idnits 2.17.1 draft-ietf-webpush-protocol-10.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (September 26, 2016) is 2768 days in the past. Is this intentional? 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'CAP-URI' ** Obsolete normative reference: RFC 2818 (Obsoleted by RFC 9110) ** Obsolete normative reference: RFC 5226 (Obsoleted by RFC 8126) ** Obsolete normative reference: RFC 5988 (Obsoleted by RFC 8288) ** Obsolete normative reference: RFC 7230 (Obsoleted by RFC 9110, RFC 9112) ** Obsolete normative reference: RFC 7231 (Obsoleted by RFC 9110) ** Obsolete normative reference: RFC 7232 (Obsoleted by RFC 9110) ** Obsolete normative reference: RFC 7525 (Obsoleted by RFC 9325) ** Obsolete normative reference: RFC 7540 (Obsoleted by RFC 9113) == Outdated reference: A later version (-09) exists of draft-ietf-webpush-encryption-03 == Outdated reference: A later version (-04) exists of draft-ietf-webpush-vapid-01 Summary: 8 errors (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 WEBPUSH M. Thomson 3 Internet-Draft Mozilla 4 Intended status: Standards Track E. Damaggio 5 Expires: March 30, 2017 B. Raymor, Ed. 6 Microsoft 7 September 26, 2016 9 Generic Event Delivery Using HTTP Push 10 draft-ietf-webpush-protocol-10 12 Abstract 14 A simple protocol for the delivery of real-time events to user agents 15 is described. This scheme uses HTTP/2 server push. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at http://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on March 30, 2017. 34 Copyright Notice 36 Copyright (c) 2016 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 52 1.1. Conventions and Terminology . . . . . . . . . . . . . . . 4 53 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 54 2.1. HTTP Resources . . . . . . . . . . . . . . . . . . . . . 6 55 3. Connecting to the Push Service . . . . . . . . . . . . . . . 7 56 4. Subscribing for Push Messages . . . . . . . . . . . . . . . . 7 57 4.1. Collecting Subscriptions into Sets . . . . . . . . . . . 8 58 5. Requesting Push Message Delivery . . . . . . . . . . . . . . 9 59 5.1. Requesting Push Message Receipts . . . . . . . . . . . . 9 60 5.2. Push Message Time-To-Live . . . . . . . . . . . . . . . . 11 61 5.3. Push Message Urgency . . . . . . . . . . . . . . . . . . 12 62 5.4. Replacing Push Messages . . . . . . . . . . . . . . . . . 13 63 6. Receiving Push Messages for a Subscription . . . . . . . . . 14 64 6.1. Receiving Push Messages for a Subscription Set . . . . . 16 65 6.2. Acknowledging Push Messages . . . . . . . . . . . . . . . 18 66 6.3. Receiving Push Message Receipts . . . . . . . . . . . . . 19 67 7. Operational Considerations . . . . . . . . . . . . . . . . . 20 68 7.1. Load Management . . . . . . . . . . . . . . . . . . . . . 20 69 7.2. Push Message Expiration . . . . . . . . . . . . . . . . . 20 70 7.3. Subscription Expiration . . . . . . . . . . . . . . . . . 21 71 7.3.1. Subscription Set Expiration . . . . . . . . . . . . . 22 72 7.4. Implications for Application Reliability . . . . . . . . 22 73 7.5. Subscription Sets and Concurrent HTTP/2 streams . . . . . 22 74 8. Security Considerations . . . . . . . . . . . . . . . . . . . 23 75 8.1. Confidentiality from Push Service Access . . . . . . . . 23 76 8.2. Privacy Considerations . . . . . . . . . . . . . . . . . 23 77 8.3. Authorization . . . . . . . . . . . . . . . . . . . . . . 24 78 8.4. Denial of Service Considerations . . . . . . . . . . . . 25 79 8.5. Logging Risks . . . . . . . . . . . . . . . . . . . . . . 26 80 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 81 9.1. Header Field Registrations . . . . . . . . . . . . . . . 26 82 9.2. Link Relation URNs . . . . . . . . . . . . . . . . . . . 26 83 9.3. Service Name and Port Number Registration . . . . . . . . 28 84 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 28 85 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 29 86 11.1. Normative References . . . . . . . . . . . . . . . . . . 29 87 11.2. Informative References . . . . . . . . . . . . . . . . . 30 88 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 31 89 A.1. Since draft-ietf-webpush-protocol-00 . . . . . . . . . . 31 90 A.2. Since draft-ietf-webpush-protocol-01 . . . . . . . . . . 31 91 A.3. Since draft-ietf-webpush-protocol-02 . . . . . . . . . . 31 92 A.4. Since draft-ietf-webpush-protocol-03 . . . . . . . . . . 31 93 A.5. Since draft-ietf-webpush-protocol-04 . . . . . . . . . . 31 94 A.6. Since draft-ietf-webpush-protocol-05 . . . . . . . . . . 32 95 A.7. Since draft-ietf-webpush-protocol-06 . . . . . . . . . . 32 96 A.8. Since draft-ietf-webpush-protocol-07 . . . . . . . . . . 32 97 A.9. Since draft-ietf-webpush-protocol-08 . . . . . . . . . . 32 98 A.10. Since draft-ietf-webpush-protocol-09 . . . . . . . . . . 32 99 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 101 1. Introduction 103 Many applications on mobile and embedded devices require continuous 104 access to network communications so that real-time events - such as 105 incoming calls or messages - can be delivered (or "pushed") in a 106 timely fashion. These devices typically have limited power reserves, 107 so finding more efficient ways to serve application requirements 108 greatly benefits the application ecosystem. 110 One significant contributor to power usage is the radio. Radio 111 communications consume a significant portion of the energy budget on 112 a wireless device. 114 Uncoordinated use of persistent connections or sessions from multiple 115 applications can contribute to unnecessary use of the device radio, 116 since each independent session can incur its own overhead. In 117 particular, keep alive traffic used to ensure that middleboxes do not 118 prematurely time out sessions, can result in significant waste. 119 Maintenance traffic tends to dominate over the long term, since 120 events are relatively rare. 122 Consolidating all real-time events into a single session ensures more 123 efficient use of network and radio resources. A single service 124 consolidates all events, distributing those events to applications as 125 they arrive. This requires just one session, avoiding duplicated 126 overhead costs. 128 The W3C Push API [API] describes an API that enables the use of a 129 consolidated push service from web applications. This document 130 expands on that work by describing a protocol that can be used to: 132 o request the delivery of a push message to a user agent, 134 o create new push message delivery subscriptions, and 136 o monitor for new push messages. 138 A standardized method of event delivery is particularly important for 139 the W3C Push API, where application servers might need to use 140 multiple push services. The subscription, management and monitoring 141 functions are currently fulfilled by proprietary protocols; these are 142 adequate, but do not offer any of the advantages that standardization 143 affords. 145 This document intentionally does not describe how a push service is 146 discovered. Discovery of push services is left for future efforts, 147 if it turns out to be necessary at all. User agents are expected to 148 be configured with a URL for a push service. 150 1.1. Conventions and Terminology 152 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 153 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 154 document are to be interpreted as described in [RFC2119]. 156 This document defines the following terms: 158 application: Both the sender and ultimate consumer of push messages. 