Subject: draft-ietf-6man-ra-pref64-00

From: Martin Huněk <[email-masked]>
Date: Thu, 28 Mar 2019 09:31:02 +0100

Hello,

I would like to express my support for this draft, as it allows possibly 
simple to configure and straight forward way how to discover NAT64 prefix.

I spoke with Jen yesterday and she suggested me to address this list with my 
remark.

Thing I have been missing is explicit statement that information about Pref64 
SHOULD be downstream transitive trough L3+ middle boxes (e.g. routers), if 
they are not configured as NAT64 and when Pref64 is reachable from their 
downstream interface. Presumably in Section 4.

So if you think of for example home router. If it receives information about 
Pref64 (by any reasonable means), then it should provide such information to 
its downstream (LAN) interface as Pref64 RA option. Of course if it is not 
configured to do NAT64/DNS64 itself.

I'm intentionally writing "by any reasonable means" because even that mobile 
connected to LAN might not talk PCP, router might or it may receive that by 
RFC7050 or even by Pref64 RA option.

Sincerely,
Martin Hunek

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From: Ole Troan <[email-masked]>
Date: Thu, 28 Mar 2019 18:08:53 +0100

> downstream interface. Presumably in Section 4.

It is not obvious that this or every RA should be reflected downstream.
The CPE is a policy enforcement point / demarcation point. The end-user network might choose not to trust this information.

There is also the issue of depending on this as a mechanism to signal deep into the network. In an arbirtary topology it would have to depend on something like HNCP.

Ole