Subject: (ngtrans) nat-pt/siit and source routing

From: [email-masked]
Date: Thu, 15 Mar 2001 12:47:34 +0200

hello all,

While implementing NAT-PT under Linux, I have come across a peculiar
problem. 

Take example of ping.

v6-host> ping6 prefix::v4 address

-take the v6 packet, translate it with destination address = the target v4
address and src address = one from the NAT-PT pool.
-calculate the route for the v4 side and put the packet on the v4 stack.

----------		  ------------	       		-----------
v6 host   | ------- |nat-pt box |--------------------	| v4 host |
----------          ------------           		-----------
		     v6 addr	pool of v4 addresses

                              configured with this i/f

notice that routing here works perfectly since the v4 addresses in the pool
are bound with the v4-side interface and there exists a valid route.

However, when there is an incoming packet (from v4 to v6), i have to do the
following:

take example of the return echo reply.
-take the v4 packet, translate it to v6.. dest addr = v6 address and src
addr = PREFIX::v4 address. But then when i feed this packet to 
the route calculation function with source routing enabled, it will not give
me any route since the src addr = PREFIX::v4 is completely alien to it. So i
guess NAT-PT and source based routing don't go along very well. I don't know
what happens in the case of SIIT since there would be mapped address as the
src address and i don't know how they are verified by the routers. Other
source address verification schemes such as RPF would also be facing the
same problems.

regards,
imran

---

From: George Tsirtsis <[email-masked]>
Date: Thu, 15 Mar 2001 07:13:20 -0500

Hi Imran,

See some comment below...

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
Sent: Thursday, March 15, 2001 10:48 AM
To: [email-masked]
Subject: (ngtrans) nat-pt/siit and source routing

hello all,

Take example of ping.

                              configured with this i/f

me any route since the src addr = PREFIX::v4 is completely alien to it. 

GT> Why is that? the PREFIX part of the PREFIX::v4 address should be an IPv6
/64 prefix pointing to the v6 side of the NAT-PT box... This should not be
alien to source routing ...unless I missed your point...

George

---

From: "Hesham Soliman (ERA)" <[email-masked]>
Date: Thu, 15 Mar 2001 21:48:12 +0100

Hello Imran, 

> I don't know
	=> In our implementation of SIIT and the SIIT-DSTM draft
	(note the second draft is required for routing inbound packets), 
	The SIIT router adds a route for each allocated IPv4 address.
	Packets are translated and then encapsulated to the IPv6
	(Global unicast) address. So you simply have a tunnel interface 
	associated with each allocated IPv4 address. 
	Geoff, feel free to add if I missed something. 

	Cheers,
	Hesham