title: Hypertext Transfer Protocol (HTTP) over QUIC abbrev: HTTP over QUIC docname: draft-ietf-quic-http-latest date: {DATE} category: std ipr: trust200902 area: Transport workgroup: QUIC
stand_alone: yes pi: [toc, sortrefs, symrefs, docmapping]
ins: M. Bishop
name: Mike Bishop
org: Microsoft
email: Michael.Bishop@microsoft.com
role: editor
normative:
QUIC-TRANSPORT: title: "QUIC: A UDP-Based Multiplexed and Secure Transport" date: {DATE} seriesinfo: Internet-Draft: draft-ietf-quic-transport-latest author: - ins: J. Iyengar name: Jana Iyengar org: Google role: editor - ins: M. Thomson name: Martin Thomson org: Mozilla role: editor
informative:
--- abstract
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_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.
Working Group information can be found at https://github.com/quicwg; source code and issues list for this draft can be found at https://github.com/quicwg/base-drafts/labels/http.
--- middle
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 document 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}}.
The words "MUST", "MUST NOT", "SHOULD", and "MAY" are used in this document. It's not shouting; when they are capitalized, they have the special meaning defined in {{!RFC2119}}.
Field definitions are given in Augmented Backus-Naur Form (ABNF), as defined in {{!RFC5234}}.
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 {{connection-establishment}}.
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 header 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. Servers MUST use the same port across all IP addresses that serve a single domain, and SHOULD NOT change this port.
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. Syntax:
quic = version-number
version-number = 1*8HEXDIG; hex-encoded QUIC versionLeading zeros SHOULD be omitted for brevity. When multiple versions are supported, the "quic" parameter MAY be repeated multiple times in a single Alt-Svc entry. For example, if a server supported both version 0x00000001 and the version rendered in ASCII as "Q034", it could specify the following header:
Alt-Svc: hq=":49288";quic=1;quic=51303334
Where multiple versions are listed, the order of the values reflects the server's preference (with the first value being the most preferred version). Origins SHOULD list only versions which are supported by the alternative, but MAY omit supported versions for any reason.
HTTP/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 crypto handshake.
While connection-level options pertaining to the core QUIC protocol are set in the initial crypto handshake, HTTP-specific settings are conveyed in the SETTINGS frame. After the QUIC connection is established, a SETTINGS frame ({{frame-settings}}) MUST be sent as the initial frame of the HTTP control stream (Stream ID 1, see {{stream-mapping}}). The server MUST NOT send data on any other stream until the client's SETTINGS frame has been received.
RFC Editor's Note: Please remove this section prior to publication of a final version of this document.
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". Note 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.
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.
QUIC reserves Stream 0 for crypto operations (the handshake, crypto config updates). Stream 1 is reserved for sending and receiving HTTP control frames, and is analogous to HTTP/2's Stream 0. This control stream is considered critical to the HTTP connection. If the control stream is closed for any reason, this MUST be treated as a connection error of type QUIC_CLOSED_CRITICAL_STREAM.
When HTTP headers and data are sent over QUIC, the QUIC layer handles most of the stream management. An HTTP request/response consumes a single stream: This means that the client's first request occurs on QUIC stream 3, the second on stream 5, and so on. The server's first push consumes stream 2.
This stream carries frames related to the request/response (see {{frames}}). 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_* in {{http-error-codes}}). Streams which terminate abruptly may be reset at any point in the frame.
Streams SHOULD be used sequentially, with no gaps. Streams used for pushed resources MAY be initiated out-of-order, but stream IDs SHOULD be allocated to promised resources sequentially.
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.
Since most connection-level concerns will be managed by QUIC, the primary use of Stream 1 will be for the SETTINGS frame when the connection opens and for PRIORITY frames subsequently.
A client sends an HTTP request on a new QUIC stream. A server sends an HTTP response on the same stream as the request.
An HTTP message (request or response) consists of:
-
one header block (see {{frame-headers}}) containing the message headers (see {{!RFC7230}}, Section 3.2),
-
the payload body (see {{!RFC7230}}, Section 3.3), sent as a series of DATA frames (see {{frame-data}}),
-
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).
