Telechat Review of draft-ietf-v6ops-framework-md-ipv6only-underlay-25
review-ietf-v6ops-framework-md-ipv6only-underlay-25-intdir-telechat-min-2026-08-16-00

Hi,

I have been assigned as the int-dir reviewer for this draft. For background on int-dir,
please see the FAQ (https://wiki.ietf.org/en/group/intdir). Please resolve these 
comments along with any other comments you may receive.

This draft describes a framework for a multi-domain IPv6-only underlay network 
from the perspective of network providers. I think this draft is well-written. At the 
same time, I have some comments for the authors to consider.

## Major Comments

None.

## Minor Comments

### Section 2

There is a term IPv4-embedded IPv6 address defined here. However IPv6 mapping 
prefix is not mentioned and that concept appears multiple times later, sometimes 
combined with IPv4-embedded IPv6 address. Suggest to add some text describing 
the relationship between IPv4-embedded IPv6 address and IPv6 mapping prefix.

### Section 3

For Figure 1, I couldn't find the expansion for BR.

### Section 4.1

Is the Pref6(PE) allocation must be unique within the multi-domain network? If yes, 
suggest to make it explicit.

### Section 4.2

For Figure 2, I couldn't find the expansion for NW.

### Section 6

It says "This allows IPv4-embedded IPv6 packets to be forwarded using existing aggregate 
routes, avoiding the need for additional FIB entries in the IPv6 core". It seems there is a 
precondition in multi-domain environment that each domain needs to employ the same 
length of IPv6 mapping prefix, if that's the case, suggest to make it explicit.

Cheers,
Xiao Min