<br>C. Darwin<br><br>"Seek freedom and become captive of your desires. Seek discipline<br>and find your liberty.", F. Herbert</span></div><span style="font-family:monospace,monospace"><br></span></div></div></div></div></div></div>
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