QUIC                                                      M. Bishop, Ed.Internet-Draft                                                    AkamaiIntended status: Standards Track                         August 15, 2018Expires: February 16, 2019              Hypertext Transfer Protocol (HTTP) over QUIC                        draft-ietf-quic-http-14Abstract   The QUIC transport protocol has several features that are desirable   in a transport for HTTP, such as stream multiplexing, per-stream flow   control, and low-latency connection establishment.  This document   describes a mapping of HTTP semantics over QUIC.  This document also   identifies HTTP/2 features that are subsumed by QUIC, and describes   how HTTP/2 extensions can be ported to QUIC.Note to Readers   Discussion of this draft takes place on the QUIC working group   mailing list (quic@ietf.org), which is archived at   https://mailarchive.ietf.org/arch/search/?email_list=quic [1].   Working Group information can be found at https://github.com/quicwg   [2]; source code and issues list for this draft can be found at   https://github.com/quicwg/base-drafts/labels/-http [3].Status of This Memo   This Internet-Draft is submitted in full conformance with the   provisions of BCP 78 and BCP 79.   Internet-Drafts are working documents of the Internet Engineering   Task Force (IETF).  Note that other groups may also distribute   working documents as Internet-Drafts.  The list of current Internet-   Drafts is at https://datatracker.ietf.org/drafts/current/.   Internet-Drafts are draft documents valid for a maximum of six months   and may be updated, replaced, or obsoleted by other documents at any   time.  It is inappropriate to use Internet-Drafts as reference   material or to cite them other than as "work in progress."   This Internet-Draft will expire on February 16, 2019.Bishop                  Expires February 16, 2019               [Page 1]Internet-Draft               HTTP over QUIC                  August 2018Copyright Notice   Copyright (c) 2018 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject to BCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (https://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Table of Contents   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3     1.1.  Notational Conventions  . . . . . . . . . . . . . . . . .   4   2.  Connection Setup and Management . . . . . . . . . . . . . . .   4     2.1.  Draft Version Identification  . . . . . . . . . . . . . .   4     2.2.  Discovering an HTTP/QUIC Endpoint . . . . . . . . . . . .   5       2.2.1.  QUIC Version Hints  . . . . . . . . . . . . . . . . .   5     2.3.  Connection Establishment  . . . . . . . . . . . . . . . .   6     2.4.  Connection Reuse  . . . . . . . . . . . . . . . . . . . .   6   3.  Stream Mapping and Usage  . . . . . . . . . . . . . . . . . .   7     3.1.  HTTP Message Exchanges  . . . . . . . . . . . . . . . . .   7       3.1.1.  Header Formatting and Compression . . . . . . . . . .   9       3.1.2.  The CONNECT Method  . . . . . . . . . . . . . . . . .   9       3.1.3.  Request Cancellation  . . . . . . . . . . . . . . . .  10     3.2.  Request Prioritization  . . . . . . . . . . . . . . . . .  11       3.2.1.  Placeholders  . . . . . . . . . . . . . . . . . . . .  11       3.2.2.  Priority Tree Maintenance . . . . . . . . . . . . . .  12     3.3.  Unidirectional Streams  . . . . . . . . . . . . . . . . .  13       3.3.1.  Reserved Stream Types . . . . . . . . . . . . . . . .  13       3.3.2.  Control Streams . . . . . . . . . . . . . . . . . . .  14       3.3.3.  Server Push . . . . . . . . . . . . . . . . . . . . .  14   4.  HTTP Framing Layer  . . . . . . . . . . . . . . . . . . . . .  15     4.1.  Frame Layout  . . . . . . . . . . . . . . . . . . . . . .  16     4.2.  Frame Definitions . . . . . . . . . . . . . . . . . . . .  16       4.2.1.  Reserved Frame Types  . . . . . . . . . . . . . . . .  16       4.2.2.  DATA  . . . . . . . . . . . . . . . . . . . . . . . .  16       4.2.3.  HEADERS . . . . . . . . . . . . . . . . . . . . . . .  17       4.2.4.  PRIORITY  . . . . . . . . . . . . . . . . . . . . . .  17       4.2.5.  CANCEL_PUSH . . . . . . . . . . . . . . . . . . . . .  19       4.2.6.  SETTINGS  . . . . . . . . . . . . . . . . . . . . . .  20       4.2.7.  PUSH_PROMISE  . . . . . . . . . . . . . . . . . . . .  23       4.2.8.  GOAWAY  . . . . . . . . . . . . . . . . . . . . . . .  24Bishop                  Expires February 16, 2019               [Page 2]Internet-Draft               HTTP over QUIC                  August 2018       4.2.9.  MAX_PUSH_ID . . . . . . . . . . . . . . . . . . . . .  26   5.  Connection Management . . . . . . . . . . . . . . . . . . . .  27   6.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .  27     6.1.  HTTP/QUIC Error Codes . . . . . . . . . . . . . . . . . .  27   7.  Extensions to HTTP/QUIC . . . . . . . . . . . . . . . . . . .  29   8.  Considerations for Transitioning from HTTP/2  . . . . . . . .  30     8.1.  Streams . . . . . . . . . . . . . . . . . . . . . . . . .  30     8.2.  HTTP Frame Types  . . . . . . . . . . . . . . . . . . . .  30     8.3.  HTTP/2 SETTINGS Parameters  . . . . . . . . . . . . . . .  32     8.4.  HTTP/2 Error Codes  . . . . . . . . . . . . . . . . . . .  33   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  34   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  34     10.1.  Registration of HTTP/QUIC Identification String  . . . .  34     10.2.  Registration of QUIC Version Hint Alt-Svc Parameter  . .  35     10.3.  Frame Types  . . . . . . . . . . . . . . . . . . . . . .  35     10.4.  Settings Parameters  . . . . . . . . . . . . . . . . . .  36     10.5.  Error Codes  . . . . . . . . . . . . . . . . . . . . . .  37     10.6.  Stream Types . . . . . . . . . . . . . . . . . . . . . .  40   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  40     11.1.  Normative References . . . . . . . . . . . . . . . . . .  41     11.2.  Informative References . . . . . . . . . . . . . . . . .  42     11.3.  URIs . . . . . . . . . . . . . . . . . . . . . . . . . .  42   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  42     A.1.  Since draft-ietf-quic-http-13 . . . . . . . . . . . . . .  42     A.2.  Since draft-ietf-quic-http-12 . . . . . . . . . . . . . .  42     A.3.  Since draft-ietf-quic-http-11 . . . . . . . . . . . . . .  43     A.4.  Since draft-ietf-quic-http-10 . . . . . . . . . . . . . .  43     A.5.  Since draft-ietf-quic-http-09 . . . . . . . . . . . . . .  43     A.6.  Since draft-ietf-quic-http-08 . . . . . . . . . . . . . .  43     A.7.  Since draft-ietf-quic-http-07 . . . . . . . . . . . . . .  43     A.8.  Since draft-ietf-quic-http-06 . . . . . . . . . . . . . .  44     A.9.  Since draft-ietf-quic-http-05 . . . . . . . . . . . . . .  44     A.10. Since draft-ietf-quic-http-04 . . . . . . . . . . . . . .  44     A.11. Since draft-ietf-quic-http-03 . . . . . . . . . . . . . .  44     A.12. Since draft-ietf-quic-http-02 . . . . . . . . . . . . . .  44     A.13. Since draft-ietf-quic-http-01 . . . . . . . . . . . . . .  44     A.14. Since draft-ietf-quic-http-00 . . . . . . . . . . . . . .  45     A.15. Since draft-shade-quic-http2-mapping-00 . . . . . . . . .  45   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  45   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  461.  Introduction   The QUIC transport protocol has several features that are desirable   in a transport for HTTP, such as stream multiplexing, per-stream flow   control, and low-latency connection establishment.  This document   describes a mapping of HTTP semantics over QUIC, drawing heavily on   the existing TCP mapping, HTTP/2.  Specifically, this documentBishop                  Expires February 16, 2019               [Page 3]Internet-Draft               HTTP over QUIC                  August 2018   identifies HTTP/2 features that are subsumed by QUIC, and describes   how the other features can be implemented atop QUIC.   QUIC is described in [QUIC-TRANSPORT].  For a full description of   HTTP/2, see [RFC7540].1.1.  Notational Conventions   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and   "OPTIONAL" in this document are to be interpreted as described in BCP   14 [RFC2119] [RFC8174] when, and only when, they appear in all   capitals, as shown here.   Field definitions are given in Augmented Backus-Naur Form (ABNF), as   defined in [RFC5234].   This document uses the variable-length integer encoding from   [QUIC-TRANSPORT].   Protocol elements called "frames" exist in both this document and   [QUIC-TRANSPORT].  Where frames from [QUIC-TRANSPORT] are referenced,   the frame name will be prefaced with "QUIC."  For example, "QUIC   APPLICATION_CLOSE frames."  References without this preface refer to   frames defined in Section 4.2.2.  Connection Setup and Management2.1.  Draft Version Identification      *RFC Editor's Note:* Please remove this section prior to      publication of a final version of this document.   HTTP/QUIC uses the token "hq" to identify itself in ALPN and Alt-Svc.   Only implementations of the final, published RFC can identify   themselves as "hq".  Until such an RFC exists, implementations MUST   NOT identify themselves using this string.   Implementations of draft versions of the protocol MUST add the string   "-" and the corresponding draft number to the identifier.  For   example, draft-ietf-quic-http-01 is identified using the string "hq-   01".   Non-compatible experiments that are based on these draft versions   MUST append the string "-" and an experiment name to the identifier.   For example, an experimental implementation based on draft-ietf-quic-   http-09 which reserves an extra stream for unsolicited transmission   of 1980s pop music might identify itself as "hq-09-rickroll".  NoteBishop                  Expires February 16, 2019               [Page 4]Internet-Draft               HTTP over QUIC                  August 2018   that any label MUST conform to the "token" syntax defined in   Section 3.2.6 of [RFC7230].  Experimenters are encouraged to   coordinate their experiments on the quic@ietf.org mailing list.2.2.  Discovering an HTTP/QUIC Endpoint   An HTTP origin advertises the availability of an equivalent HTTP/QUIC   endpoint via the Alt-Svc HTTP response header or the HTTP/2 ALTSVC   frame ([RFC7838]), using the ALPN token defined in Section 2.3.   For example, an origin could indicate in an HTTP/1.1 or HTTP/2   response that HTTP/QUIC was available on UDP port 50781 at the same   hostname by including the following header in any response:   Alt-Svc: hq=":50781"   On receipt of an Alt-Svc record indicating HTTP/QUIC support, a   client MAY attempt to establish a QUIC connection to the indicated   host and port and, if successful, send HTTP requests using the   mapping described in this document.   Connectivity problems (e.g. firewall blocking UDP) can result in QUIC   connection establishment failure, in which case the client SHOULD   continue using the existing connection or try another alternative   endpoint offered by the origin.   Servers MAY serve HTTP/QUIC on any UDP port, since an alternative   always includes an explicit port.2.2.1.  QUIC Version Hints   This document defines the "quic" parameter for Alt-Svc, which MAY be   used to provide version-negotiation hints to HTTP/QUIC clients.  QUIC   versions are four-octet sequences with no additional constraints on   format.  Leading zeros SHOULD be omitted for brevity.   Syntax:   quic = DQUOTE version-number [ "," version-number ] * DQUOTE   version-number = 1*8HEXDIG; hex-encoded QUIC version   Where multiple versions are listed, the order of the values reflects   the server's preference (with the first value being the most   preferred version).  Reserved versions MAY be listed, but unreserved   versions which are not supported by the alternative SHOULD NOT be   present in the list.  Origins MAY omit supported versions for any   reason.Bishop                  Expires February 16, 2019               [Page 5]Internet-Draft               HTTP over QUIC                  August 2018   Clients MUST ignore any included versions which they do not support.   The "quic" parameter MUST NOT occur more than once; clients SHOULD   process only the first occurrence.   For example, suppose a server supported both version 0x00000001 and   the version rendered in ASCII as "Q034".  If it opted to include the   reserved versions (from Section 4 of [QUIC-TRANSPORT]) 0x0 and   0x1abadaba, it could specify the following header:   Alt-Svc: hq=":49288";quic="1,1abadaba,51303334,0"   A client acting on this header would drop the reserved versions   (because it does not support them), then attempt to connect to the   alternative using the first version in the list which it does   support.2.3.  