--- 1/draft-ietf-dnssd-push-24.txt 2019-10-13 18:13:10.512056211 -0700 +++ 2/draft-ietf-dnssd-push-25.txt 2019-10-13 18:13:10.596058347 -0700 @@ -1,19 +1,19 @@ Internet Engineering Task Force T. Pusateri Internet-Draft Unaffiliated Intended status: Standards Track S. Cheshire -Expires: February 8, 2020 Apple Inc. - August 7, 2019 +Expires: April 15, 2020 Apple Inc. + October 13, 2019 DNS Push Notifications - draft-ietf-dnssd-push-24 + draft-ietf-dnssd-push-25 Abstract The Domain Name System (DNS) was designed to return matching records efficiently for queries for data that are relatively static. When those records change frequently, DNS is still efficient at returning the updated results when polled, as long as the polling rate is not too high. But there exists no mechanism for a client to be asynchronously notified when these changes occur. This document defines a mechanism for a client to be notified of such changes to @@ -27,21 +27,21 @@ 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 February 8, 2020. + This Internet-Draft will expire on April 15, 2020. Copyright Notice Copyright (c) 2019 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 @@ -60,38 +60,38 @@ 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. State Considerations . . . . . . . . . . . . . . . . . . . . 6 5. Transport . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 8 6.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 9 6.2. DNS Push Notification SUBSCRIBE . . . . . . . . . . . . . 13 6.2.1. SUBSCRIBE Request . . . . . . . . . . . . . . . . . . 13 6.2.2. SUBSCRIBE Response . . . . . . . . . . . . . . . . . 16 6.3. DNS Push Notification Updates . . . . . . . . . . . . . . 20 6.3.1. PUSH Message . . . . . . . . . . . . . . . . . . . . 20 - 6.4. DNS Push Notification UNSUBSCRIBE . . . . . . . . . . . . 25 - 6.4.1. UNSUBSCRIBE Message . . . . . . . . . . . . . . . . . 25 - 6.5. DNS Push Notification RECONFIRM . . . . . . . . . . . . . 27 - 6.5.1. RECONFIRM Message . . . . . . . . . . . . . . . . . . 28 - 6.6. DNS Stateful Operations TLV Context Summary . . . . . . . 30 - 6.7. Client-Initiated Termination . . . . . . . . . . . . . . 31 - 6.8. Client Fallback to Polling . . . . . . . . . . . . . . . 32 - 7. Security Considerations . . . . . . . . . . . . . . . . . . . 33 - 7.1. Security Services . . . . . . . . . . . . . . . . . . . . 33 - 7.2. TLS Name Authentication . . . . . . . . . . . . . . . . . 34 - 7.3. TLS Early Data . . . . . . . . . . . . . . . . . . . . . 34 - 7.4. TLS Session Resumption . . . . . . . . . . . . . . . . . 35 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36 - 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 36 - 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 37 - 10.1. Normative References . . . . . . . . . . . . . . . . . . 37 - 10.2. Informative References . . . . . . . . . . . . . . . . . 38 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 41 + 6.4. DNS Push Notification UNSUBSCRIBE . . . . . . . . . . . . 26 + 6.4.1. UNSUBSCRIBE Message . . . . . . . . . . . . . . . . . 26 + 6.5. DNS Push Notification RECONFIRM . . . . . . . . . . . . . 28 + 6.5.1. RECONFIRM Message . . . . . . . . . . . . . . . . . . 29 + 6.6. DNS Stateful Operations TLV Context Summary . . . . . . . 31 + 6.7. Client-Initiated Termination . . . . . . . . . . . . . . 32 + 6.8. Client Fallback to Polling . . . . . . . . . . . . . . . 33 + 7. Security Considerations . . . . . . . . . . . . . . . . . . . 34 + 7.1. Security Services . . . . . . . . . . . . . . . . . . . . 35 + 7.2. TLS Name Authentication . . . . . . . . . . . . . . . . . 35 + 7.3. TLS Early Data . . . . . . . . . . . . . . . . . . . . . 36 + 7.4. TLS Session Resumption . . . . . . . . . . . . . . . . . 36 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 + 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 37 + 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 38 + 10.1. Normative References . . . . . . . . . . . . . . . . . . 38 + 10.2. Informative References . . . . . . . . . . . . . . . . . 40 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 42 1. Introduction Domain Name System (DNS) records may be updated using DNS Update [RFC2136]. Other mechanisms such as a Discovery Proxy [DisProx] can also generate changes to a DNS zone. This document specifies a protocol for DNS clients to subscribe to receive asynchronous notifications of changes to RRsets of interest. It is immediately relevant in the case of DNS Service Discovery [RFC6763] but is not limited to that use case, and provides a general DNS mechanism for @@ -134,38 +134,38 @@ many levels throughout the network. Other network protocols have successfully deployed a publish/subscribe model following the Observer design pattern [obs]. XMPP Publish-Subscribe [XEP0060] and Atom [RFC4287] are examples. While DNS servers are generally highly tuned and capable of a high rate of query/response traffic, adding a publish/subscribe model for tracking changes to DNS records can deliver more timely notification of changes with reduced CPU usage and lower network traffic. Multicast DNS [RFC6762] implementations always listen on a well known - link-local IP multicast group address, and record changes are sent to - that multicast group address for all group members to receive. - Therefore, Multicast DNS already has asynchronous change notification - capability. However, when DNS Service Discovery [RFC6763] is used - across a wide area network using Unicast DNS (possibly facilitated - via a Discovery Proxy [DisProx]) it would be beneficial to have an + link-local IP multicast group address, and changes are sent to that + multicast group address for all group members to receive. Therefore, + Multicast DNS already has asynchronous change notification + capability. When DNS Service Discovery [RFC6763] is used across a + wide area network using Unicast DNS (possibly facilitated via a + Discovery Proxy [DisProx]) it would be beneficial to have an equivalent capability for Unicast DNS, to allow clients to learn about DNS record changes in a timely manner without polling. The DNS Long-Lived Queries (LLQ) mechanism [LLQ] is an existing deployed solution to provide asynchronous change notifications, used by Apple's Back to My Mac [RFC6281] service introduced in Mac OS X 10.5 Leopard in 2007. Back to My Mac was designed in an era when the data center operations staff asserted that it was impossible for a server to handle large numbers of mostly-idle TCP connections, so LLQ was defined as a UDP-based protocol, effectively replicating much of TCP's connection state management logic in user space, and creating - its own poor imitations of existing TCP features like the three-way + its own imitation of existing TCP features like the three-way handshake, flow control, and reliability. This document builds on experience gained with the LLQ protocol, with an improved design. Instead of using UDP, this specification uses DNS Stateful Operations (DSO) [RFC8490] running over TLS over TCP, and therefore doesn't need to reinvent existing TCP functionality. Using TCP also gives long-lived low-traffic connections better longevity through NAT gateways without depending on the gateway to support NAT Port Mapping Protocol (NAT-PMP) [RFC6886] or Port Control Protocol (PCP) [RFC6887], or resorting to excessive keepalive @@ -194,22 +194,22 @@ server" for the purposes of this specification, and communications with these two ports are handled independently. Supporting DNS Updates and DNS Push Notifications on the same server is OPTIONAL. A