159 Many applications have components that are run on a user agent and 160 other components that run on servers. 162 application server: The component of an application that usually 163 runs on a server and requests the delivery of a push message. 165 push message subscription: A message delivery context that is 166 established between the user agent and the push service and shared 167 with the application server. All push messages are associated 168 with a push message subscription. 170 push message subscription set: A message delivery context that is 171 established between the user agent and the push service that 172 collects multiple push message subscriptions into a set. 174 push message: A message sent from an application server to a user 175 agent via a push service. 177 push message receipt: A message delivery confirmation sent from the 178 push service to the application server. 180 push service: A service that delivers push messages to user agents. 182 user agent: A device and software that is the recipient of push 183 messages. 185 Examples in this document use the HTTP/1.1 message format [RFC7230]. 186 Many of the exchanges can be completed using HTTP/1.1. Where HTTP/2 187 is necessary, the more verbose frame format from [RFC7540] is used. 189 Examples do not include specific methods for push message encryption 190 or application server authentication because the protocol does not 191 define a mandatory system. The examples in Voluntary Application 192 Server Identification [I-D.ietf-webpush-vapid] and Message Encryption 193 for WebPush [I-D.ietf-webpush-encryption] demonstrate the approach 194 adopted by the W3C Push API [API] for its requirements. 196 2. Overview 198 A general model for push services includes three basic actors: a user 199 agent, a push service, and an application (server). 201 +-------+ +--------------+ +-------------+ 202 | UA | | Push Service | | Application | 203 +-------+ +--------------+ +-------------+ 204 | | | 205 | Subscribe | | 206 |--------------------->| | 207 | Monitor | | 208 |<====================>| | 209 | | | 210 | Distribute Push Resource | 211 |-------------------------------------------->| 212 | | | 213 : : : 214 | | Push Message | 215 | Push Message |<---------------------| 216 |<---------------------| | 217 | | | 219 At the very beginning of the process, a new message subscription is 220 created by the user agent and then distributed to its application 221 server. This subscription is the basis of all future interactions 222 between the actors. A subscription is used by the application server 223 to send messages to the push service for being delivered to the user 224 agent. It is used by the user agent to monitor the push service for 225 any incoming message. 227 To offer more control for authorization, a message subscription is 228 modeled as two resources with different capabilities: 230 o A subscription resource is used to receive messages from a 231 subscription and to delete a subscription. It is private to the 232 user agent. 234 o A push resource is used to send messages to a subscription. It is 235 public and shared by the user agent with its application server. 237 It is expected that a unique subscription will be distributed to each 238 application; however, there are no inherent cardinality constraints 239 in the protocol. Multiple subscriptions might be created for the 240 same application, or multiple applications could use the same 241 subscription. Note however that sharing subscriptions has security 242 and privacy implications. 244 Subscriptions have a limited lifetime. They can also be terminated 245 by either the push service or user agent at any time. User agents 246 and application servers must be prepared to manage changes in 247 subscription state. 249 2.1. HTTP Resources 251 This protocol uses HTTP resources [RFC7230] and link relations 252 [RFC5988]. The following resources are defined: 254 push service: This resource is used to create push message 255 subscriptions (Section 4). A URL for the push service is 256 configured into user agents. 258 push message subscription: This resource provides read and delete 259 access for a message subscription. A user agent receives push 260 messages (Section 6) using a push message subscription. Every 261 push message subscription has exactly one push resource associated 262 with it. 264 push message subscription set: This resource provides read and 265 delete access for a collection of push message subscriptions. A 266 user agent receives push messages (Section 6.1) for all the push 267 message subscriptions in the set. A link relation of type 268 "urn:ietf:params:push:set" identifies a push message subscription 269 set. 271 push: An application server requests the delivery (Section 5) of a 272 push message using a push resource. A link relation of type 273 "urn:ietf:params:push" identifies a push resource. 275 push message: The push service creates a push message resource to 276 identify push messages that have been accepted for delivery 277 (Section 5). The push message resource is also deleted by the 278 user agent to acknowledge receipt (Section 6.2) of a push message. 280 receipt subscription: An application server receives delivery 281 confirmations (Section 5.1) for push messages using a receipt 282 subscription. A link relation of type 283 "urn:ietf:params:push:receipt" identifies a receipt subscription. 285 3. Connecting to the Push Service 287 The push service shares the same default port number (443/TCP) with 288 HTTPS, but MAY also advertise the IANA allocated TCP System Port 1001 289 using HTTP alternative services [RFC7838]. 291 While the default port (443) offers broad reachability 292 characteristics, it is most often used for web browsing scenarios 293 with a lower idle timeout than other ports configured in middleboxes. 294 For webpush scenarios, this would contribute to unnecessary radio 295 communications to maintain the connection on battery-powered devices. 297 Advertising the alternate port (1001) allows middleboxes to optimize 298 idle timeouts for connections specific to push scenarios with the 299 expectation that data exchange will be infrequent. 301 Middleboxes SHOULD comply with REQ-5 in [RFC5382] which requires that 302 "the value of the 'established connection idle-timeout' MUST NOT be 303 less than 2 hours 4 minutes". 305 4. Subscribing for Push Messages 307 A user agent sends a POST request to its configured push service 308 resource to create a new subscription. 310 POST /subscribe HTTP/1.1 311 Host: push.example.net 313 A 201 (Created) response indicates that the a push subscription was 314 created. A URI for the push message subscription resource that was 315 created in response to the request MUST be returned in the Location 316 header field. 318 The push service MUST provide a URI for the push resource 319 corresponding to the push message subscription in a link relation of 320 type "urn:ietf:params:push". 322 An application-specific method is used to distribute the push URI to 323 the application server. Confidentiality protection and application 324 server authentication MUST be used to ensure that this URI is not 325 disclosed to unauthorized recipients (Section 8.3). 