--- 1/draft-ietf-dnssd-srp-04.txt 2020-10-29 10:13:12.516898965 -0700 +++ 2/draft-ietf-dnssd-srp-05.txt 2020-10-29 10:13:12.572900379 -0700 @@ -1,18 +1,18 @@ Internet Engineering Task Force T. Lemon Internet-Draft S. Cheshire Intended status: Informational Apple Inc. -Expires: January 14, 2021 July 13, 2020 +Expires: April 29, 2021 October 26, 2020 Service Registration Protocol for DNS-Based Service Discovery - draft-ietf-dnssd-srp-04 + draft-ietf-dnssd-srp-05 Abstract The Service Registration Protocol for DNS-Based Service Discovery uses the standard DNS Update mechanism to enable DNS-Based Service Discovery using only unicast packets. This makes it possible to deploy DNS Service Discovery without multicast, 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 @@ -27,103 +27,137 @@ 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 14, 2021. + This Internet-Draft will expire on April 29, 2021. Copyright Notice Copyright (c) 2020 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 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 . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Service Registration Protocol . . . . . . . . . . . . . . . . 4 - 2.1. What to publish . . . . . . . . . . . . . . . . . . . . . 5 - 2.2. Where to publish it . . . . . . . . . . . . . . . . . . . 6 - 2.3. How to publish it . . . . . . . . . . . . . . . . . . . . 6 + 2.1. What to publish . . . . . . . . . . . . . . . . . . . . . 6 + 2.2. Where to publish it . . . . . . . . . . . . . . . . . . . 7 + 2.3. How to publish it . . . . . . . . . . . . . . . . . . . . 7 2.3.1. How DNS-SD Service Registration differs from standard - RFC2136 DNS Update . . . . . . . . . . . . . . . . . 7 - 2.4. How to secure it . . . . . . . . . . . . . . . . . . . . 7 + RFC2136 DNS Update . . . . . . . . . . . . . . . . . 8 + 2.4. How to secure it . . . . . . . . . . . . . . . . . . . . 8 2.4.1. First-Come First-Served Naming . . . . . . . . . . . 8 - 2.4.2. Removing published services . . . . . . . . . . . . . 9 - 2.4.3. SRP Server Behavior . . . . . . . . . . . . . . . . . 9 - 2.5. TTL Consistency . . . . . . . . . . . . . . . . . . . . . 12 - 2.6. Maintenance . . . . . . . . . . . . . . . . . . . . . . . 13 - 2.6.1. Cleaning up stale data . . . . . . . . . . . . . . . 13 - 2.6.2. Sleep Proxy . . . . . . . . . . . . . . . . . . . . . 14 - 3. Security Considerations . . . . . . . . . . . . . . . . . . . 15 - 3.1. Source Validation . . . . . . . . . . . . . . . . . . . . 15 - 3.2. SIG(0) signature validation . . . . . . . . . . . . . . . 16 - 3.3. Required Signature Algorithm . . . . . . . . . . . . . . 16 - 4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 16 - 5. Delegation of 'service.arpa.' . . . . . . . . . . . . . . . . 16 - 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 + 2.4.2. Removing published services . . . . . . . . . . . . . 10 + 2.4.3. SRP Server Behavior . . . . . . . . . . . . . . . . . 10 + 2.5. TTL Consistency . . . . . . . . . . . . . . . . . . . . . 13 + 2.6. Maintenance . . . . . . . . . . . . . . . . . . . . . . . 14 + 2.6.1. Cleaning up stale data . . . . . . . . . . . . . . . 14 + 2.6.2. Sleep Proxy . . . . . . . . . . . . . . . . . . . . . 15 + 3. Security Considerations . . . . . . . . . . . . . . . . . . . 16 + 3.1. Source Validation . . . . . . . . . . . . . . . . . . . . 16 + 3.2. SIG(0) signature validation . . . . . . . . . . . . . . . 17 + 3.3. Required Signature Algorithm . . . . . . . . . . . . . . 17 + 4. Privacy Considerations . . . . . . . . . . . . . . . . . . . 17 + 5. Delegation of 'service.arpa.' . . . . . . . . . . . . . . . . 17 + 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 6.1. Registration and Delegation of 'service.arpa' as a - Special-Use Domain Name . . . . . . . . . . . . . . . . . 17 - 6.2. 'dnssd-srp' Service Name . . . . . . . . . . . . . . . . 17 - 6.3. 'dnssd-srp-tls' Service Name . . . . . . . . . . . . . . 17 - 6.4. Anycast Address . . . . . . . . . . . . . . . . . . . . . 17 - 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18 - 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 - 8.1. Normative References . . . . . . . . . . . . . . . . . . 18 - 8.2. Informative References . . . . . . . . . . . . . . . . . 19 - Appendix A. Testing using standard RFC2136-compliant servers . . 20 + Special-Use Domain Name . . . . . . . . . . . . . . . . . 18 + 6.2. 'dnssd-srp' Service Name . . . . . . . . . . . . . . . . 18 + 6.3. 'dnssd-srp-tls' Service Name . . . . . . . . . . . . . . 18 + 6.4. Anycast Address . . . . . . . . . . . . . . . . . . . . . 19 + 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 19 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 19 + 8.2. Informative References . . . . . . . . . . . . . . . . . 20 + Appendix A. Testing using standard RFC2136-compliant servers . . 22 Appendix B. How to allow services to update standard - RFC2136-compliant servers . . . . . . . . . . . . . 21 - Appendix C. Sample BIND9 configuration for default.service.arpa. 21 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 + RFC2136-compliant servers . . . . . . . . . . . . . 