DNS Push Notification server is not required to support DNS Update. Standard DNS Queries MAY be sent over a DNS Push Notification (i.e., DSO) session. For any zone for which the server is authoritative, it MUST respond authoritatively for queries for names falling within that zone (e.g., the "_dns-push-tls._tcp." SRV record) both for normal DNS queries and for DNS Push Notification subscriptions. For - names for which the server is acting as a recursive resolver, e.g., - when the server is the local recursive resolver, for any query for + names for which the server is acting as a recursive resolver (e.g., + when the server is the local recursive resolver) for any query for which it supports DNS Push Notification subscriptions, it MUST also support standard queries. DNS Push Notifications impose less load on the responding server than rapid polling would, but Push Notifications do still have a cost, so DNS Push Notification clients MUST NOT recklessly create an excessive number of Push Notification subscriptions. Specifically: (a) A subscription should only be active when there is a valid reason to need live data (for example, an on-screen display is currently @@ -226,28 +226,28 @@ Push Notification subscription active 24 hours a day, 7 days a week, just to keep a list in memory up to date so that if the user does choose to bring up an on-screen display of that data, it can be displayed really fast. DNS Push Notifications are designed to be fast enough that there is no need to pre-load a "warm" list in memory just in case it might be needed later. Generally, as described in the DNS Stateful Operations specification [RFC8490], a client must not keep a DSO session to a server open indefinitely if it has no subscriptions (or other operations) active - on that session. A client MAY close a DSO session immediately it + on that session. A client may close a DSO session immediately it becomes idle, and then if needed in the future, open a new session - when required. Alternatively, a client MAY speculatively keep an + when required. Alternatively, a client may speculatively keep an idle DSO session open for some time, subject to the constraint that it must not keep a session open that has been idle for more than the session's idle timeout (15 seconds by default) [RFC8490]. - Note that a DSO session which has an active DNS Push Notification + Note that a DSO session that has an active DNS Push Notification subscription is not considered idle, even if there is no traffic flowing for an extended period of time. In this case the DSO inactivity timeout does not apply, because the session is not inactive, but the keepalive interval does still apply, to ensure generation of sufficient messages to maintain state in middleboxes (such at NAT gateways or firewalls) and for the client and server to periodically verify that they still have connectivity to each other. This is described in Section 6.2 of the DSO specification [RFC8490]. 4. State Considerations @@ -272,39 +272,40 @@ (TCP) [RFC0793] as the transport protocol, in keeping with the historical precedent that DNS queries must first be sent over UDP [RFC1123]. This requirement to use UDP has subsequently been relaxed [RFC7766]. In keeping with the more recent precedent, DNS Push Notification is defined only for TCP. DNS Push Notification clients MUST use DNS Stateful Operations [RFC8490] running over TLS over TCP [RFC7858]. Connection setup over TCP ensures return reachability and alleviates - concerns of state overload at the server which is a potential problem - with connectionless protocols using spoofed source addresses. All + concerns of state overload at the server, which is a potential + problem with connectionless protocols, which can be more vulnerable + to being exploited by attackers using spoofed source addresses. All subscribers are guaranteed to be reachable by the server by virtue of the TCP three-way handshake. Flooding attacks are possible with any protocol, and a benefit of TCP is that there are already established industry best practices to guard against SYN flooding and similar attacks [SYN] [RFC4953]. Use of TCP also allows DNS Push Notifications to take advantage of current and future developments in TCP, such as Multipath TCP (MPTCP) - [RFC6824], TCP Fast Open (TFO) [RFC7413], RACK: a time-based fast - loss detection algorithm for TCP [I-D.ietf-tcpm-rack], and so on. + [RFC6824], TCP Fast Open (TFO) [RFC7413], the TCP RACK fast loss + detection algorithm [I-D.ietf-tcpm-rack], and so on. Transport Layer Security (TLS) [RFC8446] is well understood, and used by many application-layer protocols running over TCP. TLS is designed to prevent eavesdropping, tampering, and message forgery. TLS is REQUIRED for every connection between a client subscriber and server in this protocol specification. Additional security measures - such as client authentication during TLS negotiation MAY also be + such as client authentication during TLS negotiation may also be employed to increase the trust relationship between client and server. 6. Protocol Operation The DNS Push Notification protocol is a session-oriented protocol, and makes use of DNS Stateful Operations (DSO) [RFC8490]. For details of the DSO message format refer to the DNS Stateful Oper- ations specification [RFC8490]. Those details are not repeated here. @@ -312,27 +313,27 @@ DNS Push Notification clients and servers MUST support DSO. A single server can support DNS Queries, DNS Updates, and DNS Push Notifications (using DSO) on the same TCP port. A DNS Push Notification exchange begins with the client discovering the appropriate server, using the procedure described in Section 6.1, and then making a TLS/TCP connection to it. A typical DNS Push Notification client will immediately issue a DSO Keepalive operation to request a session timeout and/or keepalive - interval longer than the the 15-second default values, but this is - not required. A DNS Push Notification client MAY issue other - requests on the session first, and only issue a DSO Keepalive - operation later if it determines that to be necessary. Sending - either a DSO Keepalive operation or a Push Notification subscription - request over the TLS/TCP connection to the server signals the - client's support of DSO and serves to establish a DSO session. + interval longer than the 15-second default values, but this is not + required. A DNS Push Notification client MAY issue other requests on + the session first, and only issue a DSO Keepalive operation later if + it determines that to be necessary. Sending either a DSO Keepalive + operation or a Push Notification subscription request over the TLS/ + TCP connection to the server signals the client's support of DSO and + serves to establish a DSO session. In accordance with the current set of active subscriptions, the server sends relevant asynchronous Push Notifications to the client. Note that a client MUST be prepared to receive (and silently ignore) Push Notifications for subscriptions it has previously removed, since there is no way to prevent the situation where a Push Notification is in flight from server to client while the client's UNSUBSCRIBE message cancelling that subscription is simultaneously in flight from client to server. @@ -350,33 +351,32 @@ doesn't already have an active subscription for that name, type, and class, then the recursive resolver will make a corresponding Push Notification subscription on the client's behalf. Results received are relayed to the client. This is closely analogous to how a client sends a