RE: Multihoming by IP Layer Address Rewriting (MILAR)

[Iljitsch van Beijnum <iljitsch@muada.com>]

On Wed, 5 Sep 2001, Tony Hain wrote:

> Question, how does the receiver know it is supposed to replace
> the dst, and which of its possible dst addresses to replace it
> with? In other words, how can it tell the difference between
> a rewritten packet to address B vs. a second connection from
> that src that happened to be load-balanced to address B?

That is a problem. A host could sort through the list of transport layer
connections to see if the source address and ports match any of those and
see which destination address is expected for that connection.

However, a "proxy address rewriting device" would not be able to do this
without keeping track of all transport layer connections of all the hosts
it's rewriting for, which is something I think should be avoided.

So the solution I propose is to have specific alternative addresses for
each regular address. The alternative addresses would be known to the rest
of the world and to the host as such, and not be used for regular
communication.

Suppose a host has two interfaces that connect to two different address
ranges. It would then have four addresses:

A::1	; real address in address block A
A::2	; alternative address for B::2
B::1	; alternative address for A::1
B::2	; real address in address block B

If we're going to use the DNS to discover the alternative addresses, this
would be the forward zone:

host	IN	AAAA	A::1
host	IN	AAAA	B::2

The reversed zone for A:

1	IN	PTR	host.domain.
	IN	AP	B::1
2	IN	PTR	host.domain.

Iljitsch van Beijnum