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. Such a header block is a sequence of HEADERS frames with End Header Block set on the last frame. 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 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 sending a RST_STREAM with an error code of NO_ERROR after sending a complete response and closing its stream. Clients MUST NOT discard responses as a result of receiving such a RST_STREAM, though clients can always discard responses at their discretion for other reasons.
HTTP/QUIC uses HPACK header compression as described in {{!RFC7541}}. HPACK was designed for HTTP/2 with the assumption of in-order delivery such as that provided by TCP. 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.
QUIC streams provide in-order delivery of data sent on those streams, but there are no guarantees about order of delivery between streams. QUIC anticipates moving to a modified version of HPACK without this assumption. In the meantime, by fixing the size of the dynamic table at zero, HPACK can be used in an unordered environment.
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 these restrictions is malformed. The message data stream MUST NOT be 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 half-closes the request stream, 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 half-close the corresponding stream. TCP connections which remain half-closed in a single direction are not invalid, but are often handled poorly by servers, so clients SHOULD NOT half-close 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 ({{http-error-codes}}). 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.
HTTP/QUIC uses the priority scheme described in {{!RFC7540}}, Section 5.3. In this priority scheme, a given request 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.
HTTP/2 defines its priorities in terms of streams whereas HTTP over QUIC identifies requests. The PRIORITY frame {{frame-priority}} identifies a request either by identifying the stream that carries a request or by using a Push ID ({{frame-push-promise}}). Other than the means of identifying requests, the prioritization system is identical to that in HTTP/2.
Only a client can prioritize requests. A server MUST NOT send a PRIORITY frame.
HTTP/QUIC supports server push as described in {{!RFC7540}}. During connection establishment, the client indicates whether it is willing to receive server pushes via the SETTINGS_DISABLE_PUSH setting in the SETTINGS frame (see {{connection-establishment}}), which defaults to 1 (true).
As with server push for HTTP/2, the server initiates a server push by sending a PUSH_PROMISE frame that includes request header fields attributed to the request. The PUSH_PROMISE frame is sent on a response stream. Unlike HTTP/2, the PUSH_PROMISE does not reference a stream; when a server fulfills a promise, the stream that carries the stream headers references the PUSH_PROMISE. This allows a server to fulfill promises in the order that best suits its needs.
The server push response is conveyed on a push stream. A push stream is a server-initiated stream. A push stream includes a header (see {{fig-push-stream-header}}) that identifies the PUSH_PROMISE that it fulfills. This header consists of a 32-bit Push ID, which identifies a server push (see {{frame-push-promise}}).
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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 (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
{: #fig-push-stream-header title="Push Stream Header"}
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. The same Push ID can be used in multiple PUSH_PROMISE frames (see {{frame-push-promise}}).
After the push stream header, a push contains a response ({{request-response}}), with response headers and (if present) trailers carried by HEADERS frames sent on the control stream, and response body (if any) carried by DATA frames.
Frames are used on each stream. This section describes HTTP framing in QUIC and highlights some differences from HTTP/2 framing. For more detail on differences from HTTP/2, see {{h2-frames}}.
All frames have the following format:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (16) | Type (8) | Flags (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Frame Payload (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
{: #fig-frame title="HTTP/QUIC frame format"}
DATA frames (type=0x0) convey arbitrary, variable-length sequences of octets associated with an HTTP request or response payload.
The DATA frame defines no flags.
DATA frames MUST be associated with an HTTP request or response. If a DATA frame is received on the control stream, the recipient MUST respond with a connection error ({{errors}}) of type HTTP_WRONG_STREAM.
The HEADERS frame (type=0x1) is used to carry part of a header set, compressed using HPACK {{header-compression}}.
One flag is defined:
End Header Block (0x4): : This frame concludes a header block.
A HEADERS frame with any other flags set MUST be treated as a connection error of type HTTP_MALFORMED_HEADERS.
The next frame on the same stream after a HEADERS frame without the EHB flag set MUST be another HEADERS frame. A receiver MUST treat the receipt of any other type of frame as a stream error of type HTTP_INTERRUPTED_HEADERS. (Note that QUIC can intersperse data from other streams between frames, or even during transmission of frames, so multiplexing is not blocked by this requirement.)
A full header block is contained in a sequence of zero or more HEADERS frames without EHB set, followed by a HEADERS frame with EHB set.
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.
