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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 QUIC M. Bishop, Ed. 3 Internet-Draft Microsoft 4 Intended status: Standards Track October 13, 2017 5 Expires: April 16, 2018 7 Hypertext Transfer Protocol (HTTP) over QUIC 8 draft-ietf-quic-http-07 10 Abstract 12 The QUIC transport protocol has several features that are desirable 13 in a transport for HTTP, such as stream multiplexing, per-stream flow 14 control, and low-latency connection establishment. This document 15 describes a mapping of HTTP semantics over QUIC. This document also 16 identifies HTTP/2 features that are subsumed by QUIC, and describes 17 how HTTP/2 extensions can be ported to QUIC. 19 Note to Readers 21 Discussion of this draft takes place on the QUIC working group 22 mailing list (quic@ietf.org), which is archived at 23 https://mailarchive.ietf.org/arch/search/?email_list=quic [1]. 25 Working Group information can be found at https://github.com/quicwg 26 [2]; source code and issues list for this draft can be found at 27 https://github.com/quicwg/base-drafts/labels/http [3]. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at https://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on April 16, 2018. 46 Copyright Notice 48 Copyright (c) 2017 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (https://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 64 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3 65 2. QUIC Advertisement . . . . . . . . . . . . . . . . . . . . . 4 66 2.1. QUIC Version Hints . . . . . . . . . . . . . . . . . . . 4 67 3. Connection Establishment . . . . . . . . . . . . . . . . . . 5 68 3.1. Draft Version Identification . . . . . . . . . . . . . . 5 69 4. Stream Mapping and Usage . . . . . . . . . . . . . . . . . . 5 70 4.1. Stream 1: Control Stream . . . . . . . . . . . . . . . . 6 71 4.2. HTTP Message Exchanges . . . . . . . . . . . . . . . . . 6 72 4.2.1. Header Compression . . . . . . . . . . . . . . . . . 7 73 4.2.2. The CONNECT Method . . . . . . . . . . . . . . . . . 8 74 4.3. Request Prioritization . . . . . . . . . . . . . . . . . 9 75 4.4. Server Push . . . . . . . . . . . . . . . . . . . . . . . 9 76 5. HTTP Framing Layer . . . . . . . . . . . . . . . . . . . . . 10 77 5.1. Frame Layout . . . . . . . . . . . . . . . . . . . . . . 11 78 5.2. Frame Definitions . . . . . . . . . . . . . . . . . . . . 11 79 5.2.1. DATA . . . . . . . . . . . . . . . . . . . . . . . . 11 80 5.2.2. HEADERS . . . . . . . . . . . . . . . . . . . . . . . 11 81 5.2.3. PRIORITY . . . . . . . . . . . . . . . . . . . . . . 12 82 5.2.4. CANCEL_PUSH . . . . . . . . . . . . . . . . . . . . . 13 83 5.2.5. SETTINGS . . . . . . . . . . . . . . . . . . . . . . 14 84 5.2.6. PUSH_PROMISE . . . . . . . . . . . . . . . . . . . . 17 85 5.2.7. GOAWAY . . . . . . . . . . . . . . . . . . . . . . . 18 86 5.2.8. MAX_PUSH_ID . . . . . . . . . . . . . . . . . . . . . 20 87 6. Connection Management . . . . . . . . . . . . . . . . . . . . 20 88 7. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 21 89 7.1. HTTP/QUIC Error Codes . . . . . . . . . . . . . . . . . . 21 90 8. Considerations for Transitioning from HTTP/2 . . . . . . . . 22 91 8.1. HTTP Frame Types . . . . . . . . . . . . . . . . . . . . 23 92 8.2. HTTP/2 SETTINGS Parameters . . . . . . . . . . . . . . . 25 93 8.3. HTTP/2 Error Codes . . . . . . . . . . . . . . . . . . . 25 95 9. Security Considerations . . . . . . . . . . . . . . . . . . . 26 96 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27 97 10.1. Registration of HTTP/QUIC Identification String . . . . 27 98 10.2. Registration of QUIC Version Hint Alt-Svc Parameter . . 27 99 10.3. Frame Types . . . . . . . . . . . . . . . . . . . . . . 27 100 10.4. Settings Parameters . . . . . . . . . . . . . . . . . . 28 101 10.5. Error Codes . . . . . . . . . . . . . . . . . . . . . . 29 102 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 32 103 11.1. Normative References . . . . . . . . . . . . . . . . . . 32 104 11.2. Informative References . . . . . . . . . . . . . . . . . 33 105 11.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 33 106 Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 33 107 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 33 108 B.1. Since draft-ietf-quic-http-06 . . . . . . . . . . . . . . 33 109 B.2. Since draft-ietf-quic-http-05 . . . . . . . . . . . . . . 33 110 B.3. Since draft-ietf-quic-http-04 . . . . . . . . . . . . . . 33 111 B.4. Since draft-ietf-quic-http-03 . . . . . . . . . . . . . . 34 112 B.5. Since draft-ietf-quic-http-02 . . . . . . . . . . . . . . 34 113 B.6. Since draft-ietf-quic-http-01 . . . . . . . . . . . . . . 34 114 B.7. Since draft-ietf-quic-http-00 . . . . . . . . . . . . . . 35 115 B.8. Since draft-shade-quic-http2-mapping-00 . . . . . . . . . 35 116 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 35 118 1. Introduction 120 The QUIC transport protocol has several features that are desirable 121 in a transport for HTTP, such as stream multiplexing, per-stream flow 122 control, and low-latency connection establishment. This document 123 describes a mapping of HTTP semantics over QUIC, drawing heavily on 124 the existing TCP mapping, HTTP/2. Specifically, this document 125 identifies HTTP/2 features that are subsumed by QUIC, and describes 126 how the other features can be implemented atop QUIC. 128 QUIC is described in [QUIC-TRANSPORT]. For a full description of 129 HTTP/2, see [RFC7540]. 131 1.1. Notational Conventions 133 The words "MUST", "MUST NOT", "SHOULD", and "MAY" are used in this 134 document. It's not shouting; when they are capitalized, they have 135 the special meaning defined in [RFC2119]. 137 Field definitions are given in Augmented Backus-Naur Form (ABNF), as 138 defined in [RFC5234]. 140 2. QUIC Advertisement 142 An HTTP origin advertises the availability of an equivalent HTTP/QUIC 143 endpoint via the Alt-Svc HTTP response header or the HTTP/2 ALTSVC 144 frame ([RFC7838]), using the ALPN token defined in Section 3. 146 For example, an origin could indicate in an HTTP/1.1 or HTTP/2 147 response that HTTP/QUIC was available on UDP port 50781 at the same 148 hostname by including the following header in any response: 150 Alt-Svc: hq=":50781" 152 On receipt of an Alt-Svc header indicating HTTP/QUIC support, a 153 client MAY attempt to establish a QUIC connection to the indicated 154 host and port and, if successful, send HTTP requests using the 155 mapping described in this document. 157 Connectivity problems (e.g. firewall blocking UDP) can result in QUIC 158 connection establishment failure, in which case the client SHOULD 159 continue using the existing connection or try another alternative 160 endpoint offered by the origin. 162 Servers MAY serve HTTP/QUIC on any UDP port. Servers MUST use the 163 same port across all IP addresses that serve a single domain, and 164 SHOULD NOT change this port. 166 2.1. QUIC Version Hints 168 This document defines the "quic" parameter for Alt-Svc, which MAY be 169 used to provide version-negotiation hints to HTTP/QUIC clients. QUIC 170 versions are four-octet sequences with no additional constraints on 171 format. Syntax: 173 quic = version-number 174 version-number = 1*8HEXDIG; hex-encoded QUIC version 176 Leading zeros SHOULD be omitted for brevity. When multiple versions 177 are supported, the "quic" parameter MAY be repeated multiple times in 178 a single Alt-Svc entry. For example, if a server supported both 179 version 0x00000001 and the version rendered in ASCII as "Q034", it 180 could specify the following header: 182 Alt-Svc: hq=":49288";quic=1;quic=51303334 184 Where multiple versions are listed, the order of the values reflects 185 the server's preference (with the first value being the most 186 preferred version). Origins SHOULD list only versions which are 187 supported by the alternative, but MAY omit supported versions for any 188 reason. 190 3. Connection Establishment 192 HTTP/QUIC connections are established as described in 193 [QUIC-TRANSPORT]. During connection establishment, HTTP/QUIC support 194 is indicated by selecting the ALPN token "hq" in the crypto 195 handshake. 197 While connection-level options pertaining to the core QUIC protocol 198 are set in the initial crypto handshake, HTTP-specific settings are 199 conveyed in the SETTINGS frame. After the QUIC connection is 200 established, a SETTINGS frame (Section 5.2.5) MUST be sent as the 201 initial frame of the HTTP control stream (Stream ID 1, see 202 Section 4). The server MUST NOT send data on any other stream until 203 the client's SETTINGS frame has been received. 