Mboned J. Holland
Internet-Draft Akamai Technologies, Inc.
Intended status: Standards Track October 18, 2018
Expires: April 21, 2019
DNS Reverse IP AMT Discovery
draft-jholland-mboned-driad-amt-discovery-00
Abstract
This document defines a new DNS resource record (RR) used to
advertise addresses for Automatic Multicast Tunneling (AMT) relays
capable of receiving multicast traffic from the owner of the RR. The
new AMTRELAY RR makes possible a source-specific method for AMT
gateways to discover appropriate AMT relays, in order to ingest
traffic for source-specific multicast channels into multicast-capable
receiving networks when no multicast connectivity is directly
available between the sending and receiving networks.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on April 21, 2019.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
Holland Expires April 21, 2019 [Page 1]
Internet-Draft DRIAD October 2018
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Background and Terminology . . . . . . . . . . . . . . . 3
1.2. Requirements Notation . . . . . . . . . . . . . . . . . . 4
2. Relay Discovery Operation . . . . . . . . . . . . . . . . . . 4
2.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Example Receiving Networks . . . . . . . . . . . . . . . 5
2.2.1. Tier 3 ISP . . . . . . . . . . . . . . . . . . . . . 5
2.2.2. Small Office . . . . . . . . . . . . . . . . . . . . 6
2.3. Example Sending Networks . . . . . . . . . . . . . . . . 9
2.3.1. Sender-controlled Relays . . . . . . . . . . . . . . 9
2.3.2. Provider-controlled Relays . . . . . . . . . . . . . 10
3. AMTRELAY Resource Record Definition . . . . . . . . . . . . . 11
3.1. AMTRELAY RRType . . . . . . . . . . . . . . . . . . . . . 11
3.2. AMTRELAY RData Format . . . . . . . . . . . . . . . . . . 11
3.2.1. RData Format - Precedence . . . . . . . . . . . . . . 12
3.2.2. RData Format - Discovery Optional (D-bit) . . . . . . 12
3.2.3. RData Format - Type . . . . . . . . . . . . . . . . . 13
3.2.4. RData Format - Relay . . . . . . . . . . . . . . . . 13
3.3. AMTRELAY Record Presentation Format . . . . . . . . . . . 14
3.3.1. Representation of AMTRELAY RRs . . . . . . . . . . . 14
3.3.2. Examples . . . . . . . . . . . . . . . . . . . . . . 14
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
5. Security Considerations . . . . . . . . . . . . . . . . . . . 15
5.1. DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.2. Local Override . . . . . . . . . . . . . . . . . . . . . 15
5.3. Congestion . . . . . . . . . . . . . . . . . . . . . . . 15
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1. Normative References . . . . . . . . . . . . . . . . . . 16
7.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Appendix A . . . . . . . . . . . . . . . . . . . . . 18
Appendix B. Appendix B . . . . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction
AMT (Automatic Multicast Tunneling) is defined in [RFC7450], and
provides a method to transport multicast traffic in a unicast tunnel,
in order to traverse non-multicast capable network segments.
Section 4.1.5 of [RFC7450] explains that relay selection might need
to be source dependent, since a relay must be able to receive
Holland Expires April 21, 2019 [Page 2]
Internet-Draft DRIAD October 2018
multicast traffic from the desired source in order to forward it. It
suggests DNS-based queries as a possible approach. This document
defines a DNS-based solution, as suggested there. This solution also
addresses the relay discovery issues outlined in [RFC8313], in the
"Disadvantages" lists in Sections 3.3 and 3.4.
The goal is to enable multicast connectivity between separate
multicast-enabled networks when neither the sending nor the receiving
network is connected to a multicast-enabled backbone, without
requiring any peering arrangement between the networks.
1.1. Background and Terminology
The reader is assumed to be familiar with the basic DNS concepts
described in [RFC1034], [RFC1035], and the subsequent documents that
update them, particularly [RFC2181].
The reader is also assumed to be familiar with the concepts and
terminology regarding source-specific multicast as described in
[RFC4607] and the usage of group management protocols for source-
specific multicast as described in [RFC4604].
