--- 1/draft-ietf-dnssd-push-14.txt 2018-09-18 20:13:14.021271978 -0700 +++ 2/draft-ietf-dnssd-push-15.txt 2018-09-18 20:13:14.089273624 -0700 @@ -1,19 +1,19 @@ Internet Engineering Task Force T. Pusateri Internet-Draft Unaffiliated Intended status: Standards Track S. Cheshire -Expires: September 19, 2018 Apple Inc. - March 18, 2018 +Expires: March 21, 2019 Apple Inc. + September 17, 2018 DNS Push Notifications - draft-ietf-dnssd-push-14 + draft-ietf-dnssd-push-15 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 September 19, 2018. + This Internet-Draft will expire on March 21, 2019. Copyright Notice Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -92,25 +92,25 @@ 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 DNS record change notifications. Familiarity with the DNS protocol and DNS packet formats is assumed [RFC1034] [RFC1035] [RFC6895]. 1.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", - "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", - and "OPTIONAL" in this document are to be interpreted as described - in "Key words for use in RFCs to Indicate Requirement Levels", - when, and only when, they appear in all capitals, as shown here - [RFC2119] [RFC8174]. + "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and + "OPTIONAL" in this document are to be interpreted as described in + "Key words for use in RFCs to Indicate Requirement Levels", when, and + only when, they appear in all capitals, as shown here [RFC2119] + [RFC8174]. 2. Motivation As the domain name system continues to adapt to new uses and changes in deployment, polling has the potential to burden DNS servers at 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 @@ -157,29 +157,29 @@ resource record sets (RRSets) on the zone's server. This specification adopts a simplified subset of these existing syntax and semantics, and uses them for DNS Push Notification messages going in the opposite direction, from server to client, to communicate changes to a zone. The client subscribes for Push Notifications by connecting to the server and sending DNS message(s) indicating the RRSet(s) of interest. When the client loses interest in receiving further updates to these records, it unsubscribes. - The DNS Push Notification server for a zone is any server capable - of generating the correct change notifications for a name. - It may be a master, slave, or stealth name server [RFC7719]. - Consequently, the "_dns-push-tls._tcp." SRV record for a - zone MAY reference the same target host and port as that zone's + The DNS Push Notification server for a zone is any server capable of + generating the correct change notifications for a name. It may be a + primary, secondary, or stealth name server [RFC7719]. Consequently, + the "_dns-push-tls._tcp." SRV record for a zone MAY reference + the same target host and port as that zone's "_dns-update-tls._tcp." SRV record. When the same target host and port is offered for both DNS Updates and DNS Push Notifications, a client MAY use a single TCP connection to that server for both DNS - Updates and DNS Push Notification Queries. + Updates and DNS Push Notification Subscriptions. Supporting DNS Updates and DNS Push Notifications on the same server is OPTIONAL. A DNS Push Notification server does NOT also have to support DNS Update. DNS Updates and DNS Push Notifications may be handled on different ports on the same target host, in which case they are not considered to be the "same server" for the purposes of this specification, and communications with these two ports are handled independently. @@ -316,34 +316,34 @@ to it. Once the client has indicated willingness to use DSO by sending one of its own, either side of the session may then initiate further DSO messages at any time. 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 or keepalive - interval longer than the the 15-second defaults, but this is not + interval longer than the the 15-second default, 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. + it determines that to be necessary. However, Push Notification + subscriptions can also be used to establish the DSO session. - Once the session is made, the client may then add and remove Push - Notification subscriptions. 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. + 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. 