205 3.1. Draft Version Identification 207 *RFC Editor's Note:* Please remove this section prior to 208 publication of a final version of this document. 210 Only implementations of the final, published RFC can identify 211 themselves as "hq". Until such an RFC exists, implementations MUST 212 NOT identify themselves using this string. 214 Implementations of draft versions of the protocol MUST add the string 215 "-" and the corresponding draft number to the identifier. For 216 example, draft-ietf-quic-http-01 is identified using the string "hq- 217 01". 219 Non-compatible experiments that are based on these draft versions 220 MUST append the string "-" and an experiment name to the identifier. 221 For example, an experimental implementation based on draft-ietf-quic- 222 http-09 which reserves an extra stream for unsolicited transmission 223 of 1980s pop music might identify itself as "hq-09-rickroll". Note 224 that any label MUST conform to the "token" syntax defined in 225 Section 3.2.6 of [RFC7230]. Experimenters are encouraged to 226 coordinate their experiments on the quic@ietf.org mailing list. 228 4. Stream Mapping and Usage 230 A QUIC stream provides reliable in-order delivery of bytes, but makes 231 no guarantees about order of delivery with regard to bytes on other 232 streams. On the wire, data is framed into QUIC STREAM frames, but 233 this framing is invisible to the HTTP framing layer. A QUIC receiver 234 buffers and orders received STREAM frames, exposing the data 235 contained within as a reliable byte stream to the application. 237 QUIC reserves Stream 0 for crypto operations (the handshake, crypto 238 config updates). Stream 1 is reserved for sending and receiving HTTP 239 control frames, and is analogous to HTTP/2's Stream 0. This control 240 stream is considered critical to the HTTP connection. If the control 241 stream is closed for any reason, this MUST be treated as a connection 242 error of type QUIC_CLOSED_CRITICAL_STREAM. 244 When HTTP headers and data are sent over QUIC, the QUIC layer handles 245 most of the stream management. An HTTP request/response consumes a 246 single stream: This means that the client's first request occurs on 247 QUIC stream 3, the second on stream 5, and so on. The server's first 248 push consumes stream 2. 250 This stream carries frames related to the request/response (see 251 Section 5.2). When a stream terminates cleanly, if the last frame on 252 the stream was truncated, this MUST be treated as a connection error 253 (see HTTP_MALFORMED_* in Section 7.1). Streams which terminate 254 abruptly may be reset at any point in the frame. 256 Streams SHOULD be used sequentially, with no gaps. Streams used for 257 pushed resources MAY be initiated out-of-order, but stream IDs SHOULD 258 be allocated to promised resources sequentially. 260 HTTP does not need to do any separate multiplexing when using QUIC - 261 data sent over a QUIC stream always maps to a particular HTTP 262 transaction. Requests and responses are considered complete when the 263 corresponding QUIC stream is closed in the appropriate direction. 265 4.1. Stream 1: Control Stream 267 Since most connection-level concerns will be managed by QUIC, the 268 primary use of Stream 1 will be for the SETTINGS frame when the 269 connection opens and for PRIORITY frames subsequently. 271 4.2. HTTP Message Exchanges 273 A client sends an HTTP request on a new QUIC stream. A server sends 274 an HTTP response on the same stream as the request. 276 An HTTP message (request or response) consists of: 278 1. one header block (see Section 5.2.2) containing the message 279 headers (see [RFC7230], Section 3.2), 281 2. the payload body (see [RFC7230], Section 3.3), sent as a series 282 of DATA frames (see Section 5.2.1), 284 3. optionally, one header block containing the trailer-part, if 285 present (see [RFC7230], Section 4.1.2). 287 In addition, prior to sending the message header block indicated 288 above, a response may contain zero or more header blocks containing 289 the message headers of informational (1xx) HTTP responses (see 290 [RFC7230], Section 3.2 and [RFC7231], Section 6.2). 292 PUSH_PROMISE frames MAY be interleaved with the frames of a response 293 message indicating a pushed resource related to the response. These 294 PUSH_PROMISE frames are not part of the response, but carry the 295 headers of a separate HTTP request message. See Section 4.4 for more 296 details. 298 The "chunked" transfer encoding defined in Section 4.1 of [RFC7230] 299 MUST NOT be used. 301 Trailing header fields are carried in an additional header block 302 following the body. Such a header block is a sequence of HEADERS 303 frames with End Header Block set on the last frame. Senders MUST 304 send only one header block in the trailers section; receivers MUST 305 discard any subsequent header blocks. 307 An HTTP request/response exchange fully consumes a QUIC stream. 308 After sending a request, a client closes the stream for sending; 309 after sending a response, the server closes the stream for sending 310 and the QUIC stream is fully closed. 312 A server can send a complete response prior to the client sending an 313 entire request if the response does not depend on any portion of the 314 request that has not been sent and received. When this is true, a 315 server MAY request that the client abort transmission of a request 316 without error by triggering a QUIC STOP_SENDING with error code 317 HTTP_EARLY_RESPONSE, sending a complete response, and cleanly closing 318 its streams. Clients MUST NOT discard complete responses as a result 319 of having their request terminated abruptly, though clients can 320 always discard responses at their discretion for other reasons. 321 Servers MUST NOT abort a response in progress as a result of 322 receiving a solicited RST_STREAM. 324 4.2.1. Header Compression 326 HTTP/QUIC uses HPACK header compression as described in [RFC7541]. 327 HPACK was designed for HTTP/2 with the assumption of in-order 328 delivery such as that provided by TCP. A sequence of encoded header 329 blocks must arrive (and be decoded) at an endpoint in the same order 330 in which they were encoded. This ensures that the dynamic state at 331 the two endpoints remains in sync. 333 QUIC streams provide in-order delivery of data sent on those streams, 334 but there are no guarantees about order of delivery between streams. 335 QUIC anticipates moving to a modified version of HPACK without this 336 assumption. In the meantime, by fixing the size of the dynamic table 337 at zero, HPACK can be used in an unordered environment. 339 4.2.2. The CONNECT Method 341 The pseudo-method CONNECT ([RFC7231], Section 4.3.6) is primarily 342 used with HTTP proxies to establish a TLS session with an origin 343 server for the purposes of interacting with "https" resources. In 344 HTTP/1.x, CONNECT is used to convert an entire HTTP connection into a 345 tunnel to a remote host. In HTTP/2, the CONNECT method is used to 346 establish a tunnel over a single HTTP/2 stream to a remote host for 347 similar purposes. 349 A CONNECT request in HTTP/QUIC functions in the same manner as in 350 HTTP/2. The request MUST be formatted as described in [RFC7540], 351 Section 8.3. A CONNECT request that does not conform to these 352 restrictions is malformed. The message data stream MUST NOT be 353 closed at the end of the request. 355 A proxy that supports CONNECT establishes a TCP connection 356 ([RFC0793]) to the server identified in the ":authority" pseudo- 357 header field. Once this connection is successfully established, the 358 proxy sends a HEADERS frame containing a 2xx series status code to 359 the client, as defined in [RFC7231], Section 4.3.6. 361 All DATA frames on the request stream correspond to data sent on the 362 TCP connection. Any DATA frame sent by the client is transmitted by 363 the proxy to the TCP server; data received from the TCP server is 364 packaged into DATA frames by the proxy. Note that the size and 365 number of TCP segments is not guaranteed to map predictably to the 366 size and number of HTTP DATA or QUIC STREAM frames. 