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Re: Granularity (was Re: [RRG] ALT + NERD is inelegant & inefficient, compared to APT or Ivip)



Iljitsch van Beijnum wrote:
* If you want to keep host granularity stuff out of the map database, you have to encode it in the address

What do you mean? Encode the AS in the address? For N > 1 this requires that you can dynamically do a "reachable match first" lookup in your routing tables.

Yes, this is correct.

However, several of the LISP designs already separate out the "live" reachability from "mostly unchanging" mapping information.

So, this is not a *new* requirement, nor is it unique to this concept.

And yes, having the reachability info scale better than the population of any numbering system, is important - and possible.
So, there are three possibilities for host granularity:
* No host granularity
* mapping size 10^11 (not suitable for push)
* special case for N=2 only

We already have MIP so no host granualirity would be a completely reasonable choice.

MIP only supports EID host granularity, if there is a "home agent" numbered from EID space.

This doesn't provide any way for a site that doesn't already have EIDs available without going through the process of acquiring EIDs, managing an MIP router, etc. I.e., not something non-technical folks can do, so it doesn't scale very well from a global perspective.

Not that having lots of work for semi-technical IT folks is necessarily a bad thing - I'd just rather it be something that is fundamentally incapable of being engineered out of the solution space.

I see MIP as orthogonal to LISP, rather than a way of "enhancing" what LISP provides. Using MIP for non-mobile entities is just a bad design choice, IMHO.

Brian Dickson

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