6.1. Discovery The first step in DNS Push Notification subscription is to discover an appropriate DNS server that supports DNS Push Notifications for the desired zone. The client begins by opening a DSO Session to its normal configured DNS recursive resolver and requesting a Push Notification subscription. If this is successful, then the recursive resolver @@ -409,41 +409,33 @@ 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. - 6. If the zone in question does not offer DNS Push Notifications - then SRV record MUST NOT exist, and the SRV query will return a - negative answer. (The "_dns-push-tls._tcp" service type is - allocated by IANA for this purpose, and, like any allocated IANA - service type, MUST NOT be used for other services. Other - services that require an IANA service type should use a unique - service type allocated by IANA for that service [RFC6335][ST].) - - 7. If the zone in question is set up to offer DNS Push Notifications + 6. If the zone in question is set up to offer DNS Push Notifications then this SRV record MUST exist. (If this SRV record does not exist then the zone is not correctly configured for DNS Push Notifications as specified in this document.) The SRV "target" contains the name of the server providing DNS Push Notifications for the zone. The port number on which to contact the server is in the SRV record "port" field. The address(es) of the target host MAY be included in the Additional Section, however, the address records SHOULD be authenticated before use as described below in Section 7.2 and in the specification for using DANE TLSA - Records with SRV Records [RFC7673]. + Records with SRV Records [RFC7673], if applicable. - 8. More than one SRV record may be returned. In this case, the + 7. More than one SRV record may be returned. In this case, the "priority" and "weight" values in the returned SRV records are used to determine the order in which to contact the servers for 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 @@ -485,63 +477,62 @@ The MESSAGE ID field MUST be set to a unique value, that the client is not using for any other active operation on this 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 - specification [DSO]. The DNS Opcode is the DSO Opcode (tentatively - 6). The four count fields MUST be zero, and the corresponding four - sections MUST be empty (i.e., absent). + specification [DSO]. The DNS Opcode is the DSO Opcode. 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. + The DSO-TYPE is SUBSCRIBE. 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 | \ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | |QR| Opcode | Z | RCODE | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | QDCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > HEADER | ANCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | NSCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | ARCOUNT (MUST BE ZERO) | / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / - | DSO-TYPE = SUBSCRIBE (tentatively 0x40) | + | DSO-TYPE = SUBSCRIBE | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | DSO-LENGTH (number of octets in DSO-DATA) | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \ | | \ \ NAME \ | \ \ | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > DSO-DATA | TYPE | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | CLASS | / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / Figure 1: SUBSCRIBE Request - The DSO-DATA for a SUBSCRIBE request MUST contain exactly one - question. The DSO-DATA for a SUBSCRIBE request has no QDCOUNT field - to specify more than one question. Since SUBSCRIBE requests are sent - over TCP, multiple SUBSCRIBE request messages can be concatenated in - a single TCP stream and packed efficiently into TCP segments. + The DSO-DATA for a SUBSCRIBE request MUST contain exactly one NAME, + Type, and CLASS. Since SUBSCRIBE requests are sent over TCP, + multiple SUBSCRIBE 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 @@ -679,25 +671,24 @@ for the requested name, the retry delay may be any value selected by the implementer and/or configured by the operator. This is a misconfiguration, since this server is listed in a "_dns-push-tls._tcp." SRV record, but the server itself is not currently configured to support DNS Push Notifications for that zone. Since it is possible that the misconfiguration may be repaired at any time, the retry delay should not be set too high. By default, a value of 5 minutes is RECOMMENDED. - For RCODE = 11 (DNS Push SUBSCRIBE operation not supported), which - occurs on a server that doesn't implement DNS Push Notifications, - it is unlikely that the server will begin supporting DNS Push - Notifications in the next few minutes, so the retry delay SHOULD - be one hour. + For RCODE = 11 (DSOTYPENI), which occurs on a server that doesn't + implement DNS Push Notifications, it is unlikely that the server + will begin supporting DNS Push Notifications in the next few + minutes, so the retry delay SHOULD be one hour. For other RCODE values, the retry delay should be set by the server as appropriate for that error condition. By default, a value of 5 minutes is RECOMMENDED. For RCODE = 9 (NOTAUTH), the time delay applies to requests for other names falling within the same zone. Requests for names falling within other zones are not subject to the delay. For all other RCODEs the time delay applies to all subsequent requests to this server. @@ -715,37 +706,38 @@ case that the answer set was 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. 