Draft: draft-ietf-dnsop-glue-is-not-optional

Commentary: … defined in the future .
The DNS uses glue records to allow iterative clients to find the
addresses of nameservers that are contained within a delegated zone.
Authoritative Servers are expected to return all available glue
records in referrals.  If message size constraints prevent the
inclusion of all glue records in a UDP response, the server MUST set
the TC flag to inform the client that the response is incomplete, and
that the client SHOULD use TCP to retrieve the full response.  This
document updates RFC 1034 to clarify correct server behavior.
The Domain Name System (DNS) RFC1034, RFC1035 uses glue records to
allow iterative clients to find the addresses of nameservers that are
contained within a delegated zone.  Glue records are added to the
parent zone as part of the delegation process and returned in
referral responses, otherwise a resolver following the referral has
no way of finding these addresses.  Authoritative servers are
expected to return all available glue records in referrals.  If
message size constraints prevent the inclusion of all glue records in
a UDP response, the server MUST set the TC (Truncated) flag to inform
the client that the response is incomplete, and that the client
SHOULD use TCP to retrieve the full response.  This document
clarifies that expectation.
DNS responses sometimes contain optional data in the additional
section.  Glue records however are not optional.  Several other
protocol extensions, when used, are also not optional.  This includes
TSIG RFC2845, OPT RFC6891, and SIG(0) RFC2931.
The DNS uses referral glue records to allow iterative clients to find
the addresses of nameservers that are contained within a delegated
zone.  Authoritative Servers are expected to return all available
referral glue records in a referral response.  If message size
constraints prevent the inclusion of all referral glue records over
UDP transport, the server MUST set the TC flag to inform the client
that the response is incomplete, and that the client SHOULD use TCP
to retrieve the full response.  This document updates RFC 1034 to
clarify correct server behavior.
The Domain Name System (DNS) RFC1034, RFC1035 uses referral glue
records to allow iterative clients to find the addresses of
nameservers that are contained within a delegated zone.  Referral
glue records are added to the parent zone as part of the delegation
process and returned in referral responses, otherwise a resolver
following the referral has no way of finding these addresses.
Authoritative servers are expected to return all available referral
glue records in a referral response.  If message size constraints
prevent the inclusion of all glue records over UDP transport, the
server MUST set the TC (Truncated) flag to inform the client that the
response is incomplete, and that the client SHOULD use TCP to
retrieve the full response.  This document clarifies that
expectation.
DNS responses sometimes contain optional data in the additional
section.  Referral glue records, however, are not optional.  Several
other protocol extensions, when used, are also not optional.  This
includes TSIG RFC2845, OPT RFC6891, and SIG(0) RFC2931.