Connection Establishment   HTTP/QUIC relies on QUIC as the underlying transport.  The QUIC   version being used MUST use TLS version 1.3 or greater as its   handshake protocol.  HTTP/QUIC clients MUST indicate the target   domain name during the TLS handshake.  This may be done using the   Server Name Indication (SNI) [RFC6066] extension to TLS or using some   other mechanism.   QUIC connections are established as described in [QUIC-TRANSPORT].   During connection establishment, HTTP/QUIC support is indicated by   selecting the ALPN token "hq" in the TLS handshake.  Support for   other application-layer protocols MAY be offered in the same   handshake.   While connection-level options pertaining to the core QUIC protocol   are set in the initial crypto handshake, HTTP/QUIC-specific settings   are conveyed in the SETTINGS frame.  After the QUIC connection is   established, a SETTINGS frame (Section 4.2.6) MUST be sent by each   endpoint as the initial frame of their respective HTTP control stream   (see Section 3.3.2).  The server MUST NOT send data on any other   stream until the client's SETTINGS frame has been received.2.4.  Connection Reuse   Once a connection exists to a server endpoint, this connection MAY be   reused for requests with multiple different URI authority components.   The client MAY send any requests for which the client considers the   server authoritative.   An authoritative HTTP/QUIC endpoint is typically discovered because   the client has received an Alt-Svc record from the request's originBishop                  Expires February 16, 2019               [Page 6]Internet-Draft               HTTP over QUIC                  August 2018   which nominates the endpoint as a valid HTTP Alternative Service for   that origin.  As required by [RFC7838], clients MUST check that the   nominated server can present a valid certificate for the origin   before considering it authoritative.  Clients MUST NOT assume that an   HTTP/QUIC endpoint is authoritative for other origins without an   explicit signal.   A server that does not wish clients to reuse connections for a   particular origin can indicate that it is not authoritative for a   request by sending a 421 (Misdirected Request) status code in   response to the request (see Section 9.1.2 of [RFC7540]).3.  Stream Mapping and Usage   A QUIC stream provides reliable in-order delivery of bytes, but makes   no guarantees about order of delivery with regard to bytes on other   streams.  On the wire, data is framed into QUIC STREAM frames, but   this framing is invisible to the HTTP framing layer.  A QUIC receiver   buffers and orders received STREAM frames, exposing the data   contained within as a reliable byte stream to the application.   When HTTP headers and data are sent over QUIC, the QUIC layer handles   most of the stream management.   All client-initiated bidirectional streams are used for HTTP requests   and responses.  A bidirectional stream ensures that the response can   be readily correlated with the request.  This means that the client's   first request occurs on QUIC stream 0, with subsequent requests on   stream 4, 8, and so on.  HTTP/QUIC does not use server-initiated   bidirectional streams.  The use of unidirectional streams is   discussed in Section 3.3.   These streams carry frames related to the request/response (see   Section 4.2).  When a stream terminates cleanly, if the last frame on   the stream was truncated, this MUST be treated as a connection error   (see HTTP_MALFORMED_FRAME in Section 6.1).  Streams which terminate   abruptly may be reset at any point in the frame.   HTTP does not need to do any separate multiplexing when using QUIC -   data sent over a QUIC stream always maps to a particular HTTP   transaction.  Requests and responses are considered complete when the   corresponding QUIC stream is closed in the appropriate direction.3.1.  HTTP Message Exchanges   A client sends an HTTP request on a client-initiated bidirectional   QUIC stream.  A server sends an HTTP response on the same stream as   the request.Bishop                  Expires February 16, 2019               [Page 7]Internet-Draft               HTTP over QUIC                  August 2018   An HTTP message (request or response) consists of:   1.  one header block (see Section 4.2.3) containing the message       headers (see [RFC7230], Section 3.2),   2.  the payload body (see [RFC7230], Section 3.3), sent as a series       of DATA frames (see Section 4.2.2),   3.  optionally, one header block containing the trailer-part, if       present (see [RFC7230], Section 4.1.2).   In addition, prior to sending the message header block indicated   above, a response may contain zero or more header blocks containing   the message headers of informational (1xx) HTTP responses (see   [RFC7230], Section 3.2 and [RFC7231], Section 6.2).   PUSH_PROMISE frames (see Section 4.2.7) MAY be interleaved with the   frames of a response message indicating a pushed resource related to   the response.  These PUSH_PROMISE frames are not part of the   response, but carry the headers of a separate HTTP request message.   See Section 3.3.3 for more details.   The "chunked" transfer encoding defined in Section 4.1 of [RFC7230]   MUST NOT be used.   Trailing header fields are carried in an additional header block   following the body.  Senders MUST send only one header block in the   trailers section; receivers MUST discard any subsequent header   blocks.   An HTTP request/response exchange fully consumes a bidirectional QUIC   stream.  After sending a request, a client closes the stream for   sending; after sending a response, the server closes the stream for   sending and the QUIC stream is fully closed.   A server can send a complete response prior to the client sending an   entire request if the response does not depend on any portion of the   request that has not been sent and received.  When this is true, a   server MAY request that the client abort transmission of a request   without error by triggering a QUIC STOP_SENDING with error code   HTTP_EARLY_RESPONSE, sending a complete response, and cleanly closing   its streams.  Clients MUST NOT discard complete responses as a result   of having their request terminated abruptly, though clients can   always discard responses at their discretion for other reasons.   Changes to the state of a request stream, including receiving a   RST_STREAM with any error code, do not affect the state of the   server's response.  Servers do not abort a response in progressBishop                  Expires February 16, 2019               [Page 8]Internet-Draft               HTTP over QUIC                  August 2018   solely due to a state change on the request stream.  However, if the   request stream terminates without containing a usable HTTP request,   the server SHOULD abort its response with the error code   HTTP_INCOMPLETE_REQUEST.3.1.1.  Header Formatting and Compression   HTTP header fields carry information as a series of key-value pairs.   For a listing of registered HTTP headers, see the "Message Header   Field" registry maintained at https://www.iana.org/assignments/   message-headers [4].   Just as in previous versions of HTTP, header field names are strings   of ASCII characters that are compared in a case-insensitive fashion.   Properties of HTTP header names and values are discussed in more   detail in Section 3.2 of [RFC7230], though the wire rendering in   HTTP/QUIC differs.  As in HTTP/2, header field names MUST be   converted to lowercase prior to their encoding.  A request or   response containing uppercase header field names MUST be treated as   malformed.   As in HTTP/2, HTTP/QUIC uses special pseudo-header fields beginning   with ':' character (ASCII 0x3a) to convey the target URI, the method   of the request, and the status code for the response.  These pseudo-   header fields are defined in Section 8.1.2.3 and 8.1.2.4 of   [RFC7540].  Pseudo-header fields are not HTTP header fields.   Endpoints MUST NOT generate pseudo-header fields other than those   defined in [RFC7540].  The restrictions on the use of pseudo-header   fields in Section 8.1.2.1 of [RFC7540] also apply to HTTP/QUIC.   HTTP/QUIC uses QPACK header compression as described in [QPACK], a   variation of HPACK which allows the flexibility to avoid header-   compression-induced head-of-line blocking.  See that document for   additional details.3.1.2.  The CONNECT Method   The pseudo-method CONNECT ([RFC7231], Section 4.3.6) is primarily   used with HTTP proxies to establish a TLS session with an origin   server for the purposes of interacting with "https" resources.  In   HTTP/1.x, CONNECT is used to convert an entire HTTP connection into a   tunnel to a remote host.  In HTTP/2, the CONNECT method is used to   establish a tunnel over a single HTTP/2 stream to a remote host for   similar purposes.   A CONNECT request in HTTP/QUIC functions in the same manner as in   HTTP/2.  The request MUST be formatted as described in [RFC7540],   Section 8.3.  A CONNECT request that does not conform to theseBishop                  Expires February 16, 2019               [Page 9]Internet-Draft               HTTP over QUIC                  August 2018   restrictions is malformed.  The request stream MUST NOT be half-   closed at the end of the request.   A proxy that supports CONNECT establishes a TCP connection   ([RFC0793]) to the server identified in the ":authority" pseudo-   header field.  Once this connection is successfully established, the   proxy sends a HEADERS frame containing a 2xx series status code to   the client, as defined in [RFC7231], Section 4.3.6.   All DATA frames on the request stream correspond to data sent on the   TCP connection.  Any DATA frame sent by the client is transmitted by   the proxy to the TCP server; data received from the TCP server is   packaged into DATA frames by the proxy.  Note that the size and   number of TCP segments is not guaranteed to map predictably to the   size and number of HTTP DATA or QUIC STREAM frames.   The TCP connection can be closed by either peer.  When the client   ends the request stream (that is, the receive stream at the proxy   enters the "Data Recvd" state), the proxy will set the FIN bit on its   connection to the TCP server.  When the proxy receives a packet with   the FIN bit set, it will terminate the send stream that it sends to   client.  TCP connections which remain half-closed in a single   direction are not invalid, but are often handled poorly by servers,   so clients SHOULD NOT cause send a STREAM frame with a FIN bit for   connections on which they are still expecting data.   A TCP connection error is signaled with RST_STREAM.  A proxy treats   any error in the TCP connection, which includes receiving a TCP   segment with the RST bit set, as a stream error of type   HTTP_CONNECT_ERROR (Section 6.1).  Correspondingly, a proxy MUST send   a TCP segment with the RST bit set if it detects an error with the   stream or the QUIC connection.3.1.3.  Request Cancellation   Either client or server can cancel requests by aborting the stream   (QUIC RST_STREAM or STOP_SENDING frames, as appropriate) with an   error code of HTTP_REQUEST_CANCELLED (Section 6.1).  When the client   cancels a response, it indicates that this response is no longer of   interest.  Clients SHOULD cancel requests by aborting both directions   of a stream.   When the server cancels its response stream using   HTTP_REQUEST_CANCELLED, it indicates that no application processing   was performed.  The client can treat requests cancelled by the server   as though they had never been sent at all, thereby allowing them to   be retried later on a new connection.  Servers MUST NOT use theBishop                  Expires February 16, 2019              [Page 10]Internet-Draft               HTTP over QUIC                  August 2018   HTTP_REQUEST_CANCELLED status for requests which were partially or   fully processed.   Note:  In this context, "processed" means that some data from the      stream was passed to some higher layer of software that might have      taken some action as a result.   If a stream is cancelled after receiving a complete response, the   client MAY ignore the cancellation and use the response.  However, if   a stream is cancelled after receiving a partial response, the   response SHOULD NOT be used.  Automatically retrying such requests is   not possible, unless this is otherwise permitted (e.g., idempotent   actions like GET, PUT, or DELETE).3.2.  Request Prioritization   HTTP/QUIC uses a priority scheme similar to that described in   [RFC7540], Section 5.3.  