[Nfd-dev] How to handle unrecognized TLVs

[Alex Afanasyev]

On Jul 30, 2014, at 3:11 PM, Lixia Zhang <lixia at CS.UCLA.EDU> wrote:

> We discussed this issue during today's NFD call but did not reach a concrete conclusion:
> 
> 1/ TLV format allows new types to be easily introduced
> 
> 2/ However when a new type is introduced, it is almost guaranteed that some node does not recognize it.  What should the node do in this case?
> 
> a) in the current implementation (as I heard form Alex), in certain cases we do drop, in other cases we forward -- decisions embedded in implementation.
> 
> b) IETF current practice is to reserve 2 bits in the type field to define the desired action when running into unrecognized types (commonly it is some combination of (a)forward vs drop, and (b)send an error msg or not)
> 
> Do we want to do the same (reserving 2 bits in the type field)?
> If so,
> - this reduces the number of types for 1-byte type to 32

Small correction: to 64 types of each "processing type".

> - where to put these 2 bits?  since type field is variable length, 
>  the best place would be the last 2 bits, but that means renumbering
>  all the defined types :-(
> 
> - there is also a question of whether we need to reserve 2-bit, or one bit could do (just define forward/drop)
> 
> Please share your thought!
> 
> Lixia