368 The TCP connection can be closed by either peer. When the client 369 half-closes the request stream, the proxy will set the FIN bit on its 370 connection to the TCP server. When the proxy receives a packet with 371 the FIN bit set, it will half-close the corresponding stream. TCP 372 connections which remain half-closed in a single direction are not 373 invalid, but are often handled poorly by servers, so clients SHOULD 374 NOT half-close connections on which they are still expecting data. 376 A TCP connection error is signaled with RST_STREAM. A proxy treats 377 any error in the TCP connection, which includes receiving a TCP 378 segment with the RST bit set, as a stream error of type 379 HTTP_CONNECT_ERROR (Section 7.1). Correspondingly, a proxy MUST send 380 a TCP segment with the RST bit set if it detects an error with the 381 stream or the QUIC connection. 383 4.3. Request Prioritization 385 HTTP/QUIC uses the priority scheme described in [RFC7540], 386 Section 5.3. In this priority scheme, a given request can be 387 designated as dependent upon another request, which expresses the 388 preference that the latter stream (the "parent" request) be allocated 389 resources before the former stream (the "dependent" request). Taken 390 together, the dependencies across all requests in a connection form a 391 dependency tree. The structure of the dependency tree changes as 392 PRIORITY frames add, remove, or change the dependency links between 393 requests. 395 HTTP/2 defines its priorities in terms of streams whereas HTTP over 396 QUIC identifies requests. The PRIORITY frame Section 5.2.3 397 identifies a request either by identifying the stream that carries a 398 request or by using a Push ID (Section 5.2.6). Other than the means 399 of identifying requests, the prioritization system is identical to 400 that in HTTP/2. 402 Only a client can send PRIORITY frames. A server MUST NOT send a 403 PRIORITY frame. 405 4.4. Server Push 407 HTTP/QUIC supports server push as described in [RFC7540]. During 408 connection establishment, the client enables server push by sending a 409 MAX_PUSH_ID frame (see Section 5.2.8). A server cannot use server 410 push until it receives a MAX_PUSH_ID frame. 412 As with server push for HTTP/2, the server initiates a server push by 413 sending a PUSH_PROMISE frame that includes request header fields 414 attributed to the request. The PUSH_PROMISE frame is sent on a 415 response stream. Unlike HTTP/2, the PUSH_PROMISE does not reference 416 a stream; when a server fulfills a promise, the stream that carries 417 the stream headers references the PUSH_PROMISE. This allows a server 418 to fulfill promises in the order that best suits its needs. 420 The server push response is conveyed on a push stream. A push stream 421 is a server-initiated stream. A push stream includes a header (see 422 Figure 1) that identifies the PUSH_PROMISE that it fulfills. This 423 header consists of a 32-bit Push ID, which identifies a server push 424 (see Section 5.2.6). 426 0 1 2 3 427 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 428 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 429 | Push ID (32) | 430 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 432 Figure 1: Push Stream Header 434 A push stream always starts with a 32-bit Push ID. A client MUST 435 treat receiving a push stream that contains fewer than 4 octets as a 436 connection error of type HTTP_MALFORMED_PUSH. 438 A server SHOULD use Push IDs sequentially, starting at 0. A client 439 uses the MAX_PUSH_ID frame (Section 5.2.8) to limit the number of 440 pushes that a server can promise. A client MUST treat receipt of a 441 push stream with a Push ID that is greater than the maximum Push ID 442 as a connection error of type HTTP_MALFORMED_PUSH. 444 Each Push ID MUST only be used once in a push stream header. If a 445 push stream header includes a Push ID that was used in another push 446 stream header, the client MUST treat this as a connection error of 447 type HTTP_MALFORMED_PUSH. The same Push ID can be used in multiple 448 PUSH_PROMISE frames (see Section 5.2.6). 450 After the push stream header, a push contains a response 451 (Section 4.2), with response headers, a response body (if any) 452 carried by DATA frames, then trailers (if any) carried by HEADERS 453 frames. 455 If a promised server push is not needed by the client, the client 456 SHOULD send a CANCEL_PUSH frame; if the push stream is already open, 457 a QUIC STOP_SENDING frame with an appropriate error code can be used 458 instead (e.g., HTTP_PUSH_REFUSED, HTTP_PUSH_ALREADY_IN_CACHE; see 459 Section 7). This asks the server not to transfer the data and 460 indicates that it will be discarded upon receipt. 462 5. HTTP Framing Layer 464 Frames are used on each stream. This section describes HTTP framing 465 in QUIC and highlights some differences from HTTP/2 framing. For 466 more detail on differences from HTTP/2, see Section 8.1. 468 5.1. Frame Layout 470 All frames have the following format: 472 0 1 2 3 473 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 474 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 475 | Length (16) | Type (8) | Flags (8) | 476 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 477 | Frame Payload (*) ... 478 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 480 Figure 2: HTTP/QUIC frame format 482 5.2. Frame Definitions 484 5.2.1. DATA 486 DATA frames (type=0x0) convey arbitrary, variable-length sequences of 487 octets associated with an HTTP request or response payload. 489 The DATA frame defines no flags. 491 DATA frames MUST be associated with an HTTP request or response. If 492 a DATA frame is received on the control stream, the recipient MUST 493 respond with a connection error (Section 7) of type 494 HTTP_WRONG_STREAM. 496 DATA frames MUST contain a non-zero-length payload. If a DATA frame 497 is received with a payload length of zero, the recipient MUST respond 498 with a stream error (Section 7) of type HTTP_MALFORMED_DATA. 500 5.2.2. HEADERS 502 The HEADERS frame (type=0x1) is used to carry part of a header set, 503 compressed using HPACK Section 4.2.1. 505 One flag is defined: 507 End Header Block (0x4): This frame concludes a header block. 509 A HEADERS frame with any other flags set MUST be treated as a 510 connection error of type HTTP_MALFORMED_HEADERS. 512 The next frame on the same stream after a HEADERS frame without the 513 EHB flag set MUST be another HEADERS frame. A receiver MUST treat 514 the receipt of any other type of frame as a stream error of type 515 HTTP_INTERRUPTED_HEADERS. (Note that QUIC can intersperse data from 516 other streams between frames, or even during transmission of frames, 517 so multiplexing is not blocked by this requirement.) 519 A full header block is contained in a sequence of zero or more 520 HEADERS frames without EHB set, followed by a HEADERS frame with EHB 521 set. 523 5.2.3. PRIORITY 525 The PRIORITY (type=0x02) frame specifies the sender-advised priority 526 of a stream and is substantially different in format from [RFC7540]. 527 In order to ensure that prioritization is processed in a consistent 528 order, PRIORITY frames MUST be sent on the control stream. A 529 PRIORITY frame sent on any other stream MUST be treated as a 530 HTTP_WRONG_STREAM error. 532 The format has been modified to accommodate not being sent on a 533 request stream, to allow for identification of server pushes, and the 534 larger stream ID space of QUIC. The semantics of the Stream 535 Dependency, Weight, and E flag are otherwise the same as in HTTP/2. 537 The flags defined are: 539 PUSH_PRIORITIZED (0x04): Indicates that the Prioritized Stream is a 540 server push rather than a request. 542 PUSH_DEPENDENT (0x02): Indicates a dependency on a server push. 544 E (0x01): Indicates that the stream dependency is exclusive (see 545 [RFC7540], Section 5.3). 547 0 1 2 3 548 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 549 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 550 | Prioritized Request ID (32) | 551 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 552 | Stream Dependency ID (32) | 553 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 554 | Weight (8) | 555 +-+-+-+-+-+-+-+-+ 557 Figure 3: PRIORITY frame payload 559 The PRIORITY frame payload has the following fields: 561 Prioritized Request ID: A 32-bit identifier for a request. This 562 contains the stream ID of a request stream when the 563 PUSH_PRIORITIZED flag is clear, or a Push ID when the 564 PUSH_PRIORITIZED flag is set. 566 Stream Dependency ID: A 32-bit stream identifier for a dependent 567 request. This contains the stream ID of a request stream when the 568 PUSH_DEPENDENT flag is clear, or a Push ID when the PUSH_DEPENDENT 569 flag is set. A request stream ID of 0 indicates a dependency on 570 the root stream. For details of dependencies, see Section 4.3 and 571 [RFC7540], Section 5.3. 