In this priority scheme, a given stream can   be designated as dependent upon another request, which expresses the   preference that the latter stream (the "parent" request) be allocated   resources before the former stream (the "dependent" request).  Taken   together, the dependencies across all requests in a connection form a   dependency tree.  The structure of the dependency tree changes as   PRIORITY frames add, remove, or change the dependency links between   requests.   The PRIORITY frame Section 4.2.4 identifies a prioritized element.   The elements which can be prioritized are:   o  Requests, identified by the ID of the request stream   o  Pushes, identified by the Push ID of the promised resource      (Section 4.2.7)   o  Placeholders, identified by a Placeholder ID   An element can depend on another element or on the root of the tree.   A reference to an element which is no longer in the tree is treated   as a reference to the root of the tree.   Only a client can send PRIORITY frames.  A server MUST NOT send a   PRIORITY frame.3.2.1.  Placeholders   In HTTP/2, certain implementations used closed or unused streams as   placeholders in describing the relative priority of requests.   However, this created confusion as servers could not reliablyBishop                  Expires February 16, 2019              [Page 11]Internet-Draft               HTTP over QUIC                  August 2018   identify which elements of the priority tree could safely be   discarded.  Clients could potentially reference closed streams long   after the server had discarded state, leading to disparate views of   the prioritization the client had attempted to express.   In HTTP/QUIC, a number of placeholders are explicitly permitted by   the server using the "SETTINGS_NUM_PLACEHOLDERS" setting.  Because   the server commits to maintain these IDs in the tree, clients can use   them with confidence that the server will not have discarded the   state.   Placeholders are identified by an ID between zero and one less than   the number of placeholders the server has permitted.3.2.2.  Priority Tree Maintenance   Servers can aggressively prune inactive regions from the priority   tree, because placeholders will be used to "root" any persistent   structure of the tree which the client cares about retaining.  For   prioritization purposes, a node in the tree is considered "inactive"   when the corresponding stream has been closed for at least two round-   trip times (using any reasonable estimate available on the server).   This delay helps mitigate race conditions where the server has pruned   a node the client believed was still active and used as a Stream   Dependency.   Specifically, the server MAY at any time:   o  Identify and discard branches of the tree containing only inactive      nodes (i.e. a node with only other inactive nodes as descendants,      along with those descendants)   o  Identify and condense interior regions of the tree containing only      inactive nodes, allocating weight appropriately       x                x                 x       |                |                 |       P                P                 P      / \               |                 |     I   I     ==>      I      ==>        A        / \             |                 |       A   I            A                 A       |                |       A                A                Figure 1: Example of Priority Tree PruningBishop                  Expires February 16, 2019              [Page 12]Internet-Draft               HTTP over QUIC                  August 2018   In the example in Figure 1, "P" represents a Placeholder, "A"   represents an active node, and "I" represents an inactive node.  In   the first step, the server discards two inactive branches (each a   single node).  In the second step, the server condenses an interior   inactive node.  Note that these transformations will result in no   change in the resources allocated to a particular active stream.   Clients SHOULD assume the server is actively performing such pruning   and SHOULD NOT declare a dependency on a stream it knows to have been   closed.3.3.  Unidirectional Streams   Unidirectional streams, in either direction, are used for a range of   purposes.  The purpose is indicated by a stream type, which is sent   as a single octet header at the start of the stream.  The format and   structure of data that follows this header is determined by the   stream type.    0 1 2 3 4 5 6 7   +-+-+-+-+-+-+-+-+   |Stream Type (8)|   +-+-+-+-+-+-+-+-+                  Figure 2: Unidirectional Stream Header   Some stream types are reserved (Section 3.3.1).  Two stream types are   defined in this document: control streams (Section 3.3.2) and push   streams (Section 3.3.3).  Other stream types can be defined by   extensions to HTTP/QUIC.   If the stream header indicates a stream type which is not supported   by the recipient, the remainder of the stream cannot be consumed as   the semantics are unknown.  Recipients of unknown stream types MAY   trigger a QUIC STOP_SENDING frame with an error code of   HTTP_UNKNOWN_STREAM_TYPE, but MUST NOT consider such streams to be an   error of any kind.   Implementations MAY send stream types before knowing whether the peer   supports them.  However, stream types which could modify the state or   semantics of existing protocol components, including QPACK or other   extensions, MUST NOT be sent until the peer is known to support them.3.3.1.  Reserved Stream Types   Stream types of the format "0x1f * N" are reserved to exercise the   requirement that unknown types be ignored.  These streams have no   semantic meaning, and can be sent when application-layer padding isBishop                  Expires February 16, 2019              [Page 13]Internet-Draft               HTTP over QUIC                  August 2018   desired.  They MAY also be sent on connections where no request data   is currently being transferred.  Endpoints MUST NOT consider these   streams to have any meaning upon receipt.   The payload and length of the stream are selected in any manner the   implementation chooses.3.3.2.  Control Streams   The control stream is indicated by a stream type of "0x43" (ASCII   'C').  Data on this stream consists of HTTP/QUIC frames, as defined   in Section 4.2.   Each side MUST initiate a single control stream at the beginning of   the connection and send its SETTINGS frame as the first frame on this   stream.  Only one control stream per peer is permitted; receipt of a   second stream which claims to be a control stream MUST be treated as   a connection error of type HTTP_WRONG_STREAM_COUNT.  If the control   stream is closed at any point, this MUST be treated as a connection   error of type HTTP_CLOSED_CRITICAL_STREAM.   A pair of unidirectional streams is used rather than a single   bidirectional stream.  This allows either peer to send data as soon   they are able.  Depending on whether 0-RTT is enabled on the   connection, either client or server might be able to send stream data   first after the cryptographic handshake completes.3.3.3.  Server Push   HTTP/QUIC server push is similar to what is described in HTTP/2   [RFC7540], but uses different mechanisms.   The PUSH_PROMISE frame (Section 4.2.7) is sent on the client-   initiated bidirectional stream that carried the request that   generated the push.  This allows the server push to be associated   with a request.  Ordering of a PUSH_PROMISE in relation to certain   parts of the response is important (see Section 8.2.1 of [RFC7540]).   The PUSH_PROMISE frame does not reference a stream; it contains a   Push ID that uniquely identifies a server push.  This allows a server   to fulfill promises in the order that best suits its needs.  The same   Push ID can be used in multiple PUSH_PROMISE frames (see   Section 4.2.7).  When a server later fulfills a promise, the server   push response is conveyed on a push stream.   A push stream is indicated by a stream type of "0x50" (ASCII 'P'),   followed by the Push ID of the promise that it fulfills, encoded as a   variable-length integer.  The remaining data on this stream consistsBishop                  Expires February 16, 2019              [Page 14]Internet-Draft               HTTP over QUIC                  August 2018   of HTTP/QUIC frames, as defined in Section 4.2, and carries the   response side of an HTTP message exchange as described in   Section 3.1.  The request headers of the exchange are carried by a   PUSH_PROMISE frame (see Section 4.2.7) on the request stream which   generated the push.  Promised requests MUST conform to the   requirements in Section 8.2 of [RFC7540].   Only servers can push; if a server receives a client-initiated push   stream, this MUST be treated as a stream error of type   HTTP_WRONG_STREAM_DIRECTION.    0                   1                   2                   3    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |Stream Type (8)|                  Push ID (i)                ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                       Figure 3: Push Stream Header   Server push is only enabled on a connection when a client sends a   MAX_PUSH_ID frame (see Section 4.2.9).  A server cannot use server   push until it receives a MAX_PUSH_ID frame.  A client sends   additional MAX_PUSH_ID frames to control the number of pushes that a   server can promise.  A server SHOULD use Push IDs sequentially,   starting at 0.  A client MUST treat receipt of a push stream with a   Push ID that is greater than the maximum Push ID as a connection   error of type HTTP_PUSH_LIMIT_EXCEEDED.   Each Push ID MUST only be used once in a push stream header.  If a   push stream header includes a Push ID that was used in another push   stream header, the client MUST treat this as a connection error of   type HTTP_DUPLICATE_PUSH.   If a promised server push is not needed by the client, the client   SHOULD send a CANCEL_PUSH frame.  If the push stream is already open,   a QUIC STOP_SENDING frame with an appropriate error code can be used   instead (e.g., HTTP_PUSH_REFUSED, HTTP_PUSH_ALREADY_IN_CACHE; see   Section 6).  This asks the server not to transfer the data and   indicates that it will be discarded upon receipt.4.  HTTP Framing Layer   Frames are used on the control stream, request streams, and push   streams.  This section describes HTTP framing in QUIC and highlights   some differences from HTTP/2 framing.  For more detail on differences   from HTTP/2, see Section 8.2.Bishop                  Expires February 16, 2019              [Page 15]Internet-Draft               HTTP over QUIC                  August 20184.1.  Frame Layout   All frames have the following format:    0                   1                   2                   3    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                           Length (i)                        ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |    Type (8)   |               Frame Payload (*)             ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                     Figure 4: HTTP/QUIC frame format   A frame includes the following fields:   Length:  A variable-length integer that describes the length of the      Frame Payload.  This length does not include the frame header.   Type:  An 8-bit type for the frame.   Frame Payload:  A payload, the semantics of which are determined by      the Type field.4.2.  Frame Definitions4.2.1.  Reserved Frame Types   Frame types of the format "0xb + (0x1f * N)" are reserved to exercise   the requirement that unknown types be ignored.  These frames have no   semantic meaning, and can be sent when application-layer padding is   desired.  They MAY also be sent on connections where no request data   is currently being transferred.  Endpoints MUST NOT consider these   frames to have any meaning upon receipt.   The payload and length of the frames are selected in any manner the   implementation chooses.4.2.2.  DATA   DATA frames (type=0x0) convey arbitrary, variable-length sequences of   octets associated with an HTTP request or response payload.   DATA frames MUST be associated with an HTTP request or response.  If   a DATA frame is received on either control stream, the recipient MUST   respond with a connection error (Section 6) of type   HTTP_WRONG_STREAM.Bishop                  Expires February 16, 2019              [Page 16]Internet-Draft               HTTP over QUIC                  August 2018    0                   1                   2                   3    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                         Payload (*)                         ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                       Figure 5: DATA frame payload   DATA frames MUST contain a non-zero-length payload.  