Re: NAT64 in RA, draft-ietf-6man-ra-pref64

[Jen Linkova <[e-mail]>]

On Tue, Jul 9, 2019 at 1:50 AM Mudric, Dusan (Dusan) <[e-mail]> wrote:
> [Dusan] What if IPv4only client needs to initiate the session to IPv6only client? What is the solution for that use case?

https://tools.ietf.org/html/rfc7755 mentioned before.

IPv4-only client -- IPv4-enabled network--- SIIT translator ----
IPv6-only LAN --- IPv6-only server.

Let's say  your IPv4-only client needs to talk to the Ipv6-only
server, ipv6-only.example.net.
For this to happen the owner of the Ipv6-only server needs to
configure the translator (SIIT box in the diagram above).
The owner would create a DNS A RR for  ipv6-only.example.net. - let's
say, 192.0.2.2
Ipv6-only server would have an IPv6 address which has that IPv4
address encoded - for example, 2001:db8:1::192.0.2.2
That IPv4 address (or the prefix most likely) will be routed to the translator.

So your Ipv4-only client sends a DNS request to resolve
ipv6-only.example.net, gets 192.0.2.2 back, sends a packet to
192.0.2.2.
The packet reaches the translator. The translator translates IPv4
packet to IPv6 packet and sends it to the server (note that the
destination IPv6 address can be easily constructed as the translator
knows the prefix and just adds the IPv4 address - 192.0.2.2 - to that
prefix to get the destination IPv6 address. IPv6 source address is
synthesised in the same way from the client IPv4 address).

Here is a nice talk Tore Anderson gave at RIPE 7 years ago:
https://ripe64.ripe.net/presentations/67-20120417-RIPE64-The_Case_for_IPv6_Only_Data_Centres.pdf



> > For IPv4 to IPv6, if you must allow the IPv4 client to initiate the session, you'd
> > have to have preconfigure something.
> [Dusan] Where and how is this configuration done?

On the translator which connects IPv6-only network to dual-stack/IPv4-only one.
In general, when you need to let one protocol talk to another, you'd
have a point (or the edge) where those two networks meet each other.
Usually you'd have a box (or boxes) interconnecting them - quite often
it's exactly the box you'd need to configure ;)

-- 
SY, Jen Linkova aka Furry