[Ndn-interest] NFD flag clarification

Lan Wang (lanwang) lanwang at memphis.edu
Tue May 5 10:09:11 PDT 2015


On May 4, 2015, at 9:08 PM, Tai-Lin Chu <tailinchu at gmail.com> wrote:

> It is very interesting, but is it a good idea?
> 
> It sounds like two applications are now "fighting" over interests.

Why?  When this capture flag is used, the intention here is for the interests to be sent to the node advertising the more specific prefix.  There are scenarios when this may be desirable, e.g., this node has the content for /A/B, while the other node has the content for anything under /A except /A/B.

> Moreover, ChildInherit and Capture complicate lookup a lot.

We don't apply these during lookup.  They are applied by NRD during prefix registration when assigning the next hops.  NFD simply gets the correct set of next hops (after the flags are applied) from NRD.  It's too slow to do all this during forwarding.

Lan

> 
> On Mon, May 4, 2015 at 3:28 PM, Vince Lehman (vslehman)
> <vslehman at memphis.edu> wrote:
>> Hi Tai-Lin,
>> 
>> Is this understanding correct?
>> 
>> Yes, I think you have the general idea.
>> 
>> The CHILD_INHERIT flag, when applied to a route, allows a longer child name
>> prefix to use that route for forwarding. It adds the route as an option to
>> the FIB, but the route used to forward the Interest is up to the strategy. A
>> parent prefix with a route without the CHILD_INHERIT flag will not be added
>> to the FIB entry for a longer prefix.
>> 
>> CAPTURE prevents a name prefix and longer children prefixes from using a
>> route associated with a shorter parent name prefix. The CAPTURE flag will
>> not only prevent inheritance for the same name prefix but also longer
>> children prefixes.
>> 
>> What is the use case of capture?
>> 
>> The capture flag can be used to prevent traffic for a prefix from flowing to
>> another route.
>> 
>> For example, if laptop 1 registers /A with CHILD_INHERIT and laptop 2
>> registers /A/B with no flags, traffic for /A/B can be forwarded to both
>> laptop 1 and 2.
>> 
>> If laptop 2 instead registers /A/B with the CAPTURE flag, traffic for /A/B
>> will be forwarded to laptop 2 and will not be forwarded to laptop 1.
>> 
>> --
>> Vince Lehman
>> 
>> On Apr 22, 2015, at 3:54 PM, Tai-Lin Chu <tailinchu at gmail.com> wrote:
>> 
>> http://redmine.named-data.net/projects/nfd/wiki/RibMgmt
>> 
>> Is this understanding correct?
>> CHILD_INHERIT: true = usual lpm, false = exact matching
>> CAPTURE: prevent lpm to be used (in other entries with the same name)
>> 
>> What is the use case of capture?
>> 
>> 
>> Thanks.
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>> 
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