Draft: draft-ietf-dnssd-srp

Commentary: This update removes the constraint in the section titled " Host Description Instruction " that the Host Description instruction must be pointed to by at least one Service Description instruction . It also removes some duplicate constraints from the section titled " Valid SRP Update requirements " and moves the mention of subtypes to the " Service Discovery Instruction " section .
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Note that there can be more than one Service Discovery Instruction
for the same name if the SRP requestor is advertising more than one
service of the same type, or is changing the target of a PTR RR.  For
each such PTR RR add or remove, the above constraints must be met.
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Note that there can be more than one Service Discovery Instruction
for the same name if the SRP requestor is advertising more than one
service of the same type, or is changing the target of a PTR RR.
This is also true for SRP subtypes (RFC6763).  For each such PTR RR
add or remove, the above constraints must be met.
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An SRP Update MUST include zero or more Service Discovery
Instructions.  For each Service Discovery Instruction, there MUST be
at least one Service Description Instruction.  Note that in the case
of SRP subtypes (RFC6763), it's quite possible that two Service
Discovery Instructions might reference the same Service Description
Instruction.  For each Service Description Instruction there MUST be
at least one Service Discovery Instruction with its service instance
name as the target of its PTR record.  There MUST be exactly one Host
Description Instruction.  Every Service Description Instruction must
have that Host Description Instruction as the target of its SRV
record.  A DNS Update that does not meet these constraints is not an
SRP Update.
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A DNS Update that contains any additional adds or deletes that cannot
be identified as Service Discovery, Service Description or Host
Description Instructions is not an SRP Update.  A DNS update that
contains any prerequisites is not an SRP Update.  Such messages
should either be processed as regular RFC2136 updates, including
access control checks and constraint checks, if supported, or else
rejected with RCODE=REFUSED.
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In addition, in order for an update to be a valid SRP Update, the
target of every Service Discovery Instruction MUST be a Service
Description Instruction that is present in the SRP Update.  There
MUST NOT be any Service Description Instruction to which no Service
Discovery Instruction points.  The target of the SRV record in every
Service Description Instruction MUST be the single Host Description
Instruction.
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An SRP Update MUST contain exactly one Host Description Instruction.
In addition, there MUST NOT be any Service Description Instruction to
which no Service Discovery Instruction points.  A DNS Update that
contains any additional adds or deletes that cannot be identified as
Service Discovery, Service Description or Host Description
Instructions is not an SRP Update.  A DNS update that contains any
prerequisites is not an SRP Update.  An SRP registrar MAY either
process such messages are either processed as regular RFC2136
updates, including access control checks and constraint checks, if
supported, or MAY reject them with RCODE=REFUSED.