RE: Multihoming by IP Layer Address Rewriting (MILAR)

[Michel Py <py_michel@yahoo.com>]

From: Iljitsch van Beijnum 
>>>> An interesting semantics issue. To me, an ISP is
who provides
>>>> connectivity to the Internet.
>> Can't argue with you there. Now let's define
"default-free zone". I would
>> say: "the subset of routers that do not receive a
full routing table from
>> a single peer or a default route".

Or: "The subset of routers that do not use a default
route, and peer
with two or more other ASNs."

>>>> In the US, it is fairly common to buy a DS3 or
bigger
>>>> pipe with full BGP feed from one or more ISP(s)
(that would be for
>>>> companies that have an ASN and a CIDR block).
>> Having an AS number and a PI or even PA block don't
make a network part of
>> the DFZ: as long as it pays another network to
carry packets to any
>> destination, the network in question may use a
default to the other
>> network and if there is a default filtering is
possible without hurting
>> connectivity. The problem with the DFZ is that
defaults are not possible,
>> so filtering always hurts connectivity.

I think I see your point here. My ISPs are major ones,
I have the assurance
that the routers that I peer with are part of the DFZ
and do not use a default route.

>> No, that's my point: that has still nothing to do
with it. Having your own
>> block means you are visible in the DFZ, being part
of the DFZ means you
>> can't dump packets for which you don't have a route
in someone else's lap.
>> In other words: the DFZ is the top of the tree. On
all other levels, you
>> route the packet to a known destination or to the
higher level. At the
>> top, there is no higher level so all destinations
have to be known
>> destinations to be reachable.

If I have two BGP feeds from two major ISPs, why
should I use a default route?
With a 200,000 route feed, if the route is unreachable
to me it is probably
unreachable to my ISPs as well and I'd rather dump the
traffic into the bit
bucket at my site instead of wasting bandwidth on the
link.

>>>> Definitely. I guess I have not made myself clear
about the relation
>>>> between MHTP and BGP. What should I change in
6.2.9 of
>>>>
http://arneill-py.sacramento.ca.us/draft-py-multi6-mhtp-01.txt

>> Nameserver problem, can't get at the document right
now. Maybe you should
>> multihome...

This is my home^H^H^H^H serf setup. I use "The Public
DNS" for name resolution,
they have two different name servers connected to two
different networks, and I
regularly have DNS failures. Besides the fact that I
got what I paid for (none),
that makes my point about multihoming DNS servers I
guess.

Michel.

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