Subject: (ngtrans) IPv4 nodes to connect IPv6 ones

From: "Wu Xiangbin" <[email-masked]>
Date: Thu, 12 Apr 2001 10:35:54 +0800

Hello, every one,
Most of the drafts concerning IPv6 transiton mechanism only solve the problem that an IPv6 host inside an IPv6 island to initiate connections to the outside world. But there are sure some circumstances where the outside IPv4 hosts need to initiate connections to IPv6 ones in an IPv6 island. And up till now, I have only find the AIIH mechanism addresses that (holding in mind that we are short of IPv4 address, so I just rule out those dual stack ones that must have a permannent IPv4 address assigned to the host). Is there any other proposals or I just missed the idea? 
Thanks.

X.B.Wu

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From: [email-masked]
Date: Thu, 12 Apr 2001 11:57:12 +0900

>Most of the drafts concerning IPv6 transiton mechanism only solve
>the problem that an IPv6 host inside an IPv6 island to initiate
>connections to the outside world. But there are sure some circumstances
>where the outside IPv4 hosts need to initiate connections to IPv6
>ones in an IPv6 island. And up till now, I have only find the AIIH
>mechanism addresses that (holding in mind that we are short of IPv4
>address, so I just rule out those dual stack ones that must have
>a permannent IPv4 address assigned to the host). Is there any other
>proposals or I just missed the idea?

	there are other mechanisms addressing IPv6-to-IPv4 translation.

	AIIH/DSTM: assign temporary IPv4 address dynamically to the
		IPv6 machine.
	NAT-PT: use dynamic DNS mapping (see secion 4.1).
	draft-ietf-ngtrans-tcpudp-relay: should be possible if we take similar
		path as NAT-PT

	however, the problem is inherently difficult.
	suppose an IPv6 site sets up a translator for people from IPv4 internet.
	("translator B" in draft-ietf-ngtrans-translator-03.txt seciton 3.1)
	we need to map N IPv6 nodes within a site, into M IPv4 global
	addresses available to the site, and N >> M.
	N normally is 2^80 (for a /48 site), and M normally is between and 2^4.
	the problem is simlar to "make connection from external Internet to
	nodes within company NAT cloud".  yes, it is hard.

	draft-ietf-ngtrans-translator-03.txt should have good hints for you.

itojun

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From: Stig Ven�s <[email-masked]>
Date: Thu, 12 Apr 2001 08:25:01 +0200

> 	nodes within company NAT cloud".  yes, it is hard.

Doing this dynamically like AIIH might help. In theory you could also
try to assign individual ports of M to different N's, but in practice
this is of limited use for incoming connections. Application level
gateways might be of some help too.

Stig

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From: [email-masked]
Date: Thu, 12 Apr 2001 16:09:40 +0900

>this is of limited use for incoming connections.

	it helps, but still is very complex.  implementers need to think
	carefully about:
	- reuse rate/frequency for temporary IPv4 assignment
	- synchronization between DNS server and the translator address mapping
	- DNS server entry TTLs, for temporary IPv4 address mapping advertised
	  to the outside

>Application level

	like having IPv4-to-IPv6 transparent web proxy.  yes, it helps, but
	has limited applications.  it is like having static NAT mappings and
	normally does not automate things too much.

itojun

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From: Brian E Carpenter <[email-masked]>
Date: Thu, 12 Apr 2001 09:18:54 -0500

It's very likely that this problem will be solved in practice by
application level proxies at the IPv4/IPv6 boundary. We don't have
to solve every problem at the network layer.

    Brian

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From: "soohong PARK" <[email-masked]>
Date: Fri, 13 Apr 2001 17:28:27 +0900

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----- Original Message ----- 
From: "Brian E Carpenter" <[email-masked]>
To: <[email-masked]>
Cc: "Wu Xiangbin" <[email-masked]>; <[email-masked]>
Sent: Thursday, April 12, 2001 11:18 PM
Subject: Re: (ngtrans) IPv4 nodes to connect IPv6 ones

> to solve every problem at the network layer.
we are developing clear solution for this problem.
if  we have completed this solution which is based on Linux kernel 2.4.0, most people will be happy !
this solution is EnhancedNAT-PT

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From: Stig Ven�s <[email-masked]>
Date: Fri, 13 Apr 2001 11:15:48 +0200

> this solution is EnhancedNAT-PT

There are some fundamental problems which was what I was trying to say.
To some degree one could use one IPv4 address with different port numbers
for different IPv6 hosts also on connections initiated from IPv4 hosts;
the other direction is easy. There are practical problems though (you
will have to use specific non standard ports and applications must know
which ports to use), and also some technical ones like Itojun mentioned.
Personally I would prefer using application level gateways where possible.
Your solution would work reasonably well if you have enough IPv4 addresses
of course, but in that case I would personally prefer allocating IPv4
addresses to the hosts (if they have an IPv4 stack), dynamically if
necessary. I like DSTM.

I think NAT-PT has some uses though, and I think it's nice that you
implement it for Linux.

Stig