Internet Engineering Task Force S. Cheshire
Internet-Draft Apple Inc.
Intended status: Informational T. Lemon
Expires: January 15, 2019 Nibbhaya Consulting
July 14, 2018
Service Registration Protocol for DNS-Based Service Discovery
draft-sctl-service-registration-02
Abstract
The DNS-SD Service Registration Protocol uses the standard DNS Update
mechanism to enable DNS-Based Service Discovery using only unicast
packets. This eliminates the dependency on Multicast DNS as the
foundation layer, which greatly improves scalability and improves
performance on networks where multicast service is not an optimal
choice, particularly 802.11 (Wi-Fi) and 802.15.4 (IoT) networks.
DNS-SD Service registration uses public keys and SIG(0) to allow
services to defend their registrations against attack.
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 January 15, 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
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to this document. Code Components extracted from this document must
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.
1. Introduction
DNS-Based Service Discovery [RFC6763] is a component of Zero
Configuration Networking [RFC6760] [ZC] [I-D.cheshire-dnssd-roadmap].
This document describes an enhancement to DNS-Based Service Discovery
[RFC6763] that allows services to automatically register their
services using the DNS protocol rather than using mDNS. There is
already a large installed base of DNS-SD clients that can do service
discovery using the DNS protocol. This extension makes it much
easier to take advantage of this existing functionality.
This document is intended for three audiences: implementors of
software that provides services that should be advertised using DNS-
SD, implementors of DNS servers that will be used in contexts where
DNS-SD registration is needed, and administrators of networks where
DNS-SD service is required. The document is intended to provide
sufficient information to allow interoperable implementation of the
registration protocol.
DNS-Based Service Discovery (DNS-SD) allows services to advertise the
fact that they provide service, and to provide the information
required to access that service. Clients can then discover the set
of services of a particular type that are available. They can then
select a service from among those that are available and obtain the
information required to use it.
The DNS-SD Service Registration protocol, described in this document,
provides a reasonably secure mechanism for publishing this
information. Once published, these services can be readily
discovered by clients using standard DNS lookups.
In the DNS-Based Service Discovery specification [RFC6763] Section 10
"Populating the DNS with Information" briefly discusses ways that
services can publish their information in the DNS namespace. In the
case of Multicast DNS [RFC6762], it allows services to publish their
information on the local link, using names in the ".local" namespace,
which makes their services directly discoverable by peers attached to
that same local link.
RFC6763 also allows clients to discover services using the DNS
protocol [RFC1035]. This can be done by having a system
administrator manually configure service information in the DNS, but
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manually populating DNS authoritative server databases is costly and
potentially error-prone, and requires a knowledgable network
administrator. Consequently, although all DNS-SD client
implementations of which we are aware support DNS-SD using DNS
queries, in practice it is used much less frequently than mDNS. The
Discovery Proxy [I-D.ietf-dnssd-hybrid] provides one way to
automatically populate the DNS namespace, but is only appropriate on
networks where services are already advertised using mDNS. This
document describes a solution more suitable for networks where
multicast is inefficient, or undesirable for other reasons, by
supporting both offering of services, and discovery of services,
using unicast.
2. Service Registration Protocol
Services that implement the DNS-SD Service Registration Protocol use
DNS Update [RFC2136] [RFC3007] to publish service information in the
DNS. Two variants exist, one for full-featured devices, and one for
devices designed for "Constrained-Node Networks" [RFC7228].
Full-featured devices are either configured manually, or use the
"dr._dns-sd._udp" query [RFC6763] to learn the default registration
domain from the network. Using the chosen service registration
domain, full-featured devices construct the names of the SRV, TXT,
and PTR records describing their service(s). For these names they
then discover the zone apex of the closest enclosing DNS zone using
SOA queries [I-D.ietf-dnssd-push]. Having discovered the enclosing
DNS zone, they query for the "_dns-update._udp<zone>" SRV record to
discover the server to which they should send DNS updates.
