Re: [RAM] draft-lear-lisp-nerd-01

[Iljitsch van Beijnum <iljitsch at muada.com>]

On 3-jul-2007, at 14:47, Eliot Lear wrote:

> > With this limitation, ALL encapsulation devices must somehow track  
> > the reachability status of locators. In my opinion, you're solving  
> > the easy problem here and leaving the hard one.

> In part I'd have to say, "Guilty as charged", but I am thinking  
> about the other problem.  We'll need some sort of feedback  
> mechanism between ETR and ITR to indicate when an ETR is or is not  
> available.

Hm, what if we create a rather static mapping database. Then, when an  
ITR sees traffic towards a given destination, it retrieves the latest  
ETR reachability info and expresses an interest in receiving updates  
when this reachability info changes. So we flood the static info and  
pull the reachability stuff.

If we engineer this right, this should be very fast but still much  
lighter than doing end-to-end reachability checks between the  
cartesian product of the sets of ITRs and ETRs with active  
communication between them.

I.e., if you want to subscribe to Google's reachability status, you'd  
just ask the next upstream mapping server. But if you want to know  
the reachability status of some obscure destination, you'll probably  
have to talk to a mapping server fairly close to that destination.  
Extra credit: DHT so any given mapping server only has to talk to a  
limited number of other mapping servers.

And/or deltas to reachability information can be highly compressed  
since the static mapping info is known.

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