[icnrg] Question on the NIST NDN forwarder

"David R. Oran" <daveoran@orandom.net> Wed, 22 April 2020 14:29 UTC

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From: "David R. Oran" <daveoran@orandom.net>
To: "Shi, Junxiao" <junxiao.shi@nist.gov>, ICNRG <icnrg@irtf.org>
Date: Wed, 22 Apr 2020 10:29:35 -0400
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Subject: [icnrg] Question on the NIST NDN forwarder
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This may be a misunderstanding, or an NDN architecture question rather 
than a forwarder question. My knowledge of the current state of the NDN 
architecture is somewhat weak, so please excuse the noise if this is 
flat out wrong.

It relates to the CS prefix matching shown on slide 9.

I thought that NDN semantics said that an Interest with prefix match 
would match the CS entry with the longest prefix match, independent of 
how many name components the CS name entry had, or how many name 
components were expressed in the Interest. Your example shows just a 
single level of prefix indirection in the CS (which is of course fine 
for an example to illustrate the design).

But…

What if I have a named object of, for example, /a/b/c/d/e.
In order to match any interest asking for prefix match, e.g. /a/, would 
I not have to create indirect entries for /a/, /a/b/, and /a/b/c/ as 
well as the indirect entry for /a/b/c/d/ ?

If true, this seems a really sub-optimal situation for objects with long 
multi-component names, as the number of CS entries and consequent writes 
would multiply rapidly. A secondary effect might also require both a 
“real” CS entry and an indirect CS entry if an application actually 
has an object, like /a/b/c as well as one named /a/b/c/d/e.

Did something change in the NDN architecture to explicitly restrict the 
number of up-levels that are allowed in prefix matching?

Thanks for enlightening me!!

DaveO