327 HTTP/1.1 201 Created 328 Date: Thu, 11 Dec 2014 23:56:52 GMT 329 Link: ; 330 rel="urn:ietf:params:push" 331 Link: ; 332 rel="urn:ietf:params:push:set" 333 Location: https://push.example.net/subscription/LBhhw0OohO-Wl4Oi971UG 335 4.1. Collecting Subscriptions into Sets 337 Collecting multiple push message subscriptions into a subscription 338 set can represent a significant efficiency improvement for push 339 services and user agents. The push service MAY provide a URI for a 340 subscription set resource in a link relation of type 341 "urn:ietf:params:push:set". 343 When a subscription set is returned in a push message subscription 344 response, the user agent SHOULD include this subscription set in a 345 link relation of type "urn:ietf:params:push:set" in subsequent 346 requests to create new push message subscriptions. 348 A user agent MAY omit the subscription set if it is unable to receive 349 push messages in an aggregated way for the lifetime of the 350 subscription. This might be necessary if the user agent is 351 monitoring subscriptions on behalf of other push message receivers. 353 POST /subscribe HTTP/1.1 354 Host: push.example.net 355 Link: ; 356 rel="urn:ietf:params:push:set" 358 The push service SHOULD return the same subscription set in its 359 response, although it MAY return a new subscription set if it is 360 unable to reuse the one provided by the user agent. 362 HTTP/1.1 201 Created 363 Date: Thu, 11 Dec 2014 23:56:52 GMT 364 Link: ; 365 rel="urn:ietf:params:push" 366 Link: ; 367 rel="urn:ietf:params:push:set" 368 Location: https://push.example.net/subscription/i-nQ3A9Zm4kgSWg8_ZijV 370 A push service MUST return a 400 (Bad Request) status code for 371 requests which contain an invalid subscription set. A push service 372 MAY return a 429 (Too Many Requests) status code [RFC6585] to reject 373 requests which omit a subscription set. 375 How a push service detects that requests originate from the same user 376 agent is implementation-specific but could take ambient information 377 into consideration, such as the TLS connection, source IP address and 378 port. Implementers are reminded that some heuristics can produce 379 false positives and cause requests to be rejected incorrectly. 381 5. Requesting Push Message Delivery 383 An application server requests the delivery of a push message by 384 sending a HTTP POST request to a push resource distributed to the 385 application server by a user agent. The content of the push message 386 is included in the body of the request. 388 POST /push/JzLQ3raZJfFBR0aqvOMsLrt54w4rJUsV HTTP/1.1 389 Host: push.example.net 390 TTL: 15 391 Content-Type: text/plain;charset=utf8 392 Content-Length: 36 394 iChYuI3jMzt3ir20P8r_jgRR-dSuN182x7iB 396 A 201 (Created) response indicates that the push message was 397 accepted. A URI for the push message resource that was created in 398 response to the request MUST be returned in the Location header 399 field. This does not indicate that the message was delivered to the 400 user agent. 402 HTTP/1.1 201 Created 403 Date: Thu, 11 Dec 2014 23:56:55 GMT 404 Location: https://push.example.net/message/qDIYHNcfAIPP_5ITvURr-d6BGt 406 5.1. Requesting Push Message Receipts 408 An application server can include the Prefer header field [RFC7240] 409 with the "respond-async" preference to request confirmation from the 410 push service when a push message is delivered and then acknowledged 411 by the user agent. The push service MUST support delivery 412 confirmations. 414 POST /push/JzLQ3raZJfFBR0aqvOMsLrt54w4rJUsV HTTP/1.1 415 Host: push.example.net 416 Prefer: respond-async 417 TTL: 15 418 Content-Type: text/plain;charset=utf8 419 Content-Length: 36 421 iChYuI3jMzt3ir20P8r_jgRR-dSuN182x7iB 423 When the push service accepts the message for delivery with 424 confirmation, it MUST return a 202 (Accepted) response. A URI for 425 the push message resource that was created in response to the request 426 MUST be returned in the Location header field. The push service MUST 427 also provide a URI for the receipt subscription resource in a link 428 relation of type "urn:ietf:params:push:receipt". 430 HTTP/1.1 202 Accepted 431 Date: Thu, 11 Dec 2014 23:56:55 GMT 432 Link: ; 433 rel="urn:ietf:params:push:receipt" 434 Location: https://push.example.net/message/qDIYHNcfAIPP_5ITvURr-d6BGt 436 For subsequent receipt requests to the same origin [RFC6454], the 437 application server SHOULD include the returned receipt subscription 438 in a link relation of type "urn:ietf:params:push:receipt". This 439 gives the push service an option to aggregate the receipts. The push 440 service SHOULD return the same receipt subscription in its response, 441 although it MAY return a new receipt subscription if it is unable to 442 reuse the one provided by the application server. 444 An application server MAY omit the receipt subscription if it is 445 unable to receive receipts in an aggregated way for the lifetime of 446 the receipt subscription. This might be necessary if the application 447 server is monitoring receipt subscriptions on the behalf of other 448 push message senders. 450 A push service MUST return a 400 (Bad Request) status code for 451 requests which contain an invalid receipt subscription. If a push 452 service wishes to limit the number of receipt subscriptions that it 453 maintains, it MAY return a 429 (Too Many Requests) status code 454 [RFC6585] to reject receipt requests which omit a receipt 455 subscription. 457 5.2. Push Message Time-To-Live 459 A push service can improve the reliability of push message delivery 460 considerably by storing push messages for a period. User agents are 461 often only intermittently connected, and so benefit from having short 462 term message storage at the push service. 464 Delaying delivery might also be used to batch communication with the 465 user agent, thereby conserving radio resources. 467 Some push messages are not useful once a certain period of time 468 elapses. Delivery of messages after they have ceased to be relevant 469 is wasteful. For example, if the push message contains a call 470 notification, receiving a message after the caller has abandoned the 471 call is of no value; the application at the user agent is forced to 472 suppress the message so that it does not generate a useless alert. 474 An application server MUST include the TTL (Time-To-Live) header 475 field in its request for push message delivery. The TTL header field 476 contains a value in seconds that suggests how long a push message is 477 retained by the push service. 479 TTL = 1*DIGIT 481 A push service MUST return a 400 (Bad Request) status code in 482 response to requests that omit the TTL header field. 484 A push service MAY retain a push message for a shorter duration than 485 requested. It indicates this by returning a TTL header field in its 486 response with the actual TTL. This TTL value MUST be less than or 487 equal to the value provided by the application server. 489 Once the TTL period elapses, the push service MUST NOT attempt to 490 deliver the push message to the user agent. A push service might 491 adjust the TTL value to account for time accounting errors in 492 processing. For instance, distributing a push message within a 493 server cluster might accrue errors due to clock skew or propagation 494 delays. 496 A push service is not obligated to account for time spent by the 497 application server in sending a push message to the push service, or 498 delays incurred while sending a push message to the user agent. An 499 application server needs to account for transit delays in selecting a 500 TTL header field value. 