6.3.1. PUSH Message A PUSH message begins with the standard DSO 12-byte header [DSO], followed by the PUSH TLV. A PUSH message is illustrated in Figure 2. - The MESSAGE ID field MUST be zero. There is no client response to a - PUSH message. + 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 - specification [DSO]. The DNS Opcode is the DSO Opcode (tentatively - 6). The four count fields MUST be zero, and the corresponding four - sections MUST be empty (i.e., absent). + The other header fields MUST also be set as described in the DSO + specification [DSO]. The DNS Opcode is the DSO Opcode. 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 Update records. A PUSH Message MUST contain at least one Update record. If a PUSH Message is - received that contains no Update records, this is a fatal error, and - the receiver MUST immediately terminate the connection with a TCP RST - (or equivalent for other protocols). The Update records are + received that contains zero Update records, this is a fatal error, + and the receiver MUST immediately terminate the connection with a TCP + RST (or equivalent for other protocols). The Update records are formatted in the customary way for Resource Records in DNS messages. Update records in a PUSH Message are interpreted according to the same rules as for DNS Update [RFC2136] messages, namely: Delete all RRsets from a name: TTL=0, CLASS=ANY, RDLENGTH=0, TYPE=ANY. Delete an RRset from a name: TTL=0, CLASS=ANY, RDLENGTH=0; TYPE specifies the RRset being deleted. @@ -748,38 +740,39 @@ Delete an RRset from a name: TTL=0, CLASS=ANY, RDLENGTH=0; TYPE specifies the RRset being deleted. Delete an individual RR from a name: TTL=0, CLASS=NONE; TYPE, RDLENGTH and RDATA specifies the RR being deleted. Add to an RRset: + TTL, CLASS, TYPE, RDLENGTH and RDATA specifies the RR being added. 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 | Z | RCODE | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | QDCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > HEADER | ANCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | NSCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | ARCOUNT (MUST BE ZERO) | / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / - | DSO-TYPE = PUSH (tentatively 0x41) | + | DSO-TYPE = PUSH | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | DSO-LENGTH (number of octets in DSO-DATA) | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \ \ NAME \ \ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | TYPE | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | CLASS | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | TTL | | @@ -843,75 +836,75 @@ of that fact. 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 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 in a - DSO [DSO] message. This specification defines a DSO TLV for DNS Push - Notification UNSUBSCRIBE Requests/Responses (tentatively DSO Type - Code 0x42). + DSO session to the server. The UNSUBSCRIBE message is encoded as a + DSO [DSO] unidirectional message. This specification defines a DSO + TLV for DNS Push Notification UNSUBSCRIBE Requests/Responses + (tentatively DSO Type Code 0x42). A server MUST NOT initiate an UNSUBSCRIBE request. If a server does send an UNSUBSCRIBE request over a DSO session initiated by a client, this is a fatal error and the client should immediately abort the connection with a TCP RST (or equivalent for other protocols). 6.4.1. UNSUBSCRIBE Request An UNSUBSCRIBE request begins with the standard DSO 12-byte header [DSO], followed by the UNSUBSCRIBE TLV. An UNSUBSCRIBE request message is illustrated in Figure 3. The MESSAGE ID field MUST be zero. There is no server response to a UNSUBSCRIBE message. The other header fields MUST be set as described in the DSO - specification [DSO]. The DNS Opcode is the DSO Opcode (tentatively - 6). The four count fields MUST be zero, and the corresponding four - sections MUST be empty (i.e., absent). + specification [DSO]. The DNS Opcode is the DSO Opcode. The four + count fields MUST be zero, and the corresponding four sections MUST + be empty (i.e., absent). - In the UNSUBSCRIBE TLV the DSO-TYPE is UNSUBSCRIBE (tentatively - 0x42). The DSO-LENGTH is 2 octets. + In the UNSUBSCRIBE TLV the DSO-TYPE is UNSUBSCRIBE. The DSO-LENGTH + is 2 octets. The DSO-DATA contains the MESSAGE ID field of the value given in the ID field of an active SUBSCRIBE request. This is how the server knows which SUBSCRIBE request is being cancelled. After receipt of the UNSUBSCRIBE request, the SUBSCRIBE request is no longer active. It is allowable for the client to issue an UNSUBSCRIBE request 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 request. 