Subject: RE: [midcom] Topology considerations documents

From: "Christian Huitema" <[email-masked]>
Date: Fri, 7 Sep 2001 10:00:21 -0700

> > We have an inter-realm solution: IPv6.
> 
> 	While I appreciate your desire to inform, I admit that I
> actually
> was aware of IPv6 already. The Inter-Realm Router is merely an
> alternative to it.

There is no such thing as an Inter-Realm Router in the Internet
architecture; supporting such a beast is not a requirement of MIDCOM.

To be very specific, I would contend that it is not possible today to
build a single box connecting two domains A and B to the Internet,
allocate the exact same address range to A and B, and allow direct
communication between A and B. With the existing TCP-IP stacks, the only
way for an A-host to speak to a B-host is to stick in the TCP-IP header
an address that will be "natted" back to B. There is definitely no
realm-identifier anywhere in the packet; mapping has to be based solely
on the addresses and port numbers.

What we do find today are either two layers of NAT:

 <domain A: 172.16.x.x> - NAT -+
 <domain B: 172.16.x.x> - NAT -+
 <domain C: 10.34.x.x>  - FW  -+- provider X: 10.x.x.x - NAT - Global

Or "back to back" NAT configurations, such as:

           < domain A: 10.x.x.x > -- NAT --+
                                           | Interconnect: 172.16.x.x
           < domain B: 10.x.x.x > -- NAT --+

-- Christian Huitema

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---

From: "Bob Penfield" <[email-masked]>
Date: Fri, 7 Sep 2001 13:44:48 -0400

----- Original Message -----
From: "Christian Huitema" <[email-masked]>
To: "Andrew Molitor" <[email-masked]>; <[email-masked]>
Sent: Friday, September 07, 2001 1:00 PM
Subject: RE: [midcom] Topology considerations documents

> on the addresses and port numbers.

My draft has a detailed example of how this is done. The private endpoints
send to a public address which gets NATed to the private address in the
other domain.