The flags defined are:
PUSH_PRIORITIZED (0x04): : Indicates that the Prioritized Stream is a server push rather than a request. If set, this flag indicates that the Prioritized Stream identifies a response stream and the Promise Index field is present.
PUSH_DEPENDENT (0x02): : Indicates a dependency on a pushed request. If set, this flag indicates that the Dependent Stream identifies a response stream and that the Dependent Promise Index field is present.
E (0x01): : Indicates that the stream dependency is exclusive (see {{!RFC7540}}, Section 5.3).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prioritized Request (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Dependent Request (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Weight (8) |
+-+-+-+-+-+-+-+-+
{: #fig-priority title="PRIORITY frame payload"}
The PRIORITY frame payload has the following fields:
Prioritized Request: : A 32-bit identifier for a request. This contains the stream ID of a request stream when the PUSH_PRIORITIZED flag is clear, or a Push ID when the PUSH flag is set.
Stream Dependency: : A 32-bit stream identifier for a dependent request. This contains the stream ID of a request stream when the PUSH_DEPENDENT flag is clear, or a Push ID when the PUSH_DEPENDENT flag is set. A request stream ID of 0 indicates a dependency on the root stream. For details of dependencies, see {{priority}} 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 a request to priotize, and a request upon which that request is dependent. A request is identified by the stream ID of a request when the corresponding PUSH_PRIORITIZED or PUSH_DEPENDENT flag is not set. Setting the PUSH or PUSH_DEPENDENT flag causes the frame to identify a PUSH_PROMISE using a Push ID (see {{frame-push-promise}} for details).
A PRIORITY frame MAY identify no request by using a stream ID of 0; as in {{!RFC7540}}, this makes the request dependent on the root of the dependency tree.
A PRIORITY frame that does not reference a request MUST be treated as a HTTP_MALFORMED_PRIORITY error, unless it references stream ID 0. A PRIORITY that sets a PUSH_PRIORITIZED or PUSH_DEPENDENT flag, but then references a non-existent Push ID MUST be treated as a HTTP_MALFORMED_PRIORITY error.
The length of a PRIORITY frame is 9 octets. A PRIORITY frame with any other length MUST be treated as a connection error of type HTTP_MALFORMED_PRIORITY.
The CANCEL_REQUEST frame (type=0x3) is used to request cancellation of a request prior to the response stream being created. This frame can be used to cancel server push requests that are initiated with a PUSH_PROMISE.
The frame identifies a server push request is identified by Push ID (see {{frame-push-promise}}).
When a server receives this frame, it aborts sending the response for the identified request. If the server has not yet started to send the server push, it can use the receipt of a CANCEL_REQUEST frame 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, a RST_STREAM with a CANCELLED code can be used instead.
A CANCEL_REQUEST frame is sent on the control stream. Sending a CANCEL_REQUEST frame on a stream other than the control stream MUST be treated as a HTTP_WRONG_STREAM error.
The CANCEL_REQUEST frame has no defined flags.
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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 (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
{: #fig-cancel-request title="CANCEL_REQUEST frame payload"}
The CANCEL_REQUEST frame payload has the following fields:
Push ID: : A 32-bit Push ID that identifies the request (see {{frame-push-promise}}).
A CANCEL_REQUEST frame always contains a four octet payload. A server MUST treat a CANCEL_REQUEST frame payload that is other than 4 octets in length, or a CANCEL_REQUEST frame that identifies an unknown Push ID as an HTTP_MALFORMED_CANCEL_REQUEST error.
The SETTINGS frame (type=0x4) conveys configuration parameters that affect how endpoints communicate, such as preferences and constraints on peer behavior, and is substantially 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.)
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_SETTINGS.
The SETTINGS frame defines no flags.
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.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier (16) | Length (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Contents (?) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
{: #fig-ext-settings title="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_SETTINGS.
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 the control stream (see {{stream-mapping}}) 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_SETTINGS_ON_WRONG_STREAM. If an endpoint receives a second SETTINGS frame, the endpoint MUST respond with a connection error of type HTTP_MULTIPLE_SETTINGS.
The SETTINGS frame affects connection state. A badly formed or incomplete SETTINGS frame MUST be treated as a connection error ({{errors}}) of type HTTP_MALFORMED_SETTINGS.
