Subject: Additional proposed changes to mdns-05

From: Bernard Aboba <[email-masked]>
Date: Sun, 7 Oct 2001 13:18:56 -0700 (PDT)

Additional changes proposed to draft-ietf-dnsext-mdns-05.txt
Bernard Aboba

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Section 3.1

Submitted by: Bernard Aboba
Justification: IPv6 and IPv4 mDNS configuration are handled
separately. It is possible for mDNS to be enabled for IPv6 at
the same time it is disabled for IPv4. The text needs to be
modified to clarify this. 

Change:

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

For IPv6, the stateless DNS discovery mechanisms described in "IPv6
Stateless DNS Discovery" [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 Option,
described in [6], can be used to explicitly enable or disable use of
multicast DNS on an interface, as well as to specify the order in which
DNS and multicast DNS is used on that interface.

The mDNS Enable Option affects only DNS resolver behavior, that is, how
DNS resolution is performed, and whether multicast DNS is used.  The
mDNS Enable Option does not determine whether or in which order DNS
itself is used for name resolution.  This can be specified, for example,
using the Name Service Search Option for DHCP, RFC 2937 [3], which can
be used to globally determine where DNS is used within the name service
search order.

If an interface has been configured via any automatic configuration
mechanism which is able to supply DNS configuration information, then
multicast DNS SHOULD 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."

To:

"Multicast DNS usage can be configured manually or automatically.  On
interfaces where no manual or automatic configuration has been
performed for a given protocol (IPv4 or IPv6), multicast DNS SHOULD be enabled by default
for that protocol.

For IPv6, the stateless DNS discovery mechanisms described in "IPv6
Stateless DNS Discovery" [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 Option,
described in [6], can be used to explicitly enable or disable use of
multicast DNS on an interface for a given protocol, as well as to 
specify the order in which DNS and multicast DNS is used on that 
interface.

The mDNS Enable Option affects only DNS resolver behavior, that is, how
DNS resolution is performed, and whether multicast DNS is used.  The
mDNS Enable Option does not determine whether or in which order DNS
itself is used for name resolution.  This can be specified, for example,
using the Name Service Search Option for DHCP, RFC 2937 [3], which can
be used to globally determine where DNS is used within the name service
search order.

If an interface has been configured for a given protocol
via any automatic configuration mechanism which is able to 
supply DNS configuration information, then multicast DNS 
SHOULD NOT be used on that interface for that protocol 
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.

Note that it is possible for mDNS to be enabled for use with IPv6
at the same time it is disabled for IPv4, and vice versa. For example,
where a home gateway implements a DNS proxy and DHCPv4, but not 
DHCPv6 or DNS autoconfiguration, there may be no mechanism for 
allowing IPv6 hosts to resolve the names of other IPV6 hosts on the
home network. In this situation, mDNS is useful for resolution of
dynamic names, and it will be enabled for use with IPv6, even though
it is disabled for use with IPv4."

Proposed resolution: Accept

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