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 | Z | RCODE | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | QDCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > HEADER | ANCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | NSCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | ARCOUNT (MUST BE ZERO) | / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / - | DSO-TYPE = UNSUBSCRIBE (tentatively 0x42) | + | DSO-TYPE = UNSUBSCRIBE | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | DSO-LENGTH (2 octets) | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \ | SUBSCRIBE MESSAGE ID | > DSO-DATA +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / Figure 3: UNSUBSCRIBE Request 6.5. DNS Push Notification RECONFIRM @@ -946,44 +939,44 @@ 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 RECONFIRM response the server MUST echo back the MESSAGE ID value unchanged. The other header fields MUST be set as described in the DSO - specification [DSO]. The DNS Opcode is the DSO Opcode (tentatively - 6). The four count fields MUST be zero, and the corresponding four - sections MUST be empty (i.e., absent). + specification [DSO]. The DNS Opcode is the DSO Opcode. 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. 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 | Z | RCODE | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | QDCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > HEADER | ANCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | NSCOUNT (MUST BE ZERO) | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | ARCOUNT (MUST BE ZERO) | / +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ / - | DSO-TYPE = RECONFIRM (tentatively 0x43) | + | DSO-TYPE = RECONFIRM | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | DSO-LENGTH (number of octets in DSO-DATA) | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ \ \ NAME \ \ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | | TYPE | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ > DSO-DATA | CLASS | | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | \ RDATA \ / @@ -1127,24 +1120,23 @@ If a client has performed operations on this session that it would not want lost (like DNS updates) then the client SHOULD do an orderly disconnect, sending a TLS close_notify followed by a TCP FIN. (In the BSD Sockets API, sending a TCP FIN is achieved by calling "shutdown(s,SHUT_WR)" and keeping the socket open until all remaining data has been read from it.) 7. Security Considerations The Strict Privacy Usage Profile for DNS over TLS is strongly - recommended for DNS Push Notifications as defined in "Authentication - and (D)TLS Profile for DNS-over-(D)TLS" - [I-D.ietf-dprive-dtls-and-tls-profiles]. The Opportunistic Privacy - Usage Profile is permissible as a way to support incremental + recommended for DNS Push Notifications as defined in "Usage Profiles + for DNS over TLS and DNS over DTLS" [RFC8310]. The Opportunistic + Privacy Usage Profile is permissible as a way to support incremental deployment of security capabilities. Cleartext connections for DNS Push Notifications are not permissible. 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 @@ -1181,84 +1173,92 @@ record. This associates the target's name and port number with a trusted TLS certificate [RFC7673]. This procedure uses the TLS Sever Name Indication (SNI) extension [RFC6066] to inform the server of the name the client has authenticated through the use of TLSA records. Therefore, if the SRV record passes DNSSEC validation and a TLSA record matching the target name is useable, an SNI extension must be used for the target name to ensure the client is connecting to the server it has authenticated. If the target name does not have a usable TLSA record, then the use of the SNI extension is optional. - See Authentication and (D)TLS Profile for DNS-over-(D)TLS - [I-D.ietf-dprive-dtls-and-tls-profiles] for more information on - authenticating domain names. Also note that a DNS Push server is an - authoritative server and a DNS Push client is a standard DNS client. - While the terminology in Authentication and (D)TLS Profile for DNS- - over-(D)TLS [I-D.ietf-dprive-dtls-and-tls-profiles] explicitly states - it does not apply to authoritative servers, it does in this case - apply to DNS Push Notification clients and servers. + See Usage Profiles for DNS over TLS and DNS over DTLS [RFC8310] for + more information on authenticating domain names. Also note that a + DNS Push server is an authoritative server and a DNS Push client is a + standard DNS client. While the terminology in Usage Profiles for DNS + over TLS and DNS over DTLS [RFC8310] explicitly states it does not + apply to authoritative servers, it does in this case apply to DNS + Push Notification clients and servers. 