Settings which are integers are transmitted in network byte order. Leading zero octets are permitted, but implementations SHOULD use only as many bytes as are needed to represent the value. An integer MUST NOT be represented in more bytes than would be used to transfer the maximum permitted value.
The following settings are defined in HTTP/QUIC:
SETTINGS_HEADER_TABLE_SIZE (0x1): : An integer with a maximum value of 2^32 - 1. This value MUST be zero.
SETTINGS_DISABLE_PUSH (0x2): : Transmitted as a Boolean; replaces SETTINGS_ENABLE_PUSH
SETTINGS_MAX_HEADER_LIST_SIZE (0x6): : An integer with a maximum value of 2^32 - 1.
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 SHOULD cache at least the following settings about servers:
- SETTINGS_HEADER_TABLE_SIZE
- SETTINGS_MAX_HEADER_LIST_SIZE
Clients MUST comply with cached settings until the server's current settings are received. If a client does not have cached values, it SHOULD assume the following values:
- SETTINGS_HEADER_TABLE_SIZE: 0 octets
- SETTINGS_MAX_HEADER_LIST_SIZE: 16,384 octets
Servers MAY continue processing data from clients which exceed its current configuration during the initial flight. In this case, the client MUST apply the new settings immediately upon receipt.
If the connection is closed because these or other constraints were violated during the 0-RTT flight (e.g. with HTTP_HPACK_DECOMPRESSION_FAILED), clients MAY establish a new connection and retry any 0-RTT requests using the settings sent by the server on the closed connection. (This assumes that only requests that are safe to retry are sent in 0-RTT.) If the connection was closed before the SETTINGS frame was received, clients SHOULD discard any cached values and use the defaults above on the next connection.
The PUSH_PROMISE frame (type=0x05) is used to carry a request header set from server to client, as in HTTP/2. The PUSH_PROMISE frame defines no flags.
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Push ID (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Header Block (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
{: #fig-push-promise title="PUSH_PROMISE frame payload"}
The payload consists of:
Push ID: : A 32-bit identifier for the server push request. This identifier is used in push stream header ({{server-push}}), CANCEL_REQUEST frames ({{frame-cancel-request}}), and PRIORITY frames ({{frame-priority}}) to identify this request.
Header Block: : HPACK-compressed request headers for the promised response.
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 causing 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_PUSH_PROMISE.
A server SHOULD avoid sending a PUSH_PROMISE that includes a Push ID that was fulfilled prior to the request being made. Though a client needs to handle receiving a promised response prior to it being promised due to reordering of stream delivery, clients might be unable to reuse a pushed response that was long since consumed. [Editor's Note: should we include a count of the number of promises that a push fulfils in the push stream header? That would remove this problem.]
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-specific error codes which can be used to express the cause of a connection or stream error.
QUIC allocates error codes 0x0000-0x3FFF to application protocol definition. The following error codes are defined by HTTP for use in QUIC RST_STREAM, GOAWAY, and CONNECTION_CLOSE frames.
HTTP_PUSH_REFUSED (0x01): : The server has attempted to push content which the client will not accept on this connection.
HTTP_INTERNAL_ERROR (0x02): : An internal error has occurred in the HTTP stack.
HTTP_PUSH_ALREADY_IN_CACHE (0x03): : The server has attempted to push content which the client has cached.
HTTP_REQUEST_CANCELLED (0x04): : The client no longer needs the requested data.
HTTP_HPACK_DECOMPRESSION_FAILED (0x05): : HPACK failed to decompress a frame and cannot continue.
HTTP_CONNECT_ERROR (0x06): : The connection established in response to a CONNECT request was reset or abnormally closed.
HTTP_EXCESSIVE_LOAD (0x07): : The endpoint detected that its peer is exhibiting a behavior that might be generating excessive load.
HTTP_VERSION_FALLBACK (0x08): : The requested operation cannot be served over HTTP/QUIC. The peer should retry over HTTP/2.
HTTP_MALFORMED_HEADERS (0x09): : A HEADERS frame has been received with an invalid format.
HTTP_MALFORMED_PRIORITY (0x0A): : A PRIORITY frame has been received with an invalid format.
HTTP_MALFORMED_SETTINGS (0x0B): : A SETTINGS frame has been received with an invalid format.
HTTP_MALFORMED_PUSH_PROMISE (0x0C): : A PUSH_PROMISE frame has been received with an invalid format.