For devices designed for "Constrained-Node Networks" [RFC7228] some
simplifications are used. Instead of being configured with (or
discovering) the service registration domain, the (proposed) special
use domain name [RFC6761] "services.arpa" is used. Instead of
learning the server to which they should send DNS updates, a fixed
IPv6 anycast address is used (value TBD). It is the responsibility
of a "Constrained-Node Network" supporting DNS-SD Service
Registration Protocol to provide appropriate anycast routing to
deliver the DNS updates to the appropriate server. It is the
responsibility of the DNS-SD Service Registration server on a
"Constrained-Node Network" to handle the updates appropriately. In
some network environments, updates may be accepted directly into a
local "services.arpa" zone, which has only local visibility. In
other network environments, updates for names ending in
"services.arpa" may be rewritten internally to names with broader
visibility.
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The reason for these different assumptions is that "Constrained-Node
Networks" generally require special egress support, and Anycast
packets captured at the "Constrained-Node Network" egress can be
assumed to have originated locally. Low-power devices that typically
use "Constrained-Node Networks" may have very limited battery power.
The additional DNS lookups required to discover a registration server
and then communicate with it will increase the power required to
advertise a service; for low-power devices, the additional
flexibility this provides does not justify the additional use of
power.
General networks have the potential to have more complicated
topologies at the Internet layer, which makes anycast routing more
difficult. Such networks may or may not have the infrastructure
required to route anycast to a server that can process it. However,
they can be assumed to be able to provide registration domain
discovery and routing. By requiring the use of TCP, the possibility
of off-network spoofing is eliminated.
We will discuss several parts to this process: how to know what to
publish, how to know where to publish it (under what name), how to
publish it, how to secure its publication, and how to maintain the
information once published.
2.1. What to publish
We refer to the message that services using the DNSSD Registration
Protocol send as a Registration. Three types of updates appear in a
Registration: Service Discovery records, Service Description records,
and Host Description records.
o Service Discovery records are one or more PTR RRs, mapping from
the generic service type (or subtype) to the specific Service
Instance Name.
o Service Description records are exactly one SRV RR, and one or
more TXT RRs, both with the same name, the Service Instance Name
([RFC6763] section 4.1). In principle Service Description records
can include other record types, with the same Service Instance
Name, though in practice they rarely do. The Service Instance
Name MUST be referenced by one or more Service Discovery PTR
records, unless it is a placeholder service registration for an
intentionally non-discoverable service name.
o The Host Description records for a service are a KEY RR, used to
claim exclusive ownership of the service registration, and one or
more RRs of type A or AAAA, giving the IPv4 or IPv6 address(es) of
the host where the service resides.
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RFC 6763 describes the details of what each of these types of updates
contains and is the definitive source for information about what to
publish; the reason for mentioning it here is to provide the reader
with enough information about what will be published that the service
registration process can be understood at a high level without first
learning the full details of DNS-SD. Also, the "Service Instance
Name" is an important aspect of first-come, first-serve naming, which
we describe later on in this document.
2.2. Where to publish it
Multicast DNS uses a single namespace, ".local", which is valid on
the local link. This convenience is not available for DNS-SD using
the DNS protocol: services must exist in some specific unicast
namespace.
As described above, full-featured devices are responsible for knowing
in what domain they should register their services. Devices made for
"Constrained-Node Networks" register in the (proposed) special use
domain name [RFC6761] "services.arpa", and let the DNS-SD Service
Registration server handle rewriting that to a different domain if
necessary.
2.3. How to publish it
It is possible to issue a DNS Update that does several things at
once; this means that it's possible to do all the work of adding a
PTR resource record to the PTR RRset on the Service Name if it
already exists, or creating one if it doesn't, and creating or
updating the Service Instance Name and Host Description in a single
transaction.
A Registration is therefore implemented as a single DNS Update
message that contains a service's Service Discovery records, Service
Description records, and Host Description records.
Updates done according to this specification are somewhat different
than regular DNS Updates as defined in RFC2136. RFC2136 assumes that
updating is a fairly heavyweight process, so you might first attempt
to add a name if it doesn't exist, and then in a second message
update the name if it does exist but matches certain preconditions.
Because the registration protocol uses a single transaction, some of
this adaptability is lost.
In order to allow updates to happen in a single transaction,
Registrations do not include update constraints. The constraints
specified in Section 2.4.2 are implicit in the processing of
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Registrations, and so there is no need for the service sending the
Registration to put in any explicit constraints.
