Re: [RRG] Idea for shooting down

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

Hi Brian,

With your proposal:

  http://www.cs.auckland.ac.nz/~brian/DFZng.pdf

I get the impression that the result would be the Internet being
much less meshed than it is at present.  This would have negative
impacts including:

1 - Less robustness in the event of link and router failure.

2 - Often longer path lengths (AKA "stretch") as a packet has to
    get out of one of the many Level 1 domains (or the one Level 0
    domain) up to some Level 2 domain in order to get to another
    Level 1 (or the Level 0) before it could be delivered.  This is
    true even if the ISP border routers connecting to the sites with
    the sending and receiving hosts are physically close, but happen
    to be of ISPs which are in separate domains.  (I assume an ISP
    can only be in one domain, but perhaps I am wrong.)

3 - Therefore, further dimensions of "Balkanisation" of the
    Net, where actual packet delivery times and reliability
    levels depend not just on physical (partly geographic)
    topology, link capacities and traffic levels but also on
    which domain each host is in and how far the packet has to
    travel to go up and then down a level to the destination
    domain.

4 - Therefore, a lot of fuss as ISPs try to decide which domain
    to be in.

5 - Also, perhaps, more pressure on "sites" (as I think you
    nicely describe them) to multihome to various ISPs in
    different domains.  However, that only helps with the
    path length if the "site" is smart enough to send outgoing
    packets to the optimal ISP's router.  This wouldn't help
    with optimising which ISP and region an incoming packet
    arrives through when it is sent by a non-multihomed site
    or a multihomed site without the smarts to choose the
    best outgoing router.


Also, I don't understand how your proposal would help with the
central problem we are trying to solve - of a multihomed site's
router requiring a separate route for every prefix advertised by any
site anywhere at all.

The fact that the destination site is in a different domain doesn't
alter the fact that the multihomed site's router needs a separate
route for that slice of address space, because the router still
needs to decide which of the two or more upstream ISP routers to
forward the packet to.

 - Robin


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