502 A Push message with a zero TTL is immediately delivered if the user 503 agent is available to receive the message. After delivery, the push 504 service is permitted to immediately remove a push message with a zero 505 TTL. This might occur before the user agent acknowledges receipt of 506 the message by performing a HTTP DELETE on the push message resource. 507 Consequently, an application server cannot rely on receiving 508 acknowledgement receipts for zero TTL push messages. 510 If the user agent is unavailable, a push message with a zero TTL 511 expires and is never delivered. 513 5.3. Push Message Urgency 515 For a device that is battery-powered, it is often critical that it 516 remains dormant for extended periods. Radio communication in 517 particular consumes significant power and limits the length of time 518 that the device can operate. 520 To avoid consuming resources to receive trivial messages, it is 521 helpful if an application server can communicate the urgency of a 522 message and if the user agent can request that the push server only 523 forward messages of a specific urgency. 525 An application server MAY include an Urgency header field in its 526 request for push message delivery. This header field indicates the 527 message urgency. The push service MUST NOT forward the Urgency 528 header field to the user agent. A push message without the Urgency 529 header field defaults to a value of "normal". 531 A user agent MAY include the Urgency header field when monitoring for 532 push messages to indicate the lowest urgency of push messages that it 533 is willing to receive. A push service MUST NOT deliver push messages 534 with lower urgency than the value indicated by the user agent in its 535 monitoring request. Push messages of any urgency are delivered to a 536 user agent that does not include an Urgency header field when 537 monitoring for messages. 539 Urgency = 1#(urgency-option) 540 urgency-option = ("very-low" / "low" / "normal" / "high") 541 In order of increasing urgency: 543 +----------+-----------------------------+--------------------------+ 544 | Urgency | Device State | Example Application | 545 | | | Scenario | 546 +----------+-----------------------------+--------------------------+ 547 | very-low | On power and wifi | Advertisements | 548 | low | On either power or wifi | Topic updates | 549 | normal | On neither power nor wifi | Chat or Calendar Message | 550 | high | Low battery | Incoming phone call or | 551 | | | time-sensitive alert | 552 +----------+-----------------------------+--------------------------+ 554 Table 1: Illustrative Urgency Values 556 Multiple values for the Urgency header field MUST NOT be included in 557 requests; otherwise, the push service MUST return a 400 (Bad Request) 558 status code. 560 5.4. Replacing Push Messages 562 A push message that has been stored by the push service can be 563 replaced with new content. If the user agent is offline during the 564 time that the push messages are sent, updating a push message avoids 565 the situation where outdated or redundant messages are sent to the 566 user agent. 568 Only push messages that have been assigned a topic can be replaced. 569 A push message with a topic replaces any outstanding push message 570 with an identical topic. 572 A push message topic is a string carried in a Topic header field. A 573 topic is used to correlate push messages sent to the same 574 subscription and does not convey any other semantics. 576 The grammar for the Topic header field uses the "token" rule defined 577 in [RFC7230]. 579 Topic = token 581 For use with this protocol, the Topic header field MUST be restricted 582 to no more than 32 characters from the URL and filename safe Base 64 583 alphabet [RFC4648]. A push service that receives a request with a 584 Topic header field that does not meet these constraints MUST return a 585 400 (Bad Request) status code to the application server. 587 A push message replacement request creates a new push message 588 resource and simultaneously deletes any existing message resource 589 that has a matching topic. If an attempt was made to deliver the 590 deleted push message, an acknowledgment could arrive at the push 591 service after the push message has been replaced. Delivery receipts 592 for such deleted messages SHOULD be suppressed. 594 The replacement request also replaces the stored TTL, Urgency, and 595 any receipt subscription associated with the previous message in the 596 matching topic. 598 A push message with a topic that is not shared by an outstanding 599 message to the same subscription is stored or delivered as normal. 601 For example, the following message could cause an existing message to 602 be replaced: 604 POST /push/JzLQ3raZJfFBR0aqvOMsLrt54w4rJUsV HTTP/1.1 605 Host: push.example.net 606 TTL: 600 607 Topic: upd 608 Content-Type: text/plain;charset=utf8 609 Content-Length: 36 611 ZuHSZPKa2b1jtOKLGpWrcrn8cNqt0iVQyroF 613 If the push service identifies an outstanding push message with a 614 topic of "upd", then that message resource is deleted. A 201 615 (Created) response indicates that the push message replacement was 616 accepted. A URI for the new push message resource that was created 617 in response to the request is included in the Location header field. 619 HTTP/1.1 201 Created 620 Date: Thu, 11 Dec 2014 23:57:02 GMT 621 Location: https://push.example.net/message/qDIYHNcfAIPP_5ITvURr-d6BGt 623 The value of the Topic header field MUST NOT be forwarded to user 624 agents. Its value is neither encrypted nor authenticated. 626 6. Receiving Push Messages for a Subscription 628 A user agent requests the delivery of new push messages by making a 629 GET request to a push message subscription resource. The push 630 service does not respond to this request, it instead uses HTTP/2 631 server push [RFC7540] to send the contents of push messages as they 632 are sent by application servers. 634 A user agent MAY include a Urgency header field in its request. The 635 push service MUST NOT deliver messages with lower urgency than the 636 value of the header field as defined in the 637 Illustrative Urgency Values. 639 Each push message is pushed as the response to a synthesized GET 640 request sent in a PUSH_PROMISE. This GET request is made to the push 641 message resource that was created by the push service when the 642 application server requested message delivery. The response headers 643 SHOULD provide a URI for the push resource corresponding to the push 644 message subscription in a link relation of type 645 "urn:ietf:params:push". The response body is the entity body from 646 the most recent request sent to the push resource by the application 647 server. 649 The following example request is made over HTTP/2. 651 HEADERS [stream 7] +END_STREAM +END_HEADERS 652 :method = GET 653 :path = /subscription/LBhhw0OohO-Wl4Oi971UG 654 :authority = push.example.net 656 The push service permits the request to remain outstanding. When a 657 push message is sent by an application server, a server push is 658 generated in association with the initial request. The response for 659 the server push includes the push message. 