573 Weight: An unsigned 8-bit integer representing a priority weight for 574 the stream (see [RFC7540], Section 5.3). Add one to the value to 575 obtain a weight between 1 and 256. 577 A PRIORITY frame identifies a request to priotize, and a request upon 578 which that request is dependent. A Prioritized Request ID or Stream 579 Dependency ID identifies a client-initiated request using the 580 corresponding stream ID when the corresponding PUSH_PRIORITIZED or 581 PUSH_DEPENDENT flag is not set. Setting the PUSH_PRIORITIZED or 582 PUSH_DEPENDENT flag causes the Prioritized Request ID or Stream 583 Dependency ID (respectively) to identify a server push using a Push 584 ID (see Section 5.2.6 for details). 586 A PRIORITY frame MAY identify a Stream Dependency ID using a stream 587 ID of 0; as in [RFC7540], this makes the request dependent on the 588 root of the dependency tree. 590 Stream ID 0 and stream ID 1 cannot be reprioritized. A Prioritized 591 Request ID that identifies Stream 0 or 1 MUST be treated as a 592 connection error of type HTTP_MALFORMED_PRIORITY. 594 A PRIORITY frame that does not reference a request MUST be treated as 595 a HTTP_MALFORMED_PRIORITY error, unless it references stream ID 0. A 596 PRIORITY that sets a PUSH_PRIORITIZED or PUSH_DEPENDENT flag, but 597 then references a non-existent Push ID MUST be treated as a 598 HTTP_MALFORMED_PRIORITY error. 600 The length of a PRIORITY frame is 9 octets. A PRIORITY frame with 601 any other length MUST be treated as a connection error of type 602 HTTP_MALFORMED_PRIORITY. 604 5.2.4. CANCEL_PUSH 606 The CANCEL_PUSH frame (type=0x3) is used to request cancellation of 607 server push prior to the push stream being created. The CANCEL_PUSH 608 frame identifies a server push request by Push ID (see 609 Section 5.2.6). 611 When a server receives this frame, it aborts sending the response for 612 the identified server push. If the server has not yet started to 613 send the server push, it can use the receipt of a CANCEL_PUSH frame 614 to avoid opening a stream. If the push stream has been opened by the 615 server, the server SHOULD sent a QUIC RST_STREAM frame on those 616 streams and cease transmission of the response. 618 A server can send this frame to indicate that it won't be sending a 619 response prior to creation of a push stream. Once the push stream 620 has been created, sending CANCEL_PUSH has no effect on the state of 621 the push stream. A QUIC RST_STREAM frame SHOULD be used instead to 622 cancel transmission of the server push response. 624 A CANCEL_PUSH frame is sent on the control stream. Sending a 625 CANCEL_PUSH frame on a stream other than the control stream MUST be 626 treated as a stream error of type HTTP_WRONG_STREAM. 628 The CANCEL_PUSH frame has no defined flags. 630 The CANCEL_PUSH frame carries a 32-bit Push ID that identifies the 631 server push that is being cancelled (see Section 5.2.6). 633 If the client receives a CANCEL_PUSH frame, that frame might identify 634 a Push ID that has not yet been mentioned by a PUSH_PROMISE frame. 636 A server MUST treat a CANCEL_PUSH frame payload that is other than 4 637 octets in length as a connection error of type 638 HTTP_MALFORMED_CANCEL_PUSH. 640 5.2.5. SETTINGS 642 The SETTINGS frame (type=0x4) conveys configuration parameters that 643 affect how endpoints communicate, such as preferences and constraints 644 on peer behavior, and is different from [RFC7540]. Individually, a 645 SETTINGS parameter can also be referred to as a "setting". 647 SETTINGS parameters are not negotiated; they describe characteristics 648 of the sending peer, which can be used by the receiving peer. 649 However, a negotiation can be implied by the use of SETTINGS - a peer 650 uses SETTINGS to advertise a set of supported values. The recipient 651 can then choose which entries from this list are also acceptable and 652 proceed with the value it has chosen. (This choice could be 653 announced in a field of an extension frame, or in its own value in 654 SETTINGS.) 656 Different values for the same parameter can be advertised by each 657 peer. For example, a client might be willing to consume very large 658 response headers, while servers are more cautious about request size. 660 Parameters MUST NOT occur more than once. A receiver MAY treat the 661 presence of the same parameter more than once as a connection error 662 of type HTTP_MALFORMED_SETTINGS. 664 The SETTINGS frame defines no flags. 666 The payload of a SETTINGS frame consists of zero or more parameters, 667 each consisting of an unsigned 16-bit setting identifier and a 668 length-prefixed binary value. 670 0 1 2 3 671 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 672 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 673 | Identifier (16) | Length (16) | 674 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 675 | Contents (?) ... 676 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 678 Figure 4: SETTINGS value format 680 A zero-length content indicates that the setting value is a Boolean 681 and true. False is indicated by the absence of the setting. 683 Non-zero-length values MUST be compared against the remaining length 684 of the SETTINGS frame. Any value which purports to cross the end of 685 the frame MUST cause the SETTINGS frame to be considered malformed 686 and trigger a connection error of type HTTP_MALFORMED_SETTINGS. 688 An implementation MUST ignore the contents for any SETTINGS 689 identifier it does not understand. 691 SETTINGS frames always apply to a connection, never a single stream. 692 A SETTINGS frame MUST be sent as the first frame of the control 693 stream (see Section 4) by each peer, and MUST NOT be sent 694 subsequently or on any other stream. If an endpoint receives an 695 SETTINGS frame on a different stream, the endpoint MUST respond with 696 a connection error of type HTTP_WRONG_STREAM. If an endpoint 697 receives a second SETTINGS frame, the endpoint MUST respond with a 698 connection error of type HTTP_MULTIPLE_SETTINGS. 700 The SETTINGS frame affects connection state. A badly formed or 701 incomplete SETTINGS frame MUST be treated as a connection error 702 (Section 7) of type HTTP_MALFORMED_SETTINGS. 704 5.2.5.1. Integer encoding 706 Settings which are integers are transmitted in network byte order. 707 Leading zero octets are permitted, but implementations SHOULD use 708 only as many bytes as are needed to represent the value. An integer 709 MUST NOT be represented in more bytes than would be used to transfer 710 the maximum permitted value. 712 5.2.5.2. Defined SETTINGS Parameters 714 The following settings are defined in HTTP/QUIC: 716 SETTINGS_HEADER_TABLE_SIZE (0x1): An integer with a maximum value of 717 2^32 - 1. This value MUST be zero. 719 SETTINGS_MAX_HEADER_LIST_SIZE (0x6): An integer with a maximum value 720 of 2^32 - 1 722 5.2.5.3. Usage in 0-RTT 724 When a 0-RTT QUIC connection is being used, the client's initial 725 requests will be sent before the arrival of the server's SETTINGS 726 frame. Clients SHOULD cache at least the following settings about 727 servers: 729 o SETTINGS_HEADER_TABLE_SIZE 731 o SETTINGS_MAX_HEADER_LIST_SIZE 733 Clients MUST comply with cached settings until the server's current 734 settings are received. If a client does not have cached values, it 735 SHOULD assume the following values: 737 o SETTINGS_HEADER_TABLE_SIZE: 0 octets 739 o SETTINGS_MAX_HEADER_LIST_SIZE: 16,384 octets 741 Servers MAY continue processing data from clients which exceed its 742 current configuration during the initial flight. In this case, the 743 client MUST apply the new settings immediately upon receipt. 745 If the connection is closed because these or other constraints were 746 violated during the 0-RTT flight (e.g. with 747 HTTP_HPACK_DECOMPRESSION_FAILED), clients MAY establish a new 748 connection and retry any 0-RTT requests using the settings sent by 749 the server on the closed connection. (This assumes that only 750 requests that are safe to retry are sent in 0-RTT.) If the 751 connection was closed before the SETTINGS frame was received, clients 752 SHOULD discard any cached values and use the defaults above on the 753 next connection. 755 5.2.6. PUSH_PROMISE 757 The PUSH_PROMISE frame (type=0x05) is used to carry a request header 758 set from server to client, as in HTTP/2. The PUSH_PROMISE frame 759 defines no flags. 