draft-ietf-dnsext-mdns-04.txt   draft-ietf-dnsext-mdns-05.txt 
DNSEXT Working Group Levon Esibov DNSEXT Working Group Levon Esibov
INTERNET-DRAFT Bernard Aboba INTERNET-DRAFT Bernard Aboba
Category: Standards Track Dave Thaler Category: Standards Track Dave Thaler
<draft-ietf-dnsext-mdns-04.txt> Microsoft <draft-ietf-dnsext-mdns-05.txt> Microsoft
13 September 2001 14 September 2001
Multicast DNS Multicast DNS
This document is an Internet-Draft and is in full conformance with all This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026. provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Task Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups Force (IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet- Drafts. may also distribute working documents as Internet- Drafts.
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query for such a name MUST be multicast and the name SHOULD NOT be query for such a name MUST be multicast and the name SHOULD NOT be
concatenated with any suffix. concatenated with any suffix.
If a DNS server is running on a host, the host MUST NOT listen for If a DNS server is running on a host, the host MUST NOT listen for
multicast DNS queries, to prevent the host from listening on port 53 and multicast DNS queries, to prevent the host from listening on port 53 and
intercepting DNS queries directed to a DNS server. By default, a DNS intercepting DNS queries directed to a DNS server. By default, a DNS
server MUST NOT listen to multicast DNS queries. server MUST NOT listen to multicast DNS queries.
3.1. mDNS configuration 3.1. mDNS configuration
Multicast DNS usage can be configured manually or automatically. Where Multicast DNS usage can be configured manually or automatically. On
no manual or automatic configuration is provided, multicast DNS is interfaces where no manual or automatic configuration has been
enabled by default. performed, multicast DNS is enabled by default.
For IPv6, the stateless DNS discovery mechanisms described in [19] can For IPv6, the stateless DNS discovery mechanisms described in [19] can
be used to discover whether multicast DNS is enabled or disabled. be used to discover whether multicast DNS is globally enabled or
disabled.
Where DHCPv4 or DHCPv6 is implemented, DHCP options can be used to Where DHCPv4 or DHCPv6 is implemented, DHCP options can be used to
configure multicast DNS. The mDNS enable DHCP option, described in [6], configure multicast DNS on an interface. The mDNS enable DHCP option,
can be used to explicitly enable or disable use of multicast DNS. The described in [6], can be used to explicitly enable or disable use of
Name Service Search option, described in RFC 2937 [3], can be used to multicast DNS on an interface. The Name Service Search option, described
determine where multicast DNS is used within the name service search in RFC 2937 [3], can be used to globally determine where multicast DNS
order. DHCP option codes are used as RFC 2937 codes signifying name is used within the name service search order. DHCP option codes are used
services within the search order. As a result, to specify multicast DNS as RFC 2937 codes signifying name services within the search order. As a
usage within the name service search order, the option code assigned to result, to specify multicast DNS usage within the name service search
the mDNS enable option is used. order, the option code assigned to the mDNS enable option is used.
If a host is configured via automatic configuration mechanisms, either If an interface has been configured via any automatic configuration
stateful or stateless, and multicast DNS is not explicitly enabled, then mechanism which is able to supply DNS configuration information, then
multicast DNS MUST NOT be used, ensuring that upgraded hosts do not multicast DNS MUST NOT be used on that interface unless it has been
change their default behavior. This implies that the host will neither explicitly enabled, whether via that mechanism or any other. This
listen on the DNS LINKLOCAL multicast address, nor will it send queries ensures that upgraded hosts do not change their default behavior,
to that address. For a DNS server, automatic configuration mechanisms, without requiring the source of the configuration information to be
either stateful or stateless, MUST NOT enable multicast DNS. 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.
4. Sequence of events 4. Sequence of events
The sequence of events for multicast DNS usage is as follows: The sequence of events for multicast DNS usage is as follows:
1. If a sender needs to resolve a query for a name 1. If a sender needs to resolve a query for a name
"host.example.com.local.arpa", then it sends a multicast query to the "host.example.com.local.arpa", then it sends a multicast query to the
LINKLOCAL multicast address. LINKLOCAL multicast address.
2. A responder responds to this query only if it is authoritative 2. A responder responds to this query only if it is authoritative
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successors or assigns. This document and the information contained successors or assigns. This document and the information contained
herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE." WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
Expiration Date Expiration Date
This memo is filed as <draft-ietf-dnsext-mdns-04.txt>, and expires This memo is filed as <draft-ietf-dnsext-mdns-05.txt>, and expires
March 22, 2002. March 22, 2002.
 End of changes. 

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