661 PUSH_PROMISE [stream 7; promised stream 4] +END_HEADERS 662 :method = GET 663 :path = /message/qDIYHNcfAIPP_5ITvURr-d6BGt 664 :authority = push.example.net 666 HEADERS [stream 4] +END_HEADERS 667 :status = 200 668 date = Thu, 11 Dec 2014 23:56:56 GMT 669 last-modified = Thu, 11 Dec 2014 23:56:55 GMT 670 cache-control = private 671 :link = ; 672 rel="urn:ietf:params:push" 673 content-type = text/plain;charset=utf8 674 content-length = 36 676 DATA [stream 4] +END_STREAM 677 iChYuI3jMzt3ir20P8r_jgRR-dSuN182x7iB 679 HEADERS [stream 7] +END_STREAM +END_HEADERS 680 :status = 200 682 A user agent can also request the contents of the push message 683 subscription resource immediately by including a Prefer header field 684 [RFC7240] with a "wait" preference set to "0". In response to this 685 request, the push service MUST generate a server push for all push 686 messages that have not yet been delivered. 688 A 204 (No Content) status code with no associated server pushes 689 indicates that no messages are presently available. This could be 690 because push messages have expired. 692 6.1. Receiving Push Messages for a Subscription Set 694 There are minor differences between receiving push messages for a 695 subscription and a subscription set. If a subscription set is 696 available, the user agent SHOULD use the subscription set to monitor 697 for push messages rather than individual push message subscriptions. 699 A user agent requests the delivery of new push messages for a 700 collection of push message subscriptions by making a GET request to a 701 push message subscription set resource. The push service does not 702 respond to this request, it instead uses HTTP/2 server push [RFC7540] 703 to send the contents of push messages as they are sent by application 704 servers. 706 A user agent MAY include a Urgency header field in its request. The 707 push service MUST NOT deliver messages with lower urgency than the 708 value of the header field as defined in the 709 Illustrative Urgency Values. 711 Each push message is pushed as the response to a synthesized GET 712 request sent in a PUSH_PROMISE. This GET request is made to the push 713 message resource that was created by the push service when the 714 application server requested message delivery. The synthetic request 715 MUST provide a URI for the push resource corresponding to the push 716 message subscription in a link relation of type 717 "urn:ietf:params:push". This enables the user agent to differentiate 718 the source of the message. The response body is the entity body from 719 the most recent request sent to the push resource by an application 720 server. 722 The following example request is made over HTTP/2. 724 HEADERS [stream 7] +END_STREAM +END_HEADERS 725 :method = GET 726 :path = /subscription-set/4UXwi2Rd7jGS7gp5cuutF8ZldnEuvbOy 727 :authority = push.example.net 729 The push service permits the request to remain outstanding. When a 730 push message is sent by an application server, a server push is 731 generated in association with the initial request. The server push's 732 response includes the push message. 734 PUSH_PROMISE [stream 7; promised stream 4] +END_HEADERS 735 :method = GET 736 :path = /message/qDIYHNcfAIPP_5ITvURr-d6BGt 737 :authority = push.example.net 738 :link = ; 739 rel="urn:ietf:params:push" 741 HEADERS [stream 4] +END_HEADERS 742 :status = 200 743 date = Thu, 11 Dec 2014 23:56:56 GMT 744 last-modified = Thu, 11 Dec 2014 23:56:55 GMT 745 cache-control = private 746 content-type = text/plain;charset=utf8 747 content-length = 36 749 DATA [stream 4] +END_STREAM 750 iChYuI3jMzt3ir20P8r_jgRR-dSuN182x7iB 752 HEADERS [stream 7] +END_STREAM +END_HEADERS 753 :status = 200 755 A user agent can request the contents of the push message 756 subscription set resource immediately by including a Prefer header 757 field [RFC7240] with a "wait" preference set to "0". In response to 758 this request, the push service MUST generate a server push for all 759 push messages that have not yet been delivered. 761 A 204 (No Content) status code with no associated server pushes 762 indicates that no messages are presently available. This could be 763 because push messages have expired. 765 6.2. Acknowledging Push Messages 767 To ensure that a push message is properly delivered to the user agent 768 at least once, the user agent MUST acknowledge receipt of the message 769 by performing a HTTP DELETE on the push message resource. 771 DELETE /message/qDIYHNcfAIPP_5ITvURr-d6BGt HTTP/1.1 772 Host: push.example.net 773 If the push service receives the acknowledgement and the application 774 has requested a delivery receipt, the push service MUST return a 204 775 (No Content) response to the application server monitoring the 776 receipt subscription. 778 If the push service does not receive the acknowledgement within a 779 reasonable amount of time, then the message is considered to be not 780 yet delivered. The push service SHOULD continue to retry delivery of 781 the message until its advertised expiration. 783 The push service MAY cease to retry delivery of the message prior to 784 its advertised expiration due to scenarios such as an unresponsive 785 user agent or operational constraints. If the application has 786 requested a delivery receipt, then the push service MUST return a 410 787 (Gone) response to the application server monitoring the receipt 788 subscription. 790 6.3. Receiving Push Message Receipts 792 The application server requests the delivery of receipts from the 793 push service by making a HTTP GET request to the receipt subscription 794 resource. The push service does not respond to this request, it 795 instead uses HTTP/2 server push [RFC7540] to send push receipts when 796 messages are acknowledged (Section 6.2) by the user agent. 798 Each receipt is pushed as the response to a synthesized GET request 799 sent in a PUSH_PROMISE. This GET request is made to the same push 800 message resource that was created by the push service when the 801 application server requested message delivery. The response includes 802 a status code indicating the result of the message delivery and 803 carries no data. 805 The following example request is made over HTTP/2. 807 HEADERS [stream 13] +END_STREAM +END_HEADERS 808 :method = GET 809 :path = /receipt-subscription/3ZtI4YVNBnUUZhuoChl6omUvG4ZM 810 :authority = push.example.net 812 The push service permits the request to remain outstanding. When the 813 user agent acknowledges the message, the push service pushes a 814 delivery receipt to the application server. A 204 (No Content) 815 status code confirms that the message was delivered and acknowledged. 817 PUSH_PROMISE [stream 13; promised stream 82] +END_HEADERS 818 :method = GET 819 :path = /message/qDIYHNcfAIPP_5ITvURr-d6BGt 820 :authority = push.example.net 822 HEADERS [stream 82] +END_STREAM 823 +END_HEADERS 824 :status = 204 825 date = Thu, 11 Dec 2014 23:56:56 GMT 827 If the user agent fails to acknowledge the receipt of the push 828 message and the push service ceases to retry delivery of the message 829 prior to its advertised expiration, then the push service MUST push a 830 failure response with a status code of 410 (Gone). 832 7. Operational Considerations 834 7.1. Load Management 836 A push service is likely to have to maintain a very large number of 837 open TCP connections. Effective management of those connections can 838 depend on being able to move connections between server instances. 840 A user agent MUST support the 307 (Temporary Redirect) status code 841 [RFC7231], which can be used by a push service to redistribute load 842 at the time that a new subscription is requested. 