Internet DRAFT - draft-karstens-pim-ipv6-zeroconf-assignment
draft-karstens-pim-ipv6-zeroconf-assignment
Network Working Group N. Karstens
Internet-Draft Garmin International
Intended status: Standards Track D. Farinacci
Expires: 18 February 2024 lispers.net
M. McBride
Futurewei
17 August 2023
Zero-Configuration Assignment of IPv6 Multicast Addresses
draft-karstens-pim-ipv6-zeroconf-assignment-02
Abstract
Describes a zero-configuration protocol for dynamically assigning
IPv6 multicast addresses. Applications randomly assign multicast
group IDs from a reserved range and prevent collisions by using mDNS
to publish records in a new "eth-addr.arpa" special-use domain. This
protocol satisfies all of the criteria listed in draft-karstens-pim-
zeroconf-mcast-addr-alloc-ps.
Status of This Memo
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This Internet-Draft will expire on 18 February 2024.
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extracted from this document must include Revised BSD License text as
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Evaluation of Solution . . . . . . . . . . . . . . . . . . . 3
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4.1. Domain Name Reservation Considerations . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
[I-D.karstens-pim-zeroconf-mcast-addr-alloc-ps] includes a problem
statement and requirements for a zero-configuration method for
dynamically assigning multicast addresses. This document describes a
process that fulfills these requirements by having applications
randomly assign IPv6 multicast group IDs from a reserved range and
using mDNS to prevent collisions.
Once the IPv6 multicast address has been assigned, the data contained
the multicast stream may be advertised using the method described in
[I-D.karstens-dnssd-dns-msd].
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Procedure
When an application is preparing to transmit a multicast stream, it
first generates a random group ID in the range 0x90000000-0x9FFFFFFF,
which IANA should reserve from the "Dynamic Multicast Group IDs"
registry (see Section 4). It combines this with the Interface
Identifier (IID) of the intended source address for the multicast
stream to generate a link-scoped IPv6 multicast address [RFC4489].
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The application then calculates the multicast Ethernet address that
will be used to transmit the data ([RFC2464], Section 7) and uses
that to construct a string like a reverse-mapping domain, using a new
"eth-addr.arpa" special-use domain.
For example, given a source address of fe80::a12:34ff:fe56:7890, the
IPv6 multicast address may be ff32:00ff:a12:34ff:fe56:7890:9abc:def0,
the multicast Ethernet address 33:33:9A:BC:DE:F0, and the resulting
string is "0.f.e.d.c.b.a.9.3.3.3.3.eth-addr.arpa".
The application then uses the mDNS probing algorithm described in
[RFC6762], Section 8.1 to continuously query for a PTR record with
the same name as the generated string. If the probing algorithm
completes without any conflict, then the application begins
advertising its own unique PTR record using that name. The PTRDNAME
field consists of a unique application identifier, in the form of a
DNS label, followed by the device's host name (for example,
"application.example.local."). Integrating a unique identifier in
this manner allows for multiple applications to be on the same host.
Once the PTR record is advertised, the host may then begin
transmitting multicast data using the generated address.
The application shall retain the group ID value and use it the next
time the multicast stream is transmitted. This allows the network to
quickly settle on a configuration that will never have another
collision as long as the network is unchanged.
If a conflict is detected at any point, then the application stops
transmitting that multicast stream and starts the process over using
a different group ID.
The host may optionally monitor the bus for traffic that uses the
same destination multicast Ethernet address, but a different
destination multicast IPv6 address. If this is detected, then the
application responds the same as a collision.
While intended primarily for allocating IPv6 multicast addresses on
the same subnet (link-local scope), the same technique could also
apply to a larger network as long as mDNS traffic is routed between
subnets (for any scope excluding global scope).
3. Evaluation of Solution
[I-D.karstens-pim-zeroconf-mcast-addr-alloc-ps] contains a list of
criteria to evaluate potential solutions. The protocol described in
this document satisfies all of the required criteria.
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However, because mDNS is designed to be a low-bandwidth protocol, it
can take a signficant amount of time to detect a record collision
after a network partition is repaired. This is not a concern on
networks where all multicast streams are established before any
likely partition event because all group IDs will have been selected
and stored for future use.