normal DNS query to its configured DNS recursive resolver which, if it doesn't already have appropriate answer(s) in its cache, issues an upstream query to satisfy the request. In many contexts, the recursive resolver will be able to handle Push Notifications for all names that the client may need to follow. Use - of VPN tunnels and split-view DNS can create some additional + of VPN tunnels and Private DNS [RFC8499] can create some additional complexity in the client software here; the techniques to handle VPN - tunnels and split-view DNS for DNS Push Notifications are the same as + tunnels and Private DNS for DNS Push Notifications are the same as those already used to handle this for normal DNS queries. If the recursive resolver does not support DNS over TLS, or supports DNS over TLS but is not listening on TCP port 853, or supports DNS over TLS on TCP port 853 but does not support DSO on that port, then the DSO Session session establishment will fail [RFC8490]. If the recursive resolver does support DSO but not Push Notification - subscriptions, then it will return the DSO error code, DSOTYPENI - (11). + subscriptions, then it will return the DSO error code DSOTYPENI (11). In some cases, the recursive resolver may support DSO and Push Notification subscriptions, but may not be able to subscribe for Push Notifications for a particular name. In this case, the recursive resolver should return SERVFAIL to the client. This includes being unable to establish a connection to the zone's DNS Push Notification server or establishing a connection but receiving a non success response code. In some cases, where the client has a pre-established trust relationship with the owner of the zone (that is not handled via the usual mechanisms for VPN software) the client may handle @@ -435,22 +435,22 @@ operation of the DNS protocol regarding negative responses [RFC2308].) 4. If the client receives a response containing no SOA record, then it proceeds with the iterative approach. The client strips the leading label from the current query name, and if the resulting name has at least two labels in it, the client sends an SOA query for that new name, and processing continues at step 2 above, repeating the iterative search until either an SOA is received, or the query name consists of a single label, i.e., a Top Level - Domain (TLD). In the case of a single-label (TLD), this is a - network configuration error, which should not happen, and the + Domain (TLD). In the case of a single-label name (TLD), this is + a network configuration error, which should not happen, and the client gives up. The client may retry the operation at a later time, of the client's choosing, such after a change in network attachment. 5. Once the SOA is known (either by virtue of being seen in the Answer Section, or in the Authority Section), the client sends a DNS query with type SRV [RFC2782] for the record name "_dns-push-tls._tcp.", where is the owner name of the discovered SOA record. @@ -472,27 +472,31 @@ subscription requests. As described in the SRV specification [RFC2782], the server with the lowest "priority" is first contacted. If more than one server has the same "priority", the "weight" indicates the weighted probability that the client should contact that server. Higher weights have higher probabilities of being selected. If a server is not willing to accept a subscription request, or is not reachable within a reasonable time, as determined by the client, then a subsequent server is to be contacted. - Each time a client makes a new DNS Push Notification subscription - session, it SHOULD repeat the discovery process in order to determine - the preferred DNS server for subscriptions at that time. However, - the client device MUST respect the DNS TTL values on records it - receives, and store them in its local cache with this lifetime. This + Each time a client makes a new DNS Push Notification subscription, it + SHOULD repeat the discovery process in order to determine the + preferred DNS server for that subscription at that time. If a client + already has a DSO session with that DNS server the client SHOULD + reuse that existing DSO session for the new subscription, otherwise, + a new DSO session is established. The client MUST respect the DNS + TTL values on records it receives while performing the discovery + process and store them in its local cache with this lifetime (as it + will generally be do anyway for all DNS queries it performs). This means that, as long as the DNS TTL values on the authoritative - records are set to reasonable values, repeated application of this + records are set to reasonable values, repeated application of the discovery process can be completed nearly instantaneously by the client, using only locally-stored cached data. 6.2. DNS Push Notification SUBSCRIBE After connecting, and requesting a longer idle timeout and/or keepalive interval if necessary, a DNS Push Notification client then indicates its desire to receive DNS Push Notifications for a given domain name by sending a SUBSCRIBE request to the server. A SUBSCRIBE request is encoded in a DSO message [RFC8490]. @@ -502,38 +506,44 @@ DSO messages with the SUBSCRIBE TLV as the Primary TLV are permitted in TLS early data, provided that the precautions described in Section 7.3 are followed. The entity that initiates a SUBSCRIBE request is by definition the client. A server MUST NOT send a SUBSCRIBE request over an existing session from a client. If a server does send a SUBSCRIBE request over a DSO session initiated by a client, this is a fatal error and the client MUST forcibly abort the connection immediately. + Each SUBSCRIBE request generates exactly one SUBSCRIBE response from + the server. The entity that initiates a SUBSCRIBE response is by + definition the server. A client MUST NOT send a SUBSCRIBE response. + If a client does send a SUBSCRIBE response, this is a fatal error and + the server MUST forcibly abort the connection immediately. + 6.2.1. SUBSCRIBE Request A SUBSCRIBE request begins with the standard DSO 12-byte header [RFC8490], followed by the SUBSCRIBE primary TLV. A SUBSCRIBE - request message is illustrated in Figure 1. + request is illustrated in Figure 1. The MESSAGE ID field MUST be set to a unique value, that the client is not using for any other active operation on this DSO session. For the purposes here, a MESSAGE ID is in use on this session if the client has used it in a request for which it has not yet received a response, or if the client has used it for a subscription which it has not yet cancelled using UNSUBSCRIBE. In the SUBSCRIBE response the server MUST echo back the MESSAGE ID value unchanged. The other header fields MUST be set as described in the DSO spec- ification [RFC8490]. The DNS OPCODE field contains the OPCODE value - for DNS Stateful Operations (6). The four count fields MUST be zero, - and the corresponding four sections MUST be empty (i.e., absent). + for DNS Stateful Operations (6). The four count fields must be zero, + and the corresponding four sections must be empty (i.e., absent). The DSO-TYPE is SUBSCRIBE (tentatively 0x40). The DSO-LENGTH is the length of the DSO-DATA that follows, which specifies the name, type, and class of the record(s) being sought. 