If a DATA frame   is received with a payload length of zero, the recipient MUST respond   with a stream error (Section 6) of type HTTP_MALFORMED_FRAME.4.2.3.  HEADERS   The HEADERS frame (type=0x1) is used to carry a header block,   compressed using QPACK.  See [QPACK] for more details.    0                   1                   2                   3    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                       Header Block (*)                      ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                      Figure 6: HEADERS frame payload   HEADERS frames can only be sent on request / push streams.4.2.4.  PRIORITY   The PRIORITY (type=0x02) frame specifies the sender-advised priority   of a stream and is substantially different in format from [RFC7540].   In order to ensure that prioritization is processed in a consistent   order, PRIORITY frames MUST be sent on the control stream.  A   PRIORITY frame sent on any other stream MUST be treated as a   HTTP_WRONG_STREAM error.   The format has been modified to accommodate not being sent on a   request stream, to allow for identification of server pushes, and the   larger stream ID space of QUIC.  The semantics of the Stream   Dependency, Weight, and E flag are otherwise the same as in HTTP/2.Bishop                  Expires February 16, 2019              [Page 17]Internet-Draft               HTTP over QUIC                  August 2018    0                   1                   2                   3    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |PT |DT |Empty|E|   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                 Prioritized Element ID (i)                  ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                 Element Dependency ID (i)                   ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |   Weight (8)  |   +-+-+-+-+-+-+-+-+                     Figure 7: PRIORITY frame payload   The PRIORITY frame payload has the following fields:   Prioritized Type:  A two-bit field indicating the type of element      being prioritized.   Dependency Type:  A two-bit field indicating the type of element      being depended on.   Empty:  A three-bit field which MUST be zero when sent and MUST be      ignored on receipt.   Exclusive:  A flag which indicates that the stream dependency is      exclusive (see [RFC7540], Section 5.3).   Prioritized Element ID:  A variable-length integer that identifies      the element being prioritized.  Depending on the value of      Prioritized Type, this contains the Stream ID of a request stream,      the Push ID of a promised resource, or a Placeholder ID of a      placeholder.   Element Dependency ID:  A variable-length integer that identifies the      element on which a dependency is being expressed.  Depending on      the value of Dependency Type, this contains the Stream ID of a      request stream, the Push ID of a promised resource, or a      Placeholder ID of a placeholder.  For details of dependencies, see      Section 3.2 and [RFC7540], Section 5.3.   Weight:  An unsigned 8-bit integer representing a priority weight for      the stream (see [RFC7540], Section 5.3).  Add one to the value to      obtain a weight between 1 and 256.   A PRIORITY frame identifies an element to prioritize, and an element   upon which it depends.  A Prioritized ID or Dependency ID identifies   a client-initiated request using the corresponding stream ID, aBishop                  Expires February 16, 2019              [Page 18]Internet-Draft               HTTP over QUIC                  August 2018   server push using a Push ID (see Section 4.2.7), or a placeholder   using a Placeholder ID (see Section 3.2.1).   The values for the Prioritized Element Type and Element Dependency   Type imply the interpretation of the associated Element ID fields.          +-----------+------------------+---------------------+          | Type Bits | Type Description | Element ID Contents |          +-----------+------------------+---------------------+          | 00        | Request stream   | Stream ID           |          |           |                  |                     |          | 01        | Push stream      | Push ID             |          |           |                  |                     |          | 10        | Placeholder      | Placeholder ID      |          |           |                  |                     |          | 11        | Root of the tree | Ignored             |          +-----------+------------------+---------------------+   Note that the root of the tree cannot be referenced using a Stream ID   of 0, as in [RFC7540]; QUIC stream 0 carries a valid HTTP request.   The root of the tree cannot be reprioritized.  A PRIORITY frame that   prioritizes the root of the tree MUST be treated as a connection   error of type HTTP_MALFORMED_FRAME.   When a PRIORITY frame claims to reference a request, the associated   ID MUST identify a client-initiated bidirectional stream.  A server   MUST treat receipt of PRIORITY frame with a Stream ID of any other   type as a connection error of type HTTP_MALFORMED_FRAME.   A PRIORITY frame that references a non-existent Push ID or a   Placeholder ID greater than the server's limit MUST be treated as a   HTTP_MALFORMED_FRAME error.   A PRIORITY frame MUST contain only the identified fields.  A PRIORITY   frame that contains more or fewer fields, or a PRIORITY frame that   includes a truncated integer encoding MUST be treated as a connection   error of type HTTP_MALFORMED_FRAME.4.2.5.  CANCEL_PUSH   The CANCEL_PUSH frame (type=0x3) is used to request cancellation of   server push prior to the push stream being created.  The CANCEL_PUSH   frame identifies a server push request by Push ID (see Section 4.2.7)   using a variable-length integer.   When a server receives this frame, it aborts sending the response for   the identified server push.  If the server has not yet started to   send the server push, it can use the receipt of a CANCEL_PUSH frameBishop                  Expires February 16, 2019              [Page 19]Internet-Draft               HTTP over QUIC                  August 2018   to avoid opening a stream.  If the push stream has been opened by the   server, the server SHOULD sent a QUIC RST_STREAM frame on those   streams and cease transmission of the response.   A server can send this frame to indicate that it won't be sending a   response prior to creation of a push stream.  Once the push stream   has been created, sending CANCEL_PUSH has no effect on the state of   the push stream.  A QUIC RST_STREAM frame SHOULD be used instead to   cancel transmission of the server push response.   A CANCEL_PUSH frame is sent on the control stream.  Sending a   CANCEL_PUSH frame on a stream other than the control stream MUST be   treated as a stream error of type HTTP_WRONG_STREAM.    0                   1                   2                   3    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                          Push ID (i)                        ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                    Figure 8: CANCEL_PUSH frame payload   The CANCEL_PUSH frame carries a Push ID encoded as a variable-length   integer.  The Push ID identifies the server push that is being   cancelled (see Section 4.2.7).   If the client receives a CANCEL_PUSH frame, that frame might identify   a Push ID that has not yet been mentioned by a PUSH_PROMISE frame.   An endpoint MUST treat a CANCEL_PUSH frame which does not contain   exactly one properly-formatted variable-length integer as a   connection error of type HTTP_MALFORMED_FRAME.4.2.6.  SETTINGS   The SETTINGS frame (type=0x4) conveys configuration parameters that   affect how endpoints communicate, such as preferences and constraints   on peer behavior, and is different from [RFC7540].  Individually, a   SETTINGS parameter can also be referred to as a "setting".   SETTINGS parameters are not negotiated; they describe characteristics   of the sending peer, which can be used by the receiving peer.   However, a negotiation can be implied by the use of SETTINGS - a peer   uses SETTINGS to advertise a set of supported values.  The recipient   can then choose which entries from this list are also acceptable and   proceed with the value it has chosen.  (This choice could be   announced in a field of an extension frame, or in its own value in   SETTINGS.)Bishop                  Expires February 16, 2019              [Page 20]Internet-Draft               HTTP over QUIC                  August 2018   Different values for the same parameter can be advertised by each   peer.  For example, a client might be willing to consume very large   response headers, while servers are more cautious about request size.   Parameters MUST NOT occur more than once.  A receiver MAY treat the   presence of the same parameter more than once as a connection error   of type HTTP_MALFORMED_FRAME.   The payload of a SETTINGS frame consists of zero or more parameters,   each consisting of an unsigned 16-bit setting identifier and a   length-prefixed binary value.    0                   1                   2                   3    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |         Identifier (16)       |            Length (i)       ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                          Contents (?)                       ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                      Figure 9: SETTINGS value format   A zero-length content indicates that the setting value is a Boolean   and true.  False is indicated by the absence of the setting.   Non-zero-length values MUST be compared against the remaining length   of the SETTINGS frame.  Any value which purports to cross the end of   the frame MUST cause the SETTINGS frame to be considered malformed   and trigger a connection error of type HTTP_MALFORMED_FRAME.   An implementation MUST ignore the contents for any SETTINGS   identifier it does not understand.   SETTINGS frames always apply to a connection, never a single stream.   A SETTINGS frame MUST be sent as the first frame of either control   stream (see Section 3) by each peer, and MUST NOT be sent   subsequently or on any other stream.  If an endpoint receives an   SETTINGS frame on a different stream, the endpoint MUST respond with   a connection error of type HTTP_WRONG_STREAM.  If an endpoint   receives a second SETTINGS frame, the endpoint MUST respond with a   connection error of type HTTP_MALFORMED_FRAME.   The SETTINGS frame affects connection state.  A badly formed or   incomplete SETTINGS frame MUST be treated as a connection error   (Section 6) of type HTTP_MALFORMED_FRAME.Bishop                  Expires February 16, 2019              [Page 21]Internet-Draft               HTTP over QUIC                  August 20184.2.6.1.  Integer encoding   Settings which are integers use the QUIC variable-length integer   encoding.4.2.6.2.  Defined SETTINGS Parameters   The following settings are defined in HTTP/QUIC:   SETTINGS_NUM_PLACEHOLDERS (0x3):  An integer with a maximum value of      2^16 - 1.  The value SHOULD be non-zero.  The default value is 16.   SETTINGS_MAX_HEADER_LIST_SIZE (0x6):  An integer with a maximum value      of 2^30 - 1.  The default value is unlimited.   Settings values of the format "0x?a?a" are reserved to exercise the   requirement that unknown parameters be ignored.  Such settings have   no defined meaning.  Endpoints SHOULD include at least one such   setting in their SETTINGS frame.  Endpoints MUST NOT consider such   settings to have any meaning upon receipt.   Because the setting has no defined meaning, the value of the setting   can be any value the implementation selects.   Additional settings MAY be defined by extensions to HTTP/QUIC.4.2.6.3.  Initial SETTINGS Values   When a 0-RTT QUIC connection is being used, the client's initial   requests will be sent before the arrival of the server's SETTINGS   frame.  Clients MUST store the settings the server provided in the   session being resumed and MUST comply with stored settings until the   server's current settings are received.  Remembered settings apply to   the new connection until the server's SETTINGS frame is received.   A server can remember the settings that it advertised, or store an   integrity-protected copy of the values in the ticket and recover the   information when accepting 0-RTT data.  A server uses the HTTP/QUIC   settings values in determining whether to accept 0-RTT data.   A server MAY accept 0-RTT and subsequently provide different settings   in its SETTINGS frame.  If 0-RTT data is accepted by the server, its   SETTINGS frame MUST NOT reduce any limits or alter any values that   might be violated by the client with its 0-RTT data.   