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

[Robin Whittle <rw@firstpr.com.au>]

Hi Dino,

You wrote:

> I said what is left to do is 1) make a decision (see text right above
> this line) or 2) blend two mapping database scheme. We don't know yet.
> We need to experiment.

How would experimentation with your current prototype LISP system
lead to any fresh insights about the fundamental limitations of ALT
or NERD?

NERD on its own won't work because every ITR in the world would need
the full feed of mapping updates.

ALT on its own won't work because the ITR drops or greatly delays
(sending them to the ETR via the ALT network) the initial packets
while it waits for the mapping information.  This would make EID
address space suck - so no-one would want to use it.

The logic of this seems inexorable: Any global query system would
often be so slow that it wouldn't be acceptable unless every ITR is
able to deliver the initial packets via some other mechanism within
a fraction of a second.  If all caching ITRs can do that, then why
bother with a global query server network at all?

I don't think anyone believes ALT or NERD alone could possibly form
an acceptable solution, far less the optimal one.

So that leaves your other suggestion: blending the two systems
together.  This is what I explored - making changes to them starting
from the position of the two systems running alongside each other.

When you have NERD ITRs around the place, there is no need to build
the ALT global query and packet delivery system, because it makes
much more sense to use the nearest NERD ITR as a default mapper and
to have a full database Query Server at the same location - perhaps
in the same device as the NERD ITR.  Then there is no need for ALT,
CONS or any other global (expensive, hard to administer, slow and
unreliable) query server system.


If you or anyone else disagrees with my sequence of improvements to
LISP, you will be able to argue why a particular stage of my
improvements makes the system worse and/or suggest some better set
of improvements.


  - Robin         http://www.firstpr.com.au/ip/ivip/


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