HTTP_MALFORMED_DATA (0x0D): : A HEADERS frame has been received with an invalid format.
HTTP_INTERRUPTED_HEADERS (0x0E): : A HEADERS frame without the End Header Block flag was followed by a frame other than HEADERS.
HTTP_SETTINGS_ON_WRONG_STREAM (0x0F): : A SETTINGS frame was received on a request control stream.
HTTP_MULTIPLE_SETTINGS (0x10): : More than one SETTINGS frame was received.
HTTP_DUPLICATE_PUSH (0x11): : Multiple push streams used the same Push ID.
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.
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.
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 frame 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.
Other than this issue, frame type HTTP/2 extensions are typically portable to QUIC simply by replacing Stream 0 in HTTP/2 with Stream 1 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 {{frame-data}}.
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 {{frame-headers}}.
PRIORITY (0x2): : As described above, the PRIORITY frame is sent on the control stream. See {{frame-priority}}.
RST_STREAM (0x3): : RST_STREAM frames do not exist, since QUIC provides stream lifecycle management. The same code point is used for the CANCEL_REQUEST frame ({{frame-cancel-request}}).
SETTINGS (0x4): : SETTINGS frames are sent only at the beginning of the connection. See {{frame-settings}} and {{h2-settings}}.
PUSH_PROMISE (0x5): : The PUSH_PROMISE does not reference the stream that carries the response to the pushed request; instead the push stream references the PUSH_PROMISE frame. See {{frame-push-promise}}.
PING (0x6): : PING frames do not exist, since QUIC provides equivalent functionality.
GOAWAY (0x7): : GOAWAY frames do not exist, since QUIC provides equivalent functionality.
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 {{iana-frames}}.
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 {{settings-parameters}}.
SETTINGS_ENABLE_PUSH: : See SETTINGS_DISABLE_PUSH in {{settings-parameters}}.
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 {{settings-parameters}}.
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 {{iana-settings}}.
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 QUIC error codes as follows:
NO_ERROR (0x0): : QUIC_NO_ERROR
PROTOCOL_ERROR (0x1): : No single mapping. See new HTTP_MALFORMED_* error codes defined in {{http-error-codes}}.
INTERNAL_ERROR (0x2): : HTTP_INTERNAL_ERROR in {{http-error-codes}}.
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.
FRAME_SIZE_ERROR (0x6) : No single mapping. See new error codes defined in {{http-error-codes}}.
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 {{http-error-codes}}.
COMPRESSION_ERROR (0x9): : HTTP_HPACK_DECOMPRESSION_FAILED in {{http-error-codes}}.
CONNECT_ERROR (0xa): : HTTP_CONNECT_ERROR in {{http-error-codes}}.
ENHANCE_YOUR_CALM (0xb): : HTTP_EXCESSIVE_LOAD in {{http-error-codes}}.
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 {{http-error-codes}}.
Error codes need to be defined for HTTP/2 and HTTP/QUIC separately. See {{iana-error-codes}}.
The security considerations of HTTP over QUIC should be comparable to those of HTTP/2.
The modified SETTINGS format contains nested length elements, which could pose a security risk to an uncautious implementer. A SETTINGS frame parser MUST ensure that the length of the frame exactly matches the length of the settings it contains.
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 QUIC
Identification Sequence: : 0x68 0x71 ("hq")
Specification: : This document
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, {{alt-svc-version-hint}}
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 {{?RFC5226}} for values between 0x00 and 0xef, with values between 0xf0 and 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, its semantics, and flags that the frame type uses, including any parts of the frame that are conditionally present based on the value of flags.
The entries in the following table are registered by this document.