844 A server that wishes to redistribute load can do so using HTTP 845 alternative services [RFC7838]. HTTP alternative services allows for 846 redistribution of load while maintaining the same URIs for various 847 resources. A user agent can ensure a graceful transition by using 848 the GOAWAY frame once it has established a replacement connection. 850 7.2. Push Message Expiration 852 Storage of push messages based on the TTL header field comprises a 853 potentially significant amount of storage for a push service. A push 854 service is not obligated to store messages indefinitely. A push 855 service is able to indicate how long it intends to retain a message 856 to an application server using the TTL header field (Section 5.2). 858 A user agent that does not actively monitor for push messages will 859 not receive messages that expire during that interval. 861 Push messages that are stored and have not been delivered to a user 862 agent are delivered when the user agent recommences monitoring. 863 Stored push messages SHOULD include a Last-Modified header field 864 (Section 2.2 of [RFC7232]) indicating when delivery was requested by 865 an application server. 867 A GET request to a push message subscription resource with only 868 expired messages results in a response as though no push message was 869 ever sent. 871 Push services might need to limit the size and number of stored push 872 messages to avoid overloading. To limit the size of messages, the 873 push service MAY return a 413 (Payload Too Large) status code 874 [RFC7231] in response to requests that include an entity body that is 875 too large. Push services MUST NOT return a 413 status code in 876 responses to an entity body that is 4096 bytes or less in size. 878 To limit the number of stored push messages, the push service MAY 879 either expire messages prior to their advertised Time-To-Live or 880 reduce their advertised Time-To-Live. 882 7.3. Subscription Expiration 884 In some cases, it may be necessary to terminate subscriptions so that 885 they can be refreshed. This applies to both push message 886 subscriptions and receipt subscriptions. 888 A push service MAY expire a subscription at any time. If there are 889 outstanding requests to an expired push message subscription resource 890 (Section 6) from a user agent or to an expired receipt subscription 891 resource (Section 6.3) from an application server, this MUST be 892 signaled by returning a 404 (Not Found) status code. 894 A push service MUST return a 404 (Not Found) status code if an 895 application server attempts to send a push message to an expired push 896 message subscription. 898 A user agent can remove its push message subscription by sending a 899 DELETE request to the corresponding URI. An application server can 900 remove its receipt subscription by sending a DELETE request to the 901 corresponding URI. 903 7.3.1. Subscription Set Expiration 905 A push service MAY expire a subscription set at any time and MUST 906 also expire all push message subscriptions in the set. If a user 907 agent has an outstanding request to a push subscription set 908 (Section 6.1) this MUST be signaled by returning a 404 (Not Found) 909 status code. 911 A user agent can request that a subscription set be removed by 912 sending a DELETE request to the subscription set URI. This MUST also 913 remove all push message subscriptions in the set. 915 If a specific push message subscription that is a member of a 916 subscription set is expired or removed, then it MUST also be removed 917 from its subscription set. 919 7.4. Implications for Application Reliability 921 A push service that does not support reliable delivery over 922 intermittent network connections or failing applications on devices, 923 forces the device to acknowledge receipt directly to the application 924 server, incurring additional power drain in order to establish 925 (usually secure) connections to the individual application servers. 927 Push message reliability can be important if messages contain 928 information critical to the state of an application. Repairing state 929 can be expensive, particularly for devices with limited 930 communications capacity. Knowing that a push message has been 931 correctly received avoids retransmissions, polling, and state 932 resynchronization. 934 The availability of push message delivery receipts ensures that the 935 application developer is not tempted to create alternative mechanisms 936 for message delivery in case the push service fails to deliver a 937 critical message. Setting up a polling mechanism or a backup 938 messaging channel in order to compensate for these shortcomings 939 negates almost all of the advantages a push service provides. 941 However, reliability might not be necessary for messages that are 942 transient (e.g. an incoming call) or messages that are quickly 943 superceded (e.g. the current number of unread emails). 945 7.5. Subscription Sets and Concurrent HTTP/2 streams 947 If the push service requires that the user agent use push message 948 subscription sets, then it MAY limit the number of concurrently 949 active streams with the SETTINGS_MAX_CONCURRENT_STREAMS parameter 950 within a HTTP/2 SETTINGS frame [RFC7540]. The user agent MAY be 951 limited to one concurrent stream to manage push message subscriptions 952 and one concurrent stream for each subscription set returned by the 953 push service. This could force the user agent to serialize 954 subscription requests to the push service. 956 8. Security Considerations 958 This protocol MUST use HTTP over TLS [RFC2818] following the 959 recommendations in [RFC7525]. This includes any communications 960 between user agent and push service, plus communications between the 961 application and the push service. All URIs therefore use the "https" 962 scheme. This provides confidentiality and integrity protection for 963 subscriptions and push messages from external parties. 965 Applications using this protocol MUST use mechanisms that provide 966 confidentiality, integrity and data origin authentication. The 967 application server sending the push message and the application on 968 the user agent that receives it are frequently just different 969 instances of the same application, so no standardized protocol is 970 needed to establish a proper security context. The distribution of 971 subscription information from the user agent to its application 972 server also offers a convenient medium for key agreement. 974 8.1. Confidentiality from Push Service Access 976 The protection afforded by TLS does not protect content from the push 977 service. Without additional safeguards, a push service can inspect 978 and modify the message content. 980 For its requirements, the W3C Push API [API] has adopted Message 981 Encryption for WebPush [I-D.ietf-webpush-encryption] to secure the 982 content of messages from the push service. Other scenarios can be 983 addressed by similar policies. 985 The Topic header field exposes information that allows more granular 986 correlation of push messages on the same subject. This might be used 987 to aid traffic analysis of push messages by the push service. 989 8.2. Privacy Considerations 991 Push message confidentiality does not ensure that the identity of who 992 is communicating and when they are communicating is protected. 993 However, the amount of information that is exposed can be limited. 995 The URIs provided for push resources MUST NOT provide any basis to 996 correlate communications for a given user agent. It MUST NOT be 997 possible to correlate any two push resource URIs based solely on 998 their contents. This allows a user agent to control correlation 999 across different applications, or over time. Of course, this does 1000 not prevent correlation using other information that a user agent 1001 might expose. 