2.3.1. How DNS-SD Service Registration differs from standard RFC2136
DNS Update
DNS-SD Service Registration is based on standard RFC2136 DNS Update,
with some differences:
o It implements first-come first-served name allocation, protected
using SIG(0).
o It enforces policy about what updates are allowed.
o It optionally performs rewriting of "services.arpa" to some other
domain.
o It optionally performs automatic population of the address-to-name
reverse mapping domains.
o A DNS-SD Service Registration server is not required to implement
general DNS Update prerequsite processing.
o Simplified clients are allowed to send updates to an anycast
address, for names ending in "services.arpa"
2.3.2. Testing using standard RFC2136-compliant servers
It may be useful to set up a DNS server for testing that does not
implement the Registration protocol. This can be done by configuring
the server to listen on the anycast address, or advertising it in the
_dns-update._udp SRV record. It must be configured to be
authoritative for "services.arpa", and to accept updates from hosts
on local networks for names under "services.arpa" without
authentication.
A server configured in this way will be able to successfully accept
and process Registrations from services that send Registrations.
However, no constraints will be applied, and this means that the test
server will accept internally inconsistent Registrations, and will
not stop two Registrations, sent by different services, that claim
the same name(s), from overwriting each other.
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2.3.3. How to allow services to update standard RFC2136-compliant
servers
Ordinarily Registrations will fail when sent to any non-Registration
Protocol server because the zone being updated is "services.arpa",
and no DNS server that is not a Registration Protocol server should
normally be configured to be authoritative for "services.arpa".
Therefore, a service that sends a Registration can tell that the
receiving server does not support the Registration Protocol, but does
support RFC2136, because the RCODE will either be NOTZONE, NOTAUTH or
REFUSED, or because there is no response to the update request (when
using the anycast address)
In this case a service MAY attempt to register itself using regular
RFC2136 DNS updates. To do so, it must discover default registration
zone and the DNS server designated to receive updates for that zone,
as described earlier using the _dns-update._udp SRV record. It can
then make the update using the port and host pointed to by the SRV
record, and should use appropriate constraints to avoid overwriting
competing records. Such updates are out of scope for the DNSSD
Registration Protocol, and a service that implements the DNSSD
Registration Protocol MUST first attempt to use the Registration
Protocol to register itself, and should only attempt to use RFC2136
backwards compatibility if that fails.
2.4. How to secure it
Traditional DNS update is secured using the TSIG protocol, which uses
a secret key shared between the client (which issues the update) and
the server (which authenticates it). This model does not work for
automatic service registration.
The goal of securing the DNS-SD Registration Protocol is to provide
the best possible security given the constraint that service
registration has to be automatic. It is possible to layer more
operational security on top of what we describe here, but what we
describe here improves upon the security of mDNS. The goal is not to
provide the level of security of a network managed by a skilled
operator.
2.4.1. First-Come First-Served Naming
First-Come First-Serve naming provides a limited degree of security:
a service that registers its service using DNS-SD Registration
protocol is given ownership of a name for an extended period of time
based on the key used to authenticate the DNS Update. As long as the
registration service remembers the Service Instance Name and the key
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used to register that Service Instance Name, no other service can add
or update the information associated with that Service Instance Name.
2.4.1.1. Service Behavior
The service generates a public/private key pair. This key pair MUST
be stored in stable storage; if there is no writable stable storage
on the client, the client MUST be pre-configured with a public/
private key pair that can be used.
When sending DNS updates, the service includes a KEY record
containing the public portion of the key in each Host Description
update. The update is signed using SIG(0), using the private key
that corresponds to the public key in the KEY record. The lifetimes
of the records in the update is set using the EDNS(0) Update Lease
option.
The lifetime of the DNS-SD PTR, SRV, A, AAAA and TXT records
[RFC6763] is typically set to two hours. This means that if a device
is disconnected from the network, it does not appear in the user
interfaces of devices looking for services of that type for too long.
However, the lifetime of its KEY record should be set to a much
longer time, typically 14 days. The result of this is that even
though a device may be temporarily unplugged, disappearing from the
network for a few days, it makes a claim on its name that lasts much
longer.
