Internet DRAFT - draft-karstens-dnssd-dns-msd
draft-karstens-dnssd-dns-msd
Network Working Group N. Karstens
Internet-Draft Garmin International
Intended status: Informational D. Farinacci
Expires: 9 May 2024 lispers.net
M. McBride
Futurewei
6 November 2023
DNS-Based Multicast Stream Discovery
draft-karstens-dnssd-dns-msd-02
Abstract
This document describes an application of DNS-SD for the
advertisement and discovery of multicast streams. This is especially
useful with multicast streams that use a dynamically-assigned
multicast address.
Status of This Memo
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This Internet-Draft will expire on 9 May 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Stream Instance Enumeration and Resolution . . . . . . . . . 3
3. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5.1. Domain Name Reservation Considerations . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 5
8.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Several documents describe locally-scoped or administratively-scoped
allocation of multicast addresses. Some examples of this include:
* [RFC2365]
* [RFC3307] (Section 4.3)
* [RFC4489]
* [I-D.ietf-pim-ipv6-zeroconf-assignment]
These documents do not specify a mechanism for how these multicast
streams should be advertised or discovered. This document specifies
an application of DNS-Based Service Discovery (DNS-SD, [RFC6763]) for
advertisement and discovery of multicast streams.
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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. Stream Instance Enumeration and Resolution
DNS-SD uses PTR, SRV, and TXT records to describe a service. DNS-MSD
also makes use of these records to describe a multicast stream, but
makes a few modifications to the method described in [RFC6763].
First, DNS-MSD uses a new "mcast.arpa." special use domain in all
records to indicate that the advertised service is a multicast
stream.
The second label in the <Service> portion of a Service Instance Name
MUST be "_udp".
The port advertised in the SRV record has a restriction not seen with
unicast services. Unicast services can dynamically allocate a free
port for the service. Multicast streams cannot use a dynamic port
because there is no guarantee that applications on all clients can
bind to the dynamic port. If all devices on the network are purpose-
built for the application, then multicast streams may use a pre-
determined port in the dynamic range. Otherwise, multicast streams
should use a port registered with IANA. In either case, the chosen
port is advertised in the SRV record.
The hostname advertised in the SRV, A, and AAAA records is a
combination of the <Instance> portion of the Service Instance Name,
the hostname of the stream's origin, and the "mcast.arpa." special
use domain name.
Finally, the address advertised in A and AAAA records is the chosen
multicast address. The "in-addr.arpa." and "ip6.arpa." records
advertised for reverse lookup also reflect the chosen multicast
address.
3. Notes
When used with Mulicast DNS [RFC6762], DNS-MSD can provide a zero-
configuration mechanism for advertising and discovering multicast
streams.
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Nothing in DNS-MSD restricts its usage to link-local scope multicast
addresses. If Multicast DNS is needed to provide zero-configuration
address advertisement in other scopes, then the recommendation is to
consider using it with larger-scoped addresses (see [RFC7558] and
note in Section 22 of [RFC6762]).
4. Example
An example host has an Ethernet MAC address of 00-00-5E-00-53-00.
This is used to create IPv6 link local address
fe80::200:5eff:fe00:5300. It creates a link-scoped IPv6 multicast
address ff32:ff:200:5eff:fe00:5300:aabb:ccdd to transmit with. Its
hostname is "example", the service name is "_heartbeat._udp", service
instance is "instance", and by pre-agreement all hosts on the network
reserve port 62000 for this protocol. It has no additional data to
include in a TXT record. The following DNS records are created:
_heartbeat._udp 4500 IN PTR instance._heartbeat._udp.mcast.arpa.
instance._heartbeat._udp.mcast.arpa. \
120 IN SRV 0 0 62000 instance.example.mcast.arpa.
instance._heartbeat._udp.mcast.arpa. 4500 IN TXT ""
instance.example.mcast.arpa. \
120 IN AAAA ff32:ff:200:5eff:fe00:5300:aabb:ccdd
d.d.c.c.b.b.a.a.0.0.3.5.0.0.e.f. \
f.f.e.5.0.0.2.0.f.f.0.0.2.3.f.f. \
ip6.arpa. 120 PTR instance.example.mcast.arpa.
Note that the backslash ('\') denotes a line that was divided for
publication.
5. IANA Considerations
The special-use domain "mcast.arpa" should be registered in the
"Special-Use Domain Names" registry https://www.iana.org/assignments/
special-use-domain-names.
5.1. Domain Name Reservation Considerations
Domain name reservation considerations for "mcast.arpa." as required
by Section 5 of [RFC6761]:
1. Users will not use the "mcast.arpa." domain directly.
2. Applications SHOULD recognize the "mcast.arpa." domain and reject
any use in a unicast context.
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3. Name resolution APIs and libraries SHOULD resolve the
"mcast.arpa." domain to the multicast address that carries the
service's data.
4. Caching DNS servers SHOULD NOT recognize the "mcast.arpa." domain
as special.
5. Authoritative DNS servers SHOULD NOT recognize the "mcast.arpa."
domain as special.
6. DNS server operators SHOULD be aware of the "mcast.arpa."
domain's use in resolving multicast services.
7. DNS registries/registrars MUST NOT allow the "mcast.arpa." domain
to be registered to any person or entity.
6. Security Considerations
This document does not have any additional security notes beyond what
is described in Section 15 of [RFC6763].
7. Acknowledgement
Special thanks to the National Marine Electronics Association for
their contributions in developing marine industry standards and their
support for this research.
8. References
8.1. Normative References
[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>.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
<https://www.rfc-editor.org/info/rfc6763>.
[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>.
8.2. Informative References
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[I-D.ietf-pim-ipv6-zeroconf-assignment]
Karstens, N., Farinacci, D., and M. McBride, "Zero-
Configuration Assignment of IPv6 Multicast Addresses",
Work in Progress, Internet-Draft, draft-ietf-pim-ipv6-
zeroconf-assignment-00, 5 November 2023,
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ietf-pim-ipv6-zeroconf-assignment/>.
[RFC2365] Meyer, D., "Administratively Scoped IP Multicast", BCP 23,
RFC 2365, DOI 10.17487/RFC2365, July 1998,
<https://www.rfc-editor.org/info/rfc2365>.
[RFC3307] Haberman, B., "Allocation Guidelines for IPv6 Multicast
Addresses", RFC 3307, DOI 10.17487/RFC3307, August 2002,
<https://www.rfc-editor.org/info/rfc3307>.
[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>.
[RFC7558] Lynn, K., Cheshire, S., Blanchet, M., and D. Migault,
"Requirements for Scalable DNS-Based Service Discovery
(DNS-SD) / Multicast DNS (mDNS) Extensions", RFC 7558,
DOI 10.17487/RFC7558, July 2015,
<https://www.rfc-editor.org/info/rfc7558>.
Authors' Addresses
Nate Karstens
Garmin International
Email: nate.karstens@gmail.com
Dino Farinacci
lispers.net
Email: farinacci@gmail.com
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Mike McBride
Futurewei
Email: michael.mcbride@futurewei.com
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