The reader should also be familiar with AMT, particularly the
terminology listed in Section 3.2 and Section 3.3 of [RFC7450].
It's especially helpful to recall that once an AMT tunnel is
established, the relay receives native multicast traffic and
encapsulates it into the unicast tunnel, and the gateway receives the
unicast tunnel traffic, unencapsulates it, and forwards it as native
multicast:
|
Multicast |
v
+-----------+
| AMT relay |
+-----------+
|
Unicast |
Tunnel |
v
+-------------+
| AMT gateway |
+-------------+
|
Multicast |
v
Holland Expires April 21, 2019 [Page 3]
Internet-Draft DRIAD October 2018
1.2. Requirements Notation
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
[RFC2119] and [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Relay Discovery Operation
2.1. Overview
The AMTRELAY resource record (RR) is used to publish the address or
host name of an AMT relay that can forward multicast traffic from a
particular source host. The owner of the RR is the sender of native
multicast traffic, and the RR provides the address or hostname of an
AMT relay that can receive traffic from it.
The primary use case for the AMTRELAY RR is when a router that can
act as an AMT gateway gets a signal indicating that a client in its
receiving network has joined a new source-specific multicast channel,
(hereafter called an (S,G), as defined in [RFC4607]), for example by
receiving a PIM-SM (S,G) join message as described in Section 4.5.2
of [RFC7761].
When the source of a newly joined (S,G) is not reachable via a
multicast-enabled next hop, the AMT gateway can connect to an AMT
relay and propagate the join signal to that relay. The goal for
source-specific relay discovery in this situation is to ensure that
the AMT relay chosen is able to receive multicast traffic from the
given source. More detailed example use cases are provided in
Section 2.2 and Section 2.3, and other applicable examples appear in
[RFC8313], Sections 3.3, 3.4, and 3.5.
Often an AMT gateway will only have access to the source and group IP
addresses of the desired traffic, and will not know any other name
for the source of the traffic. Because of this, typically the best
way of looking up AMTRELAY RRs will be by using the source IP address
as an index into one of the reverse mapping trees (in-addr.arpa for
IPv4, as described in Section 3.5 of [RFC1035], or ip6.arpa for IPv6,
as described in Section 2.5 of [RFC3596]).
Therefore, it is RECOMMENDED that AMTRELAY RRs be added to reverse IP
zones as appropriate. AMTRELAY records MAY also appear in other
zones, but the primary intended use case requires a reverse IP
mapping for the source from an (S,G) in order to be useful to most
AMT gateways.
Holland Expires April 21, 2019 [Page 4]
Internet-Draft DRIAD October 2018
When the reverse IP mapping has no AMTRELAY RR but does have a PTR
record, the lookup is done in the fashion usual for PTR records. The
IP address' octets (IPv4) or nibbles (IPv6) are reversed and looked
up with the appropriate suffix. Any CNAMEs or DNAMEs found MUST be
followed, and the AMTRELAY RR is queried with the resulting domain
name.
When AMTRELAY RRs as defined in this document are available, it is
RECOMMENDED that AMT gateways give the AMTRELAY RR precedence over
AMT discovery using the anycast IPs defined in Section 7 of
[RFC7450].
2.2. Example Receiving Networks
2.2.1. Tier 3 ISP
One example of a receiving network is an ISP that offers multicast
ingest services to its subscribers, illustrated in Figure 1.
In the example network below, subscribers can join (S,G)s with MLDv2
or IGMPv3 as described in [RFC4604], and the AMT gateway in this ISP
can receive and forward multicast traffic from one of the example
sending networks in Section 2.3 by discovering the appropriate AMT
relays with a DNS lookup for the AMTRELAY RR with the reverse IP of
the source in the (S,G).
