Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing
draft-ietf-httpbis-p1-messaging-22
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 7230.
|
|
|---|---|---|---|
| Authors | Roy T. Fielding , Julian Reschke | ||
| Last updated | 2013-02-23 | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
GENART Telechat review
(of
-25)
by Meral Shirazipour
Ready w/issues
SECDIR Last Call review
(of
-24)
by Ben Laurie
Serious Issues
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 7230 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Barry Leiba | ||
| Send notices to | httpbis-chairs@tools.ietf.org, draft-ietf-httpbis-p1-messaging@tools.ietf.org |
draft-ietf-httpbis-p1-messaging-22
directly instead of properly encoding or excluding the disallowed
characters. Recipients of an invalid request-line SHOULD respond
with either a 400 (Bad Request) error or a 301 (Moved Permanently)
redirect with the request-target properly encoded. Recipients SHOULD
NOT attempt to autocorrect and then process the request without a
redirect, since the invalid request-line might be deliberately
crafted to bypass security filters along the request chain.
HTTP does not place a pre-defined limit on the length of a request-
line. A server that receives a method longer than any that it
implements SHOULD respond with a 501 (Not Implemented) status code.
A server MUST be prepared to receive URIs of unbounded length and
respond with the 414 (URI Too Long) status code if the received
request-target would be longer than the server wishes to handle (see
Section 6.5.12 of [Part2]).
Various ad-hoc limitations on request-line length are found in
practice. It is RECOMMENDED that all HTTP senders and recipients
support, at a minimum, request-line lengths of 8000 octets.
3.1.2. Status Line
The first line of a response message is the status-line, consisting
of the protocol version, a space (SP), the status code, another
space, a possibly-empty textual phrase describing the status code,
and ending with CRLF.
status-line = HTTP-version SP status-code SP reason-phrase CRLF
The status-code element is a 3-digit integer code describing the
result of the server's attempt to understand and satisfy the client's
corresponding request. The rest of the response message is to be
interpreted in light of the semantics defined for that status code.
See Section 6 of [Part2] for information about the semantics of
status codes, including the classes of status code (indicated by the
first digit), the status codes defined by this specification,
considerations for the definition of new status codes, and the IANA
registry.
status-code = 3DIGIT
The reason-phrase element exists for the sole purpose of providing a
textual description associated with the numeric status code, mostly
out of deference to earlier Internet application protocols that were
more frequently used with interactive text clients. A client SHOULD
ignore the reason-phrase content.
reason-phrase = *( HTAB / SP / VCHAR / obs-text )
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3.2. Header Fields
Each HTTP header field consists of a case-insensitive field name
followed by a colon (":"), optional whitespace, and the field value.
header-field = field-name ":" OWS field-value BWS
field-name = token
field-value = *( field-content / obs-fold )
field-content = *( HTAB / SP / VCHAR / obs-text )
obs-fold = CRLF ( SP / HTAB )
; obsolete line folding
; see Section 3.2.4
The field-name token labels the corresponding field-value as having
the semantics defined by that header field. For example, the Date
header field is defined in Section 7.1.1.2 of [Part2] as containing
the origination timestamp for the message in which it appears.
3.2.1. Field Extensibility
HTTP header fields are fully extensible: there is no limit on the
introduction of new field names, each presumably defining new
semantics, nor on the number of header fields used in a given
message. Existing fields are defined in each part of this
specification and in many other specifications outside the core
standard. New header fields can be introduced without changing the
protocol version if their defined semantics allow them to be safely
ignored by recipients that do not recognize them.
New HTTP header fields ought to be be registered with IANA in the
Message Header Field Registry, as described in Section 8.3 of
[Part2]. A proxy MUST forward unrecognized header fields unless the
field-name is listed in the Connection header field (Section 6.1) or
the proxy is specifically configured to block, or otherwise
transform, such fields. Other recipients SHOULD ignore unrecognized
header fields.