1003 Similarly, the URIs provided by the push service to identify a push 1004 message MUST NOT provide any information that allows for correlation 1005 across subscriptions. Push message URIs for the same subscription 1006 MAY contain information that would allow correlation with the 1007 associated subscription or other push messages for that subscription. 1009 User and device information MUST NOT be exposed through a push or 1010 push message URI. 1012 In addition, push URIs established by the same user agent or push 1013 message URIs for the same subscription MUST NOT include any 1014 information that allows them to be correlated with the user agent. 1016 Note: This need not be perfect as long as the resulting anonymity 1017 set ([RFC6973], Section 6.1.1) is sufficiently large. A push URI 1018 necessarily identifies a push service or a single server instance. 1019 It is also possible that traffic analysis could be used to 1020 correlate subscriptions. 1022 A user agent MUST be able to create new subscriptions with new 1023 identifiers at any time. 1025 8.3. Authorization 1027 This protocol does not define how a push service establishes whether 1028 a user agent is permitted to create a subscription, or whether push 1029 messages can be delivered to the user agent. A push service MAY 1030 choose to authorize requests based on any HTTP-compatible 1031 authorization method available, of which there are numerous options. 1032 The authorization process and any associated credentials are expected 1033 to be configured in the user agent along with the URI for the push 1034 service. 1036 Authorization is managed using capability URLs for the push message 1037 subscription, push, and receipt subscription resources ([CAP-URI]). 1038 A capability URL grants access to a resource based solely on 1039 knowledge of the URL. 1041 Capability URLs are used for their "easy onward sharing" and "easy 1042 client API" properties. These make it possible to avoid relying on 1043 relationships between push services and application servers, with the 1044 protocols necessary to build and support those relationships. 1046 Capability URLs act as bearer tokens. Knowledge of a push message 1047 subscription URI implies authorization to either receive push 1048 messages or delete the subscription. Knowledge of a push URI implies 1049 authorization to send push messages. Knowledge of a push message URI 1050 allows for reading and acknowledging that specific message. 1051 Knowledge of a receipt subscription URI implies authorization to 1052 receive push receipts. 1054 Encoding a large amount of random entropy (at least 120 bits) in the 1055 path component ensures that it is difficult to successfully guess a 1056 valid capability URL. 1058 8.4. Denial of Service Considerations 1060 A user agent can control where valid push messages originate by 1061 limiting the distribution of push URIs to authorized application 1062 servers. Ensuring that push URIs are hard to guess ensures that only 1063 application servers that have received a push URI can use it. 1065 Push messages that are not successfully authenticated by the user 1066 agent will not be delivered, but this can present a denial of service 1067 risk. Even a relatively small volume of push messages can cause 1068 battery-powered devices to exhaust power reserves. 1070 To address this case, the W3C Push API [API] has adopted Voluntary 1071 Application Server Identification [I-D.ietf-webpush-vapid], which 1072 allows a user agent to restrict a subscription to a specific 1073 application server. The push service can then identify and reject 1074 unwanted messages without contacting the user agent. 1076 A malicious application with a valid push URI could use the greater 1077 resources of a push service to mount a denial of service attack on a 1078 user agent. Push services SHOULD limit the rate at which push 1079 messages are sent to individual user agents. 1081 A push service MAY return a 429 (Too Many Requests) status code 1082 [RFC6585] when an application server has exceeded its rate limit for 1083 push message delivery to a push resource. The push service SHOULD 1084 also include a Retry-After header [RFC7231] to indicate how long the 1085 application server is requested to wait before it makes another 1086 request to the push resource. 1088 A push service or user agent MAY also terminate subscriptions 1089 (Section 7.3) that receive too many push messages. 1091 A push service is also able to deny service to user agents. 1092 Intentional failure to deliver messages is difficult to distinguish 1093 from faults, which might occur due to transient network errors, 1094 interruptions in user agent availability, or genuine service outages. 1096 8.5. Logging Risks 1098 Server request logs can reveal subscription-related URIs or 1099 relationships between subscription-related URIs for the same user 1100 agent. Limitations on log retention and strong access control 1101 mechanisms can ensure that URIs are not revealed to unauthorized 1102 entities. 1104 9. IANA Considerations 1106 This protocol defines new HTTP header fields in Section 9.1. New 1107 link relation types are identified using the URNs defined in 1108 Section 9.2. Port registration is defined in Section 9.3 1110 9.1. Header Field Registrations 1112 HTTP header fields are registered within the "Message Headers" 1113 registry maintained at . 1116 This document defines the following HTTP header fields, so their 1117 associated registry entries shall be added according to the permanent 1118 registrations below ([RFC3864]): 1120 +-------------------+----------+----------+--------------+ 1121 | Header Field Name | Protocol | Status | Reference | 1122 +-------------------+----------+----------+--------------+ 1123 | TTL | http | standard | Section 5.2 | 1124 | Urgency | http | standard | Section 5.3 | 1125 | Topic | http | standard | Section 5.4 | 1126 +-------------------+----------+----------+--------------+ 1128 The change controller is: "IETF (iesg@ietf.org) - Internet 1129 Engineering Task Force". 1131 9.2. Link Relation URNs 1133 This document registers URNs for use in identifying link relation 1134 types. These are added to a new "Web Push Identifiers" registry 1135 according to the procedures in Section 4 of [RFC3553]; the 1136 corresponding "push" sub-namespace is entered in the "IETF URN Sub- 1137 namespace for Registered Protocol Parameter Identifiers" registry. 1139 The "Web Push Identifiers" registry operates under the IETF Review 1140 policy [RFC5226]. 1142 Registry name: Web Push Identifiers 1144 URN Prefix: urn:ietf:params:push 1146 Specification: (this document) 1148 Repository: [Editor/IANA note: please include a link to the final 1149 registry location.] 1151 Index value: Values in this registry are URNs or URN prefixes that 1152 start with the prefix "urn:ietf:params:push". Each is registered 1153 independently. 1155 New registrations in the "Web Push Identifiers" are encouraged to 1156 include the following information: 1158 URN: A complete URN or URN prefix. 1160 Description: A summary description. 1162 Specification: A reference to a specification describing the 1163 semantics of the URN or URN prefix. 1165 Contact: Email for the person or group making the registration. 