This way, even if a device is unplugged from the network for a few
days, and its services are not available for that time, no other
rogue device can come along and immediately claim its name the moment
it disappears from the network. In the event that a device is
unplugged from the network and permanently discarded, then its name
is eventually cleaned up and made available for re-use.
2.4.2. Registration Server Behavior
The Registration server checks each update in the Registration to see
that it contains a Service Discovery update, a Service Description
update, and a Host Description update.
An update is a Service Discovery update if it contains
o exactly one RRset update,
o which is for a PTR RR,
o which points to a Service Instance Name
o for which an update is present in the Registration.
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An update is a Service Description update if, for the appropriate
Service Instance Name, it contains
o exactly one "Delete all RRsets from a name" update,
o exactly one SRV RRset update,
o one or more TXT RRset updates,
o and the target of the SRV record update references a hostname for
which there is a Host Description update in the Registration.
An update is a Host Description update if, for the appropriate
hostname, it contains
o exactly one "Delete all RRsets from a name" update,
o A or AAAA RR update(s)
o a KEY RR update that adds a KEY RR that contains the public key
corresponding to the private key that was used to sign the
message,
o there is a Service Instance Name update in the Registration that
updates an SRV RR so that it points to the hostname being updated
by this update.
A Registration MUST include at least one Service Name update, at
least one Service Description update, and exactly one Host
Description update. An update message that does not is not a
Registration. An update message that contains any other updates, or
any update constraints, is not a Registration. Such messages should
either be processed as regular RFC2136 updates, including access
control checks and constraint checks, if supported, or else rejected
with RCODE=REFUSED.
Note that if the definitions of each of these update types are
followed carefully, this means that many things that look very much
like Registrations nevertheless are not. For example, a Registration
that contains an update to a Service Name and an update to a Service
Instance Name, where the Service Name does not reference the Service
Instance Name, is not a valid Registration message, but may be a
valid RFC2136 update.
Assuming that an update message has been validated with these
conditions and is a valid Registration, the server checks that the
name in the Host Description update exists. If so, then the server
checks to see if the KEY record on the name is the same as the KEY
record in the update. If it is not, then the server MUST reject the
Registration with the YXDOMAIN RCODE.
Otherwise, the server validates the update using SIG(0) on the public
key in the KEY record of the Host Description update. If the
validation fails, the server MUST reject the rejectration rejected
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with the REFUSED RCODE. Otherwise, the update is considered valid
and authentic, and is processed according to the method described in
RFC2136. The status that is returned depends on the result of
processing the update.
The server MAY add a Reverse Mapping that corresponds to the Host
Description. This is not required because the Reverse Mapping serves
no protocol function, but it may be useful for debugging, e.g. in
annotating network packet traces or logs.
The server MAY apply additional criteria when accepting updates. In
some networks, it may be possible to do out-of-band registration of
keys, and only accept updates from pre-registered keys. In this
case, an update for a key that has not been registered should be
rejected with the REFUSED RCODE.
There are at least two benefits to doing this rather than simply
using normal SIG(0) DNS updates. First, the same registration
protocol can be used in both cases, so both use cases can be
addressed by the same service implementation. Second, the
registration protocol includes maintenance functionality not present
with normal DNS updates.
Note that the semantics of using the Registration Protocol in this
way are different than for typical RFC2136 implementations: the KEY
used to sign the update in the Registration Protocol only allows the
client to update records that refer to its Host Description. RFC2136
implementations do not normally provide a way to enforce a constraint
of this type.
The server may also have a dictionary of names or name patterns that
are not permitted. If such a list is used, updates for Service
Instance Names that match entries in the dictionary are rejected with
YXDOMAIN.
2.5. TTL Consistency
All RRs within an RRset are required to have the same TTL
(Clarifications to the DNS Specification [RFC2181], Section 5.2). In
order to avoid inconsistencies, the Registration Protocol places
restrictions on TTLs sent by services and requires that Registration
Protocol Servers enforce consistency.
Services sending Registrations MUST use consistent TTLs in all RRs
within the Registration.
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Registration Protocol servers MUST check that the TTLs for all RRs
within the Registration are the same. If they are not, the
Registration MUST be rejected with a REFUSED RCODE.