Holland Expires April 21, 2019 [Page 5]
Internet-Draft DRIAD October 2018
Internet
^ ^ Multicast-enabled
| | Receiving Network
+------|------------|-------------------------+
| | | |
| +--------+ +--------+ +=========+ |
| | Border |---| Border | | AMT | |
| | Router | | Router | | gateway | |
| +--------+ +--------+ +=========+ |
| | | | |
| +-----+------+-----------+--+ |
| | | |
| +-------------+ +-------------+ |
| | Agg Routers | .. | Agg Routers | |
| +-------------+ +-------------+ |
| / \ \ / \ |
| +---------------+ +---------------+ |
| |Access Systems | ....... |Access Systems | |
| |(CMTS/OLT/etc.)| |(CMTS/OLT/etc.)| |
| +---------------+ +---------------+ |
| | | |
+--------|------------------------|-----------+
| |
+---+-+-+---+---+ +---+-+-+---+---+
| | | | | | | | | |
/-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\ /-\
|_| |_| |_| |_| |_| |_| |_| |_| |_| |_|
Subscribers
Figure 1: Receiving ISP Example
2.2.2. Small Office
Another example receiving network is a small branch office that
regularly accesses some multicast content, illustrated in Figure 2.
This office has desktop devices that need to receive some multicast
traffic, so an AMT gateway runs on a LAN with these devices, to pull
traffic in through a non-multicast next-hop.
The office also hosts some mobile devices that have AMT gateway
instances embedded in apps, in order to receive multicast traffic
over their non-multicast wireless LAN.
Holland Expires April 21, 2019 [Page 6]
Internet-Draft DRIAD October 2018
Internet
(non-multicast)
^
| Office Network
+----------|----------------------------------+
| | |
| +---------------+ (Wifi) Mobile apps |
| | Modem+ | Wifi | - - - - w/ embedded |
| | Router | AP | AMT gateways |
| +---------------+ |
| | |
| | |
| +----------------+ |
| | Legacy Router | |
| | (unicast) | |
| +----------------+ |
| / | \ |
| / | \ |
| +--------+ +--------+ +--------+=========+ |
| | Phones | | ConfRm | | Desks | AMT | |
| | subnet | | subnet | | subnet | gateway | |
| +--------+ +--------+ +--------+=========+ |
| |
+---------------------------------------------+
Figure 2: Small Office (no multicast up)
By adding an AMT relay to this office network as in Figure 3, it's
possible to make use of multicast services from the example
multicast-capable ISP in Section 2.2.1, provided that the AMT
gateways contact the local AMT relay instead of an AMT relay upstream
of the multicast-capable ISP, and the uplink router performs IGMP/MLD
Proxying, as described in [RFC4605].
Holland Expires April 21, 2019 [Page 7]
Internet-Draft DRIAD October 2018
Multicast-capable ISP
^
| Office Network
+----------|----------------------------------+
| | |
| +---------------+ (Wifi) Mobile apps |
| | Modem+ | Wifi | - - - - w/ embedded |
| | Router | AP | AMT gateways |
| +---------------+ |
| | +=======+ |
| +---Wired LAN---| AMT | |
| | | relay | |
| +----------------+ +=======+ |
| | Legacy Router | |
| | (unicast) | |
| +----------------+ |
| / | \ |
| / | \ |
| +--------+ +--------+ +--------+=========+ |
| | Phones | | ConfRm | | Desks | AMT | |
| | subnet | | subnet | | subnet | gateway | |
| +--------+ +--------+ +--------+=========+ |
| |
+---------------------------------------------+
Figure 3: Small Office Example
For this reason, it's RECOMMENDED to provide an AMTRELAY RR
referencing _amt._udp.home.arpa for sources, with a more-preferred
precedence than the known relays close to source relays like those
described in Section 2.3.
Holland Expires April 21, 2019 [Page 8]
Internet-Draft DRIAD October 2018
<TBD>
.home.arpa is pretty close to what's needed, but since this use case
is not a residential home network, should this be another different
special-use domain name?
https://tools.ietf.org/html/rfc8375
https://www.iana.org/assignments/
locally-served-dns-zones/locally-served-dns-zones.xhtml
special-use-domain-names/special-use-domain-names.xhtml
e.g. _amt._udp.home.arpa
e.g. _amt._udp.most-local.arpa =>
.local if it's there,
.home.arpa if it's not,
.isp.arpa if it's not
(most-local because if somebody bothered to deploy a relay, they did
so in a spot where it can do a next-hop receive of multicast, as
long as no upstream gateway finds this relay and creates a loop.)