22 + Appendix C. Sample BIND9 configuration for default.service.arpa. 23 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24 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 Multicast DNS - [RFC6762] (mDNS). There is already a large installed base of DNS-SD - clients that can discover services using the DNS protocol. This - extension makes it much easier to take advantage of this existing - functionality. + [RFC6763] that allows services to register their services using the + DNS protocol rather than using Multicast DNS [RFC6762] (mDNS). There + is already a large installed base of DNS-SD clients that can discover + services using the DNS protocol. 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. + information required to use it. Although DNS-SD using the DNS + protocol (as opposed to mDNS) can be more efficient and versatile, it + is not common in practice, because of the difficulties associated + with updating authoritative DNS services with service information. + + Existing practice for updating DNS zones is to either manually enter + new data, or else use DNS Update [RFC2136]. Unfortunately DNS Update + requires either that the authoritative DNS server automatically trust + updates, or else that the DNS Update client have some kind of shared + secret or public key that is known to the DNS server and can be used + to authenticate the update. Furthermore, DNS Update can be a fairly + chatty process, requiring multiple round trips with different + conditional predicates to complete the update process. + + The SRP protocol adds a set of default heuristics for processing DNS + updates that eliminates the need for DNS update conditional + predicates: instead, the SRP server has a set of default predicates + that are applied to the update, and the update either succeeds + entirely, or fails in a way that allows the registering service to + know what went wrong and construct a new update. + + SRP also adds a feature called First-Come, First-Served Naming, which + allows the registering service to claim a name that is not yet in + use, and, using SIG(0) [RFC2931], to authenticate both the initial + claim and subsequent updates. This prevents name conflicts, since a + second SRP service attempting to claim the same name will not possess + the SIG(0) key used by the first service to claim it, and so its + claim will be rejected and the second service will have to choose a + new name. + + Finally, SRP adds the concept of a 'lease,' similar to leases in + Dynamic Host Configuration Protocol [RFC8415]. The SRP registration + itself has a lease which may be on the order of an hour; if the + registering service does not renew the lease before it has elapsed, + the registration is removed. The claim on the name can have a longer + lease, so that another service cannot claim the name, even though the + registration has expired. The Service Registration Protocol for DNS-SD (SRP), 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. The DNS-SD 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 mDNS, it allows services to publish their information on the local link, using @@ -132,60 +166,58 @@ 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 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 easily advertised using mDNS. This - document describes a solution more suitable for networks where - multicast is inefficient, or where sleepy devices are common, by - supporting both offering of services, and discovery of services, - using unicast. + The Discovery Proxy [RFC8766] provides one way to automatically + populate the DNS namespace, but is only appropriate on networks where + services are easily advertised using mDNS. This document describes a + solution more suitable for networks where multicast is inefficient, + or where sleepy devices are common, by supporting both offering of + services, and discovery of services, using unicast. 2. Service Registration Protocol Services that implement SRP use DNS Update [RFC2136] [RFC3007] to publish service information in the DNS. Two variants exist, one for full-featured hosts, and one for devices designed for "Constrained- Node Networks" [RFC7228]. Full-featured hosts are either configured manually with a registration domain, or use the "dr._dns-sd._udp." query ([RFC6763] Section 11) to learn the default registration domain from the network. RFC6763 says to discover the registration domain using either ".local" or a network-supplied domain name for . Services using SRP MUST use the domain name received through the DHCPv4 Domain Name option ([RFC2132] section 3.17), if available, or the Neighbor Discovery DNS Search List option [RFC8106]. If the DNS Search List option contains more than one domain name, it MUST NOT be used. If neither option is available, the Service Registration protocol is not available on the local network. - Manual configuration of the registraton domain can be done either by + Manual configuration of the registration domain can be done either by querying the list of available registration zones ("r._dns-sd._udp") and allowing the user to select one from the UI, or by any other means appropriate to the particular use case being addressed. Full- featured devices construct the names of the SRV, TXT, and PTR records describing their service(s) as subdomains of the chosen service registration domain. 