Re: nhrp-05 ????? - Destination Prefix Extension

[Bruce Cole <[e-mail]>]

> > > > 6. Proposal to add prefix mask to purge packet
> > > 
> > > The consensus on item #6 follows:
> > > Allow the destination prefix extension to be sent in Purge packets.
> > 
> > I saw no disagreement to this proposal, and it seems like a sensible
> > compromise.  Objections?
> 
> I tried to argue against this proposal merely on the grounds of not
> having seen any real justification that it would save much traffic in 
> realistic scenarios and that nobody seemed to have evaluated the overall
> system impact very thoroughly. Are we operating on the "guilty until proven 
> innocent" principle here?

Certainly not.  Consensus on this item didn't seem clear, which is why
I hadn't listed it as a seemingly resolved issue in the first place.
Your disagreement seemed to be that it was unclear what the
semantics are for a purge with an associated mask.  The subsequent proposal
to simply allow the destination prefix extension to be included in purge
packets seemed to go undisputed.  So I asked if there were objections...

Shall we first further discuss what we think the semantics are for a mask
that is included in a purge request?  It doesn't look like we have that
clearly defined yet.  I could tell you what I think it means :)

> But, if we are going to adopt the mask stuff at all then I propose strongly 
> that we add it's support in receivers as MANDATORY citing both the "options 
> are bad" and the "be liberal in what you accept" principles.

For a station to efficiently support cache invalidation requests that include
a network mask, the cache should be tree based instead of a simple
linked list/hash table.  Basically you're requiring all NHRP stations to
support aggregation of NBMA information, and a sophisticated cache.  I
think this is a bit of a leap over current requirements.

> BTW, I think these NHRP client complexity arguments are bogus when compared 
> to the complexity of any ATM signaling client that might sit below NHRP!

For some of us, ATM is not the only media type that is being supported by
NHRP.  For other media such as SMDS, the complexity is much less...
(Just playing devil's advocate here.)