Additionally, when adding RRs to an RRset, for example when
processing Service Discovery records, the server MUST use the same
TTL on all RRs in the RRset. How this consistency is enforced is up
to the implementation.
2.6. Maintenance
2.6.1. Cleaning up stale data
Because the DNS-SD registration protocol is automatic, and not
managed by humans, some additional bookkeeping is required. When an
update is constructed by the client, it MUST include include an
EDNS(0) Update Lease Option [I-D.sekar-dns-ul]. The Update Lease
Option contains two lease times: the Update Lease Time and the
Instance Lease Time.
These leases are promises, similar to DHCP leases [RFC2131], from the
client that it will send a new update for the service registration
before the lease time expires. The Update Lease time is chosen to
represent the time after the update during which the registered
records other than the KEY record should be assumed to be valid. The
Instance Lease time represents the time after the update during which
the KEY record should be assumed to be valid.
The reasoning behind the different lease times is discussed in the
section on first-come, first-served naming Section 2.4.1. DNS-SD
Registration Protocol servers may be configured with limits for these
values. A default limit of two hours for the Update Lease and 14
days for the SIG(0) KEY are currently thought to be good choices.
Clients that are going to continue to use names on which they hold
leases should update well before the lease ends, in case the
registration service is unavailable or under heavy load.
The Registration Protocol server MUST include an EDNS(0) Update Lease
option in the response if the lease time proposed by the service has
been shortened. The service MUST check for the EDNS(0) Update Lease
option in the response and MUST use the lease times from that option
in place of the options that it sent to the server when deciding when
to update its registration.
Clients should assume that each lease ends N seconds after the update
was first transmitted, where N is the lease duration. Servers should
assume that each lease ends N seconds after the update that was
successfully processed was received. Because the server will always
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receive the update after the client sent it, this avoids the
possibility of misunderstandings.
DNS-SD Registration Protocol servers MUST reject updates that do not
include an EDNS(0) Update Lease option. Dual-use servers MAY accept
updates that don't include leases, but SHOULD differentiate between
DNS-SD registration protocol updates and other updates, and MUST
reject updates that are known to be DNS-SD Registration Protocol
updates if they do not include leases.
2.6.2. Sleep Proxy
Another use of Service Registration Protocol is for devices that
sleep to reduce power consumption.
In this case, in addition to the DNS Update Lease option
[I-D.sekar-dns-ul] described above, the device includes an EDNS(0)
OWNER Option [I-D.cheshire-edns0-owner-option].
The EDNS(0) Update Lease option constitutes a promise by the device
that it will wake up before this time elapses, to renew its
registration and thereby demonstrate that it is still attached to the
network. If it fails to renew the registration by this time, that
indicates that it is no longer attached to the network, and its
registration (except for the KEY in the Host Description) should be
deleted.
The EDNS(0) OWNER Option indicates that the device will be asleep,
and will not be receptive to normal network traffic. When a DNS
server receives a DNS Update with an EDNS(0) OWNER Option, that
signifies that the Registration Protocol server should set up a proxy
for any IPv4 or IPv6 address records in the DNS Update message. This
proxy should send ARP or ND messages claiming ownership of the IPv4
and/or IPv6 addresses in the records in question. In addition, proxy
should answer future ARP or ND requests for those IPv4 and/or IPv6
addresses, claiming ownership of them. When the DNS server receives
a TCP SYN or UDP packet addressed to one of the IPv4 or IPv6
addresses for which it proxying, it should then wake up the sleeping
device using the information in the EDNS(0) OWNER Option. At present
version 0 of the OWNER Option specifies the "Wake-on-LAN Magic
Packet" that needs to be sent; future versions could be extended to
specify other wakeup mechanisms.
Note that although the authoritative DNS server that implements the
DNSSD Service Registration Protocol function need not be on the same
link as the sleeping host, the Sleep Proxy must be on the same link.
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3. Security Considerations
DNS-SD Service Registration Protocol updates have no authorization
semantics other than first-come, first-served. This means that if an
attacker from outside of the administrative domain of the server
knows the server's IP address, it can in principle send updates to
the server that will be processed successfully. Servers should
therefore be configured to reject updates from source addresses
outside of the administrative domain of the server.
