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

[Brian E Carpenter <[e-mail]>]

On 21/07/2016 21:23, Toerless Eckert wrote:
> Btw: There where two other flooding refinements we discussed:
> 
> Store the original-loop-count in the packet so the GRASP API on
> receivers could provide the hopcount distance of the announcer
> distance = original-loop-count - loop-count.

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.

>  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, 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).

    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
>