1 1 1 1 1 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \ | MESSAGE ID | \ @@ -545,48 +555,46 @@ | ANCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | NSCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | ARCOUNT (MUST BE ZERO) | / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / | DSO-TYPE = SUBSCRIBE (tentatively 0x40) | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | DSO-LENGTH (number of octets in DSO-DATA) | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \ - | | \ - \ NAME \ | - \ \ | - +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > DSO-DATA - | TYPE | | + \ NAME \ \ + +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | + | TYPE | > DSO-DATA +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | CLASS | / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / Figure 1: SUBSCRIBE Request The DSO-DATA for a SUBSCRIBE request MUST contain exactly one NAME, TYPE, and CLASS. Since SUBSCRIBE requests are sent over TCP, multiple SUBSCRIBE DSO request messages can be concatenated in a single TCP stream and packed efficiently into TCP segments. If accepted, the subscription will stay in effect until the client cancels the subscription using UNSUBSCRIBE or until the DSO session between the client and the server is closed. SUBSCRIBE requests on a given session MUST be unique. A client MUST NOT send a SUBSCRIBE message that duplicates the NAME, TYPE and CLASS of an existing active subscription on that DSO session. For the purpose of this matching, the established DNS case-insensitivity for - US-ASCII letters applies (e.g., "example.com" and "Example.com" are - the same). If a server receives such a duplicate SUBSCRIBE message, - this is a fatal error and the server MUST forcibly abort the - connection immediately. + US-ASCII letters [RFC0020] applies (e.g., "example.com" and + "Example.com" are the same). If a server receives such a duplicate + SUBSCRIBE message, this is a fatal error and the server MUST forcibly + abort the connection immediately. DNS wildcarding is not supported. That is, a wildcard ("*") in a SUBSCRIBE message matches only a literal wildcard character ("*") in the zone, and nothing else. Aliasing is not supported. That is, a CNAME in a SUBSCRIBE message matches only a literal CNAME record in the zone, and no other records with the same owner name. A client may SUBSCRIBE to records that are unknown to the server at @@ -610,59 +618,57 @@ people sometimes imagine. When used in conjunction with SUBSCRIBE, TYPE and CLASS 255 should be interpreted to mean "ALL", not "ANY". After accepting a subscription where one or both of TYPE or CLASS are 255, the server MUST send Push Notification Updates for ALL record changes that match the subscription, not just some of them. 6.2.2. SUBSCRIBE Response - Each SUBSCRIBE request generates exactly one SUBSCRIBE response from - the server. - A SUBSCRIBE response begins with the standard DSO 12-byte header [RFC8490]. The QR bit in the header is set indicating it is a response. The header MAY be followed by one or more optional TLVs, - such as a Retry Delay TLV. + such as a Retry Delay TLV. A SUBSCRIBE response is illustrated in + Figure 2. The MESSAGE ID field MUST echo the value given in the MESSAGE ID field of the SUBSCRIBE request. This is how the client knows which request is being responded to. + The other header fields MUST be set as described in the DSO spec- + ification [RFC8490]. The DNS OPCODE field contains the OPCODE value + for DNS Stateful Operations (6). The four count fields must be zero, + and the corresponding four sections must be empty (i.e., absent). + A SUBSCRIBE response message MUST NOT include a SUBSCRIBE TLV. If a client receives a SUBSCRIBE response message containing a SUBSCRIBE TLV then the response message is processed but the SUBSCRIBE TLV MUST be silently ignored. - A client MUST NOT send a SUBSCRIBE response. If a client does send a - SUBSCRIBE message, with the QR bit set indicating that it is a - response, this is a fatal error and the server MUST forcibly abort - the connection immediately. - 1 1 1 1 1 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \ | MESSAGE ID | \ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | |QR| OPCODE(6) | Z | RCODE | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | QDCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > HEADER | ANCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | NSCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | ARCOUNT (MUST BE ZERO) | / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / - Figure 2: SUBSCRIBE Response Message + Figure 2: SUBSCRIBE Response In the SUBSCRIBE response the RCODE indicates whether or not the subscription was accepted. Supported RCODEs are as follows: +-----------+-------+-----------------------------------------------+ | Mnemonic | Value | Description | +-----------+-------+-----------------------------------------------+ | NOERROR | 0 | SUBSCRIBE successful. | | FORMERR | 1 | Server failed to process request due to a | | | | malformed request. | @@ -682,27 +688,27 @@ Responses. Servers sending SUBSCRIBE Responses SHOULD use one of these values. Note that NXDOMAIN is not a valid RCODE in response to a SUBSCRIBE Request. However, future circumstances may create situations where other RCODE values are appropriate in SUBSCRIBE Responses, so clients MUST be prepared to accept SUBSCRIBE Responses with any other RCODE value. If the server sends a nonzero RCODE in the SUBSCRIBE response, that means: - a. the client is (at least partially) misconfigured, + a. the client is (at least partially) misconfigured, or b. the server resources are exhausted, or c. there is some other unknown failure on the server. In any case, the client shouldn't retry the subscription to this server right away. If multiple SRV records were returned as - described in Section 6.1, Paragraph 7, a subsequent server can be + described in Section 6.1, Paragraph 7, a subsequent server MAY be tried immediately. If the client has other successful subscriptions to this server, these subscriptions remain even though additional subscriptions may be refused. Neither the client nor the server are required to close the connection, although, either end may choose to do so. If the server sends a nonzero RCODE then it SHOULD append a Retry Delay TLV [RFC8490] to the response specifying a delay before the client attempts this operation again. Recommended values for the @@ -782,106 +788,112 @@ 6.3. DNS Push Notification Updates Once a subscription has been successfully established, the server generates PUSH messages to send to the client as appropriate. In the case that the answer set was already non-empty at the moment the subscription was established, an initial PUSH message will be sent immediately following the SUBSCRIBE Response. Subsequent changes to the answer set are then communicated to the client in subsequent PUSH messages. + A client MUST NOT send a PUSH message. If a client does send a PUSH + message, or a PUSH message is sent with the QR bit set indicating + that it is a response, this is a fatal error and the receiver MUST + forcibly abort the connection immediately. + 6.3.1. PUSH Message A PUSH unidirectional message begins with the standard DSO 12-byte header [RFC8490], followed by the PUSH primary TLV. A PUSH message is illustrated in Figure 3. In accordance with the definition of DSO unidirectional messages, the MESSAGE ID field MUST be zero. There is no client response to a PUSH message. The other header fields MUST be set as described in the DSO spec- ification [RFC8490]. The DNS OPCODE field contains the OPCODE value - for DNS Stateful Operations (6). The four count fields MUST be zero, - and the corresponding four sections MUST be empty (i.e., absent). - - A client MUST NOT send a PUSH message. If a client does send a