(Can/should "most-local.arpa" be done with the well-known anycast ip?
Not sure...)
<\TBD>
2.3. Example Sending Networks
2.3.1. Sender-controlled Relays
When a sender network is also operating AMT relays to distribute
multicast traffic, as in Figure 4, each address could appear as an
AMTRELAY RR for the reverse IP of the sender, or one or more domain
names could appear in AMTRELAY RRs, and the AMT relay addresses can
be discovered by finding an A or AAAA record from those domain names.
Holland Expires April 21, 2019 [Page 9]
Internet-Draft DRIAD October 2018
Sender Network
+-----------------------------------+
| |
| +--------+ +=======+ +=======+ |
| | Sender | | AMT | | AMT | |
| +--------+ | relay | | relay | |
| | +=======+ +=======+ |
| | | | |
| +-----+------+----------+ |
| | |
+-----------|-----------------------+
v
Internet
(non-multicast)
Figure 4: Small Office Example
2.3.2. Provider-controlled Relays
When an ISP offers a service to transmit outbound multicast traffic
through a forwarding network, they might also offer AMT relays in
order to reach receivers without multicast connectivity to the
forwarding network, as in Figure 5. In this case it's RECOMMENDED
that a domain name for the AMT relays also be provided for use with
the discovery process defined in this document.
When the sender wishes to use the relays provided by the ISP for
forwarding multicast traffic, an AMTRELAY RR should be configured to
use the domain name provided by the ISP, to allow for address
reassignment of the relays without forcing the sender to reconfigure
the corresponding AMTRELAY RRs.
Holland Expires April 21, 2019 [Page 10]
Internet-Draft DRIAD October 2018
+--------+
| Sender |
+---+----+ Multicast-enabled
| Sending Network
+-----------|-------------------------------+
| v |
| +------------+ +=======+ +=======+ |
| | Agg Router | | AMT | | AMT | |
| +------------+ | relay | | relay | |
| | +=======+ +=======+ |
| | | | |
| +-----+------+--------+---------+ |
| | | |
| +--------+ +--------+ |
| | Border |---| Border | |
| | Router | | Router | |
| +--------+ +--------+ |
+-----|------------|------------------------+
| |
v v
Internet
(non-multicast)
Figure 5: Sending ISP Example
3. AMTRELAY Resource Record Definition
3.1. AMTRELAY RRType
The AMTRELAY RRType has the mnemonic AMTRELAY and type code 68
(decimal).
3.2. AMTRELAY RData Format
The AMTRELAY RData consists of a 8-bit precedence field, a 1-bit
"Discovery Optional" field, a 7-bit type field, and a variable length
relay field.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| precedence |D| type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
~ relay ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Holland Expires April 21, 2019 [Page 11]
Internet-Draft DRIAD October 2018
3.2.1. RData Format - Precedence
This is an 8-bit precedence for this record. It is interpreted in
the same way as the PREFERENCE field described in Section 3.3.9 of
[RFC1035].
Relays listed in AMTRELAY records with a lower value for precedence
are to be attempted first.
Where there is a tie in precedence, the default choice of relay MUST
be non-deterministic, to support load balancing. The AMT gateway
operator MAY override this default choice with explicit configuration
when it's necessary for administrative purposes.
For example, one network might prefer to tunnel IPv6 multicast
traffic over IPv6 AMT and IPv4 multicast traffic over IPv4 AMT to
avoid routeability problems in IPv6 from affecting IPv4 traffic and
vice versa, while another network might prefer to tunnel both kinds
of traffic over IPv6 to reduce the IPv4 space used by its AMT
gateways. In this example scenario or other cases where there is an
administrative preference that requires explicit configuration, a
receiving network MAY make systematically different precedence
choices among records with the same precedence value.
3.2.2. RData Format - Discovery Optional (D-bit)
The D bit is a "Discovery Optional" flag.
If the D bit is set to 0, a gateway using this RR MUST perform AMT
relay discovery as described in Section 4.2.1.1 of [RFC7450], rather
than directly sending an AMT request message to the relay.
