[Nfd-dev] A Potential Conflict in Developer Guide about FIB Entry's NextHop Collection

[Junxiao Shi]

Hi Ju

FIB entry with zero length name may have zero next hop records. Such an
empty isn't stored in FIB, but FIB lookup methods may return it so that
forwarding doesn't need to check whether FIB entry is null.

Yours, Junxiao


On Thu, Jul 4, 2019, 17:46 Ju Pan <pjokk722 at email.arizona.edu> wrote:

> Dear folks,
>
> In NFD Developer Guide, there is a potential conflict in the
> description about a Fib entry's nexthop collection.
>
> 1. In Chapter3 Tables --> 3.1 Forwarding Information Base (FIB) -->
> 3.1.1 Structure and Semantics
> --> FIB entry and NextHop record, it says:
>
> "A FIB entry (nfd::fib::Entry) contains a name prefix and a non-empty
> collection of NextHop records."
> (It says a FIB entry contains a non-empty collection of NextHop
> records, in 3.1.2 Usage part, it says a FIB entry losing its last
> nexthop record is deleted.)
>
> 2. In Chapter 4 Forwarding --> 4.5 Helper Algorithms --> 4.5.1 FIB
> lookup --> 1, it says:
>
> "FIB guarantees that Longest Prefix Match returns a valid FIB entry;
> however, a FIB entry may contain empty set of NextHop records, which
> could effectively result (but, strictly speaking, is not required to
> happen) in the strategy rejecting the Interest."
> (It says a FIB entry may contain an empty set of NextHop records.)
>
> I think the actual NFD was implemented as the former way. (erase the
> Fib entry if it doesn't have any nexthop)
>
> Could someone confirm this conflict or point out what did I
> misunderstand? Thanks.
>
> Regard,
> Ju
>
>
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