When a 1-RTT QUIC connection is being used, the client MUST NOT send   requests prior to receiving and processing the server's SETTINGS   frame.Bishop                  Expires February 16, 2019              [Page 22]Internet-Draft               HTTP over QUIC                  August 20184.2.7.  PUSH_PROMISE   The PUSH_PROMISE frame (type=0x05) is used to carry a request header   set from server to client, as in HTTP/2.    0                   1                   2                   3    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                          Push ID (i)                        ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                       Header Block (*)                      ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                   Figure 10: PUSH_PROMISE frame payload   The payload consists of:   Push ID:  A variable-length integer that identifies the server push      request.  A push ID is used in push stream header (Section 3.3.3),      CANCEL_PUSH frames (Section 4.2.5), and PRIORITY frames      (Section 4.2.4).   Header Block:  QPACK-compressed request headers for the promised      response.  See [QPACK] for more details.   A server MUST NOT use a Push ID that is larger than the client has   provided in a MAX_PUSH_ID frame (Section 4.2.9).  A client MUST treat   receipt of a PUSH_PROMISE that contains a larger Push ID than the   client has advertised as a connection error of type   HTTP_MALFORMED_FRAME.   A server MAY use the same Push ID in multiple PUSH_PROMISE frames.   This allows the server to use the same server push in response to   multiple concurrent requests.  Referencing the same server push   ensures that a PUSH_PROMISE can be made in relation to every response   in which server push might be needed without duplicating pushes.   A server that uses the same Push ID in multiple PUSH_PROMISE frames   MUST include the same header fields each time.  The octets of the   header block MAY be different due to differing encoding, but the   header fields and their values MUST be identical.  Note that ordering   of header fields is significant.  A client MUST treat receipt of a   PUSH_PROMISE with conflicting header field values for the same Push   ID as a connection error of type HTTP_MALFORMED_FRAME.   Allowing duplicate references to the same Push ID is primarily to   reduce duplication caused by concurrent requests.  A server SHOULD   avoid reusing a Push ID over a long period.  Clients are likely toBishop                  Expires February 16, 2019              [Page 23]Internet-Draft               HTTP over QUIC                  August 2018   consume server push responses and not retain them for reuse over   time.  Clients that see a PUSH_PROMISE that uses a Push ID that they   have since consumed and discarded are forced to ignore the   PUSH_PROMISE.4.2.8.  GOAWAY   The GOAWAY frame (type=0x7) is used to initiate graceful shutdown of   a connection by a server.  GOAWAY allows a server to stop accepting   new requests while still finishing processing of previously received   requests.  This enables administrative actions, like server   maintenance.  GOAWAY by itself does not close a connection.    0                   1                   2                   3    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                          Stream ID (i)                      ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                      Figure 11: GOAWAY frame payload   The GOAWAY frame carries a QUIC Stream ID for a client-initiated   bidirectional stream encoded as a variable-length integer.  A client   MUST treat receipt of a GOAWAY frame containing a Stream ID of any   other type as a connection error of type HTTP_MALFORMED_FRAME.   Clients do not need to send GOAWAY to initiate a graceful shutdown;   they simply stop making new requests.  A server MUST treat receipt of   a GOAWAY frame as a connection error (Section 6) of type   HTTP_UNEXPECTED_GOAWAY.   The GOAWAY frame applies to the connection, not a specific stream.   An endpoint MUST treat a GOAWAY frame on a stream other than the   control stream as a connection error (Section 6) of type   HTTP_WRONG_STREAM.   New client requests might already have been sent before the client   receives the server's GOAWAY frame.  The GOAWAY frame contains the   Stream ID of the last client-initiated request that was or might be   processed in this connection, which enables client and server to   agree on which requests were accepted prior to the connection   shutdown.  This identifier MAY be lower than the stream limit   identified by a QUIC MAX_STREAM_ID frame, and MAY be zero if no   requests were processed.  Servers SHOULD NOT increase the   MAX_STREAM_ID limit after sending a GOAWAY frame.   Once sent, the server MUST cancel requests sent on streams with an   identifier higher than the included last Stream ID.  Clients MUST NOTBishop                  Expires February 16, 2019              [Page 24]Internet-Draft               HTTP over QUIC                  August 2018   send new requests on the connection after receiving GOAWAY, although   requests might already be in transit.  A new connection can be   established for new requests.   If the client has sent requests on streams with a higher Stream ID   than indicated in the GOAWAY frame, those requests are considered   cancelled (Section 3.1.3).  Clients SHOULD reset any streams above   this ID with the error code HTTP_REQUEST_CANCELLED.  Servers MAY also   cancel requests on streams below the indicated ID if these requests   were not processed.   Requests on Stream IDs less than or equal to the Stream ID in the   GOAWAY frame might have been processed; their status cannot be known   until they are completed successfully, reset individually, or the   connection terminates.   Servers SHOULD send a GOAWAY frame when the closing of a connection   is known in advance, even if the advance notice is small, so that the   remote peer can know whether a stream has been partially processed or   not.  For example, if an HTTP client sends a POST at the same time   that a server closes a QUIC connection, the client cannot know if the   server started to process that POST request if the server does not   send a GOAWAY frame to indicate what streams it might have acted on.   For unexpected closures caused by error conditions, a QUIC   APPLICATION_CLOSE frame MUST be used.  However, a GOAWAY MAY be sent   first to provide additional detail to clients and to allow the client   to retry requests.  Including the GOAWAY frame in the same packet as   the QUIC APPLICATION_CLOSE frame improves the chances of the frame   being received by clients.   If a connection terminates without a GOAWAY frame, the last Stream ID   is effectively the highest possible Stream ID (as determined by   QUIC's MAX_STREAM_ID).   An endpoint MAY send multiple GOAWAY frames if circumstances change.   For instance, an endpoint that sends GOAWAY without an error code   during graceful shutdown could subsequently encounter an error   condition.  The last stream identifier from the last GOAWAY frame   received indicates which streams could have been acted upon.  A   server MUST NOT increase the value they send in the last Stream ID,   since clients might already have retried unprocessed requests on   another connection.   A client that is unable to retry requests loses all requests that are   in flight when the server closes the connection.  A server that is   attempting to gracefully shut down a connection SHOULD send an   initial GOAWAY frame with the last Stream ID set to the current valueBishop                  Expires February 16, 2019              [Page 25]Internet-Draft               HTTP over QUIC                  August 2018   of QUIC's MAX_STREAM_ID and SHOULD NOT increase the MAX_STREAM_ID   thereafter.  This signals to the client that a shutdown is imminent   and that initiating further requests is prohibited.  After allowing   time for any in-flight requests (at least one round-trip time), the   server MAY send another GOAWAY frame with an updated last Stream ID.   This ensures that a connection can be cleanly shut down without   losing requests.   Once all requests on streams at or below the identified stream number   have been completed or cancelled, and all promised server push   responses associated with those requests have been completed or   cancelled, the connection can be closed using an Immediate Close (see   [QUIC-TRANSPORT]).  An endpoint that completes a graceful shutdown   SHOULD use the QUIC APPLICATION_CLOSE frame with the HTTP_NO_ERROR   code.4.2.9.  MAX_PUSH_ID   The MAX_PUSH_ID frame (type=0xD) is used by clients to control the   number of server pushes that the server can initiate.  This sets the   maximum value for a Push ID that the server can use in a PUSH_PROMISE   frame.  Consequently, this also limits the number of push streams   that the server can initiate in addition to the limit set by the QUIC   MAX_STREAM_ID frame.   The MAX_PUSH_ID frame is always sent on a control stream.  Receipt of   a MAX_PUSH_ID frame on any other stream MUST be treated as a   connection error of type HTTP_WRONG_STREAM.   A server MUST NOT send a MAX_PUSH_ID frame.  A client MUST treat the   receipt of a MAX_PUSH_ID frame as a connection error of type   HTTP_MALFORMED_FRAME.   The maximum Push ID is unset when a connection is created, meaning   that a server cannot push until it receives a MAX_PUSH_ID frame.  A   client that wishes to manage the number of promised server pushes can   increase the maximum Push ID by sending a MAX_PUSH_ID frame as the   server fulfills or cancels server pushes.    0                   1                   2                   3    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   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   |                          Push ID (i)                        ...   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                   Figure 12: MAX_PUSH_ID frame payloadBishop                  Expires February 16, 2019              [Page 26]Internet-Draft               HTTP over QUIC                  August 2018   The MAX_PUSH_ID frame carries a single variable-length integer that   identifies the maximum value for a Push ID that the server can use   (see Section 4.2.7).  A MAX_PUSH_ID frame cannot reduce the maximum   Push ID; receipt of a MAX_PUSH_ID that contains a smaller value than   previously received MUST be treated as a connection error of type   HTTP_MALFORMED_FRAME.   A server MUST treat a MAX_PUSH_ID frame payload that does not contain   a single variable-length integer as a connection error of type   HTTP_MALFORMED_FRAME.5.  Connection Management   QUIC connections are persistent.  All of the considerations in   Section 9.1 of [RFC7540] apply to the management of QUIC connections.   HTTP clients are expected to use QUIC PING frames to keep connections   open.  Servers SHOULD NOT use PING frames to keep a connection open.   A client SHOULD NOT use PING frames for this purpose unless there are   responses outstanding for requests or server pushes.  If the client   is not expecting a response from the server, allowing an idle   connection to time out (based on the idle_timeout transport   parameter) is preferred over expending effort maintaining a   connection that might not be needed.  A gateway MAY use PING to   maintain connections in anticipation of need rather than incur the   latency cost of connection establishment to servers.6.  Error Handling   QUIC allows the application to abruptly terminate (reset) individual   streams or the entire connection when an error is encountered.  These   are referred to as "stream errors" or "connection errors" and are   described in more detail in [QUIC-TRANSPORT].   This section describes HTTP/QUIC-specific error codes which can be   used to express the cause of a connection or stream error.6.1.  HTTP/QUIC Error Codes   The following error codes are defined for use in QUIC RST_STREAM,   STOP_SENDING, and APPLICATION_CLOSE frames when using HTTP/QUIC.   STOPPING (0x00):  This value is reserved by the transport to be used      in response to QUIC STOP_SENDING frames.   HTTP_NO_ERROR (0x01):  No error.  This is used when the connection or      stream needs to be closed, but there is no error to signal.Bishop                  Expires February 16, 2019              [Page 27]Internet-Draft               HTTP over QUIC                  August 2018   HTTP_PUSH_REFUSED (0x02):  The server has attempted to push content      which the client will not accept on this connection.   HTTP_INTERNAL_ERROR (0x03):  An internal error has occurred in the      HTTP stack.   