DNS/RFC/8499/referralsについて、ここに記述してください。
Referrals:
- A type of response in which a server, signaling that it
- is not (completely) authoritative for an answer, provides the querying resolver with an alternative place to send its query. Referrals can be partial.
Delegation:
- The process by which a separate zone is created in the
- name space beneath the apex of a given domain. Delegation happens when an NS RRset is added in the parent zone for the child origin. Delegation inherently happens at a zone cut. The term is also commonly a noun: the new zone that is created by the act of delegating.
Lame delegation: "A lame delegations exists [sic] when a nameserver
- is delegated responsibility for providing nameservice for a zone (via NS records) but is not performing nameservice for that zone (usually because it is not set up as a primary or secondary for the zone)." (Quoted from [RFC1912], Section 2.8) Another definition is that a lame delegation "...happens when a name server is listed in the NS records for some domain and in fact it is not a server for that domain. Queries are thus sent to the wrong servers, who don't know nothing [sic] (at least not as expected) about the queried domain. Furthermore, sometimes these hosts (if they exist!) don't even run name servers." (Quoted from [RFC1713], Section 2.3)
Glue records: "...[Resource records] which are not part of the
- authoritative data [of the zone], and are address RRs for the [name] servers [in subzones]. These RRs are only necessary if the name server's name is 'below' the cut, and are only used as part of a referral response." Without glue "we could be faced with the situation where the NS RRs tell us that in order to learn a name server's address, we should contact the server using the address we wish to learn." (Quoted from [RFC1034], Section 4.2.1) A later definition is that glue "includes any record in a zone file that is not properly part of that zone, including nameserver records of delegated sub-zones (NS records), address records that accompany those NS records (A, AAAA, etc), and any other stray data that might appear." (Quoted from [RFC2181], Section 5.4.1)
Although glue is sometimes used today with this wider definition
- in mind, the context surrounding the definition in [RFC2181] suggests it is intended to apply to the use of glue within the document itself and not necessarily beyond.