1167 Index value: As described in [RFC3553], URN prefixes that are 1168 registered include a description of how the URN is constructed. 1169 This is not applicable for specific URNs. 1171 These values are entered as the initial content of the "Web Push 1172 Identifiers" registry. 1174 URN: urn:ietf:params:push 1176 Description: This link relation type is used to identify a resource 1177 for sending push messages. 1179 Specification: (this document) 1181 Contact: The Web Push WG (webpush@ietf.org) 1183 URN: urn:ietf:params:push:set 1185 Description: This link relation type is used to identify a 1186 collection of push message subscriptions. 1188 Specification: (this document) 1189 Contact: The Web Push WG (webpush@ietf.org) 1191 URN: urn:ietf:params:push:receipt 1193 Description: This link relation type is used to identify a resource 1194 for receiving delivery confirmations for push messages. 1196 Specification: (this document) 1198 Contact: The Web Push WG (webpush@ietf.org) 1200 9.3. Service Name and Port Number Registration 1202 Service names and port numbers are registered within the "Service 1203 Name and Transport Protocol Port Number Registry" maintained at 1204 . 1207 IANA is requested to assign the System Port number 1001 and the 1208 service name "webpush" in accordance with [RFC6335]. 1210 Service Name: 1211 webpush 1213 Transport Protocol: 1214 tcp 1216 Assignee: 1217 The IESG (iesg@ietf.org) 1219 Contact: 1220 The IETF Chair (chair@ietf.org) 1222 Description: 1223 HTTP Web Push 1225 Reference: 1226 [RFCthis] 1228 Port Number: 1229 1001 1231 10. Acknowledgements 1233 Significant technical input to this document has been provided by Ben 1234 Bangert, Peter Beverloo, Kit Cambridge, JR Conlin, Lucas Jenss, 1235 Matthew Kaufman, Costin Manolache, Mark Nottingham, Idel Pivnitskiy, 1236 Robert Sparks, Darshak Thakore and many others. 1238 11. References 1240 11.1. Normative References 1242 [CAP-URI] Tennison, J., "Good Practices for Capability URLs", FPWD 1243 capability-urls, February 2014, 1244 . 1246 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1247 Requirement Levels", BCP 14, RFC 2119, March 1997. 1249 [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. 1251 [RFC3553] Mealling, M., Masinter, L., Hardie, T., and G. Klyne, "An 1252 IETF URN Sub-namespace for Registered Protocol 1253 Parameters", BCP 73, RFC 3553, June 2003. 1255 [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration 1256 Procedures for Message Header Fields", BCP 90, RFC 3864, 1257 September 2004. 1259 [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data 1260 Encodings", RFC 4648, October 2006. 1262 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1263 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1264 May 2008. 1266 [RFC5382] Biswas, K., Ford, B., Sivakumar, S., and P. Srisuresh, 1267 "NAT Behavioral Requirements for TCP", RFC 5382, October 1268 2008. 1270 [RFC5988] Nottingham, M., "Web Linking", RFC 5988, October 2010. 1272 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. 1273 Cheshire, "Internet Assigned Numbers Authority (IANA) 1274 Procedures for the Management of the Service Name and 1275 Transport Protocol Port Number Registry", RFC 6335, August 1276 2011. 1278 [RFC6454] Barth, A., "The Web Origin Concept", RFC 6454, December 1279 2011. 1281 [RFC6585] Nottingham, M. and R. Fielding, "Additional HTTP Status 1282 Codes", RFC 6585, April 2012. 1284 [RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol 1285 (HTTP/1.1): Message Syntax and Routing", RFC 7230, June 1286 2014. 1288 [RFC7231] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol 1289 (HTTP/1.1): Semantics and Content", RFC 7231, June 2014. 1291 [RFC7232] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol 1292 (HTTP/1.1): Conditional Requests", RFC 7232, June 2014. 1294 [RFC7240] Snell, J., "Prefer Header for HTTP", RFC 7240, June 2014. 1296 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 1297 "Recommendations for Secure Use of Transport Layer 1298 Security (TLS) and Datagram Transport Layer Security 1299 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 1300 2015. 1302 [RFC7540] Belshe, M., Peon, R., and M. Thomson, "Hypertext Transfer 1303 Protocol Version 2", RFC 7540, May 2015. 1305 [RFC7838] Nottingham, M., McManus, P., and J. Reschke, "HTTP 1306 Alternative Services", RFC 7838, April 2016. 1308 11.2. Informative References 1310 [API] van Ouwerkerk, M., Thomson, M., Sullivan, B., and E. 1311 Fullea, "W3C Push API", ED push-api, August 2016, 1312 . 1314 [I-D.ietf-webpush-encryption] 1315 Thomson, M., "Message Encryption for Web Push", draft- 1316 ietf-webpush-encryption-03 (work in progress), June 2016, 1317 . 1320 [I-D.ietf-webpush-vapid] 1321 Thomson, M. and P. Beverloo, "Voluntary Application Server 1322 Identification for Web Push", draft-ietf-webpush-vapid-01 1323 (work in progress), June 2016, 1324 . 1327 [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., 1328 Morris, J., Hansen, M., and R. Smith, "Privacy 1329 Considerations for Internet Protocols", RFC 6973, July 1330 2013. 1332 Appendix A. Change Log 1334 [[The RFC Editor is requested to remove this section at 1335 publication.]] 1337 A.1. Since draft-ietf-webpush-protocol-00 1339 Editorial changes for Push Message Time-To-Live 1341 Editorial changes for Push Acknowledgements 1343 Removed subscription expiration based on HTTP cache headers 1345 A.2. Since draft-ietf-webpush-protocol-01 1347 Added Subscription Sets 1349 Added System Port as an alternate service with guidance for idle 1350 timeouts 1352 Finalized status codes for acknowledgements 1354 Editorial changes for Rate Limits 1356 A.3. Since draft-ietf-webpush-protocol-02 1358 Added explicit correlation for Subscription Sets 1360 Added Push Message Updates (message collapsing) 1362 Renamed the push:receipt link relation to push:receipts and 1363 transitioned the Push-Receipt header field to the push:receipt link 1364 relation type 1366 A.4. Since draft-ietf-webpush-protocol-03 1368 An application server MUST include the TTL (Time-To-Live) header 1369 field in its request for push message delivery. 1371 Added Push Message Urgency header field 1373 A.5. Since draft-ietf-webpush-protocol-04 1375 Simplified design for Push Receipts and eliminated the 1376 urn:ietf:params:push:receipts link relation 1377 Clarified Security Considerations section and added informative 1378 references to Message Encryption and Voluntary Application Server 1379 Identification 1381 A.6. Since draft-ietf-webpush-protocol-05 1383 Addressed feedback from Working Group Last Call 1385 A.7. Since draft-ietf-webpush-protocol-06 1387 Updated informative references to W3C Push API, Message Encryption, 1388 and Voluntary Application Server Identification 1390 A.8. Since draft-ietf-webpush-protocol-07 1392 Minor editorial changes 1394 A.9. Since draft-ietf-webpush-protocol-08 1396 Minor correction to Acknowledgements 1398 Updated dates for informative references 1400 A.10. Since draft-ietf-webpush-protocol-09 1402 Updates for Area Director (Alissa Cooper) evaluation 1404 Authors' Addresses 1406 Martin Thomson 1407 Mozilla 1408 331 E Evelyn Street 1409 Mountain View, CA 94041 1410 US 1412 Email: martin.thomson@gmail.com 1414 Elio Damaggio 1415 Microsoft 1416 One Microsoft Way 1417 Redmond, WA 98052 1418 US 1420 Email: elioda@microsoft.com 1421 Brian Raymor (editor) 1422 Microsoft 1423 One Microsoft Way 1424 Redmond, WA 98052 1425 US 1427 Email: brian.raymor@microsoft.com