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 "_dnssd-srp._tcp" SRV record to discover the - server to which they should send DNS updates. Hosts that support SRP - updates using TLS use the "_dnssd-srp-tls._tcp" SRV record - instead. + apex of the closest enclosing DNS zone using SOA queries [RFC8765]. + Having discovered the enclosing DNS zone, they query for the + "_dnssd-srp._tcp" SRV record to discover the server to which + they should send DNS updates. Hosts that support SRP updates using + TLS use the "_dnssd-srp-tls._tcp" SRV record instead. For devices designed for Constrained-Node Networks [RFC7228] some simplifications are available. Instead of being configured with (or discovering) the service registration domain, the (proposed) special- use domain name (see [RFC6761]) "default.service.arpa" is used. The details of how SRP server(s) are discovered will be specific to the constrained network, and therefore we do not suggest a specific mechanism here. SRP clients on constrained networks are expected to receive from the @@ -306,21 +338,21 @@ o It enforces policy about what updates are allowed. o It optionally performs rewriting of "default.service.arpa" to some other domain. o It optionally performs automatic population of the address-to-name reverse mapping domains. o An SRP server is not required to implement general DNS Update - prerequsite processing. + prerequisite processing. o Clients are allowed to send updates to the generic domain "default.service.arpa" 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. @@ -343,21 +375,24 @@ that name, no other service can add or update the information associated with that. FCFS naming is used to protect both the Service Description and the Host Description. 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 in read-only storage that can be used. This key - pair MUST be unique to the device. + pair MUST be unique to the device. This key pair MUST be unique to + the device. A device with rewritable storage + should retain this + key indefinitely; the key MAY be overwritten as a result of + a full + reset of the device (e.g., a "factory reset"). When sending DNS updates, the service includes a KEY record containing the public portion of the key in each Host Description update and each Service Description update. Each KEY record MUST contain the same public key. 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 [I-D.sekar-dns-ul]. The KEY record in Service Description updates MAY be omitted for @@ -452,20 +487,25 @@ o one or more "Add to an RRset" TXT RRs, o and the target of the SRV RR Add points to a hostname for which there is a Host Description Instruction in the SRP Update. o Service Descriptions Instructions do not modify any other RRs. An Instruction is a Host Description Instruction if, for the appropriate hostname, it contains o exactly one "Delete all RRsets from a name" RR, o one or more "Add to an RRset" RRs of type A and/or AAAA, + o A and/or AAAA records must be of sufficient scope to be reachable + by all hosts that might query the DNS. If a link-scope address or + IPv4 autoconfiguration address is provided by the SRP client, the + SRP server MUST treat this as if no address records were received; + that is, the Host Description is not valid. o exactly one "Add to an RRset" RR 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 Instruction in the SRP update for which the SRV RR that is added points to the hostname being updated by this update. o Host Description updates do not modify any other records. An SRP Update MUST include at least one Service Discovery Instruction, at least one Service Description Instruction, and @@ -565,36 +605,36 @@ 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. TTLs sent in SRP updates are advisory: they indicate the client's guess as to what a good TTL would be. SRP servers may override these TTLs. SRP servers SHOULD ensure that TTLs are reasonable: neither too long nor too short. The TTL should never be longer than the lease time Section 2.6.1. Shorter TTLs will result in more frequent - data refreshes; this increases latency on the client side, and - increases load on any caching resolvers and on the authoritative - server. Longer TTLs will increase the likelihood that data in caches - will be stale. TTL minimums and maximums SHOULD be configurable by - the operator of the SRP server. + data refreshes; this increases latency on the client side, increases + load on any caching resolvers and on the authoritative server, and + also increases network load, which may be an + issue for constrained + networks. Longer TTLs will increase the likelihood that data in + caches will be stale. TTL minimums and maximums SHOULD be + configurable by the operator of the SRP server. 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 Lease Time and the Key Lease - Time. + update is constructed by the client, it MUST include an EDNS(0) + Update Lease Option [I-D.sekar-dns-ul]. The Update Lease Option + contains two lease times: the Lease Time and the Key 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 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 Key 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 @@ -619,21 +659,21 @@ 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 receive the update after the client sent it, this avoids the possibility of misunderstandings. SRP 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 SRP updates and other updates, and MUST reject updates that would otherwise be SRP updates - updates if they do not include leases. + if they do not include leases. Lease times have a completely different function than TTLs. On an authoritative DNS server, the TTL on a resource record is a constant: whenever that RR is served in a DNS response, the TTL value sent in the answer is the same. The lease time is never sent as a TTL; its sole purpose is to determine when the authoritative DNS server will delete stale records. It is not an error to send a DNS response with a TTL of 'n' when the remaining time on the lease is less than 'n'. 