HTTP_PUSH_ALREADY_IN_CACHE (0x04):  The server has attempted to push      content which the client has cached.   HTTP_REQUEST_CANCELLED (0x05):  The client no longer needs the      requested data.   HTTP_INCOMPLETE_REQUEST (0x06):  The client's stream terminated      without containing a fully-formed request.   HTTP_CONNECT_ERROR (0x07):  The connection established in response to      a CONNECT request was reset or abnormally closed.   HTTP_EXCESSIVE_LOAD (0x08):  The endpoint detected that its peer is      exhibiting a behavior that might be generating excessive load.   HTTP_VERSION_FALLBACK (0x09):  The requested operation cannot be      served over HTTP/QUIC.  The peer should retry over HTTP/2.   HTTP_WRONG_STREAM (0x0A):  A frame was received on a stream where it      is not permitted.   HTTP_PUSH_LIMIT_EXCEEDED (0x0B):  A Push ID greater than the current      maximum Push ID was referenced.   HTTP_DUPLICATE_PUSH (0x0C):  A Push ID was referenced in two      different stream headers.   HTTP_UNKNOWN_STREAM_TYPE (0x0D):  A unidirectional stream header      contained an unknown stream type.   HTTP_WRONG_STREAM_COUNT (0x0E):  A unidirectional stream type was      used more times than is permitted by that type.   HTTP_CLOSED_CRITICAL_STREAM (0x0F):  A stream required by the      connection was closed or reset.   HTTP_WRONG_STREAM_DIRECTION (0x0010):  A unidirectional stream type      was used by a peer which is not permitted to do so.   HTTP_EARLY_RESPONSE (0x0011):  The remainder of the client's request      is not needed to produce a response.  For use in STOP_SENDING      only.Bishop                  Expires February 16, 2019              [Page 28]Internet-Draft               HTTP over QUIC                  August 2018   HTTP_GENERAL_PROTOCOL_ERROR (0x00FF):  Peer violated protocol      requirements in a way which doesn't match a more specific error      code, or endpoint declines to use the more specific error code.   HTTP_MALFORMED_FRAME (0x01XX):  An error in a specific frame type.      The frame type is included as the last octet of the error code.      For example, an error in a MAX_PUSH_ID frame would be indicated      with the code (0x10D).7.  Extensions to HTTP/QUIC   HTTP/QUIC permits extension of the protocol.  Within the limitations   described in this section, protocol extensions can be used to provide   additional services or alter any aspect of the protocol.  Extensions   are effective only within the scope of a single HTTP/QUIC connection.   This applies to the protocol elements defined in this document.  This   does not affect the existing options for extending HTTP, such as   defining new methods, status codes, or header fields.   Extensions are permitted to use new frame types (Section 4.2), new   settings (Section 4.2.6.2), new error codes (Section 6), or new   unidirectional stream types (Section 3.3).  Registries are   established for managing these extension points: frame types   (Section 10.3), settings (Section 10.4), error codes (Section 10.5),   and stream types (Section 10.6).   Implementations MUST ignore unknown or unsupported values in all   extensible protocol elements.  Implementations MUST discard frames   and unidirectional streams that have unknown or unsupported types.   This means that any of these extension points can be safely used by   extensions without prior arrangement or negotiation.   Extensions that could change the semantics of existing protocol   components MUST be negotiated before being used.  For example, an   extension that changes the layout of the HEADERS frame cannot be used   until the peer has given a positive signal that this is acceptable.   In this case, it could also be necessary to coordinate when the   revised layout comes into effect.   This document doesn't mandate a specific method for negotiating the   use of an extension but notes that a setting (Section 4.2.6.2) could   be used for that purpose.  If both peers set a value that indicates   willingness to use the extension, then the extension can be used.  If   a setting is used for extension negotiation, the default value MUST   be defined in such a fashion that the extension is disabled if the   setting is omitted.Bishop                  Expires February 16, 2019              [Page 29]Internet-Draft               HTTP over QUIC                  August 20188.  Considerations for Transitioning from HTTP/2   HTTP/QUIC is strongly informed by HTTP/2, and bears many   similarities.  This section describes the approach taken to design   HTTP/QUIC, points out important differences from HTTP/2, and   describes how to map HTTP/2 extensions into HTTP/QUIC.   HTTP/QUIC begins from the premise that HTTP/2 code reuse is a useful   feature, but not a hard requirement.  HTTP/QUIC departs from HTTP/2   primarily where necessary to accommodate the differences in behavior   between QUIC and TCP (lack of ordering, support for streams).  We   intend to avoid gratuitous changes which make it difficult or   impossible to build extensions with the same semantics applicable to   both protocols at once.   These departures are noted in this section.8.1.  Streams   HTTP/QUIC permits use of a larger number of streams (2^62-1) than   HTTP/2.  The considerations about exhaustion of stream identifier   space apply, though the space is significantly larger such that it is   likely that other limits in QUIC are reached first, such as the limit   on the connection flow control window.8.2.  HTTP Frame Types   Many framing concepts from HTTP/2 can be elided away on QUIC, because   the transport deals with them.  Because frames are already on a   stream, they can omit the stream number.  Because frames do not block   multiplexing (QUIC's multiplexing occurs below this layer), the   support for variable-maximum-length packets can be removed.  Because   stream termination is handled by QUIC, an END_STREAM flag is not   required.  This permits the removal of the Flags field from the   generic frame layout.   Frame payloads are largely drawn from [RFC7540].  However, QUIC   includes many features (e.g. flow control) which are also present in   HTTP/2.  In these cases, the HTTP mapping does not re-implement them.   As a result, several HTTP/2 frame types are not required in HTTP/   QUIC.  Where an HTTP/2-defined frame is no longer used, the frame ID   has been reserved in order to maximize portability between HTTP/2 and   HTTP/QUIC implementations.  However, even equivalent frames between   the two mappings are not identical.   Many of the differences arise from the fact that HTTP/2 provides an   absolute ordering between frames across all streams, while QUIC   provides this guarantee on each stream only.  As a result, if a frameBishop                  Expires February 16, 2019              [Page 30]Internet-Draft               HTTP over QUIC                  August 2018   type makes assumptions that frames from different streams will still   be received in the order sent, HTTP/QUIC will break them.   For example, implicit in the HTTP/2 prioritization scheme is the   notion of in-order delivery of priority changes (i.e., dependency   tree mutations): since operations on the dependency tree such as   reparenting a subtree are not commutative, both sender and receiver   must apply them in the same order to ensure that both sides have a   consistent view of the stream dependency tree.  HTTP/2 specifies   priority assignments in PRIORITY frames and (optionally) in HEADERS   frames.  To achieve in-order delivery of priority changes in HTTP/   QUIC, PRIORITY frames are sent on the control stream and the PRIORITY   section is removed from the HEADERS frame.   Likewise, HPACK was designed with the assumption of in-order   delivery.  A sequence of encoded header blocks must arrive (and be   decoded) at an endpoint in the same order in which they were encoded.   This ensures that the dynamic state at the two endpoints remains in   sync.  As a result, HTTP/QUIC uses a modified version of HPACK,   described in [QPACK].   Frame type definitions in HTTP/QUIC often use the QUIC variable-   length integer encoding.  In particular, Stream IDs use this   encoding, which allow for a larger range of possible values than the   encoding used in HTTP/2.  Some frames in HTTP/QUIC use an identifier   rather than a Stream ID (e.g.  Push IDs in PRIORITY frames).   Redefinition of the encoding of extension frame types might be   necessary if the encoding includes a Stream ID.   Because the Flags field is not present in generic HTTP/QUIC frames,   those frames which depend on the presence of flags need to allocate   space for flags as part of their frame payload.   Other than this issue, frame type HTTP/2 extensions are typically   portable to QUIC simply by replacing Stream 0 in HTTP/2 with a   control stream in HTTP/QUIC.  HTTP/QUIC extensions will not assume   ordering, but would not be harmed by ordering, and would be portable   to HTTP/2 in the same manner.   Below is a listing of how each HTTP/2 frame type is mapped:   DATA (0x0):  Padding is not defined in HTTP/QUIC frames.  See      Section 4.2.2.   HEADERS (0x1):  As described above, the PRIORITY region of HEADERS is      not supported.  A separate PRIORITY frame MUST be used.  Padding      is not defined in HTTP/QUIC frames.  See Section 4.2.3.Bishop                  Expires February 16, 2019              [Page 31]Internet-Draft               HTTP over QUIC                  August 2018   PRIORITY (0x2):  As described above, the PRIORITY frame is sent on      the control stream and can reference either a Stream ID or a Push      ID.  See Section 4.2.4.   RST_STREAM (0x3):  RST_STREAM frames do not exist, since QUIC      provides stream lifecycle management.  The same code point is used      for the CANCEL_PUSH frame (Section 4.2.5).   SETTINGS (0x4):  SETTINGS frames are sent only at the beginning of      the connection.  See Section 4.2.6 and Section 8.3.   PUSH_PROMISE (0x5):  The PUSH_PROMISE does not reference a stream;      instead the push stream references the PUSH_PROMISE frame using a      Push ID.  See Section 4.2.7.   PING (0x6):  PING frames do not exist, since QUIC provides equivalent      functionality.   GOAWAY (0x7):  GOAWAY is sent only from server to client and does not      contain an error code.  See Section 4.2.8.   WINDOW_UPDATE (0x8):  WINDOW_UPDATE frames do not exist, since QUIC      provides flow control.   CONTINUATION (0x9):  CONTINUATION frames do not exist; instead,      larger HEADERS/PUSH_PROMISE frames than HTTP/2 are permitted, and      HEADERS frames can be used in series.   Frame types defined by extensions to HTTP/2 need to be separately   registered for HTTP/QUIC if still applicable.  The IDs of frames   defined in [RFC7540] have been reserved for simplicity.  See   Section 10.3.8.3.  HTTP/2 SETTINGS Parameters   An important difference from HTTP/2 is that settings are sent once,   at the beginning of the connection, and thereafter cannot change.   This eliminates many corner cases around synchronization of changes.   Some transport-level options that HTTP/2 specifies via the SETTINGS   frame are superseded by QUIC transport parameters in HTTP/QUIC.  The   HTTP-level options that are retained in HTTP/QUIC have the same value   as in HTTP/2.   Below is a listing of how each HTTP/2 SETTINGS parameter is mapped:   SETTINGS_HEADER_TABLE_SIZE:  See Section 4.2.6.2.Bishop                  Expires February 16, 2019              [Page 32]Internet-Draft               HTTP over QUIC                  August 2018   SETTINGS_ENABLE_PUSH:  This is removed in favor of the MAX_PUSH_ID      which provides a more granular control over server push.   SETTINGS_MAX_CONCURRENT_STREAMS:  QUIC controls the largest open      Stream ID as part of its flow control logic.  Specifying      SETTINGS_MAX_CONCURRENT_STREAMS in the SETTINGS frame is an error.   SETTINGS_INITIAL_WINDOW_SIZE:  QUIC requires both stream and      connection flow control window sizes to be specified in the      initial transport handshake.  Specifying      SETTINGS_INITIAL_WINDOW_SIZE in the SETTINGS frame is an error.   SETTINGS_MAX_FRAME_SIZE:  This setting has no equivalent in HTTP/      QUIC.  Specifying it in the SETTINGS frame is an error.   SETTINGS_MAX_HEADER_LIST_SIZE:  See Section 4.2.6.2.   Settings need to be defined separately for HTTP/2 and HTTP/QUIC.  The   IDs of settings defined in [RFC7540] have been reserved for   simplicity.  See Section 10.4.8.4.  HTTP/2 Error Codes   QUIC has the same concepts of "stream" and "connection" errors that   HTTP/2 provides.  However, because the error code space is shared   between multiple components, there is no direct portability of HTTP/2   error codes.   The HTTP/2 error codes defined in Section 7 of [RFC7540] map to the   HTTP over QUIC error codes as follows:   NO_ERROR (0x0):  HTTP_NO_ERROR in Section 6.1.   