WDIFF

draft-aboba-dhc-mdns-conf-00.txt --> draft-aboba-dhc-mdns-conf-01.txt

Network Working Group Bernard Aboba
INTERNET-DRAFT Levon Esibov
INTERNET-DRAFT Bernard Aboba
Category: Standards Track Dave Thaler
<draft-aboba-dhc-mdns-conf-00.txt>
<draft-aboba-dhc-mdns-conf-01.txt> Microsoft
20 February
10 March 2000
Expires: October 1, 2000

Multicast DNS Node Type Configuration Option

This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.

Internet-Drafts are working documents of the Internet Engineering Task
Force (IETF), its areas, and its working groups. Note that other groups
may also distribute working documents as Internet- Drafts.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt

The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.

1. Copyright Notice

2. Abstract

This document defines a new DHCP option which is passed from the DHCP
Server to the DHCP Client to specify the multicast DNS configuration.

3. Introduction

Multicast DNS was first defined in [5], and behavior was further
specified in [3]. The Dynamic Host Configuration Protocol (DHCP)[1]
provides a framework for passing configuration information to hosts on a
TCP/IP network. RFC 2132 [2] allows DHCP servers to specify
configuration information for various kinds of name servers to be passed
to DHCP clients. However, no information is provided as to the
configuration desired for multicast DNS. The purpose of this document
is to allow DHCP servers to specify the multicast DNS configuration to
be used by DHCP clients.

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3.1. Requirements terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [4].

3.2. DHCP terminology

This document uses the following terms:

DHCP client
DHCP client or "client" is an Internet host using DHCP to
obtain configuration parameters such as a network address.

DHCP server
A DHCP server or "server" is an Internet host that returns
configuration parameters to DHCP clients.

4. Format of the mDNS node type multicast DNS configuration option

The following diagram defines the format of the mDNS multicast DNS
configuration option:

0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Length | Node Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Code

TBD

Length

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Node type

The node type field, which is one octet, describes how the host
should behave
behaves as an mDNS multicast DNS querier and listener. Values are defined as
follows:

Value Node Type
----- ---------
0x1 B-node
0x2 P-node
0x3 Reserved
0x4 M-node
0x5 - 0x7 Reserved
0x8 H-node
0x9 - 0xFF Reserved

4.1. B-node

B-nodes MUST act as multicast DNS queriers and listeners, but do not MUST NOT
send unicast DNS queries. As a result, they are unable to resolve non-local
names. names
outside the scope of the multicast DNS, as defined in [3].

Hosts configured as B-nodes MUST listen for mDNS queries on both the
linklocal and local scope addresses, and MUST respond to mDNS queries as
described in [3].

4.2. P-node

P-nodes MUST only send unicast DNS queries, and MUST NOT listen for mDNS
multicast DNS queries or respond to them in any way. Hosts configured as
P-nodes MUST NOT send multicast DNS queries for any purpose, including
DNS server location. Thus, if By default, both IPv4 and IPv6 hosts that are
configured via DHCP but do not receive a multicast DNS configuration
option behave as P-nodes. If no DNS server option is provided, a P-node
host will be unable to resolve names.

4.3. M-node

M-nodes MUST use multicast DNS queries for resolving local names prior to
querying the unicast DNS server, but use the unicast DNS server
exclusively for resolving non-local names. using unicast. M-nodes not configured with
the address of without a unicast DNS
server will send only multicast DNS queries, and will be unable to
resolve non-local names. names outside the scope of the multicast DNS, as defined in [3].

Hosts configured as M-nodes MUST listen for mDNS queries on both the
linklocal and local scopes, scope addresses, and MUST respond to mDNS queries for their
own name, via unicast. M-nodes MUST NOT send unicast DNS queries for
local names without first sending an mDNS linklocal and then local query
for the name.

If a host receives an mDNS node type option corresponding to an M-node
without receiving a DNS server option, then the host SHOULD send an mDNS
query in order to locate a local DNS server, as
described in [5].