761 0 1 2 3 762 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 763 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 764 | Push ID (32) | 765 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 766 | Header Block (*) ... 767 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 769 Figure 5: PUSH_PROMISE frame payload 771 The payload consists of: 773 Push ID: A 32-bit identifier for the server push request. A push ID 774 is used in push stream header (Section 4.4), CANCEL_PUSH frames 775 (Section 5.2.4), and PRIORITY frames (Section 5.2.3). 777 Header Block: HPACK-compressed request headers for the promised 778 response. 780 A server MUST NOT use a Push ID that is larger than the client has 781 provided in a MAX_PUSH_ID frame (Section 5.2.8). A client MUST treat 782 receipt of a PUSH_PROMISE that contains a larger Push ID than the 783 client has advertised as a connection error of type 784 HTTP_MALFORMED_PUSH_PROMISE. 786 A server MAY use the same Push ID in multiple PUSH_PROMISE frames. 787 This allows the server to use the same server push in response to 788 multiple concurrent requests. Referencing the same server push 789 ensures that a PUSH_PROMISE can be made in relation to every response 790 in which server push might be needed without duplicating pushes. 792 A server that uses the same Push ID in multiple PUSH_PROMISE frames 793 MUST include the same header fields each time. The octets of the 794 header block MAY be different due to differing encoding, but the 795 header fields and their values MUST be identical. Note that ordering 796 of header fields is significant. A client MUST treat receipt of a 797 PUSH_PROMISE with conflicting header field values for the same Push 798 ID as a connection error of type HTTP_MALFORMED_PUSH_PROMISE. 800 Allowing duplicate references to the same Push ID is primarily to 801 reduce duplication caused by concurrent requests. A server SHOULD 802 avoid reusing a Push ID over a long period. Clients are likely to 803 consume server push responses and not retain them for reuse over 804 time. Clients that see a PUSH_PROMISE that uses a Push ID that they 805 have since consumed and discarded are forced to ignore the 806 PUSH_PROMISE. 808 5.2.7. GOAWAY 810 The GOAWAY frame (type=0x7) is used to initiate graceful shutdown of 811 a connection by a server. GOAWAY allows a server to stop accepting 812 new requests while still finishing processing of previously received 813 requests. This enables administrative actions, like server 814 maintenance. GOAWAY by itself does not close a connection. (Note 815 that clients do not need to send GOAWAY to gracefully close a 816 connection; they simply stop making new requests.) 818 The GOAWAY frame does not define any flags, and the payload is a QUIC 819 stream identifier. The GOAWAY frame applies to the connection, not a 820 specific stream. An endpoint MUST treat a GOAWAY frame on a stream 821 other than the control stream as a connection error (Section 7) of 822 type HTTP_WRONG_STREAM. 824 New client requests might already have been sent before the client 825 receives the server's GOAWAY frame. The GOAWAY frame contains the 826 stream identifier of the last client-initiated request that was or 827 might be processed in this connection, which enables client and 828 server to agree on which requests were accepted prior to the 829 connection shutdown. This identifier MAY be lower than the stream 830 limit identified by a QUIC MAX_STREAM_ID frame, and MAY be zero if no 831 requests were processed. Servers SHOULD NOT increase the 832 MAX_STREAM_ID limit after sending a GOAWAY frame. 834 Note: In this context, "processed" means that some data from the 835 stream was passed to some higher layer of software that might have 836 taken some action as a result. 838 Once sent, the server will refuse requests sent on streams with an 839 identifier higher than the included last stream identifier. Clients 840 MUST NOT send new requests on the connection after receiving GOAWAY, 841 although requests might already be in transit. A new connection can 842 be established for new requests. 844 If the client has sent requests on streams with a higher stream 845 identifier than indicated in the GOAWAY frame, those requests were 846 not and will not be processed. Endpoints SHOULD reset any streams 847 above this ID with the error code HTTP_REQUEST_CANCELLED. Servers 848 MAY also reset streams below the indicated ID with 849 HTTP_REQUEST_CANCELLED if the associated requests were not processed. 850 Servers MUST NOT use the HTTP_REQUEST_CANCELLED status for requests 851 which were partially or fully processed. 853 The client can treat requests cancelled by the server as though they 854 had never been sent at all, thereby allowing them to be retried later 855 on a new connection. If a stream is cancelled after receiving a 856 complete response, the client MAY ignore the cancellation and use the 857 response. However, if a stream is cancelled after receiving a 858 partial response, the response SHOULD NOT be used. Automatically 859 retrying such requests is not possible, unless this is otherwise 860 permitted (e.g. idempotent actions like GET, PUT, or DELETE). 861 Requests on stream IDs less than or equal to the stream ID in the 862 GOAWAY frame might have been processed; their status cannot be known 863 until they are completed successfully, reset individually, or the 864 connection terminates. 866 Servers SHOULD send a GOAWAY frame when the closing of a connection 867 is known in advance, even if the advance notice is small, so that the 868 remote peer can know whether a stream has been partially processed or 869 not. For example, if an HTTP client sends a POST at the same time 870 that a server closes a QUIC connection, the client cannot know if the 871 server started to process that POST request if the server does not 872 send a GOAWAY frame to indicate what streams it might have acted on. 874 For unexpected closures caused by error conditions, a QUIC 875 CONNECTION_CLOSE frame MUST be used. However, a GOAWAY MAY be sent 876 first to provide additional detail to clients. If a connection 877 terminates without a GOAWAY frame, the last stream identifier is 878 effectively the highest possible stream identifier (as determined by 879 QUIC's MAX_STREAM_ID). 881 An endpoint MAY send multiple GOAWAY frames if circumstances change. 882 For instance, an endpoint that sends GOAWAY without an error code 883 during graceful shutdown could subsequently encounter an error 884 condition. The last stream identifier from the last GOAWAY frame 885 received indicates which streams could have been acted upon. 886 Endpoints MUST NOT increase the value they send in the last stream 887 identifier, since the peers might already have retried unprocessed 888 requests on another connection. 890 A client that is unable to retry requests loses all requests that are 891 in flight when the server closes the connection. A server that is 892 attempting to gracefully shut down a connection SHOULD send an 893 initial GOAWAY frame with the last stream identifier set to the 894 current value of QUIC's MAX_STREAM_ID and SHOULD NOT increase the 895 MAX_STREAM_ID thereafter. This signals to the client that a shutdown 896 is imminent and that initiating further requests is prohibited. 897 After allowing time for any in-flight requests (at least one round- 898 trip time), the server MAY send another GOAWAY frame with an updated 899 last stream identifier. This ensures that a connection can be 900 cleanly shut down without losing requests. 902 5.2.8. MAX_PUSH_ID 904 The MAX_PUSH_ID frame (type=0xD) is used by clients to control the 905 number of server pushes that the server can initiate. This sets the 906 maximum value for a Push ID that the server can use in a PUSH_PROMISE 907 frame. Consequently, this also limits the number of push streams 908 that the server can initiate in addition to the limit set by the QUIC 909 MAX_STREAM_ID frame. 911 The MAX_PUSH_ID frame is always sent on the control stream. Receipt 912 of a MAX_PUSH_ID frame on any other stream MUST be treated as a 913 connection error of type HTTP_WRONG_STREAM. 915 A server MUST NOT send a MAX_PUSH_ID frame. A client MUST treat the 916 receipt of a MAX_PUSH_ID frame as a connection error of type 917 HTTP_MALFORMED_MAX_PUSH_ID. 919 The maximum Push ID is unset when a connection is created, meaning 920 that a server cannot push until it receives a MAX_PUSH_ID frame. A 921 client that wishes to manage the number of promised server pushes can 922 increase the maximum Push ID by sending a MAX_PUSH_ID frame as the 923 server fulfills or cancels server pushes. 