3.2.2. Field Order
The order in which header fields with differing field names are
received is not significant. However, it is "good practice" to send
header fields that contain control data first, such as Host on
requests and Date on responses, so that implementations can decide
when not to handle a message as early as possible. A server MUST
wait until the entire header section is received before interpreting
a request message, since later header fields might include
conditionals, authentication credentials, or deliberately misleading
duplicate header fields that would impact request processing.
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A sender MUST NOT generate multiple header fields with the same field
name in a message unless either the entire field value for that
header field is defined as a comma-separated list [i.e., #(values)]
or the header field is a well-known exception (as noted below).
Multiple header fields with the same field name can be combined into
one "field-name: field-value" pair, without changing the semantics of
the message, by appending each subsequent field value to the combined
field value in order, separated by a comma. The order in which
header fields with the same field name are received is therefore
significant to the interpretation of the combined field value; a
proxy MUST NOT change the order of these field values when forwarding
a message.
Note: In practice, the "Set-Cookie" header field ([RFC6265]) often
appears multiple times in a response message and does not use the
list syntax, violating the above requirements on multiple header
fields with the same name. Since it cannot be combined into a
single field-value, recipients ought to handle "Set-Cookie" as a
special case while processing header fields. (See Appendix A.2.3
of [Kri2001] for details.)
3.2.3. Whitespace
This specification uses three rules to denote the use of linear
whitespace: OWS (optional whitespace), RWS (required whitespace), and
BWS ("bad" whitespace).
The OWS rule is used where zero or more linear whitespace octets
might appear. OWS SHOULD either not be generated or be generated as
a single SP. Multiple OWS octets that occur within field-content
SHOULD either be replaced with a single SP or transformed to all SP
octets (each octet other than SP replaced with SP) before
interpreting the field value or forwarding the message downstream.
RWS is used when at least one linear whitespace octet is required to
separate field tokens. RWS SHOULD be generated as a single SP.
Multiple RWS octets that occur within field-content SHOULD either be
replaced with a single SP or transformed to all SP octets before
interpreting the field value or forwarding the message downstream.
BWS is used where the grammar allows optional whitespace, for
historical reasons, but senders SHOULD NOT generate it in messages;
recipients MUST accept such bad optional whitespace and remove it
before interpreting the field value or forwarding the message
downstream.
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OWS = *( SP / HTAB )
; optional whitespace
RWS = 1*( SP / HTAB )
; required whitespace
BWS = OWS
; "bad" whitespace
3.2.4. Field Parsing
No whitespace is allowed between the header field-name and colon. In
the past, differences in the handling of such whitespace have led to
security vulnerabilities in request routing and response handling. A
server MUST reject any received request message that contains
whitespace between a header field-name and colon with a response code
of 400 (Bad Request). A proxy MUST remove any such whitespace from a
response message before forwarding the message downstream.
A field value is preceded by optional whitespace (OWS); a single SP
is preferred. The field value does not include any leading or
trailing white space: OWS occurring before the first non-whitespace
octet of the field value or after the last non-whitespace octet of
the field value is ignored and SHOULD be removed before further
processing (as this does not change the meaning of the header field).
Historically, HTTP header field values could be extended over
multiple lines by preceding each extra line with at least one space
or horizontal tab (obs-fold). This specification deprecates such
line folding except within the message/http media type
(Section 7.3.1). Senders MUST NOT generate messages that include
line folding (i.e., that contain any field-value that contains a
match to the obs-fold rule) unless the message is intended for
packaging within the message/http media type. When an obs-fold is
received in a message, recipients MUST do one of:
o accept the message and replace any embedded obs-fold whitespace
with either a single SP or a matching number of SP octets (to
avoid buffer copying) prior to interpreting the field value or
forwarding the message downstream;
o if it is a request, reject the message by sending a 400 (Bad
Request) response with a representation explaining that obsolete
line folding is unacceptable; or,
o if it is a response, discard the message and generate a 502 (Bad
Gateway) response with a representation explaining that
unacceptable line folding was received.
