> Subject: WG Last Call: draft-ietf-dnsop-3901bis-07 (Ends 2025-12-04)

Sorry for not reading this document carefully at an earlier time.
I have one editiorial comment that should be easy to fix. But also one
recommendation (that occurs in two places) that I disagree with.
Switching that from RECOMMENDED to MAY would solve the problem.

Otherwise, I think this draft is in good condition and should advance.

Section 3. Name Space Fragmentation

"A resolver that tries to look up a name starts out at the root, and follows 
referrals until it is referred to a name server that is authoritative for the 
name. If somewhere down the chain of referrals it is referred to a name server 
that is, based on the referral, only accessible over a transport which the 
resolver cannot use, the resolver is unable to continue DNS resolution."

I think this description needs to be improved. A zone is unreachable when
all nameservers are unreachable. So if an IPv6-only recursor encouters an
IPv4-only nameserver, then the above description suggests that resolution
will fail even if other nameservers do support IPv6.

So it should say that resolution fails when all name servers are only
accessible over transports that the resolver cannot use.

Section 3.2. Network Conditions Causing IP Version Related Name Space 
Fragmentation 

"It is therefore RECOMMENDED that DNS servers set an MSS of no more than 1388 
octets for TCP connections."

Given that the intended status is a BCP, is there any operational
experience with this? Other there other TCP-based protocols that implement
this? Personally, I have never seen applications set the MSS value of a
TCP connection.

Section  4.1. Guidelines for Authoritative DNS Server Configuration 

"Furthermore, similar to the guidance in [RFC9715], it is RECOMMENDED that 
authoritative DNS servers sets an MSS of 1220 in TCP sessions carrying DNS
responses."

The same comment applies but now the suggested MSS value is different, so
this seems inconsistent.

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