Re: [RRG] ALT's strong aggregation often leads to *very* long paths

[jnc@mercury.lcs.mit.edu (Noel Chiappa)]

    > From: Brian E Carpenter <brian.e.carpenter@gmail.com>

    > Regardless of the details, is it a surprise that the path taken by
    > initial packets while waiting for a mapping have significantly greater
    > length than the path established after the mapping arrives?

Except in full-push systems like NERD...

    > There seems to be an inevitable design choice between:
    >  1. Discard those packets;
    >  2. Queue them;
    >  3. Send them a long way round.

Excellent point. There are obviously engineering implications behind doors #2
(queue management) and #3 (hot-spots at the top of the resolution hierarchy,
if you do some sort of hierarchy-based alternative forwarding), but that's to
be expected.

    > All these choices are compatible with the datagram model, so I don't
    > see how any of them can be architecturally "wrong".

"The difference between theory and practise is even bigger in practise than it
is in theory." :-) Yes, in theory one could chose door #1, and just toss them,
but in the real world people don't seem to like that one.

    > From an engineering viewpoint, #3 seems reasonable (i.e. this minor
    > delay will be added to the other delays for starting an
    > application-level session).

Yes... which is why a number of ideas have been floated for how to do that
(multicast groups, forwarding along the resolution tree, etc). I wonder if
there are any good ideas we haven't explored yet on how to do this?

	Noel

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