925 The MAX_PUSH_ID frame has no defined flags. 927 The MAX_PUSH_ID frame carries a 32-bit Push ID that identifies the 928 maximum value for a Push ID that the server can use (see 929 Section 5.2.6). A MAX_PUSH_ID frame cannot reduce the maximum Push 930 ID; receipt of a MAX_PUSH_ID that contains a smaller value than 931 previously received MUST be treated as a connection error of type 932 HTTP_MALFORMED_MAX_PUSH_ID. 934 A server MUST treat a MAX_PUSH_ID frame payload that is other than 4 935 octets in length as a connection error of type 936 HTTP_MALFORMED_MAX_PUSH_ID. 938 6. Connection Management 940 QUIC connections are persistent. All of the considerations in 941 Section 9.1 of [RFC7540] apply to the management of QUIC connections. 943 HTTP clients are expected to use QUIC PING frames to keep connections 944 open. Servers SHOULD NOT use PING frames to keep a connection open. 945 A client SHOULD NOT use PING frames for this purpose unless there are 946 responses outstanding for requests or server pushes. If the client 947 is not expecting a response from the server, allowing an idle 948 connection to time out (based on the idle_timeout transport 949 parameter) is preferred over expending effort maintaining a 950 connection that might not be needed. A gateway MAY use PING to 951 maintain connections in anticipation of need rather than incur the 952 latency cost of connection establishment to servers. 954 7. Error Handling 956 QUIC allows the application to abruptly terminate (reset) individual 957 streams or the entire connection when an error is encountered. These 958 are referred to as "stream errors" or "connection errors" and are 959 described in more detail in [QUIC-TRANSPORT]. 961 This section describes HTTP-specific error codes which can be used to 962 express the cause of a connection or stream error. 964 7.1. HTTP/QUIC Error Codes 966 The following error codes are defined for use in QUIC RST_STREAM, 967 STOP_SENDING, and CONNECTION_CLOSE frames when using HTTP/QUIC. 969 STOPPING (0x00): This value is reserved by the transport to be used 970 in response to QUIC STOP_SENDING frames. 972 HTTP_NO_ERROR (0x01): No error. This is used when the connection or 973 stream needs to be closed, but there is no error to signal. 975 HTTP_PUSH_REFUSED (0x02): The server has attempted to push content 976 which the client will not accept on this connection. 978 HTTP_INTERNAL_ERROR (0x03): An internal error has occurred in the 979 HTTP stack. 981 HTTP_PUSH_ALREADY_IN_CACHE (0x04): The server has attempted to push 982 content which the client has cached. 984 HTTP_REQUEST_CANCELLED (0x05): The client no longer needs the 985 requested data. 987 HTTP_HPACK_DECOMPRESSION_FAILED (0x06): HPACK failed to decompress a 988 frame and cannot continue. 990 HTTP_CONNECT_ERROR (0x07): The connection established in response to 991 a CONNECT request was reset or abnormally closed. 993 HTTP_EXCESSIVE_LOAD (0x08): The endpoint detected that its peer is 994 exhibiting a behavior that might be generating excessive load. 996 HTTP_VERSION_FALLBACK (0x09): The requested operation cannot be 997 served over HTTP/QUIC. The peer should retry over HTTP/2. 999 HTTP_MALFORMED_HEADERS (0x0A): A HEADERS frame has been received 1000 with an invalid format. 1002 HTTP_MALFORMED_PRIORITY (0x0B): A PRIORITY frame has been received 1003 with an invalid format. 1005 HTTP_MALFORMED_SETTINGS (0x0C): A SETTINGS frame has been received 1006 with an invalid format. 1008 HTTP_MALFORMED_PUSH_PROMISE (0x0D): A PUSH_PROMISE frame has been 1009 received with an invalid format. 1011 HTTP_MALFORMED_DATA (0x0E): A DATA frame has been received with an 1012 invalid format. 1014 HTTP_INTERRUPTED_HEADERS (0x0F): A HEADERS frame without the End 1015 Header Block flag was followed by a frame other than HEADERS. 1017 HTTP_WRONG_STREAM (0x10): A frame was received on stream where it is 1018 not permitted. 1020 HTTP_MULTIPLE_SETTINGS (0x11): More than one SETTINGS frame was 1021 received. 1023 HTTP_MALFORMED_PUSH (0x12): A push stream header was malformed or 1024 included an invalid Push ID. 1026 HTTP_MALFORMED_MAX_PUSH_ID (0x13): A MAX_PUSH_ID frame has been 1027 received with an invalid format. 1029 8. Considerations for Transitioning from HTTP/2 1031 HTTP/QUIC is strongly informed by HTTP/2, and bears many 1032 similarities. This section describes the approach taken to design 1033 HTTP/QUIC, points out important differences from HTTP/2, and 1034 describes how to map HTTP/2 extensions into HTTP/QUIC. 1036 HTTP/QUIC begins from the premise that HTTP/2 code reuse is a useful 1037 feature, but not a hard requirement. HTTP/QUIC departs from HTTP/2 1038 primarily where necessary to accommodate the differences in behavior 1039 between QUIC and TCP (lack of ordering, support for streams). We 1040 intend to avoid gratuitous changes which make it difficult or 1041 impossible to build extensions with the same semantics applicable to 1042 both protocols at once. 1044 These departures are noted in this section. 1046 8.1. HTTP Frame Types 1048 Many framing concepts from HTTP/2 can be elided away on QUIC, because 1049 the transport deals with them. Because frames are already on a 1050 stream, they can omit the stream number. Because frames do not block 1051 multiplexing (QUIC's multiplexing occurs below this layer), the 1052 support for variable-maximum-length packets can be removed. Because 1053 stream termination is handled by QUIC, an END_STREAM flag is not 1054 required. 1056 Frame payloads are largely drawn from [RFC7540]. However, QUIC 1057 includes many features (e.g. flow control) which are also present in 1058 HTTP/2. In these cases, the HTTP mapping does not re-implement them. 1059 As a result, several HTTP/2 frame types are not required in HTTP/ 1060 QUIC. Where an HTTP/2-defined frame is no longer used, the frame ID 1061 has been reserved in order to maximize portability between HTTP/2 and 1062 HTTP/QUIC implementations. However, even equivalent frames between 1063 the two mappings are not identical. 1065 Many of the differences arise from the fact that HTTP/2 provides an 1066 absolute ordering between frames across all streams, while QUIC 1067 provides this guarantee on each stream only. As a result, if a frame 1068 type makes assumptions that frames from different streams will still 1069 be received in the order sent, HTTP/QUIC will break them. 1071 For example, implicit in the HTTP/2 prioritization scheme is the 1072 notion of in-order delivery of priority changes (i.e., dependency 1073 tree mutations): since operations on the dependency tree such as 1074 reparenting a subtree are not commutative, both sender and receiver 1075 must apply them in the same order to ensure that both sides have a 1076 consistent view of the stream dependency tree. HTTP/2 specifies 1077 priority assignments in PRIORITY frames and (optionally) in HEADERS 1078 frames. To achieve in-order delivery of priority changes in HTTP/ 1079 QUIC, PRIORITY frames are sent on the control stream and the PRIORITY 1080 section is removed from the HEADERS frame. 1082 Other than this issue, frame type HTTP/2 extensions are typically 1083 portable to QUIC simply by replacing Stream 0 in HTTP/2 with Stream 1 1084 in HTTP/QUIC. HTTP/QUIC extensions will not assume ordering, but 1085 would not be harmed by ordering, and would be portable to HTTP/2 in 1086 the same manner. 1088 Below is a listing of how each HTTP/2 frame type is mapped: 1090 DATA (0x0): Padding is not defined in HTTP/QUIC frames. See 1091 Section 5.2.1. 1093 HEADERS (0x1): As described above, the PRIORITY region of HEADERS is 1094 not supported. A separate PRIORITY frame MUST be used. Padding 1095 is not defined in HTTP/QUIC frames. See Section 5.2.2. 1097 PRIORITY (0x2): As described above, the PRIORITY frame is sent on 1098 the control stream. See Section 5.2.3. 1100 RST_STREAM (0x3): RST_STREAM frames do not exist, since QUIC 1101 provides stream lifecycle management. The same code point is used 1102 for the CANCEL_PUSH frame (Section 5.2.4). 1104 SETTINGS (0x4): SETTINGS frames are sent only at the beginning of 1105 the connection. See Section 5.2.5 and Section 8.2. 1107 PUSH_PROMISE (0x5): The PUSH_PROMISE does not reference a stream; 1108 instead the push stream references the PUSH_PROMISE frame using a 1109 Push ID. See Section 5.2.6. 1111 PING (0x6): PING frames do not exist, since QUIC provides equivalent 1112 functionality. 1114 GOAWAY (0x7): GOAWAY is sent only from server to client and does not 1115 contain an error code. See Section 5.2.7. 