|----------------|------|--------------------------|
| Frame Type | Code | Specification |
|---|---|---|
| DATA | 0x0 | {{frame-data}} |
| HEADERS | 0x1 | {{frame-headers}} |
| PRIORITY | 0x2 | {{frame-priority}} |
| CANCEL_REQUEST | 0x3 | {{frame-cancel-request}} |
| SETTINGS | 0x4 | {{frame-settings}} |
| PUSH_PROMISE | 0x5 | {{frame-push-promise}} |
| Reserved | 0x6 | N/A |
| Reserved | 0x7 | N/A |
| Reserved | 0x8 | N/A |
| Reserved | 0x9 | N/A |
| ---------------- | ------ | -------------------------- |
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 {{?RFC5226}} 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, every 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 |
|---|---|---|
| HEADER_TABLE_SIZE | 0x1 | {{settings-parameters}} |
| DISABLE_PUSH | 0x2 | {{settings-parameters}} |
| Reserved | 0x3 | N/A |
| Reserved | 0x4 | N/A |
| Reserved | 0x5 | N/A |
| MAX_HEADER_LIST_SIZE | 0x6 | {{settings-parameters}} |
| ---------------------------- | ------ | ------------------------- |
This document establishes a registry for HTTP/QUIC error codes. The "HTTP/QUIC Error Code" registry manages a 30-bit space. The "HTTP/QUIC Error Code" registry operates under the "Expert Review" policy {{?RFC5226}}.
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.
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 30-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 |
|---|---|---|---|
| HTTP_PUSH_REFUSED | 0x01 | Client refused pushed content | {{http-error-codes}} |
| HTTP_INTERNAL_ERROR | 0x02 | Internal error | {{http-error-codes}} |
| HTTP_PUSH_ALREADY_IN_CACHE | 0x03 | Pushed content already cached | {{http-error-codes}} |
| HTTP_REQUEST_CANCELLED | 0x04 | Data no longer needed | {{http-error-codes}} |
| HTTP_HPACK_DECOMPRESSION_FAILED | 0x05 | HPACK cannot continue | {{http-error-codes}} |
| HTTP_CONNECT_ERROR | 0x06 | TCP reset or error on CONNECT request | {{http-error-codes}} |
| HTTP_EXCESSIVE_LOAD | 0x07 | Peer generating excessive load | {{http-error-codes}} |
| HTTP_VERSION_FALLBACK | 0x08 | Retry over HTTP/2 | {{http-error-codes}} |
| HTTP_MALFORMED_HEADERS | 0x09 | Invalid HEADERS frame | {{http-error-codes}} |
| HTTP_MALFORMED_PRIORITY | 0x0A | Invalid PRIORITY frame | {{http-error-codes}} |
| HTTP_MALFORMED_SETTINGS | 0x0B | Invalid SETTINGS frame | {{http-error-codes}} |
| HTTP_MALFORMED_PUSH_PROMISE | 0x0C | Invalid PUSH_PROMISE frame | {{http-error-codes}} |
| HTTP_INTERRUPTED_HEADERS | 0x0E | Incomplete HEADERS block | {{http-error-codes}} |
| HTTP_WRONG_STREAM | 0x0F | A frame was sent on the wrong stream | {{http-error-codes}} |
| HTTP_MULTIPLE_SETTINGS | 0x10 | Multiple SETTINGS frames | {{http-error-codes}} |
| HTTP_DUPLICATE_PUSH | 0x11 | Duplicate server push | {{http-error-codes}} |
| ----------------------------------- | -------- | ---------------------------------------- | ---------------------- |
--- back
The original authors of this specification were Robbie Shade and Mike Warres.
RFC Editor's Note: Please remove this section prior to publication of a final version of this document.
- Cite RFC 5234 (#404)
- Return to a single stream per request (#245,#557)
- Use separate frame type and settings registries from HTTP/2 (#81)
None.
- Track changes in transport draft
-
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 time
- Boolean format updated
-
Alt-Svc parameter changed from "v" to "quic"; format updated (#229)
-
Closing the connection control stream or any message control stream is a fatal error (#176)
-
HPACK Sequence counter can wrap (#173)
-
0-RTT guidance added
-
Guide to differences from HTTP/2 and porting HTTP/2 extensions added (#127,#242)
- Changed "HTTP/2-over-QUIC" to "HTTP/QUIC" throughout (#11,#29)
- Changed from using HTTP/2 framing within Stream 3 to new framing format and two-stream-per-request model (#71,#72,#73)
- Adopted SETTINGS format from draft-bishop-httpbis-extended-settings-01
- Reworked SETTINGS_ACK to account for indeterminate inter-stream order (#75)
- Described CONNECT pseudo-method (#95)
- Updated ALPN token and Alt-Svc guidance (#13,#87)
- Application-layer-defined error codes (#19,#74)
- Adopted as base for draft-ietf-quic-http
- Updated authors/editors list