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== 2.4.2.  AliasMode ==

In AliasMode, the SVCB record aliases a service to a TargetName.

   SVCB RRsets SHOULD only have a single RR in AliasMode.  If multiple
   AliasMode RRs are present, clients or recursive resolvers SHOULD pick
   one at random.

   The primary purpose of AliasMode is to allow aliasing at the zone
   apex, where CNAME is not allowed (see, for example, [RFC1912],
   Section 2.4). 
In AliasMode, the TargetName will be the name of a
domain that resolves to SVCB, AAAA, and/or A records.  (See Section 6
for aliasing of SVCB-compatible RR types.)  

Unlike CNAME, AliasMode
   records do not affect the resolution of other RR types and apply only
   to a specific service, not an entire domain name.

   The AliasMode TargetName SHOULD NOT be equal to the owner name, as
   this would result in a loop.  
In AliasMode, recipients MUST ignore any SvcParams that are present.  
   Zone-file parsers MAY emit a warning
   if an AliasMode record has SvcParams.  The use of SvcParams in
   AliasMode records is currently not defined, but a future
   specification could extend AliasMode records to include SvcParams.

   For example, the operator of "foo://example.com:8080" could point
   requests to a service operating at "foosvc.example.net" by
   publishing:

   _8080._foo.example.com. 3600 IN SVCB 0 foosvc.example.net.

Using AliasMode maintains a separation of concerns: the owner of
   "foosvc.example.net" can add or remove ServiceMode SVCB records
   without requiring a corresponding change to "example.com".  Note that
   if "foosvc.example.net" promises to always publish a SVCB record,
   this AliasMode record can be replaced by a CNAME at the same owner
   name.

AliasMode is especially useful for SVCB-compatible RR types that do
   not require an underscore prefix, such as the HTTPS RR type. 

For example, the operator of "https://example.com" could point requests
   to a server at "svc.example.net" by publishing this record at the zone apex:

   example.com. 3600 IN HTTPS 0 svc.example.net.

   Note that the SVCB record's owner name MAY be the canonical name of a
   CNAME record, and the TargetName MAY be the owner of a CNAME record.
   Clients and recursive resolvers MUST follow CNAMEs as normal.

   To avoid unbounded alias chains, clients and recursive resolvers MUST
   impose a limit on the total number of SVCB aliases they will follow
   for each resolution request.  This limit MUST NOT be zero, i.e.,
   implementations MUST be able to follow at least one AliasMode record.
   The exact value of this limit is left to implementations.

   Zones that require following multiple AliasMode records could
   encounter compatibility and performance issues.

   As legacy clients will not know to use this record, service operators
   will likely need to retain fallback AAAA and A records alongside this
   SVCB record, although in a common case the target of the SVCB record
   might offer better performance, and therefore would be preferable for
   clients implementing this specification to use.

AliasMode records only apply to queries for the specific RR type.
   For example, a SVCB record cannot alias to an HTTPS record or vice versa.
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