1117 WINDOW_UPDATE (0x8): WINDOW_UPDATE frames do not exist, since QUIC 1118 provides flow control. 1120 CONTINUATION (0x9): CONTINUATION frames do not exist; instead, 1121 larger HEADERS/PUSH_PROMISE frames than HTTP/2 are permitted, and 1122 HEADERS frames can be used in series. 1124 Frame types defined by extensions to HTTP/2 need to be separately 1125 registered for HTTP/QUIC if still applicable. The IDs of frames 1126 defined in [RFC7540] have been reserved for simplicity. See 1127 Section 10.3. 1129 8.2. HTTP/2 SETTINGS Parameters 1131 An important difference from HTTP/2 is that settings are sent once, 1132 at the beginning of the connection, and thereafter cannot change. 1133 This eliminates many corner cases around synchronization of changes. 1135 Some transport-level options that HTTP/2 specifies via the SETTINGS 1136 frame are superseded by QUIC transport parameters in HTTP/QUIC. The 1137 HTTP-level options that are retained in HTTP/QUIC have the same value 1138 as in HTTP/2. 1140 Below is a listing of how each HTTP/2 SETTINGS parameter is mapped: 1142 SETTINGS_HEADER_TABLE_SIZE: See Section 5.2.5.2. 1144 SETTINGS_ENABLE_PUSH: This is removed in favor of the MAX_PUSH_ID 1145 which provides a more granular control over server push. 1147 SETTINGS_MAX_CONCURRENT_STREAMS: QUIC controls the largest open 1148 stream ID as part of its flow control logic. Specifying 1149 SETTINGS_MAX_CONCURRENT_STREAMS in the SETTINGS frame is an error. 1151 SETTINGS_INITIAL_WINDOW_SIZE: QUIC requires both stream and 1152 connection flow control window sizes to be specified in the 1153 initial transport handshake. Specifying 1154 SETTINGS_INITIAL_WINDOW_SIZE in the SETTINGS frame is an error. 1156 SETTINGS_MAX_FRAME_SIZE: This setting has no equivalent in HTTP/ 1157 QUIC. Specifying it in the SETTINGS frame is an error. 1159 SETTINGS_MAX_HEADER_LIST_SIZE: See Section 5.2.5.2. 1161 Settings need to be defined separately for HTTP/2 and HTTP/QUIC. The 1162 IDs of settings defined in [RFC7540] have been reserved for 1163 simplicity. See Section 10.4. 1165 8.3. HTTP/2 Error Codes 1167 QUIC has the same concepts of "stream" and "connection" errors that 1168 HTTP/2 provides. However, because the error code space is shared 1169 between multiple components, there is no direct portability of HTTP/2 1170 error codes. 1172 The HTTP/2 error codes defined in Section 7 of [RFC7540] map to the 1173 HTTP over QUIC error codes as follows: 1175 NO_ERROR (0x0): HTTP_NO_ERROR in Section 7.1. 1177 PROTOCOL_ERROR (0x1): No single mapping. See new HTTP_MALFORMED_* 1178 error codes defined in Section 7.1. 1180 INTERNAL_ERROR (0x2): HTTP_INTERNAL_ERROR in Section 7.1. 1182 FLOW_CONTROL_ERROR (0x3): Not applicable, since QUIC handles flow 1183 control. Would provoke a QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA 1184 from the QUIC layer. 1186 SETTINGS_TIMEOUT (0x4): Not applicable, since no acknowledgement of 1187 SETTINGS is defined. 1189 STREAM_CLOSED (0x5): Not applicable, since QUIC handles stream 1190 management. Would provoke a QUIC_STREAM_DATA_AFTER_TERMINATION 1191 from the QUIC layer. 1193 FRAME_SIZE_ERROR (0x6) No single mapping. See new error codes 1194 defined in Section 7.1. 1196 REFUSED_STREAM (0x7): Not applicable, since QUIC handles stream 1197 management. Would provoke a QUIC_TOO_MANY_OPEN_STREAMS from the 1198 QUIC layer. 1200 CANCEL (0x8): HTTP_REQUEST_CANCELLED in Section 7.1. 1202 COMPRESSION_ERROR (0x9): HTTP_HPACK_DECOMPRESSION_FAILED in 1203 Section 7.1. 1205 CONNECT_ERROR (0xa): HTTP_CONNECT_ERROR in Section 7.1. 1207 ENHANCE_YOUR_CALM (0xb): HTTP_EXCESSIVE_LOAD in Section 7.1. 1209 INADEQUATE_SECURITY (0xc): Not applicable, since QUIC is assumed to 1210 provide sufficient security on all connections. 1212 HTTP_1_1_REQUIRED (0xd): HTTP_VERSION_FALLBACK in Section 7.1. 1214 Error codes need to be defined for HTTP/2 and HTTP/QUIC separately. 1215 See Section 10.5. 1217 9. Security Considerations 1219 The security considerations of HTTP over QUIC should be comparable to 1220 those of HTTP/2. 1222 The modified SETTINGS format contains nested length elements, which 1223 could pose a security risk to an uncautious implementer. A SETTINGS 1224 frame parser MUST ensure that the length of the frame exactly matches 1225 the length of the settings it contains. 1227 10. IANA Considerations 1229 10.1. Registration of HTTP/QUIC Identification String 1231 This document creates a new registration for the identification of 1232 HTTP/QUIC in the "Application Layer Protocol Negotiation (ALPN) 1233 Protocol IDs" registry established in [RFC7301]. 1235 The "hq" string identifies HTTP/QUIC: 1237 Protocol: HTTP over QUIC 1239 Identification Sequence: 0x68 0x71 ("hq") 1241 Specification: This document 1243 10.2. Registration of QUIC Version Hint Alt-Svc Parameter 1245 This document creates a new registration for version-negotiation 1246 hints in the "Hypertext Transfer Protocol (HTTP) Alt-Svc Parameter" 1247 registry established in [RFC7838]. 1249 Parameter: "quic" 1251 Specification: This document, Section 2.1 1253 10.3. Frame Types 1255 This document establishes a registry for HTTP/QUIC frame type codes. 1256 The "HTTP/QUIC Frame Type" registry manages an 8-bit space. The 1257 "HTTP/QUIC Frame Type" registry operates under either of the "IETF 1258 Review" or "IESG Approval" policies [RFC8126] for values between 0x00 1259 and 0xef, with values between 0xf0 and 0xff being reserved for 1260 Experimental Use. 1262 While this registry is separate from the "HTTP/2 Frame Type" registry 1263 defined in [RFC7540], it is preferable that the assignments parallel 1264 each other. If an entry is present in only one registry, every 1265 effort SHOULD be made to avoid assigning the corresponding value to 1266 an unrelated operation. 1268 New entries in this registry require the following information: 1270 Frame Type: A name or label for the frame type. 1272 Code: The 8-bit code assigned to the frame type. 1274 Specification: A reference to a specification that includes a 1275 description of the frame layout, its semantics, and flags that the 1276 frame type uses, including any parts of the frame that are 1277 conditionally present based on the value of flags. 1279 The entries in the following table are registered by this document. 1281 +--------------+------+---------------+ 1282 | Frame Type | Code | Specification | 1283 +--------------+------+---------------+ 1284 | DATA | 0x0 | Section 5.2.1 | 1285 | | | | 1286 | HEADERS | 0x1 | Section 5.2.2 | 1287 | | | | 1288 | PRIORITY | 0x2 | Section 5.2.3 | 1289 | | | | 1290 | CANCEL_PUSH | 0x3 | Section 5.2.4 | 1291 | | | | 1292 | SETTINGS | 0x4 | Section 5.2.5 | 1293 | | | | 1294 | PUSH_PROMISE | 0x5 | Section 5.2.6 | 1295 | | | | 1296 | Reserved | 0x6 | N/A | 1297 | | | | 1298 | GOAWAY | 0x7 | Section 5.2.7 | 1299 | | | | 1300 | Reserved | 0x8 | N/A | 1301 | | | | 1302 | Reserved | 0x9 | N/A | 1303 | | | | 1304 | MAX_PUSH_ID | 0xD | Section 5.2.8 | 1305 +--------------+------+---------------+ 1307 10.4. Settings Parameters 1309 This document establishes a registry for HTTP/QUIC settings. The 1310 "HTTP/QUIC Settings" registry manages a 16-bit space. The "HTTP/QUIC 1311 Settings" registry operates under the "Expert Review" policy 1312 [RFC8126] for values in the range from 0x0000 to 0xefff, with values 1313 between and 0xf000 and 0xffff being reserved for Experimental Use. 1314 The designated experts are the same as those for the "HTTP/2 1315 Settings" registry defined in [RFC7540]. 1317 While this registry is separate from the "HTTP/2 Settings" registry 1318 defined in [RFC7540], it is preferable that the assignments parallel 1319 each other. If an entry is present in only one registry, every 1320 effort SHOULD be made to avoid assigning the corresponding value to 1321 an unrelated operation. 1323 New registrations are advised to provide the following information: 1325 Name: A symbolic name for the setting. Specifying a setting name is 1326 optional. 1328 Code: The 16-bit code assigned to the setting. 1330 Specification: An optional reference to a specification that 1331 describes the use of the setting. 1333 The entries in the following table are registered by this document. 