That is, the gateway MUST receive an AMT relay advertisement message
(Section 5.1.2 of [RFC7450]) for an address before sending an AMT
request message (Section 5.1.3 for [RFC7450]) to that address.
Before receiving the relay advertisement message, this record has
only indicated that the address can be used for AMT relay discovery,
not for a request message. This is necessary for devices that are
not fully functional AMT relays, but rather load balancers or
brokers, as mentioned in Section 4.2.1.1 of [RFC7450].
If the D bit is set to 1, the gateway MAY send an AMT request message
directly to the discovered relay address without first sending an AMT
discovery message.
This bit should be set according to advice from the AMT relay
operator. The D bit MUST be set to zero when no information is
available from the AMT relay operator about its suitability.
Holland Expires April 21, 2019 [Page 12]
Internet-Draft DRIAD October 2018
3.2.3. RData Format - Type
The type field indicates the format of the information that is stored
in the relay field.
The following values are defined:
o type = 0:
The relay field is empty (0 bytes).
o type = 1:
The relay field contains a 4-octet IPv4 address.
o type = 2:
The relay field contains a 16-octet IPv6 address.
o type = 3:
The relay field contains a wire-encoded domain name. The wire-
encoded format is self-describing, so the length is implicit. The
domain name MUST NOT be compressed. (See Section 3.3 of [RFC1035]
and Section 4 of [RFC3597].)
3.2.4. RData Format - Relay
The relay field is the address or domain name of the AMT relay. It
is formatted according to the type field.
When the type field is 0, the length of the relay field is 0, and it
indicates that no AMT relay should be used for multicast traffic from
this source.
When the type field is 1, the length of the relay field is 4 octets,
and a 32-bit IPv4 address is present. This is an IPv4 address as
described in Section 3.4.1 of [RFC1035]. This is a 32-bit number in
network byte order.
When the type field is 2, the length of the relay field is 16 octets,
and a 128-bit IPv6 address is present. This is an IPv6 address as
described in Section 2.2 of [RFC3596]. This is a 128-bit number in
network byte order.
When the type field is 3, the relay field is a normal wire-encoded
domain name, as described in Section 3.3 of [RFC1035]. Compression
MUST NOT be used, for the reasons given in Section 4 of [RFC3597].
Holland Expires April 21, 2019 [Page 13]
Internet-Draft DRIAD October 2018
3.3. AMTRELAY Record Presentation Format
3.3.1. Representation of AMTRELAY RRs
AMTRELAY RRs may appear in a zone data master file. The precedence,
D-bit, relay type, and relay fields are REQUIRED.
If the relay type field is 0, the relay field MUST be ".".
The presentation for the record is as follows:
IN AMTRELAY precedence D-bit type relay
3.3.2. Examples
For zone files in resolvers that don't support the value natively,
it's possible as a transition path to use the format for unknown RR
types, as described in [RFC3597].
IN AMTRELAY 128 0 3 amtrelays.example.com.
or (see Appendix B):
IN TYPE68 \# ( 24 ; length
80 ; precedence
83 ; D=1, relay type=3
616d7472656c6179732e6578616d706c652e636f6d2e ) ; relay
As described in Section 2.2.2, a record for _amt._udp.home.arpa
SHOULD also be present with a more preferred precedence:
IN AMTRELAY 16 0 3 _amt._udp.home.arpa.
or (see Appendix B):
IN TYPE68 \# ( 22 ; length
10 ; precedence
03 ; D=0, relay type=3
5f616d742e5f7564702e686f6d652e617270612e ) ; relay
4. IANA Considerations
This document updates the IANA Registry for DNS Resource Record Types
by assigning type 68 to the AMTRELAY record.
Holland Expires April 21, 2019 [Page 14]
Internet-Draft DRIAD October 2018
[ To be removed (TBD):
Dear IANA, we request 68, since 68 is unassigned and easier to
remember than other valid numbers, because the AMT UDP port number
is 2268.