It is a greater concern on networks where multicast streams may be
established at any time. Deployments on these networks may consider
engaging a detection mechanism and prompting hosts to send
unsolicited mDNS response messages when the partition is repaired.
The protocol described in this document also satisfies the
recommended criteria, to the extent that a deployment supports
publishing mDNS-based DNS-SD records across multiple subnets (see
[RFC8766]).
4. IANA Considerations
IANA should allocate a block of group IDs from the "Dynamic Multicast
Group IDs" registry in the "IPv6 Multicast Address Space Registry"
registry group that was created by
[I-D.karstens-pim-updt-ipv6-dyn-mcast-addr-grp-id]. The range of
this block should be 0x90000000-0x9FFFFFFF and the description should
be the title of this document.
The special-use domain "eth-addr.arpa" should be registered in the
.arpa registry (https://www.iana.org/domains/arpa) and the "Special-
Use Domain Names" registry (https://www.iana.org/assignments/special-
use-domain-names). This domain should not be delegated.
4.1. Domain Name Reservation Considerations
The "eth-addr.arpa." domain is effectively a reverse-mapping domain
and so has the same considerations as the reverse-mapping domains
listed in [RFC6761], Section 6.1.
5. Security Considerations
This algorithm only works in environments where all hosts are
cooperating. Malicious hosts could deny service by either repeatedly
responding to queries for a given address or by flooding the network
with traffic.
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6. Acknowledgement
Special thanks to the National Marine Electronics Association for
their contributions in developing marine industry standards and their
support for this research.
Thanks also to the members of the PIM working group for their early
brainstorming sessions and review of this draft.
7. References
7.1. Normative References
[I-D.karstens-pim-zeroconf-mcast-addr-alloc-ps]
Karstens, N., Farinacci, D., and M. McBride, "Zeroconf
Multicast Address Allocation Problem Statement and
Requirements", Work in Progress, Internet-Draft, draft-
karstens-pim-zeroconf-mcast-addr-alloc-ps-01, 28 July
2023, <https://datatracker.ietf.org/doc/html/draft-
karstens-pim-zeroconf-mcast-addr-alloc-ps-01>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2464] Crawford, M., "Transmission of IPv6 Packets over Ethernet
Networks", RFC 2464, DOI 10.17487/RFC2464, December 1998,
<https://www.rfc-editor.org/info/rfc2464>.
[RFC4489] Park, J., Shin, M., and H. Kim, "A Method for Generating
Link-Scoped IPv6 Multicast Addresses", RFC 4489,
DOI 10.17487/RFC4489, April 2006,
<https://www.rfc-editor.org/info/rfc4489>.
[RFC6761] Cheshire, S. and M. Krochmal, "Special-Use Domain Names",
RFC 6761, DOI 10.17487/RFC6761, February 2013,
<https://www.rfc-editor.org/info/rfc6761>.
[RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
DOI 10.17487/RFC6762, February 2013,
<https://www.rfc-editor.org/info/rfc6762>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
7.2. Informative References
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[I-D.karstens-dnssd-dns-msd]
Karstens, N., Farinacci, D., and M. McBride, "DNS-Based
Multicast Stream Discovery", Work in Progress, Internet-
Draft, draft-karstens-dnssd-dns-msd-01, 26 March 2023,
<https://datatracker.ietf.org/doc/html/draft-karstens-
dnssd-dns-msd-01>.
[I-D.karstens-pim-updt-ipv6-dyn-mcast-addr-grp-id]
Karstens, N., Farinacci, D., and M. McBride, "Updates to
Dynamic IPv6 Multicast Address Group IDs", Work in
Progress, Internet-Draft, draft-karstens-pim-updt-ipv6-
dyn-mcast-addr-grp-id-02, 28 July 2023,
<https://datatracker.ietf.org/doc/html/draft-karstens-pim-
updt-ipv6-dyn-mcast-addr-grp-id-02>.
[RFC8766] Cheshire, S., "Discovery Proxy for Multicast DNS-Based
Service Discovery", RFC 8766, DOI 10.17487/RFC8766, June
2020, <https://www.rfc-editor.org/info/rfc8766>.
Authors' Addresses
Nate Karstens
Garmin International
Email: nate.karstens@gmail.com
Dino Farinacci
lispers.net
Email: farinacci@gmail.com
Mike McBride
Futurewei
Email: michael.mcbride@futurewei.com
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