PUSH - message, or a PUSH message is sent with the QR bit set indicating - that it is a response, this is a fatal error and the receiver MUST - forcibly abort the connection immediately. + for DNS Stateful Operations (6). The four count fields must be zero, + and the corresponding four sections must be empty (i.e., absent). The DSO-TYPE is PUSH (tentatively 0x41). The DSO-LENGTH is the length of the DSO-DATA that follows, which specifies the changes being communicated. The DSO-DATA contains one or more change notifications. A PUSH Message MUST contain at least one change notification. If a PUSH Message is received that contains no change notifications, this is a fatal error, and the client MUST forcibly abort the connection immediately. The change notification records are formatted similarly to how DNS Resource Records are conventionally expressed in DNS messages, as illustrated in Figure 3, and are interpreted as described below. The TTL field holds an unsigned 32-bit integer [RFC2181]. If the TTL - is in the range 0 to 2,147,483,647 seconds (2^31 - 1, or 0x7FFFFFFF), - then a new DNS Resource Record with the given name, type, class and - RDATA is added. A TTL of 0 means that this record should be retained - for as long as the subscription is active, and should be discarded - immediately the moment the subscription is cancelled. + is in the range 0 to 2,147,483,647 seconds (0 to 2^31 - 1, or + 0x7FFFFFFF), then a new DNS Resource Record with the given name, + type, class and RDATA is added. Type and class MUST NOT be 255 + (ANY). If either type or class are 255 (ANY) this is a fatal error, + and the client MUST forcibly abort the connection immediately. A TTL + of 0 means that this record should be retained for as long as the + subscription is active, and should be discarded immediately the + moment the subscription is cancelled. If the TTL has the value 0xFFFFFFFF, then the DNS Resource Record - with the given name, type, class and RDATA is removed. + with the given name, type, class and RDATA is removed. Type and + class MUST NOT be 255 (ANY). If either type or class are 255 (ANY) + this is a fatal error, and the client MUST forcibly abort the + connection immediately. If the TTL has the value 0xFFFFFFFE, then this is a 'collective' remove notification. For collective remove notifications RDLEN MUST be zero and consequently the RDATA MUST be empty. If a change notification is received where TTL = 0xFFFFFFFE and RDLEN is not zero, this is a fatal error, and the client MUST forcibly abort the connection immediately. There are three types of collective remove notification: For collective remove notifications, if CLASS is not 255 (ANY) and - TYPE is not 255 (ANY) then for the given name this deletes all + TYPE is not 255 (ANY) then for the given name this removes all records of the specified type in the specified class. For collective remove notifications, if CLASS is not 255 (ANY) and - TYPE is 255 (ANY) then for the given name this deletes all records of + TYPE is 255 (ANY) then for the given name this removes all records of all types in the specified class. For collective remove notifications, if CLASS is 255 (ANY), then for - the given name this deletes all records of all types in all classes. + the given name this removes all records of all types in all classes. In this case TYPE MUST be set to zero on transmission, and MUST be silently ignored on reception. Summary of change notification types: - Delete all RRsets from a name, in all classes + Remove all RRsets from a name, in all classes TTL = 0xFFFFFFFE, RDLEN = 0, CLASS = 255 (ANY) - Delete all RRsets from a name, in given class: + Remove all RRsets from a name, in given class: TTL = 0xFFFFFFFE, RDLEN = 0, CLASS gives class, TYPE = 255 (ANY) - Delete specified RRset from a name, in given class: + Remove specified RRset from a name, in given class: TTL = 0xFFFFFFFE, RDLEN = 0 - CLASS and TYPE specify the RRset being deleted + CLASS and TYPE specify the RRset being removed - Delete an individual RR from a name: + Remove an individual RR from a name: TTL = 0xFFFFFFFF - CLASS, TYPE, RDLEN and RDATA specify the RR being deleted. + CLASS, TYPE, RDLEN and RDATA specify the RR being removed Add individual RR to a name TTL >= 0 and TTL <= 0x7FFFFFFF - CLASS, TYPE, RDLEN, RDATA and TTL specify the RR being added. + CLASS, TYPE, RDLEN, RDATA and TTL specify the RR being added Note that it is valid for the RDATA of an added or removed DNS Resource Record to be empty (zero length). For example, an Address Prefix List Resource Record [RFC3123] may have empty RDATA. Therefore, a change notification with RDLEN = 0 does not automatically indicate a remove notification. If RDLEN = 0 and TTL is the in the range 0 - 0x7FFFFFFF, this change notification signals the addition of a record with the given name, type, class, and empty RDATA. If RDLEN = 0 and TTL = 0xFFFFFFFF, this change notification signals the removal specifically of that single record with the given @@ -961,53 +973,55 @@ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | \ RDATA (sized as necessary) \ | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | : NAME, TYPE, CLASS, TTL, RDLEN, RDATA : | : Repeated As Necessary : / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / Figure 3: PUSH Message When processing the records received in a PUSH Message, the receiving - client MUST validate that the records being added or deleted + client MUST validate that the records being added or removed correspond with at least one currently active subscription on that session. Specifically, the record name MUST match the name given in - a SUBSCRIBE request, subject to the usual established DNS case- - insensitivity for US-ASCII letters. If the TYPE in the SUBSCRIBE - request was not ANY (255) then the TYPE of the record must match the - TYPE given in the SUBSCRIBE request. If the CLASS in the SUBSCRIBE - request was not ANY (255) then the CLASS of the record must match the - CLASS given in the SUBSCRIBE request. If a matching active - subscription on that session is not found, then that individual - record addition/deletion is silently ignored. Processing of other - additions and deletions in this message is not affected. The DSO - session is not closed. This is to allow for the unavoidable race - condition where a client sends an outbound UNSUBSCRIBE while inbound - PUSH messages for that subscription from the server are still in - flight. + the SUBSCRIBE request, subject to the usual established DNS case- + insensitivity for US-ASCII letters. For individual additions and + removals, if the TYPE in the SUBSCRIBE request was not ANY (255) then + the TYPE of the record must match the TYPE given in the SUBSCRIBE + request, and if the CLASS in the SUBSCRIBE request was not ANY (255) + then the CLASS of the record must match the CLASS given in the + SUBSCRIBE request. For collective removals, at least one of the + records being removed must match an active subscription. If a + matching active subscription on that session is not found, then that + particular addition/removal record is silently ignored. Processing + of other additions and removal records in this message is not + affected. The DSO session is not closed. This is to allow for the + unavoidable race condition where a client sends an outbound + UNSUBSCRIBE while inbound PUSH messages for that subscription from + the server are still in flight. In the case where a single change affects more than one active subscription, only one PUSH message is sent. For example, a PUSH message adding