7.3. TLS Compression In order to reduce the chances of compression-related attacks, TLS- level compression SHOULD be disabled when using TLS versions 1.2 and - earlier. In the draft version of TLS 1.3 [I-D.ietf-tls-tls13], TLS- - level compression has been removed completely. + earlier. In TLS 1.3 [RFC8446], TLS-level compression has been + removed completely. 7.4. TLS Session Resumption TLS Session Resumption is permissible on DNS Push Notification servers. The server may keep TLS state with Session IDs [RFC5246] or operate in stateless mode by sending a Session Ticket [RFC5077] to the client for it to store. However, once the DSO session is closed, any existing subscriptions will be dropped. 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 allows a new 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 the service name: "_dns-push-tls._tcp". - It is only applicable for the TCP protocol. - This name is to be published in the IANA Registry Service Types - [RFC6335][ST]. + 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 four DNS Stateful Operations TLV types: - SUBSCRIBE with (tentative) value 0x40 (64), PUSH with (tentative) - value 0x41 (65), UNSUBSCRIBE with (tentative) value 0x42 (66), and - RECONFIRM with (tentative) value 0x43 (67). + This document also defines four new DNS Stateful Operation TLV types + to be recorded in the IANA DSO Type Code Registry. + + +----------------------------+----------------------+---------------+ + | Name | Value | Definition | + +----------------------------+----------------------+---------------+ + | DNS Push Notifcation | "_dns-push-tls._tcp" | Section 6.1 | + | Service Type | | | + | SUBSCRIBE | TBA (tentatively | Section 6.2 | + | | 0x40) | | + | PUSH | TBA (tentatively | Section 6.3.1 | + | | 0x41) | | + | UNSUBSCRIBE | TBA (tentatively | Section 6.4 | + | | 0x42) | | + | RECONFIRM | TBA (tentatively | Section 6.5.1 | + | | 0x43) | | + +----------------------------+----------------------+---------------+ + + Table 1: IANA Assignments 9. Acknowledgements The authors would like to thank Kiren Sekar and Marc Krochmal for previous work completed in this field. This draft has been improved due to comments from Ran Atkinson, Tim Chown, Mark Delany, Ralph Droms, Bernie Volz, Jan Komissar, Manju Shankar Rao, Markus Stenberg, Dave Thaler, Soraia Zlatkovic, Sara Dickinson, and Andrew Sullivan. 10. References 10.1. Normative References [DSO] Bellis, R., Cheshire, S., Dickinson, J., Dickinson, S., - Mankin, A., and T. Pusateri, "DNS Stateful Operations", - draft-ietf-dnsop-session-signal-05 (work in progress), - January 2018. - - [I-D.ietf-tls-tls13] - Rescorla, E., "The Transport Layer Security (TLS) Protocol - Version 1.3", draft-ietf-tls-tls13-26 (work in progress), - March 2018. + Lemon, T., and T. Pusateri, "DNS Stateful Operations", + draft-ietf-dnsop-session-signal-14 (work in progress), + August 2018. [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", @@ -1317,42 +1317,40 @@ [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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . + [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol + Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, + . + [ST] "Service Name and Transport Protocol Port Number Registry", . 10.2. Informative References [DisProx] Cheshire, S., "Discovery Proxy for Multicast DNS-Based Service Discovery", draft-ietf-dnssd-hybrid-08 (work in progress), March 2018. [I-D.dukkipati-tcpm-tcp-loss-probe] Dukkipati, N., Cardwell, N., Cheng, Y., and M. Mathis, "Tail Loss Probe (TLP): An Algorithm for Fast Recovery of Tail Losses", draft-dukkipati-tcpm-tcp-loss-probe-01 (work in progress), February 2013. - [I-D.ietf-dprive-dtls-and-tls-profiles] - Dickinson, S., Gillmor, D., and T. Reddy, "Usage and - (D)TLS Profiles for DNS-over-(D)TLS", draft-ietf-dprive- - dtls-and-tls-profiles-11 (work in progress), September - 2017. - [LLQ] Sekar, K., "DNS Long-Lived Queries", draft-sekar-dns- llq-01 (work in progress), August 2006. [obs] "Observer Pattern", . [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998, . @@ -1400,29 +1398,34 @@ [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", RFC 8010, + 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", RFC 8011, + 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, + . + [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 Tom Pusateri