Re: [icnrg] Review of draft-irtf-nwcrg-nwc-ccn-reqs

Marie-Jose Montpetit <> Fri, 13 December 2019 16:23 UTC

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Subject: Re: [icnrg] Review of draft-irtf-nwcrg-nwc-ccn-reqs
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Thank you for your comments.

In order to push this draft to last call we will limit the further comments
to January 15 2020 to account for the upcoming Holidays.


On December 7, 2019 at 8:55:36 AM, David R. Oran (

With <ICNRG Chair Hat On>
A reminder to ICNRG’ers to please review this document soon, as the NWCRG
would like to progress to last call in the near future.

With <ICNRG Chair Hat Off>
Here are my comments as individual on draft-irtf-nwcrg-nwc-ccn-reqs. They
are divided into general, technical, and editorial/nits.
General Comments


   The document contains a lot of thought-provoking material, and is
   technically sound in terms of its discussion of the issues and tradeoffs.
   Therefore, I think it’s appropriate to advance it now as it can form the
   basis to guide future research work and experimentation with the
   combination of ICN and NWC.

   While not a pre-condition to advancing this to RG last call in NWCRG,
   the writing does need a fair amount of work on clarity of English language
   exposition, grammar and usage. It would be very helpful if this could be
   done before sending it to IRSG review, as IRSG members are neither NWC nor
   ICN experts, and could very easily be left scratching their heads in a
   number of places.

   The introductory tutorial material on ICN is appropriate to level-set
   for the NWC community, but there’s a need for an equivalent tutorial
   section on NWC to level set for the ICN community. Concepts like “degrees
   of freedom”, “innovative packets”, “RLNC”, don’t appear in the (terse)
   terminology list in the Definitions section. It might be good to expand
   this with more tutorial text.

   There are a number of places where the document confounds security with
   privacy; these need to be clearly separated and the considerations

   A pass needs to be done to align the text here with the current RFC
   status of CCNx. I have some specific comments on this in the technical
   comments below, but I may have missed some places so an overall scrub ought
   to be done, either now, or during RG last call.

Technical Comments


   In the second paragraph on page 8, you discuss the interaction of the
   naming scheme choices with forwarding, but don’t address which, if any, of
   the characteristics would necessitate a change to the semantic-free
   matching currently done by CCNs and NDN, and/or the prefix match semantics
   of NDN versus exact match of CCNx. Instead you concentrate on the size of
   the TLV headers, which doesn’t seem to be a first-order problem.

   Material touching on in-network recoding is scattered around in various
   places and probably ought to be consolidated or alternatively summarized in
   a section near the end to pull things together. One approach you don’t
   consider (but probably ought to) is exploiting multi-signature capability
   some signing schemes that would work with CCNx. This way you can use
   different signing keys for the original and coded packets, allowing the
   entities responsible for coding to be different from the authors of the
   original content. This way in-network recoding could be allowed by giving
   the signing keys for coded packets to routers - this would not require them
   to be trusted to maintain the integrity of the original data since they
   would not have the original signing keys.

   In section 4.2.2 you bring up video streaming, and seem to have an
   assumption that your network code is systematic rather than non-systematic
   (aside: another thing probably needing some material in the introductory
   section), further asserting that sequential delivery is important, and
   hence there’s some disadvantage to fetching coded packets first. I had a
   somewhat hard time following this, and unless I’m misreading your logic, I
   think it’s actually wrong since today’s streaming decoders don’t care at
   all about packet arrival order and need enough computing capacity to decode
   NWC packets within the playout deadline in order to work decently anyway.

   In the second paragraph of 4.3, you seem to be unaware that CCNx has
   exactly the feature you want for packets you don’t want to cache. The
   producer just sets the RCT (Recommended Cache Time) to zero.

   The discussion about whether routers need to decode and validate coded
   packets is a bit confused and I think actually wrong in some places. There
   are two issues. First, the text confounds cache pollution with cache
   poisoning; these are separate phenomena that need different
   mitigation/avoidance approaches. Second, while you probably ought to
   discuss both, cache poisoning is pretty thoroughly addressed in the current
   CCNx design (less so in NDN) in a way that does *not* require routers to
   validate signatures on packets, or in the case of NWC, decode them.

   I didn’t get the use of the term “virtual logical link” when talking
   about fetching content from multiple producer sites. None of the transport
   or congestion control schemes I’m familiar with for ICN use this term, and
   in fact I’m not sure the concept is at all useful in the context of
   multi-path/multi-destination forwarding in CCNx o NDN. Instead you might
   just reference existing work on multi-path/multi-destination congestion
   control and transport.

   As the first sentence of a security considerations section, saying “This
   document does not impact the security of the Internet” is a big red flag in
   front of a bull. Get rid of it (see may editorial suggestion to consolidate
   all of the security and privacy material see rather than a separate section

Editorial Comments & Nits


   Need to do a global replace of CCN with CCNx.

   Get rid of the first paragraph of section 2 and the normative reference,
   since this document doesn’t use any of the RFC2119 terminology.

   Everywhere you say “seamless mobility” it needs to say “seamless
   *consumer* mobility”.

   the second paragraph on page 7 (which begins “the CCN/NDN core
   abstraction”) is really hard to follow. There’s also a confounding between
   what NDN cals the “Strategy layer” and “specific…transport” since in NDN
   forwarding strategy does not provide what are classically considered to be
   transport functions.

   Section 4 probably should not be called “requirements” since (a)this
   document is not an appropriate vehicle for expressing NWC/ICN integration
   requirements, and (b)it doesn’t really state requirements, but rather some
   general technical considerations.

   the first paragraph of section 4.1 is under naming, but talks mostly
   about fragmentation. Some re-organization might help by moving the
   fragmentation issues to the end of 4.1 rather than the beginning.

   page 8, second paragraph s/not be able to obtain degrees of freedom/not
   be able top obtain sufficient degrees of freedom/

   Page 11, Section 4.3 Caching is *not* essential for improving throughput
   and latency. It’s useful, but not essential.

   Given the paucity of material in section 4.5 on security and privacy, it
   might be better to just move this (and hopefully expand it a bit) to
   section 6 as a conventional security considerations section.

[End of Comments]

On 21 Nov 2019, at 0:47, David Oran wrote:

This is joint work of NWCRG and ICNRG, managed out of NWCRG. It has needed
serious review from the ICNRG participants for quite some time, and at this
point our review is what is holding up its last call and progression.

You can find the current version at

PLEASE review this and send comments to both the ICNRG and NWCRG mailing

I would like to set a deadline of three weeks (December 13) after which if
no comments that need to be addressed prior to further advancement are
received, I’ll advise the NWCRG chairs to proceed with RG Last call in

Thanks, and have a good trip home for those of you who joined us in

DaveO (for Dirk and Börje), ICNRG co-chairs.

iDevice - please excuse typos.

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