a given record may match both a SUBSCRIBE request with the same TYPE and a different SUBSCRIBE request with TYPE = 255 (ANY). It is not the case that two PUSH messages are sent because the new record matches two active subscriptions. The server SHOULD encode change notifications in the most efficient - manner possible. For example, when three AAAA records are deleted + manner possible. For example, when three AAAA records are removed from a given name, and no other AAAA records exist for that name, the - server SHOULD send a "delete an RRset from a name" PUSH message, not - three separate "delete an individual RR from a name" PUSH messages. - Similarly, when both an SRV and a TXT record are deleted from a given + server SHOULD send a "remove an RRset from a name" PUSH message, not + three separate "remove an individual RR from a name" PUSH messages. + Similarly, when both an SRV and a TXT record are removed from a given name, and no other records of any kind exist for that name, the - server SHOULD send a "delete all RRsets from a name" PUSH message, - not two separate "delete an RRset from a name" PUSH messages. + server SHOULD send a "remove all RRsets from a name" PUSH message, + not two separate "remove an RRset from a name" PUSH messages. A server SHOULD combine multiple change notifications in a single PUSH message when possible, even if those change notifications apply to different subscriptions. Conceptually, a PUSH message is a session-level mechanism, not a subscription-level mechanism. The TTL of an added record is stored by the client. While the subscription is active, the TTL is not decremented, because a change to the TTL would produce a new update. For as long as a relevant subscription remains active, the client SHOULD assume that when a @@ -1015,54 +1029,53 @@ Consequently, a client does not have to poll to verify that the record is still there. Once a subscription is cancelled (individually, or as a result of the DSO session being closed) record aging for records covered by the subscription resumes and records are removed from the local cache when their TTL reaches zero. 6.4. DNS Push Notification UNSUBSCRIBE To cancel an individual subscription without closing the entire DSO session, the client sends an UNSUBSCRIBE message over the established - DSO session to the server. The UNSUBSCRIBE message is encoded as a - DSO unidirectional message [RFC8490]. This specification defines a - primary unidirectional DSO TLV for DNS Push Notification UNSUBSCRIBE - Messages (tentatively DSO Type Code 0x42). + DSO session to the server. - A server MUST NOT send an UNSUBSCRIBE message. If a server does send - an UNSUBSCRIBE message over a DSO session initiated by a client, or - an UNSUBSCRIBE message is sent with the QR bit set indicating that it - is a response, this is a fatal error and the receiver MUST forcibly - abort the connection immediately. + The entity that initiates an UNSUBSCRIBE message is by definition the + client. A server MUST NOT send an UNSUBSCRIBE message over an + existing session from a client. If a server does send an UNSUBSCRIBE + message over a DSO session initiated by a client, or an UNSUBSCRIBE + message is sent with the QR bit set indicating that it is a response, + this is a fatal error and the receiver MUST forcibly abort the + connection immediately. 6.4.1. UNSUBSCRIBE Message An UNSUBSCRIBE unidirectional message begins with the standard DSO 12-byte header [RFC8490], followed by the UNSUBSCRIBE primary TLV. An UNSUBSCRIBE message is illustrated in Figure 4. In accordance with the definition of DSO unidirectional messages, the MESSAGE ID field MUST be zero. There is no server response to an UNSUBSCRIBE message. The other header fields MUST be set as described in the DSO spec- ification [RFC8490]. The DNS OPCODE field contains the OPCODE value - for DNS Stateful Operations (6). The four count fields MUST be zero, - and the corresponding four sections MUST be empty (i.e., absent). + for DNS Stateful Operations (6). The four count fields must be zero, + and the corresponding four sections must be empty (i.e., absent). The DSO-TYPE is UNSUBSCRIBE (tentatively 0x42). The DSO-LENGTH field contains the value 2, the length of the 2-octet MESSAGE ID contained in the DSO-DATA. - The DSO-DATA contains the value given in the MESSAGE ID field of an - active SUBSCRIBE request. This is how the server knows which - SUBSCRIBE request is being cancelled. After receipt of the + The DSO-DATA contains the value previously given in the MESSAGE ID + field of an active SUBSCRIBE request. This is how the server knows + which SUBSCRIBE request is being cancelled. After receipt of the UNSUBSCRIBE message, the SUBSCRIBE request is no longer active. It is allowable for the client to issue an UNSUBSCRIBE message for a previous SUBSCRIBE request for which the client has not yet received a SUBSCRIBE response. This is to allow for the case where a client starts and stops a subscription in less than the round-trip time to the server. The client is NOT required to wait for the SUBSCRIBE response before issuing the UNSUBSCRIBE message. Consequently, it is possible for a server to receive an UNSUBSCRIBE @@ -1102,21 +1115,21 @@ Sometimes, particularly when used with a Discovery Proxy [DisProx], a DNS Zone may contain stale data. When a client encounters data that it believes may be stale (e.g., an SRV record referencing a target host+port that is not responding to connection requests) the client can send a RECONFIRM message to ask the server to re-verify that the data is still valid. For a Discovery Proxy, this causes it to issue new Multicast DNS queries to ascertain whether the target device is still present. How the Discovery Proxy causes these new Multicast DNS queries to be issued depends on the details of the underlying Multicast DNS implementation being used. For example, a Discovery - Proxy built on Apple's dns_sd.h API responds to a DNS Push + Proxy built on Apple's dns_sd.h API [SD-API] responds to a DNS Push Notification RECONFIRM message by calling the underlying API's DNSServiceReconfirmRecord() routine. For other types of DNS server, the RECONFIRM operation is currently undefined, and SHOULD result in a NOERROR response, but otherwise need not cause any action to occur. Frequent use of RECONFIRM operations may be a sign of network unreliability, or some kind of misconfiguration, so RECONFIRM operations MAY be logged or otherwise communicated to a human @@ -1124,40 +1137,42 @@ problems. If, after receiving a valid RECONFIRM message, the server determines that the disputed records are in fact no longer valid, then subsequent DNS PUSH Messages will be generated to inform interested clients. Thus, one client discovering that a previously-advertised device (like a network printer) is no longer present has the side effect of informing all other interested clients that the device in question is now gone. - A server MUST NOT send a RECONFIRM message. If a server does send a - RECONFIRM message over a DSO session initiated by a client, or a - RECONFIRM message is sent with the QR bit set indicating that it is a - response, this is a fatal error and the receiver MUST forcibly abort - the connection immediately. + The entity that initiates a RECONFIRM message is by definition the + client. A server MUST NOT send a RECONFIRM message over an existing + session from a client. If a server does send a RECONFIRM message + over a DSO session initiated by a client, or a RECONFIRM message is + sent with the QR bit set indicating that it is a response, this is a + fatal error and the receiver MUST forcibly abort the connection + immediately. 