Aboba, Esibov [3].

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4.4. H-nodes

H-nodes MUST send multicast DNS queries only if they have not been able
to resolve the name via a query to a unicast DNS server. server using unicast. H-nodes not
configured with the address of
lacking a unicast DNS server will send only multicast DNS queries, and will be
unable to resolve non-local names. names outside the scope of the multicast DNS as
defined in [3].

Hosts configured as H-nodes MUST listen for mDNS queries on both the
linklocal and local scopes, scope addresses, and MUST respond to mDNS queries for their
own name, via unicast. as
described in [3]. H-nodes MUST NOT send mDNS queries without first
querying the unicast DNS server if one is available.

If a host receives an mDNS node type option corresponding to an H-node
without receiving a

5. Scalability considerations

Since B and M-nodes function as multicast DNS server option, then listeners as well as
multicast DNS queriers of first resort, the host SHOULD send an mDNS
query presence of these nodes can
result in order to locate a considerable multicast traffic propagating within the local
administrative scope zone. This could represent a scalability problem in
large enterprise networks, and so in this scenario, configuration of
hosts as B and M-nodes is discouraged. Instead, it is recommended that
enterprise networks deploy dynamic DNS server, utilizing hosts configured as described in [5].

5. P-
nodes, which is the default behavior where no mDNS configuration option
is provided.

6. References

[1] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March
1997.

[2] Alexander, S., Droms, R., "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.

[3] Woodcock, B., Manning, Esibov, L., Aboba, B., Thaler, D. "Multicast Discovery of DNS Services", DNS", Internet draft
(work in progress), draft-manning-multicast-
dns-01.txt, October 1998. draft-aboba-dnsext-mdns-00.txt, March 2000.

[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.

[5] Braden, R., "Requirements for Internet Hosts -- Application and
Support", RFC 1123, October 1989.

7. Security Considerations

The option described in this draft may be used in situations where DHCP
is authenticated or unauthenticated. In situations where authenticated
DHCP is not used, it is possible for a rogue DHCP server to respond to
the DHCP client with an inappropriate mDNS configuration option. For

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example, the rogue DHCP server could specify an mDNS configuration
option of 0x1. This would cause the host to become both an mDNS querier
and listener (B-node). Were hosts to be widely configured this way, this
could result in propagation of mDNS queries throughout the enterprise.

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8. IANA Considerations

This draft does not create any new number or name spaces for IANA
administration.

9. Acknowledgements

This draft has been enriched by comments from Rick Lamb Erik Guttman of Microsoft.

9. Sun
Microsystems.

10. Authors' Addresses

Bernard Aboba

Levon Esibov
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052

Phone: +1 (425) 936-6605

EMail: bernarda@microsoft.com

Dave Thaler levone@microsoft.com

Bernard Aboba
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052

Phone: +1 (425) 703-8835 936-6605
EMail: dthaler@microsoft.com

Levon Esibov bernarda@microsoft.com

Dave Thaler
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052

Phone: +1 (425) 936-2464 703-8835
EMail: levone@microsoft.com

10. dthaler@microsoft.com

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intellectual property or other rights that might be claimed to pertain
to the implementation or use of the technology described in this
document or the extent to which any license under such rights might or
might not be available; neither does it represent that it has made any

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effort to identify any such rights. Information on the IETF's
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The IETF invites any interested party to bring to its attention any
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12. Full Copyright Statement

Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to
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may not be modified in any way, such as by removing the copyright notice
or references to the Internet Society or other Internet organizations,
except as needed for the purpose of developing Internet standards in

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INTERNET-DRAFT Multicast DNS Configuration Option 20 February 2000
which case the procedures for copyrights defined in the Internet
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11.

13. Expiration Date

This memo is filed as <draft-aboba-dhc-mdns-conf-00.txt>, <draft-aboba-dhc-mdns-conf-01.txt>, and expires
September
October 1, 2000.

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