Recipients that choose not to implement obs-fold processing (as
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described above) MUST NOT accept messages containing header fields
with leading whitespace, as this can expose them to attacks that
exploit this difference in processing.
Historically, HTTP has allowed field content with text in the ISO-
8859-1 [ISO-8859-1] charset, supporting other charsets only through
use of [RFC2047] encoding. In practice, most HTTP header field
values use only a subset of the US-ASCII charset [USASCII]. Newly
defined header fields SHOULD limit their field values to US-ASCII
octets. Recipients SHOULD treat other octets in field content (obs-
text) as opaque data.
3.2.5. Field Limits
HTTP does not place a pre-defined limit on the length of each header
field or on the length of the header block as a whole. Various ad-
hoc limitations on individual header field length are found in
practice, often depending on the specific field semantics.
A server MUST be prepared to receive request header fields of
unbounded length and respond with an appropriate 4xx (Client Error)
status code if the received header field(s) are larger than the
server wishes to process.
A client MUST be prepared to receive response header fields of
unbounded length. A client MAY discard or truncate received header
fields that are larger than the client wishes to process if the field
semantics are such that the dropped value(s) can be safely ignored
without changing the response semantics.
3.2.6. Field value components
Many HTTP header field values consist of words (token or quoted-
string) separated by whitespace or special characters. These special
characters MUST be in a quoted string to be used within a parameter
value (as defined in Section 4).
word = token / quoted-string
token = 1*tchar
tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*"
/ "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
/ DIGIT / ALPHA
; any VCHAR, except special
special = "(" / ")" / "<" / ">" / "@" / ","
/ ";" / ":" / "\" / DQUOTE / "/" / "["
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/ "]" / "?" / "=" / "{" / "}"
A string of text is parsed as a single word if it is quoted using
double-quote marks.
quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
qdtext = HTAB / SP /%x21 / %x23-5B / %x5D-7E / obs-text
obs-text = %x80-FF
The backslash octet ("\") can be used as a single-octet quoting
mechanism within quoted-string constructs:
quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text )
Recipients that process the value of a quoted-string MUST handle a
quoted-pair as if it were replaced by the octet following the
backslash.
Senders SHOULD NOT generate a quoted-pair in a quoted-string except
where necessary to quote DQUOTE and backslash octets occurring within
that string.
Comments can be included in some HTTP header fields by surrounding
the comment text with parentheses. Comments are only allowed in
fields containing "comment" as part of their field value definition.
comment = "(" *( ctext / quoted-cpair / comment ) ")"
ctext = HTAB / SP / %x21-27 / %x2A-5B / %x5D-7E / obs-text
The backslash octet ("\") can be used as a single-octet quoting
mechanism within comment constructs:
quoted-cpair = "\" ( HTAB / SP / VCHAR / obs-text )
Senders SHOULD NOT escape octets in comments that do not require
escaping (i.e., other than the backslash octet "\" and the
parentheses "(" and ")").
3.3. Message Body
The message body (if any) of an HTTP message is used to carry the
payload body of that request or response. The message body is
identical to the payload body unless a transfer coding has been
applied, as described in Section 3.3.1.
message-body = *OCTET
The rules for when a message body is allowed in a message differ for
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requests and responses.
The presence of a message body in a request is signaled by a Content-
Length or Transfer-Encoding header field. Request message framing is
independent of method semantics, even if the method does not define
any use for a message body.
The presence of a message body in a response depends on both the
request method to which it is responding and the response status code
(Section 3.1.2). Responses to the HEAD request method never include
a message body because the associated response header fields (e.g.,
Transfer-Encoding, Content-Length, etc.), if present, indicate only
what their values would have been if the request method had been GET
(Section 4.3.2 of [Part2]). 2xx (Successful) responses to CONNECT
switch to tunnel mode instead of having a message body (Section 4.3.6
of [Part2]). All 1xx (Informational), 204 (No Content), and 304 (Not
Modified) responses do not include a message body. All other
responses do include a message body, although the body might be of
zero length.