6.5.1. RECONFIRM Message A RECONFIRM unidirectional message begins with the standard DSO 12-byte header [RFC8490], followed by the RECONFIRM primary TLV. A RECONFIRM message is illustrated in Figure 5. In accordance with the definition of DSO unidirectional messages, the MESSAGE ID field MUST be zero. There is no server response to a RECONFIRM message. The other header fields MUST be set as described in the DSO spec- ification [RFC8490]. The DNS OPCODE field contains the OPCODE value - for DNS Stateful Operations (6). The four count fields MUST be zero, - and the corresponding four sections MUST be empty (i.e., absent). + for DNS Stateful Operations (6). The four count fields must be zero, + and the corresponding four sections must be empty (i.e., absent). The DSO-TYPE is RECONFIRM (tentatively 0x43). The DSO-LENGTH is the length of the data that follows, which specifies the name, type, class, and content of the record being disputed. The DSO-DATA for a RECONFIRM message MUST contain exactly one record. The DSO-DATA for a RECONFIRM message has no count field to specify more than one record. Since RECONFIRM messages are sent over TCP, @@ -1175,21 +1190,21 @@ matches only a literal CNAME record in the zone, and no other records with the same owner name. Note that there is no RDLEN field, since the length of the RDATA can be inferred from DSO-LENGTH, so an additional RDLEN field would be redundant. 1 1 1 1 1 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \ - | MESSAGE ID | \ + | MESSAGE ID (MUST BE ZERO) | \ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | |QR| OPCODE(6) | Z | RCODE | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | QDCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > HEADER | ANCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | NSCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | ARCOUNT (MUST BE ZERO) | / @@ -1204,23 +1219,23 @@ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > DSO-DATA | CLASS | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | \ RDATA \ / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / Figure 5: RECONFIRM Message 6.6. DNS Stateful Operations TLV Context Summary - This document defines four new DSO TLVs. As suggested in Section 8.2 - of the DNS Stateful Operations specification [RFC8490], the valid - contexts of these new TLV types are summarized below. + This document defines four new DSO TLVs. As recommended in + Section 8.2 of the DNS Stateful Operations specification [RFC8490], + the valid contexts of these new TLV types are summarized below. The client TLV contexts are: C-P: Client request message, primary TLV C-U: Client unidirectional message, primary TLV C-A: Client request or unidirectional message, additional TLV CRP: Response back to client, primary TLV CRA: Response back to client, additional TLV +-------------+-----+-----+-----+-----+-----+ @@ -1253,21 +1268,21 @@ Table 3: DSO TLV Server Context Summary 6.7. Client-Initiated Termination An individual subscription is terminated by sending an UNSUBSCRIBE TLV for that specific subscription, or all subscriptions can be cancelled at once by the client closing the DSO session. When a client terminates an individual subscription (via UNSUBSCRIBE) or all subscriptions on that DSO session (by ending the session) it is - signaling to the server that it is longer interested in receiving + signaling to the server that it is no longer interested in receiving those particular updates. It is informing the server that the server may release any state information it has been keeping with regards to these particular subscriptions. After terminating its last subscription on a session via UNSUBSCRIBE, a client MAY close the session immediately, or it may keep it open if it anticipates performing further operations on that session in the future. If a client wishes to keep an idle session open, it MUST respect the maximum idle time required by the server [RFC8490]. @@ -1370,46 +1385,47 @@ client-server security or end-to-end security. However, recommendations for security in particular deployment scenarios are outside the scope of this document. DNSSEC is RECOMMENDED for the authentication of DNS Push Notification servers. TLS alone does not provide complete security. TLS certificate verification can provide reasonable assurance that the client is really talking to the server associated with the desired host name, but since the desired host name is learned via a DNS SRV query, if the SRV query is subverted then the client may have a - secure connection to a rogue server. DNSSEC can provided added + secure connection to a rogue server. DNSSEC can provide added confidence that the SRV query has not been subverted. 7.1. Security Services It is the goal of using TLS to provide the following security services: Confidentiality: All application-layer communication is encrypted with the goal that no party should be able to decrypt it except the intended receiver. Data integrity protection: Any changes made to the communication in transit are detectable by the receiver. Authentication: An end-point of the TLS communication is authenticated as the intended entity to communicate with. Anti-replay protection: TLS provides for the detection of and prevention against messages sent previously over a TLS connection - (such as DNS Push Notifications). Prior messages cannot be re- - sent at a later time as a form of a man-in-the-middle attack. + (such as DNS Push Notifications). If prior messages are re-sent + at a later time as a form of a man-in-the-middle attack then the + receiver will detect this and reject the replayed messages. Deployment recommendations on the appropriate key lengths and cypher suites are beyond the scope of this document. Please refer to TLS - Recommendations [RFC7525] for the best current practices. Keep in + Recommendations [BCP195] for the best current practices. Keep in mind that best practices only exist for a snapshot in time and recommendations will continue to change. Updated versions or errata may exist for these recommendations. 7.2. TLS Name Authentication As described in Section 6.1, the client discovers the DNS Push Notification server using an SRV lookup for the record name "_dns-push-tls._tcp.". The server connection endpoint SHOULD then be authenticated using DANE TLSA records for the associated SRV @@ -1441,66 +1457,61 @@ With TLS early data there are no guarantees of non-replay between connections. If packets are duplicated and delayed in the network, the later arrivals could be mistaken for new subscription requests. Generally this is not a major concern, since the amount of state generated on the server for these spurious subscriptions is small and short-lived, since the TCP connection will not complete the three-way handshake. Servers MAY choose to implement rate-limiting measures that are activated when the server detects an excessive number of spurious subscription requests. - For further guidance please see Section 2.3, Section 8, and - Appendix E.5 of the TLS 1.3 specification [RFC8446]. + For further guidance please see discussion of zero round-trip data + (Section 2.3, Section 8, and Appendix E.5) in the TLS 1.3 + specification, [RFC8446]. 