Re: [Anima-signaling] Concern about GRASP Flood message

[Toerless Eckert <[e-mail]>]

On Thu, Jul 21, 2016 at 10:31:32PM +1200, Brian E Carpenter wrote:
> The loop count is already a mandatory field in every objective.
> We can add original-loop-count as a specific field in this
> objective. No problem.

Ok. Any guidelines when you consider some attrbite to be part of
an objective as opposed to eg: a GRASP header ?

> >  Refine flood pruning as: 
> >  If the distance of a received announcement is smaller than the
> >  distsance of the cached announcement, flood the new packet (and put
> >  into cache).
> 
> I have a problem with that but it's connected with another change
> we have to make: caching multiple versions of a flooded objective
> iff they come from different sources. We need to do that so that
> in your use case (and probably others), the user ASA can make its
> own choice among several alternatives. So in the flood cache we
> will overwrite the cached value from address A if we receive a
> new value from A, but the cached value from address B will not be
> overwritten. As long as we do that, the distance comparison isn't
> in the cache, it's in the user ASA.

So there are two comparisons:

The first comparison is in GRASP when a new message from A is received.
It's compared with the exxisting cache of A, and when it's better
(longer remaining cache time or lower distance), then it does get into
the cache and is flooded. Else it's dropped, and existing cache is better.

The second comparison is as you said in the ASA between the A cache and B
cache.

> So, to be clear, the objective syntax is:
> 
> objective = ["ANI_Registrar", objective-flags, loop-count, original-loop-count, stack-list]
> 
> and in the flood cache, it is tagged with its sending address (which
> I noticed is already in the Flood message anyway, so that part is solved).

Ok.

And the stack list will have the locators ?

Cheers
    Toerless

>     Brian
> 
> > Cheers
> >     Toerless
> > 
> > On Thu, Jul 21, 2016 at 09:06:02PM +1200, Brian E Carpenter wrote:
> >> On 21/07/2016 20:45, Carsten Bormann wrote:
> >>> Brian E Carpenter wrote:
> >>>> There is already one use case emerging: using Flood
> >>>> to announce bootstrap Registrars to all bootstrap Proxies. A proxy needs to
> >>>> be able to choose which registrar to use, so needs to
> >>>
> >>> Well, the content of the message then appears to be "x is offering to be
> >>> bootstrap registrar".  This can of course alternatively be represented
> >>> by "x says: 'I am offering to be bootstrap registrar'".
> >>
> >> Exactly, but the Flood mechanism loses track of x when the message is relayed.
> >> That would need a protocol change.
> >>
> >>    Brian
> > 

-- 
---
Toerless Eckert, [e-mail]