PROTOCOL_ERROR (0x1):  No single mapping.  See new      HTTP_MALFORMED_FRAME error codes defined in Section 6.1.   INTERNAL_ERROR (0x2):  HTTP_INTERNAL_ERROR in Section 6.1.   FLOW_CONTROL_ERROR (0x3):  Not applicable, since QUIC handles flow      control.  Would provoke a QUIC_FLOW_CONTROL_RECEIVED_TOO_MUCH_DATA      from the QUIC layer.   SETTINGS_TIMEOUT (0x4):  Not applicable, since no acknowledgement of      SETTINGS is defined.   STREAM_CLOSED (0x5):  Not applicable, since QUIC handles stream      management.  Would provoke a QUIC_STREAM_DATA_AFTER_TERMINATION      from the QUIC layer.Bishop                  Expires February 16, 2019              [Page 33]Internet-Draft               HTTP over QUIC                  August 2018   FRAME_SIZE_ERROR (0x6):  No single mapping.  See new error codes      defined in Section 6.1.   REFUSED_STREAM (0x7):  Not applicable, since QUIC handles stream      management.  Would provoke a QUIC_TOO_MANY_OPEN_STREAMS from the      QUIC layer.   CANCEL (0x8):  HTTP_REQUEST_CANCELLED in Section 6.1.   COMPRESSION_ERROR (0x9):  HTTP_QPACK_DECOMPRESSION_FAILED in [QPACK].   CONNECT_ERROR (0xa):  HTTP_CONNECT_ERROR in Section 6.1.   ENHANCE_YOUR_CALM (0xb):  HTTP_EXCESSIVE_LOAD in Section 6.1.   INADEQUATE_SECURITY (0xc):  Not applicable, since QUIC is assumed to      provide sufficient security on all connections.   HTTP_1_1_REQUIRED (0xd):  HTTP_VERSION_FALLBACK in Section 6.1.   Error codes need to be defined for HTTP/2 and HTTP/QUIC separately.   See Section 10.5.9.  Security Considerations   The security considerations of HTTP over QUIC should be comparable to   those of HTTP/2 with TLS.  Note that where HTTP/2 employs PADDING   frames to make a connection more resistant to traffic analysis, HTTP/   QUIC can rely on QUIC's own PADDING frames or employ the reserved   frame and stream types discussed in Section 4.2.1 and Section 3.3.1.   The modified SETTINGS format contains nested length elements, which   could pose a security risk to an incautious implementer.  A SETTINGS   frame parser MUST ensure that the length of the frame exactly matches   the length of the settings it contains.10.  IANA Considerations10.1.  Registration of HTTP/QUIC Identification String   This document creates a new registration for the identification of   HTTP/QUIC in the "Application Layer Protocol Negotiation (ALPN)   Protocol IDs" registry established in [RFC7301].   The "hq" string identifies HTTP/QUIC:   Protocol:  HTTP over QUICBishop                  Expires February 16, 2019              [Page 34]Internet-Draft               HTTP over QUIC                  August 2018   Identification Sequence:  0x68 0x71 ("hq")   Specification:  This document10.2.  Registration of QUIC Version Hint Alt-Svc Parameter   This document creates a new registration for version-negotiation   hints in the "Hypertext Transfer Protocol (HTTP) Alt-Svc Parameter"   registry established in [RFC7838].   Parameter:  "quic"   Specification:  This document, Section 2.2.110.3.  Frame Types   This document establishes a registry for HTTP/QUIC frame type codes.   The "HTTP/QUIC Frame Type" registry manages an 8-bit space.  The   "HTTP/QUIC Frame Type" registry operates under either of the "IETF   Review" or "IESG Approval" policies [RFC8126] for values from 0x00 up   to and including 0xef, with values from 0xf0 up to and including 0xff   being reserved for Experimental Use.   While this registry is separate from the "HTTP/2 Frame Type" registry   defined in [RFC7540], it is preferable that the assignments parallel   each other.  If an entry is present in only one registry, every   effort SHOULD be made to avoid assigning the corresponding value to   an unrelated operation.   New entries in this registry require the following information:   Frame Type:  A name or label for the frame type.   Code:  The 8-bit code assigned to the frame type.   Specification:  A reference to a specification that includes a      description of the frame layout and its semantics, including any      parts of the frame that are conditionally present.   The entries in the following table are registered by this document.Bishop                  Expires February 16, 2019              [Page 35]Internet-Draft               HTTP over QUIC                  August 2018                  +--------------+------+---------------+                  | Frame Type   | Code | Specification |                  +--------------+------+---------------+                  | DATA         | 0x0  | Section 4.2.2 |                  |              |      |               |                  | HEADERS      | 0x1  | Section 4.2.3 |                  |              |      |               |                  | PRIORITY     | 0x2  | Section 4.2.4 |                  |              |      |               |                  | CANCEL_PUSH  | 0x3  | Section 4.2.5 |                  |              |      |               |                  | SETTINGS     | 0x4  | Section 4.2.6 |                  |              |      |               |                  | PUSH_PROMISE | 0x5  | Section 4.2.7 |                  |              |      |               |                  | Reserved     | 0x6  | N/A           |                  |              |      |               |                  | GOAWAY       | 0x7  | Section 4.2.8 |                  |              |      |               |                  | Reserved     | 0x8  | N/A           |                  |              |      |               |                  | Reserved     | 0x9  | N/A           |                  |              |      |               |                  | MAX_PUSH_ID  | 0xD  | Section 4.2.9 |                  +--------------+------+---------------+   Additionally, each code of the format "0xb + (0x1f * N)" for values   of N in the range (0..7) (that is, "0xb", "0x2a", "0x49", "0x68",   "0x87", "0xa6", "0xc5", and "0xe4"), the following values should be   registered:   Frame Type:  Reserved - GREASE   Specification:  Section 4.2.110.4.  Settings Parameters   This document establishes a registry for HTTP/QUIC settings.  The   "HTTP/QUIC Settings" registry manages a 16-bit space.  The "HTTP/QUIC   Settings" registry operates under the "Expert Review" policy   [RFC8126] for values in the range from 0x0000 to 0xefff, with values   between and 0xf000 and 0xffff being reserved for Experimental Use.   The designated experts are the same as those for the "HTTP/2   Settings" registry defined in [RFC7540].   While this registry is separate from the "HTTP/2 Settings" registry   defined in [RFC7540], it is preferable that the assignments parallel   each other.  If an entry is present in only one registry, everyBishop                  Expires February 16, 2019              [Page 36]Internet-Draft               HTTP over QUIC                  August 2018   effort SHOULD be made to avoid assigning the corresponding value to   an unrelated operation.   New registrations are advised to provide the following information:   Name:  A symbolic name for the setting.  Specifying a setting name is      optional.   Code:  The 16-bit code assigned to the setting.   Specification:  An optional reference to a specification that      describes the use of the setting.   The entries in the following table are registered by this document.             +----------------------+------+-----------------+             | Setting Name         | Code | Specification   |             +----------------------+------+-----------------+             | Reserved             | 0x2  | N/A             |             |                      |      |                 |             | NUM_PLACEHOLDERS     | 0x3  | Section 4.2.6.2 |             |                      |      |                 |             | Reserved             | 0x4  | N/A             |             |                      |      |                 |             | Reserved             | 0x5  | N/A             |             |                      |      |                 |             | MAX_HEADER_LIST_SIZE | 0x6  | Section 4.2.6.2 |             +----------------------+------+-----------------+   Additionally, each code of the format "0x?a?a" where each "?" is any   four bits (that is, "0x0a0a", "0x0a1a", etc. through "0xfafa"), the   following values should be registered:   Name:  Reserved - GREASE   Specification:  Section 4.2.6.210.5.  Error Codes   This document establishes a registry for HTTP/QUIC error codes.  The   "HTTP/QUIC Error Code" registry manages a 16-bit space.  The "HTTP/   QUIC Error Code" registry operates under the "Expert Review" policy   [RFC8126].   Registrations for error codes are required to include a description   of the error code.  An expert reviewer is advised to examine new   registrations for possible duplication with existing error codes.   Use of existing registrations is to be encouraged, but not mandated.Bishop                  Expires February 16, 2019              [Page 37]Internet-Draft               HTTP over QUIC                  August 2018   New registrations are advised to provide the following information:   Name:  A name for the error code.  Specifying an error code name is      optional.   Code:  The 16-bit error code value.   Description:  A brief description of the error code semantics, longer      if no detailed specification is provided.   Specification:  An optional reference for a specification that      defines the error code.   The entries in the following table are registered by this document.   +-------------------------+-------+---------------+-----------------+   | Name                    | Code  | Description   | Specification   |   +-------------------------+-------+---------------+-----------------+   | STOPPING                | 0x000 | Reserved by   | [QUIC-TRANSPORT |   |                         | 0     | QUIC          | ]               |   |                         |       |               |                 |   | HTTP_NO_ERROR           | 0x000 | No error      | Section 6.1     |   |                         | 1     |               |                 |   |                         |       |               |                 |   | HTTP_PUSH_REFUSED       | 0x000 | Client        | Section 6.1     |   |                         | 2     | refused       |                 |   |                         |       | pushed        |                 |   |                         |       | content       |                 |   |                         |       |               |                 |   | HTTP_INTERNAL_ERROR     | 0x000 | Internal      | Section 6.1     |   |                         | 3     | error         |                 |   |                         |       |               |                 |   | HTTP_PUSH_ALREADY_IN_CA | 0x000 | Pushed        | Section 6.1     |   | CHE                     | 4     | content       |                 |   |                         |       | already       |                 |   |                         |       | cached        |                 |   |                         |       |               |                 |   | HTTP_REQUEST_CANCELLED  | 0x000 | Data no       | Section 6.1     |   |                         | 5     | longer needed |                 |   |                         |       |               |                 |   | HTTP_INCOMPLETE_REQUEST | 0x000 | Stream        | Section 6.1     |   |                         | 6     | terminated    |                 |   |                         |       | early         |                 |   |                         |       |               |                 |   | HTTP_CONNECT_ERROR      | 0x000 | TCP reset or  | Section 6.1     |   |                         | 7     | error on      |                 |   |                         |       | CONNECT       |                 |   |                         |       | request       |                 |Bishop                  Expires February 16, 2019              [Page 38]Internet-Draft               HTTP over QUIC                  August 2018   |                         |       |               |                 |   | HTTP_EXCESSIVE_LOAD     | 0x000 | Peer          | Section 6.1     |   |                         | 8     | generating    |                 |   |                         |       | excessive     |                 |   |                         |       | load          |                 |   |                         |       |               |                 |   | HTTP_VERSION_FALLBACK   | 0x000 | Retry over    | Section 6.1     |   |                         | 9     | HTTP/2        |                 |   |                         |       |               |                 |   | HTTP_WRONG_STREAM       | 0x000 | A frame was   | Section 6.1     |   |                         | A     | sent on the   |                 |   |                         |       | wrong stream  |                 |   |                         |       |               |                 |   | HTTP_PUSH_LIMIT_EXCEEDE | 0x000 | Maximum Push  | Section 6.1     |   | D                       | B     | ID exceeded   |                 |   |                         |       |               |                 |   | HTTP_DUPLICATE_PUSH     | 0x000 | Push ID was   | Section 6.1     |   |                         | C     | fulfilled     |                 |   |                         |       | multiple      |                 |   |                         |       | times         |                 |   |                         |       |               |                 |   | HTTP_UNKNOWN_STREAM_TYP | 0x000 | Unknown unidi | Section 6.1     |   | E                       | D     | rectional     |                 |   |                         |       | stream type   |                 |   |                         |       |               |                 |   | HTTP_WRONG_STREAM_COUNT | 0x000 | Too many unid | Section 6.1     |   |                         | E     | irectional    |                 |   |                         |       | streams       |                 |   |                         |       |               |                 |   | HTTP_CLOSED_CRITICAL_ST | 0x000 | Critical      | Section 6.1     |   | REAM                    | F     | stream was    |                 |   |                         |       | closed        |                 |   |                         |       |               |                 |   | HTTP_WRONG_STREAM_DIREC | 0x001 | Unidirectiona | Section 6.1     |   | TION                    | 0     | l stream in   |                 |   |                         |       | wrong         |                 |   |                         |       | direction     |                 |   |                         |       |               |                 |   | HTTP_EARLY_RESPONSE     | 0x001 | Remainder of  | Section 6.1     |   |                         | 1     | request not   |                 |   |                         |       | needed        |                 |   |                         |       |               |                 |   | HTTP_MALFORMED_FRAME    | 0x01X | Error in      | Section 6.1     |   |                         | X     | frame         |                 |   |                         |       | formatting or |                 |   |                         |       | use           |                 |   +-------------------------+-------+---------------+-----------------+Bishop                  Expires February 16, 2019              [Page 39]Internet-Draft               HTTP over QUIC                  August 201810.6.  Stream Types   This document establishes a registry for HTTP/QUIC unidirectional   stream types.  The "HTTP/QUIC Stream Type" registry manages an 8-bit   space.  The "HTTP/QUIC Stream Type" registry operates under either of   the "IETF Review" or "IESG Approval" policies [RFC8126] for values   from 0x00 up to and including 0xef, with values from 0xf0 up to and   including 0xff being reserved for Experimental Use.   New entries in this registry require the following information:   Stream Type:  A name or label for the stream type.   Code:  The 8-bit code assigned to the stream type.   Specification:  A reference to a specification that includes a      description of the stream type, including the layout semantics of      its payload.   Sender:  Which endpoint on a connection may initiate a stream of this      type.  Values are "Client", "Server", or "Both".   The entries in the following table are registered by this document.            +----------------+------+---------------+--------+            | Stream Type    | Code | Specification | Sender |            +----------------+------+---------------+--------+            | Control Stream | 0x43 | Section 3.3.2 | Both   |            |                |      |               |        |            | Push Stream    | 0x50 | Section 3.3.3 | Server |            +----------------+------+---------------+--------+   Additionally, for each code of the format "0x1f * N" for values of N   in the range (0..8) (that is, "0x00", "0x1f", "0x3e", "0x5d", "0x7c",   "0x9b", "0xba", "0xd9", "0xf8"), the following values should be   registered:   Stream Type:  Reserved - GREASE   Specification:  Section 3.3.1   Sender:  Both11.  ReferencesBishop                  Expires February 16, 2019              [Page 40]Internet-Draft               HTTP over QUIC                  August 201811.1.  Normative References   [QPACK]    Krasic, C., Bishop, M., and A. Frindell, Ed., "QPACK:              Header Compression for HTTP over QUIC", draft-ietf-quic-              qpack-02 (work in progress), August 2018.   [QUIC-TRANSPORT]              Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based              Multiplexed and Secure Transport", draft-ietf-quic-              transport-13 (work in progress), August 2018.   [RFC0793]  Postel, J., "Transmission Control Protocol", STD 7,              RFC 793, DOI 10.17487/RFC0793, September 1981,              <https://www.rfc-editor.org/info/rfc793>.   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels", BCP 14, RFC 2119,              DOI 10.17487/RFC2119, March 1997,              <https://www.rfc-editor.org/info/rfc2119>.   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax              Specifications: ABNF", STD 68, RFC 5234,              DOI 10.17487/RFC5234, January 2008,              <https://www.rfc-editor.org/info/rfc5234>.   [RFC6066]  Eastlake 3rd, D., "Transport Layer Security (TLS)              Extensions: Extension Definitions", RFC 6066,              DOI 10.17487/RFC6066, January 2011,              <https://www.rfc-editor.org/info/rfc6066>.   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer              Protocol (HTTP/1.1): Message Syntax and Routing",              RFC 7230, DOI 10.17487/RFC7230, June 2014,              <https://www.rfc-editor.org/info/rfc7230>.   [RFC7231]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer              Protocol (HTTP/1.1): Semantics and Content", RFC 7231,              DOI 10.17487/RFC7231, June 2014,              <https://www.rfc-editor.org/info/rfc7231>.   [RFC7540]  Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext              Transfer Protocol Version 2 (HTTP/2)", RFC 7540,              DOI 10.17487/RFC7540, May 2015,              <https://www.rfc-editor.org/info/rfc7540>.   [RFC7838]  Nottingham, M., McManus, P., and J. Reschke, "HTTP              Alternative Services", RFC 7838, DOI 10.17487/RFC7838,              April 2016, <https://www.rfc-editor.org/info/rfc7838>.Bishop                  Expires February 16, 2019              [Page 41]Internet-Draft               HTTP over QUIC                  August 2018   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,              May 2017, <https://www.rfc-editor.org/info/rfc8174>.11.2.  Informative References   [RFC7301]  Friedl, S., Popov, A., Langley, A., and E. Stephan,              "Transport Layer Security (TLS) Application-Layer Protocol              Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,              July 2014, <https://www.rfc-editor.org/info/rfc7301>.   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for              Writing an IANA Considerations Section in RFCs", BCP 26,              RFC 8126, DOI 10.17487/RFC8126, June 2017,              <https://www.rfc-editor.org/info/rfc8126>.11.3.  URIs   [1] https://mailarchive.ietf.org/arch/search/?email_list=quic   [2] https://github.com/quicwg   [3] https://github.com/quicwg/base-drafts/labels/-http   [4] https://www.iana.org/assignments/message-headersAppendix A.  Change Log      *RFC Editor's Note:* Please remove this section prior to      publication of a final version of this document.A.1.  Since draft-ietf-quic-http-13   o  Reserved some frame types for grease (#1333, #1446)   o  Unknown unidirectional stream types are tolerated, not errors;      some reserved for grease (#1490, #1525)   o  Require settings to be remembered for 0-RTT, prohibit reductions      (#1541, #1641)   o  Specify behavior for truncated requests (#1596, #1643)A.2.  Since draft-ietf-quic-http-12   o  TLS SNI extension isn't mandatory if an alternative method is used      (#1459, #1462, #1466)Bishop                  Expires February 16, 2019              [Page 42]Internet-Draft               HTTP over QUIC                  August 2018   o  Removed flags from HTTP/QUIC frames (#1388, #1398)   o  Reserved frame types and settings for use in preserving      extensibility (#1333, #1446)   o  Added general error code (#1391, #1397)   o  Unidirectional streams carry a type byte and are extensible      (#910,#1359)   o  Priority mechanism now uses explicit placeholders to enable      persistent structure in the tree (#441,#1421,#1422)A.3.  Since draft-ietf-quic-http-11   o  Moved QPACK table updates and acknowledgments to dedicated streams      (#1121, #1122, #1238)A.4.  Since draft-ietf-quic-http-10   o  Settings need to be remembered when attempting and accepting 0-RTT      (#1157, #1207)A.5.  Since draft-ietf-quic-http-09   o  Selected QCRAM for header compression (#228, #1117)   o  The server_name TLS extension is now mandatory (#296, #495)   o  Specified handling of unsupported versions in Alt-Svc (#1093,      #1097)A.6.  Since draft-ietf-quic-http-08   o  Clarified connection coalescing rules (#940, #1024)A.7.  Since draft-ietf-quic-http-07   o  Changes for integer encodings in QUIC (#595,#905)   o  Use unidirectional streams as appropriate (#515, #240, #281, #886)   o  Improvement to the description of GOAWAY (#604, #898)   o  Improve description of server push usage (#947, #950, #957)Bishop                  Expires February 16, 2019              [Page 43]Internet-Draft               HTTP over QUIC                  August 2018A.8.  Since draft-ietf-quic-http-06   o  Track changes in QUIC error code usage (#485)A.9.  Since draft-ietf-quic-http-05   o  Made push ID sequential, add MAX_PUSH_ID, remove      SETTINGS_ENABLE_PUSH (#709)   o  Guidance about keep-alive and QUIC PINGs (#729)   o  Expanded text on GOAWAY and cancellation (#757)A.10.  Since draft-ietf-quic-http-04   o  Cite RFC 5234 (#404)   o  Return to a single stream per request (#245,#557)   o  Use separate frame type and settings registries from HTTP/2 (#81)   o  SETTINGS_ENABLE_PUSH instead of SETTINGS_DISABLE_PUSH (#477)   o  Restored GOAWAY (#696)   o  Identify server push using Push ID rather than a stream ID      (#702,#281)   o  DATA frames cannot be empty (#700)A.11.  Since draft-ietf-quic-http-03   None.A.12.  Since draft-ietf-quic-http-02   o  Track changes in transport draftA.13.  Since draft-ietf-quic-http-01   o  SETTINGS changes (#181):      *  SETTINGS can be sent only once at the start of a connection; no         changes thereafter      *  SETTINGS_ACK removed      *  Settings can only occur in the SETTINGS frame a single timeBishop                  Expires February 16, 2019              [Page 44]Internet-Draft               HTTP over QUIC                  August 2018      *  Boolean format updated   o  Alt-Svc parameter changed from "v" to "quic"; format updated      (#229)   o  Closing the connection control stream or any message control      stream is a fatal error (#176)   o  HPACK Sequence counter can wrap (#173)   o  0-RTT guidance added   o  Guide to differences from HTTP/2 and porting HTTP/2 extensions      added (#127,#242)A.14.  Since draft-ietf-quic-http-00   o  Changed "HTTP/2-over-QUIC" to "HTTP/QUIC" throughout (#11,#29)   o  Changed from using HTTP/2 framing within Stream 3 to new framing      format and two-stream-per-request model (#71,#72,#73)   o  Adopted SETTINGS format from draft-bishop-httpbis-extended-      settings-01   o  Reworked SETTINGS_ACK to account for indeterminate inter-stream      order (#75)   o  Described CONNECT pseudo-method (#95)   o  Updated ALPN token and Alt-Svc guidance (#13,#87)   o  Application-layer-defined error codes (#19,#74)A.15.  Since draft-shade-quic-http2-mapping-00   o  Adopted as base for draft-ietf-quic-http   o  Updated authors/editors listAcknowledgements   The original authors of this specification were Robbie Shade and Mike   Warres.   A substantial portion of Mike's contribution was supported by   Microsoft during his employment there.Bishop                  Expires February 16, 2019              [Page 45]Internet-Draft               HTTP over QUIC                  August 2018Author's Address   Mike Bishop (editor)   Akamai   Email: mbishop@evequefou.beBishop                  Expires February 16, 2019              [Page 46]