7.4. TLS Session Resumption - TLS Session Resumption is permissible on DNS Push Notification - servers. The server may keep TLS state with Session IDs [RFC8446] or - operate in stateless mode by sending a Session Ticket [RFC5077] to - the client for it to store. However, closing the TLS connection - terminates the DSO session. When the TLS session is resumed, the DNS - Push Notification server will not have any subscription state and - will proceed as with any other new DSO session. Use of TLS Session + TLS Session Resumption [RFC8446] is permissible on DNS Push + Notification servers. However, closing the TLS connection terminates + the DSO session. When the TLS session is resumed, the DNS Push + Notification server will not have any subscription state and will + proceed as with any other new DSO session. Use of TLS Session Resumption may allow a TLS connection to be set up more quickly, but the client will still have to recreate any desired subscriptions. 8. IANA Considerations - This document defines a new service name to be published in the IANA - Registry Service Types [RFC6335][ST] that is only applicable for the - TCP protocol. + This document defines a new service name, only applicable for the TCP + protocol, to be recorded in the IANA Service Type Registry + [RFC6335][SRVTYPE]. +-----------------------+------+----------------------+-------------+ | Name | Port | Value | Definition | +-----------------------+------+----------------------+-------------+ | DNS Push Notification | None | "_dns-push-tls._tcp" | Section 6.1 | | Service Type | | | | +-----------------------+------+----------------------+-------------+ Table 4: IANA Service Type Assignments - This document also defines four new DNS Stateful Operation TLV types - to be recorded in the IANA DSO Type Code Registry. + This document defines four new DNS Stateful Operation TLV types to be + recorded in the IANA DSO Type Code Registry [RFC8490][DSOTYPE]. - +-------------+------------+---------+-----------------+------------+ + +-------------+------------+--------+-----------------+-------------+ | Name | Value | Early | Status | Definition | | | | Data | | | - +-------------+------------+---------+-----------------+------------+ - | SUBSCRIBE | TBA (0x40) | OK | Standards Track | Section | - | | | | | 6.2 | - | PUSH | TBA (0x41) | NO | Standards Track | Section | - | | | | | 6.3 | - | UNSUBSCRIBE | TBA (0x42) | NO | Standards Track | Section | - | | | | | 6.4 | - | RECONFIRM | TBA (0x43) | NO | Standards Track | Section | - | | | | | 6.5 | - +-------------+------------+---------+-----------------+------------+ + +-------------+------------+--------+-----------------+-------------+ + | SUBSCRIBE | TBA (0x40) | OK | Standards Track | Section 6.2 | + | PUSH | TBA (0x41) | NO | Standards Track | Section 6.3 | + | UNSUBSCRIBE | TBA (0x42) | NO | Standards Track | Section 6.4 | + | RECONFIRM | TBA (0x43) | NO | Standards Track | Section 6.5 | + +-------------+------------+--------+-----------------+-------------+ Table 5: IANA DSO TLV Type Code Assignments This document defines no new DNS OPCODEs or RCODEs. 9. Acknowledgements The authors would like to thank Kiren Sekar and Marc Krochmal for previous work completed in this field. @@ -1509,20 +1520,27 @@ Rescorla, Michael Richardson, David Schinazi, Manju Shankar Rao, Robert Sparks, Markus Stenberg, Andrew Sullivan, Michael Sweet, Dave Thaler, Brian Trammell, Bernie Volz, Eric Vyncke, Christopher Wood, Liang Xia, and Soraia Zlatkovic. Ted Lemon provided clarifying text that was greatly appreciated. 10. References 10.1. Normative References + [DSOTYPE] "DSO Type Code Registry", + . + + [RFC0020] Cerf, V., "ASCII format for network interchange", STD 80, + RFC 20, DOI 10.17487/RFC0020, October 1969, + . + [RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768, DOI 10.17487/RFC0768, August 1980, . [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793, DOI 10.17487/RFC0793, September 1981, . [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987, @@ -1575,39 +1593,55 @@ [RFC7673] Finch, T., Miller, M., and P. Saint-Andre, "Using DNS- Based Authentication of Named Entities (DANE) TLSA Records with SRV Records", RFC 7673, DOI 10.17487/RFC7673, October 2015, . [RFC7766] Dickinson, J., Dickinson, S., Bellis, R., Mankin, A., and D. Wessels, "DNS Transport over TCP - Implementation Requirements", RFC 7766, DOI 10.17487/RFC7766, March 2016, . + [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, . + [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . + [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, + . + [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . [RFC8490] Bellis, R., Cheshire, S., Dickinson, J., Dickinson, S., Lemon, T., and T. Pusateri, "DNS Stateful Operations", RFC 8490, DOI 10.17487/RFC8490, March 2019, . - [ST] "Service Name and Transport Protocol Port Number - Registry", . + [SRVTYPE] "Service Name and Transport Protocol Port Number + Registry", . 10.2. Informative References + [BCP195] Sheffer, Y., Holz, R., and P. Saint-Andre, + "Recommendations for Secure Use of Transport Layer + Security (TLS) and Datagram Transport Layer Security + (DTLS)", BCP 195, RFC 7525, May 2015, + . + [DisProx] Cheshire, S., "Discovery Proxy for Multicast DNS-Based Service Discovery", draft-ietf-dnssd-hybrid-10 (work in progress), March 2019. [I-D.ietf-tcpm-rack] Cheng, Y., Cardwell, N., Dukkipati, N., and P. Jha, "RACK: a time-based fast loss detection algorithm for TCP", draft-ietf-tcpm-rack-05 (work in progress), April 2019. [LLQ] Cheshire, S. and M. Krochmal, "DNS Long-Lived Queries", @@ -1625,25 +1659,20 @@ . [RFC4287] Nottingham, M., Ed. and R. Sayre, Ed., "The Atom Syndication Format", RFC 4287, DOI 10.17487/RFC4287, December 2005, . [RFC4953] Touch, J., "Defending TCP Against Spoofing Attacks", RFC 4953, DOI 10.17487/RFC4953, July 2007, . - [RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, - "Transport Layer Security (TLS) Session Resumption without - Server-Side State", RFC 5077, DOI 10.17487/RFC5077, - January 2008, . - [RFC6281] Cheshire, S., Zhu, Z., Wakikawa, R., and L. Zhang, "Understanding Apple's Back to My Mac (BTMM) Service", RFC 6281, DOI 10.17487/RFC6281, June 2011, . [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, DOI 10.17487/RFC6762, February 2013, . [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service @@ -1661,49 +1690,41 @@ [RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and P. Selkirk, "Port Control Protocol (PCP)", RFC 6887, DOI 10.17487/RFC6887, April 2013, . [RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014, . - [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, - "Recommendations for Secure Use of Transport Layer - Security (TLS) and Datagram Transport Layer Security - (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May - 2015, . - [RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS Terminology", RFC 7719, DOI 10.17487/RFC7719, December 2015, . - [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, . - [RFC8010] Sweet, M. and I. McDonald, "Internet Printing Protocol/1.1: Encoding and Transport", STD 92, RFC 8010, DOI 10.17487/RFC8010, January 2017, . [RFC8011] Sweet, M. and I. McDonald, "Internet Printing Protocol/1.1: Model and Semantics", STD 92, RFC 8011, DOI 10.17487/RFC8011, January 2017, . - [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, - . + [RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS + Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499, + January 2019, . + + [SD-API] "dns_sd.h API", + . [SYN] Eddy, W., "Defenses Against TCP SYN Flooding Attacks", The Internet Protocol Journal, Cisco Systems, Volume 9, Number 4, December 2006. [XEP0060] Millard, P., Saint-Andre, P., and R. Meijer, "Publish- Subscribe", XSF XEP 0060, July 2010. Authors' Addresses