Subject: Re: revised mDNS configuration language

From: Bernard Aboba <[email-masked]>
Date: Mon, 17 Sep 2001 07:56:49 -0700 (PDT)

Erik Guttman spake thusly:

>
> Bernard,
> 
> I support this new text. 
> 
> Aidan,
> 
> This changes the focus of the 2937 revision.  The idea is to separate
> the question of 'whether?' from 'which order?'  The reason for this is
> the search order can't say NO, it only says which order (from which you
> imply YES).
>
> Also, the mDNS enable/disable option provides per interface
> configuration while RFC 2937 provides global configuration.
 
Here is another shot at the text for section 3.1, that tries to take
this into account:

3.1.  mDNS configuration

Multicast DNS usage can be configured manually or automatically.  
On interfaces where no manual or automatic configuration has been 
performed, multicast DNS is enabled by default.

For IPv6, the stateless DNS discovery mechanisms described in [19] can
be used to discover whether multicast DNS is globally enabled or
disabled.

Where DHCPv4 or DHCPv6 is implemented, DHCP options can be used to
configure multicast DNS on an interface. The mDNS enable DHCP option,
described in [6], can be used to explicitly enable or disable use of
multicast DNS on an interface. The Name Service Search option, described
in RFC 2937 [3], can be used to globally configure where multicast DNS is
used within the name service search order. DHCP option codes are used as
RFC 2937 codes signifying name services within the search order. As a
result, to specify multicast DNS usage within the name service search
order, the option code assigned to the mDNS enable option is used.

If an interface has been configured via any automatic configuration
mechanism which is able to supply DNS configuration information, then
multicast DNS MUST NOT be used on that interface unless it has been
explicitly enabled, whether via that mechanism or any other. This
ensures that upgraded hosts do not change their default behavior,
without requiring the source of the configuration information to be
simultaneously updated.  This implies that on the interface, the host
will neither listen on the DNS LINKLOCAL multicast address, nor will it
send queries to that address.  For a DNS server, automatic configuration
mechanisms MUST NOT  enable multicast DNS on any interface.

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