Subject: (ngtrans) Questions about DSTM

From: [email-masked]
Date: Fri, 15 Sep 2000 13:21:25 +0200

Hi,

I have two questions about the example in chapter 4.1 of the DSTM draft.

1. If host X6 is running an application compiled for IPv6, wouldn't you
need a header translator for the packets from host Z4 to the IPv6
application 
in host X6?

2. What if the IPv6 application running on host X6 has embedded IPv6
addresses in the payload, 
wouldn't you need some sort of ALG?

Thanks,

Geir Egeland

---

From: Francis Dupont <[email-masked]>
Date: Sat, 16 Sep 2000 13:31:44 +0200

In your previous mail you wrote:

   1. If host X6 is running an application compiled for IPv6,

=> the node X is dual-stack and is running application for IPv6+IPv4
(standard applications) and for IPv4-only (legacy applications).
For these applications DSTM works.

   wouldn't you need a header translator for the packets from host Z4
   to the IPv6 application in host X6?

=> I think an IPv6-only application will use IPv6 specific tricks (which one?
I don't know good examples...) then the communication with the node Z4
(4 for IPv4 only) will never work, with or without a header translator:
such applications are by definition out of the scope of a transition
mechanism (it is transition from IPv4 to IPv6).

=> an IPv6+IPv4 application which uses embedded IPv6 addresses when it
communicates with an IPv4 node is broken.

=> you can use ALGs but you should not need them. In the real life
a combination of DSTM and ALGs will be used and the ALGs will be for
some protocols where a proxy or a relay is natural (ie. a part of
the architecture), for instance SMTP (the side MTA will be an ALG).

Regards

[email-masked]

PS: you should reread the definition of a dual-stack node (RFC 2893 *).
DSTM is based on it and extends its application to cases where there
are not enough IPv4 addresses (lack of address space: the main reason
to go to IPv6) and/or the infrastructure supports only IPv6 (lack of
network/system engineers: the main reason to give up NATs).
PPS *: is it a better text? RFC 2893 is more about IPv6 over IPv4
(the opposite of DSTM).