Registry URI:
https://www.iana.org/assignments/
dns-parameters/dns-parameters.xhtml#dns-parameters-4
]
This document creates a new IANA registry specific to the AMTRELAY
for the relay type field.
Values 0, 1, 2, and 3 are defined in Section 3.2.3. Relay type
numbers 4 through 255 can be assigned with a policy of Specification
Required (see [RFC8126]).
[TBD: should the relay type registry try to combine with the
gateway type from [RFC4025], Section 2.3 and 2.5? They are semantically
very similar.
https://www.ietf.org/assignments/
ipseckey-rr-parameters/ipseckey-rr-parameters.xml
]
5. Security Considerations
[TBD: these 3 are just the first few most obvious issues, with just
sketches of the problem. Explain better, and look for trickier issues.]
5.1. DNSSEC
If AMT is used to ingest multicast traffic, spoofing this record can
enable spoofed multicast traffic.
Depending on service model, spoofing the relay may also be an attempt
to steal services or induce extra charges.
5.2. Local Override
The local relays, while important for overall network performance,
can't be secured by DNSSEC.
5.3. Congestion
Multicast traffic, particularly interdomain multicast traffic,
carries some congestion risks, as described in Section 4 of
[RFC8085]. Network operators are advised to take precautions
including monitoring of application traffic behavior, traffic
Holland Expires April 21, 2019 [Page 15]
Internet-Draft DRIAD October 2018
authentication, and rate-limiting of multicast traffic, in order to
ensure network health.
6. Acknowledgements
This specification was inspired by the previous work of Doug Nortz,
Robert Sayko, David Segelstein, and Percy Tarapore, presented in the
MBONED working group at IETF 93.
Thanks also to Jeff Goldsmith for his helpful review and feedback.
7. References
7.1. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[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>.
[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
<https://www.rfc-editor.org/info/rfc2181>.
[RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,
"DNS Extensions to Support IP Version 6", STD 88,
RFC 3596, DOI 10.17487/RFC3596, October 2003,
<https://www.rfc-editor.org/info/rfc3596>.
[RFC3597] Gustafsson, A., "Handling of Unknown DNS Resource Record
(RR) Types", RFC 3597, DOI 10.17487/RFC3597, September
2003, <https://www.rfc-editor.org/info/rfc3597>.
[RFC4604] Holbrook, H., Cain, B., and B. Haberman, "Using Internet
Group Management Protocol Version 3 (IGMPv3) and Multicast
Listener Discovery Protocol Version 2 (MLDv2) for Source-
Specific Multicast", RFC 4604, DOI 10.17487/RFC4604,
August 2006, <https://www.rfc-editor.org/info/rfc4604>.
Holland Expires April 21, 2019 [Page 16]
Internet-Draft DRIAD October 2018
[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, DOI 10.17487/RFC4607, August 2006,
<https://www.rfc-editor.org/info/rfc4607>.
[RFC7450] Bumgardner, G., "Automatic Multicast Tunneling", RFC 7450,
DOI 10.17487/RFC7450, February 2015,
<https://www.rfc-editor.org/info/rfc7450>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[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
[RFC4025] Richardson, M., "A Method for Storing IPsec Keying
Material in DNS", RFC 4025, DOI 10.17487/RFC4025, March
2005, <https://www.rfc-editor.org/info/rfc4025>.
[RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick,
"Internet Group Management Protocol (IGMP) / Multicast
Listener Discovery (MLD)-Based Multicast Forwarding
("IGMP/MLD Proxying")", RFC 4605, DOI 10.17487/RFC4605,
August 2006, <https://www.rfc-editor.org/info/rfc4605>.
[RFC5507] IAB, Faltstrom, P., Ed., Austein, R., Ed., and P. Koch,
Ed., "Design Choices When Expanding the DNS", RFC 5507,
DOI 10.17487/RFC5507, April 2009,
<https://www.rfc-editor.org/info/rfc5507>.
[RFC6895] Eastlake 3rd, D., "Domain Name System (DNS) IANA
Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895,
April 2013, <https://www.rfc-editor.org/info/rfc6895>.
[RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
Multicast - Sparse Mode (PIM-SM): Protocol Specification
(Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
2016, <https://www.rfc-editor.org/info/rfc7761>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
Holland Expires April 21, 2019 [Page 17]
Internet-Draft DRIAD October 2018
[RFC8313] Tarapore, P., Ed., Sayko, R., Shepherd, G., Eckert, T.,
Ed., and R. Krishnan, "Use of Multicast across Inter-
domain Peering Points", BCP 213, RFC 8313,
DOI 10.17487/RFC8313, January 2018,
<https://www.rfc-editor.org/info/rfc8313>.
Appendix A. Appendix A
This is the template for requesting a new RRType recommended in
Appendix A of [RFC6895].
A. Submission Date:
B.1 Submission Type:
[x] New RRTYPE [ ] Modification to RRTYPE
B.2 Kind of RR:
[x] Data RR [ ] Meta-RR
C. Contact Information for submitter (will be publicly posted):
Name: Jake Holland
Email Address: jakeholland.net@gmail.com
International telephone number: +1-626-486-3706
Other contact handles: none
D. Motivation for the new RRTYPE application.
It provides a bootstrap so that AMT (RFC 7450) gateways can find the
specific AMT relays that can receive multicast traffic from a
known source, in order to signal multicast group membership and
receive multicast traffic over a unicast tunnel using AMT.
E. Description of the proposed RR type.
This description can be provided in-line in the template, as an
attachment, or with a publicly available URL.
https://datatracker.ietf.org/doc/
draft-jholland-mboned-driad-amt-discovery
F. What existing RRTYPE or RRTYPEs come closest to filling that need
and why are they unsatisfactory?
Some similar concepts appear in IPSECKEY, as described in
Section 1.2 of [RFC4025]. The IPSECKEY RRType is unsatisfactory
because it refers to IPSec Keys instead of to AMT relays, but
the motivating considerations for using reverse IP and for
providing a precedence are similar--an AMT gateway often
has access to a source address for a multicast (S,G), but does
not have access to a domain name or a good relay address, without
administrative configuration.
Defining a format for a TXT record could serve the need for AMT
Holland Expires April 21, 2019 [Page 18]
Internet-Draft DRIAD October 2018
relay discovery semantics, but Section 5 of [RFC5507] provides a
compelling argument for requesting a new RRType instead.
G. What mnemonic is requested for the new RRTYPE (optional)?
AMTRELAY
H. Does the requested RRTYPE make use of any existing IANA registry
or require the creation of a new IANA subregistry in DNS
Parameters?
No.
I. Does the proposal require/expect any changes in DNS
servers/resolvers that prevent the new type from being processed
as an unknown RRTYPE (see RFC3597)?
No.
J. Comments:
None.
Appendix B. Appendix B
In a DNS resolver that understands the AMTRELAY type, the zone file
might contain this line:
IN AMTRELAY 128 0 3 amtrelays.example.com.
In order to translate this example to appear as an unknown RRType as
defined in [RFC3597], one could run the following program:
<CODE BEGINS>
$ cat translate.py
#!/usr/bin/python3
import sys
name=sys.argv[1]
print(len(name))
print(''.join('%02x'%ord(x) for x in name))
$ ./translate.py amtrelays.example.com.
22
616d7472656c6179732e6578616d706c652e636f6d2e
<CODE ENDS>
The length and the hex string for the domain name
"amtrelays.example.com" are the outputs of this program, yielding a
length of 22 and the above hex string.
Holland Expires April 21, 2019 [Page 19]
Internet-Draft DRIAD October 2018
22 is the length of the domain name, so to this we add 2 (1 for the
precedence field and 1 for the combined D-bit and relay type fields)
to get the length of the unknown RData.
This results in a zone file line for an unknown resolver of:
IN TYPE68 \# ( 24 ; length
80 ; precedence
03 ; relay type=domain
616d7472656c6179732e6578616d706c652e636f6d2e ) ; relay
Author's Address
Jake Holland
Akamai Technologies, Inc.
150 Broadway
Cambridge, MA 02144
United States of America
Email: jakeholland.net@gmail.com
Holland Expires April 21, 2019 [Page 20]