For Anycast updates, this validation must be enforced by every router
that connects the CDN to the unconstrained portion of the network.
For TCP updates, the initial SYN-SYN+ACK handshake prevents updates
being forged from off-network. In order to ensure that this
handshake happens, Service Discovery Protocol servers MUST NOT accept
0-RTT TCP payloads.
Note that these rules only apply to the validation of DNS-SD
registration protocol updates. A server that accepts updates from
DNS-SD registration protocol clients may also accept other DNS
updates, and those DNS updates may be validated using different
rules. However, in the case of a DNS service that accepts automatic
updates, the intersection of the DNS-SD service registration update
rules and whatever other update rules are present must be considered
very carefully.
For example, a normal, authenticated RFC2136 update to any RR that
was added using the Registration protocol, but that is authenticated
using a different key, could be used to override a promise made by
the registration protocol, by replacing all or part of the service
registration information with information provided by a different
client. An implementation that allows both kinds of updates should
not allow updates to records added by Registrations using different
authentication and authorization credentials.
4. Privacy Considerations
5. Acknowledgments
Thanks to Toke Hoeiland-Joergensen for a thorough technical review,
to Tamara Kemper for doing a nice developmental edit, Tim Wattenberg
for doing a service implementation at the Montreal Hackathon at IETF
102, and [...] more reviewers to come, hopefully.
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6. References
6.1. Normative References
[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>.
[I-D.sekar-dns-ul]
Sekar, K., "Dynamic DNS Update Leases", draft-sekar-dns-
ul-01 (work in progress), August 2006.
6.2. Informative 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>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997,
<https://www.rfc-editor.org/info/rfc2131>.
[RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, DOI 10.17487/RFC2136, April 1997,
<https://www.rfc-editor.org/info/rfc2136>.
[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>.
[RFC2931] Eastlake 3rd, D., "DNS Request and Transaction Signatures
( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September
2000, <https://www.rfc-editor.org/info/rfc2931>.
[RFC3007] Wellington, B., "Secure Domain Name System (DNS) Dynamic
Update", RFC 3007, DOI 10.17487/RFC3007, November 2000,
<https://www.rfc-editor.org/info/rfc3007>.
[RFC3152] Bush, R., "Delegation of IP6.ARPA", BCP 49, RFC 3152,
DOI 10.17487/RFC3152, August 2001,
<https://www.rfc-editor.org/info/rfc3152>.
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[RFC6760] Cheshire, S. and M. Krochmal, "Requirements for a Protocol
to Replace the AppleTalk Name Binding Protocol (NBP)",
RFC 6760, DOI 10.17487/RFC6760, February 2013,
<https://www.rfc-editor.org/info/rfc6760>.
[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>.
[RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for
Constrained-Node Networks", RFC 7228,
DOI 10.17487/RFC7228, May 2014,
<https://www.rfc-editor.org/info/rfc7228>.
[I-D.ietf-dnssd-hybrid]
Cheshire, S., "Discovery Proxy for Multicast DNS-Based
Service Discovery", draft-ietf-dnssd-hybrid-08 (work in
progress), March 2018.
[I-D.ietf-dnssd-push]
Pusateri, T. and S. Cheshire, "DNS Push Notifications",
draft-ietf-dnssd-push-14 (work in progress), March 2018.
[I-D.cheshire-dnssd-roadmap]
Cheshire, S., "Service Discovery Road Map", draft-
cheshire-dnssd-roadmap-01 (work in progress), March 2018.
[I-D.cheshire-edns0-owner-option]
Cheshire, S. and M. Krochmal, "EDNS0 OWNER Option", draft-
cheshire-edns0-owner-option-01 (work in progress), July
2017.
[ZC] Cheshire, S. and D. Steinberg, "Zero Configuration
Networking: The Definitive Guide", O'Reilly Media, Inc. ,
ISBN 0-596-10100-7, December 2005.
Authors' Addresses
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Stuart Cheshire
Apple Inc.
One Apple Park Way
Cupertino, California 95014
USA
Phone: +1 408 974 3207
Email: cheshire@apple.com
Ted Lemon
Nibbhaya Consulting
P.O. Box 958
Brattleboro, Vermont 05302
United States of America
Email: mellon@fugue.com
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