2.6.2. Sleep Proxy @@ -652,21 +692,21 @@ 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 SRP 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 + addresses in the records in question. In addition, the 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 @@ -726,45 +766,50 @@ Constrained Network/Constrained Node clients, such validation isn't practical because there's no way to establish trust. In principle, a KEY RR could be used by a non-constrained SRP client to validate responses from the server, but this is not required, nor do we specify a mechanism for determining which key to use. 3.3. Required Signature Algorithm For validation, SRP Servers MUST implement the ECDSAP256SHA256 signature algorithm. SRP servers SHOULD implement the algorithms - specified in [I-D.ietf-dnsop-algorithm-update] section 3.1, in the - validation column of the table, starting with algorithm number 13. - SRP clients MUST NOT assume that any algorithm numbered lower than 13 - is available for use in validating SIG(0) signatures. + specified in [RFC8624] section 3.1, in the validation column of the + table, starting with algorithm number 13. SRP clients MUST NOT + assume that any algorithm numbered lower than 13 is available for use + in validating SIG(0) signatures. 4. Privacy Considerations Because DNSSD SRP updates can be sent off-link, the privacy implications of SRP are different than for multicast DNS responses. Host implementations that are using TCP SHOULD also use TLS if available. Server implementations MUST offer TLS support. The use of TLS with DNS is described in [RFC7858] and [RFC8310]. Hosts that implement TLS support SHOULD NOT fall back to TCP; since servers are required to support TLS, it is entirely up to the host implementation whether to use it. + Public keys can be used as identifiers to track hosts. SRP servers + MAY elect not to return KEY records for queries for SRP + registrations. + 5. Delegation of 'service.arpa.' In order to be fully functional, there must be a delegation of 'service.arpa.' in the '.arpa.' zone [RFC3172]. This delegation should be set up as was done for 'home.arpa', as a result of the specification in [RFC8375]Section 7. 6. IANA Considerations + 6.1. Registration and Delegation of 'service.arpa' as a Special-Use Domain Name IANA is requested to record the domain name 'service.arpa.' in the Special-Use Domain Names registry [SUDN]. IANA is requested, with the approval of IAB, to implement the delegation requested in Section 5. IANA is further requested to add a new entry to the "Transport- Independent Locally-Served Zones" subregistry of the the "Locally- @@ -839,24 +884,24 @@ [RFC8106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli, "IPv6 Router Advertisement Options for DNS Configuration", RFC 8106, DOI 10.17487/RFC8106, March 2017, . [RFC8375] Pfister, P. and T. Lemon, "Special-Use Domain 'home.arpa.'", RFC 8375, DOI 10.17487/RFC8375, May 2018, . - [I-D.ietf-dnsop-algorithm-update] - Wouters, P. and O. Sury, "Algorithm Implementation - Requirements and Usage Guidance for DNSSEC", draft-ietf- - dnsop-algorithm-update-10 (work in progress), April 2019. + [RFC8624] Wouters, P. and O. Sury, "Algorithm Implementation + Requirements and Usage Guidance for DNSSEC", RFC 8624, + DOI 10.17487/RFC8624, June 2019, + . [SUDN] "Special-Use Domain Names Registry", July 2012, . [LSDZ] "Locally-Served DNS Zones Registry", July 2011, . 8.2. Informative References @@ -907,28 +952,33 @@ [RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D., and P. Hoffman, "Specification for DNS over Transport Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May 2016, . [RFC8310] Dickinson, S., Gillmor, D., and T. Reddy, "Usage Profiles for DNS over TLS and DNS over DTLS", RFC 8310, DOI 10.17487/RFC8310, March 2018, . - [I-D.ietf-dnssd-hybrid] - Cheshire, S., "Discovery Proxy for Multicast DNS-Based - Service Discovery", draft-ietf-dnssd-hybrid-10 (work in - progress), March 2019. + [RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A., + Richardson, M., Jiang, S., Lemon, T., and T. Winters, + "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", + RFC 8415, DOI 10.17487/RFC8415, November 2018, + . - [I-D.ietf-dnssd-push] - Pusateri, T. and S. Cheshire, "DNS Push Notifications", - draft-ietf-dnssd-push-25 (work in progress), October 2019. + [RFC8765] Pusateri, T. and S. Cheshire, "DNS Push Notifications", + RFC 8765, DOI 10.17487/RFC8765, June 2020, + . + + [RFC8766] Cheshire, S., "Discovery Proxy for Multicast DNS-Based + Service Discovery", RFC 8766, DOI 10.17487/RFC8766, June + 2020, . [I-D.cheshire-dnssd-roadmap] Cheshire, S., "Service Discovery Road Map", draft- cheshire-dnssd-roadmap-03 (work in progress), October 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.