1335 +----------------------+------+-----------------+ 1336 | Setting Name | Code | Specification | 1337 +----------------------+------+-----------------+ 1338 | HEADER_TABLE_SIZE | 0x1 | Section 5.2.5.2 | 1339 | | | | 1340 | Reserved | 0x2 | N/A | 1341 | | | | 1342 | Reserved | 0x3 | N/A | 1343 | | | | 1344 | Reserved | 0x4 | N/A | 1345 | | | | 1346 | Reserved | 0x5 | N/A | 1347 | | | | 1348 | MAX_HEADER_LIST_SIZE | 0x6 | Section 5.2.5.2 | 1349 +----------------------+------+-----------------+ 1351 10.5. Error Codes 1353 This document establishes a registry for HTTP/QUIC error codes. The 1354 "HTTP/QUIC Error Code" registry manages a 16-bit space. The "HTTP/ 1355 QUIC Error Code" registry operates under the "Expert Review" policy 1356 [RFC8126]. 1358 Registrations for error codes are required to include a description 1359 of the error code. An expert reviewer is advised to examine new 1360 registrations for possible duplication with existing error codes. 1361 Use of existing registrations is to be encouraged, but not mandated. 1363 New registrations are advised to provide the following information: 1365 Name: A name for the error code. Specifying an error code name is 1366 optional. 1368 Code: The 16-bit error code value. 1370 Description: A brief description of the error code semantics, longer 1371 if no detailed specification is provided. 1373 Specification: An optional reference for a specification that 1374 defines the error code. 1376 The entries in the following table are registered by this document. 1378 +-----------------------------+-----+-------------+-----------------+ 1379 | Name | Cod | Description | Specification | 1380 | | e | | | 1381 +-----------------------------+-----+-------------+-----------------+ 1382 | STOPPING | 0x0 | Reserved by | [QUIC-TRANSPORT | 1383 | | 0 | QUIC | ] | 1384 | | | | | 1385 | HTTP_NO_ERROR | 0x0 | No error | Section 7.1 | 1386 | | 1 | | | 1387 | | | | | 1388 | HTTP_PUSH_REFUSED | 0x0 | Client | Section 7.1 | 1389 | | 2 | refused | | 1390 | | | pushed | | 1391 | | | content | | 1392 | | | | | 1393 | HTTP_INTERNAL_ERROR | 0x0 | Internal | Section 7.1 | 1394 | | 3 | error | | 1395 | | | | | 1396 | HTTP_PUSH_ALREADY_IN_CACHE | 0x0 | Pushed | Section 7.1 | 1397 | | 4 | content | | 1398 | | | already | | 1399 | | | cached | | 1400 | | | | | 1401 | HTTP_REQUEST_CANCELLED | 0x0 | Data no | Section 7.1 | 1402 | | 5 | longer | | 1403 | | | needed | | 1404 | | | | | 1405 | HTTP_HPACK_DECOMPRESSION_FA | 0x0 | HPACK | Section 7.1 | 1406 | ILED | 6 | cannot | | 1407 | | | continue | | 1408 | | | | | 1409 | HTTP_CONNECT_ERROR | 0x0 | TCP reset | Section 7.1 | 1410 | | 7 | or error on | | 1411 | | | CONNECT | | 1412 | | | request | | 1413 | | | | | 1414 | HTTP_EXCESSIVE_LOAD | 0x0 | Peer | Section 7.1 | 1415 | | 8 | generating | | 1416 | | | excessive | | 1417 | | | load | | 1418 | | | | | 1419 | HTTP_VERSION_FALLBACK | 0x0 | Retry over | Section 7.1 | 1420 | | 9 | HTTP/2 | | 1421 | | | | | 1422 | HTTP_MALFORMED_HEADERS | 0x0 | Invalid | Section 7.1 | 1423 | | A | HEADERS | | 1424 | | | frame | | 1425 | | | | | 1426 | HTTP_MALFORMED_PRIORITY | 0x0 | Invalid | Section 7.1 | 1427 | | B | PRIORITY | | 1428 | | | frame | | 1429 | | | | | 1430 | HTTP_MALFORMED_SETTINGS | 0x0 | Invalid | Section 7.1 | 1431 | | C | SETTINGS | | 1432 | | | frame | | 1433 | | | | | 1434 | HTTP_MALFORMED_PUSH_PROMISE | 0x0 | Invalid PUS | Section 7.1 | 1435 | | D | H_PROMISE | | 1436 | | | frame | | 1437 | | | | | 1438 | HTTP_MALFORMED_DATA | 0x0 | Invalid | Section 7.1 | 1439 | | E | DATA frame | | 1440 | | | | | 1441 | HTTP_INTERRUPTED_HEADERS | 0x0 | Incomplete | Section 7.1 | 1442 | | F | HEADERS | | 1443 | | | block | | 1444 | | | | | 1445 | HTTP_WRONG_STREAM | 0x1 | A frame was | Section 7.1 | 1446 | | 0 | sent on the | | 1447 | | | wrong | | 1448 | | | stream | | 1449 | | | | | 1450 | HTTP_MULTIPLE_SETTINGS | 0x1 | Multiple | Section 7.1 | 1451 | | 1 | SETTINGS | | 1452 | | | frames | | 1453 | | | | | 1454 | HTTP_MALFORMED_PUSH | 0x1 | Invalid | Section 7.1 | 1455 | | 2 | push stream | | 1456 | | | header | | 1457 | | | | | 1458 | HTTP_MALFORMED_MAX_PUSH_ID | 0x1 | Invalid | Section 7.1 | 1459 | | 3 | MAX_PUSH_ID | | 1460 | | | frame | | 1461 +-----------------------------+-----+-------------+-----------------+ 1463 11. References 1465 11.1. Normative References 1467 [QUIC-TRANSPORT] 1468 Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based 1469 Multiplexed and Secure Transport", draft-ietf-quic- 1470 transport-07 (work in progress), October 2017. 1472 [RFC0793] Postel, J., "Transmission Control Protocol", STD 7, 1473 RFC 793, DOI 10.17487/RFC0793, September 1981, 1474 . 1476 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1477 Requirement Levels", BCP 14, RFC 2119, 1478 DOI 10.17487/RFC2119, March 1997, 1479 . 1481 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 1482 Specifications: ABNF", STD 68, RFC 5234, 1483 DOI 10.17487/RFC5234, January 2008, 1484 . 1486 [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1487 Protocol (HTTP/1.1): Message Syntax and Routing", 1488 RFC 7230, DOI 10.17487/RFC7230, June 2014, 1489 . 1491 [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer 1492 Protocol (HTTP/1.1): Semantics and Content", RFC 7231, 1493 DOI 10.17487/RFC7231, June 2014, 1494 . 1496 [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext 1497 Transfer Protocol Version 2 (HTTP/2)", RFC 7540, 1498 DOI 10.17487/RFC7540, May 2015, 1499 . 1501 [RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for 1502 HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015, 1503 . 1505 [RFC7838] Nottingham, M., McManus, P., and J. Reschke, "HTTP 1506 Alternative Services", RFC 7838, DOI 10.17487/RFC7838, 1507 April 2016, . 1509 11.2. Informative References 1511 [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan, 1512 "Transport Layer Security (TLS) Application-Layer Protocol 1513 Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301, 1514 July 2014, . 1516 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1517 Writing an IANA Considerations Section in RFCs", BCP 26, 1518 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1519 . 1521 11.3. URIs 1523 [1] https://mailarchive.ietf.org/arch/search/?email_list=quic 1525 [2] https://github.com/quicwg 1527 [3] https://github.com/quicwg/base-drafts/labels/http 1529 Appendix A. Contributors 1531 The original authors of this specification were Robbie Shade and Mike 1532 Warres. 1534 Appendix B. Change Log 1536 *RFC Editor's Note:* Please remove this section prior to 1537 publication of a final version of this document. 1539 B.1. Since draft-ietf-quic-http-06 1541 Nothing yet. 1543 B.2. Since draft-ietf-quic-http-05 1545 o Made push ID sequential, add MAX_PUSH_ID, remove 1546 SETTINGS_ENABLE_PUSH (#709) 1548 o Guidance about keep-alive and QUIC PINGs (#729) 1550 o Expanded text on GOAWAY and cancellation (#757) 1552 B.3. Since draft-ietf-quic-http-04 1554 o Cite RFC 5234 (#404) 1556 o Return to a single stream per request (#245,#557) 1557 o Use separate frame type and settings registries from HTTP/2 (#81) 1559 o SETTINGS_ENABLE_PUSH instead of SETTINGS_DISABLE_PUSH (#477) 1561 o Restored GOAWAY (#696) 1563 o Identify server push using Push ID rather than a stream ID 1564 (#702,#281) 1566 o DATA frames cannot be empty (#700) 1568 B.4. Since draft-ietf-quic-http-03 1570 None. 1572 B.5. Since draft-ietf-quic-http-02 1574 o Track changes in transport draft 1576 B.6. Since draft-ietf-quic-http-01 1578 o SETTINGS changes (#181): 1580 * SETTINGS can be sent only once at the start of a connection; no 1581 changes thereafter 1583 * SETTINGS_ACK removed 1585 * Settings can only occur in the SETTINGS frame a single time 1587 * Boolean format updated 1589 o Alt-Svc parameter changed from "v" to "quic"; format updated 1590 (#229) 1592 o Closing the connection control stream or any message control 1593 stream is a fatal error (#176) 1595 o HPACK Sequence counter can wrap (#173) 1597 o 0-RTT guidance added 1599 o Guide to differences from HTTP/2 and porting HTTP/2 extensions 1600 added (#127,#242) 1602 B.7. Since draft-ietf-quic-http-00 1604 o Changed "HTTP/2-over-QUIC" to "HTTP/QUIC" throughout (#11,#29) 1606 o Changed from using HTTP/2 framing within Stream 3 to new framing 1607 format and two-stream-per-request model (#71,#72,#73) 1609 o Adopted SETTINGS format from draft-bishop-httpbis-extended- 1610 settings-01 1612 o Reworked SETTINGS_ACK to account for indeterminate inter-stream 1613 order (#75) 1615 o Described CONNECT pseudo-method (#95) 1617 o Updated ALPN token and Alt-Svc guidance (#13,#87) 1619 o Application-layer-defined error codes (#19,#74) 1621 B.8. Since draft-shade-quic-http2-mapping-00 1623 o Adopted as base for draft-ietf-quic-http 1625 o Updated authors/editors list 1627 Author's Address 1629 Mike Bishop (editor) 1630 Microsoft 1632 Email: Michael.Bishop@microsoft.com