[Ndn-interest] Multiple names for lookup-by-content?

Ignacio.Solis at parc.com Ignacio.Solis at parc.com
Mon Sep 29 15:46:29 PDT 2014

CCN 1.0 has a separate field in interest for match-by-hash.  It¹s called
the ContentObjectHash.  An interest that contains that field is said to
have a ContentObjectHash restriction. Forwarding of the interest happens
on the regular name.  Matching of the content object happens on the hash.

Given an interest with a Name and a Hash, the systems considers it a match
to an object that either:
a- Has the same Name and same Hash
b- Has no/empty Name and the same Hash

This latter mode effectively is a hash of the content.

The ContentObjectHash is a type of self-certified name.  For CCN the hash
is not used for forwarding since we believe flat routing is too expensive.

Finally, at the last CCNxCon I presented a matching system with order of
preference based on labels (which included hashes of content). You can
find a video of my presentation at
http://www.ccnx.org/events/ccnxcon-2013/  (video link =
http://www.ccnx.org/video/CCNxCon2013/CCN-9-06-2013-pt3.mp4 , my
presentation is at 21:50).


Nacho (Ignacio) Solis
Protocol Architect
Principal Scientist
Palo Alto Research Center (PARC)
Ignacio.Solis at parc.com

On 9/29/14, 12:56 PM, "Felix Rabe" <felix at rabe.io> wrote:

>I've just thought of something - sorry if this is a duplicate, I can't
>possibly completely follow what has been discussed before, so feel free
>to point me to earlier discussions (even if just 4 days old) of the same
>The idea of a lookup by content via its hash intrigues me. I've heard of
>a suggestion of including this hash as a special field, so routing can
>happen either by name (if content with such a hash is unknown) or by
>content hash.
>I think of a content hash as yet another name. Why not include ... both?
>"/canonical/path/to/a/file" and "/hash-of-file"?
>Their order could indicate precedence, so the first name would be
>matched wherever a router only looks at one name (I'm thinking of
>performance here), whereas multiple names could be supported and matched
>in special situations (like a distributed database that uses NDN as its
>transport), but are optional to match.
>- Felix
>Ndn-interest mailing list
>Ndn-interest at lists.cs.ucla.edu

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