Re: [RRG] Re: Aggregation Implies Provider Dependence (LISP-ALT) & Ivip dependencies too

[Scott Brim <swb@employees.org>]

Excerpts from Christian Vogt on Fri, Feb 08, 2008 09:02:44PM +0200:
> Any ALT deployment has to effect a trade-off between aggregation and
> provider-independence.  If ALT is to aggregate EIDs, then an edge
> network E's entry to the ALT infrastructure will have to be at a
> particular ALT router, R1, that is defined by E's EID space.  And this
> implies a dependence on R1's operator.  Otherwise, if you want to avoid
> this dependence, you cannot aggregate.
>
> You need to make the same trade-off even if, as you describe, E's direct
> provider sets up an ALT router R2 to which E may connect.  Then again:
>
> - You either prioritize aggregatability, in which case R2 must relay to
>   R1.  E then remains technically dependent on R1's operator, even
>   though business relationships may be transitive from E to E's direct
>   provider to R1's operator.
>
> - Or you prioritize independence from R1's operator, in which case R2
>   must connect to the ALT infrastructure directly.  In this case you
>   lose aggregatability.

You do not need to lose independence or aggregatability.

There can/should be multiple ALT nodes responsible for a prefix.  This
is not really a hierarchy.  So, you could have

              R3  R4    routes to mappings for 192.0.0.0/8
	     /|\  /|\  
	    / | \/ | \
	 ...  | /\ |  ...
	      |/  \|
	      R1  R2    routes to mappings for 192.68.0.0/16
	      |\  /|  
	      | \/ |
	      | /\ |
	      |/  \|
	      ETR ETR   responsible for site 192.68.1.0/24

You do not lose independence or aggregatability.  The redundancy at a
particular level is abstracted out at the next level.  This is true no
matter how many ALT nodes you have within a level.


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