3.3.1. Transfer-Encoding
The Transfer-Encoding header field lists the transfer coding names
corresponding to the sequence of transfer codings that have been (or
will be) applied to the payload body in order to form the message
body. Transfer codings are defined in Section 4.
Transfer-Encoding = 1#transfer-coding
Transfer-Encoding is analogous to the Content-Transfer-Encoding field
of MIME, which was designed to enable safe transport of binary data
over a 7-bit transport service ([RFC2045], Section 6). However, safe
transport has a different focus for an 8bit-clean transfer protocol.
In HTTP's case, Transfer-Encoding is primarily intended to accurately
delimit a dynamically generated payload and to distinguish payload
encodings that are only applied for transport efficiency or security
from those that are characteristics of the selected resource.
All HTTP/1.1 recipients MUST implement the chunked transfer coding
(Section 4.1) because it plays a crucial role in framing messages
when the payload body size is not known in advance. If chunked is
applied to a payload body, the sender MUST NOT apply chunked more
than once (i.e., chunking an already chunked message is not allowed).
If any transfer coding is applied to a request payload body, the
sender MUST apply chunked as the final transfer coding to ensure that
the message is properly framed. If any transfer coding is applied to
a response payload body, the sender MUST either apply chunked as the
final transfer coding or terminate the message by closing the
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connection.
For example,
Transfer-Encoding: gzip, chunked
indicates that the payload body has been compressed using the gzip
coding and then chunked using the chunked coding while forming the
message body.
Unlike Content-Encoding (Section 3.1.2.1 of [Part2]), Transfer-
Encoding is a property of the message, not of the representation, and
any recipient along the request/response chain MAY decode the
received transfer coding(s) or apply additional transfer coding(s) to
the message body, assuming that corresponding changes are made to the
Transfer-Encoding field-value. Additional information about the
encoding parameters MAY be provided by other header fields not
defined by this specification.
Transfer-Encoding MAY be sent in a response to a HEAD request or in a
304 (Not Modified) response (Section 4.1 of [Part4]) to a GET
request, neither of which includes a message body, to indicate that
the origin server would have applied a transfer coding to the message
body if the request had been an unconditional GET. This indication
is not required, however, because any recipient on the response chain
(including the origin server) can remove transfer codings when they
are not needed.
Transfer-Encoding was added in HTTP/1.1. It is generally assumed
that implementations advertising only HTTP/1.0 support will not
understand how to process a transfer-encoded payload. A client MUST
NOT send a request containing Transfer-Encoding unless it knows the
server will handle HTTP/1.1 (or later) requests; such knowledge might
be in the form of specific user configuration or by remembering the
version of a prior received response. A server MUST NOT send a
response containing Transfer-Encoding unless the corresponding
request indicates HTTP/1.1 (or later).
A server that receives a request message with a transfer coding it
does not understand SHOULD respond with 501 (Not Implemented).
3.3.2. Content-Length
When a message does not have a Transfer-Encoding header field, a
Content-Length header field can provide the anticipated size, as a
decimal number of octets, for a potential payload body. For messages
that do include a payload body, the Content-Length field-value
provides the framing information necessary for determining where the
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body (and message) ends. For messages that do not include a payload
body, the Content-Length indicates the size of the selected
representation (Section 3 of [Part2]).
Content-Length = 1*DIGIT
An example is
Content-Length: 3495
A sender MUST NOT send a Content-Length header field in any message
that contains a Transfer-Encoding header field.
A user agent SHOULD send a Content-Length in a request message when
no Transfer-Encoding is sent and the request method defines a meaning
for an enclosed payload body. For example, a Content-Length header
field is normally sent in a POST request even when the value is 0
(indicating an empty payload body). A user agent SHOULD NOT send a
Content-Length header field when the request message does not contain
a payload body and the method semantics do not anticipate such a
body.
A server MAY send a Content-Length header field in a response to a
HEAD request (Section 4.3.2 of [Part2]); a server MUST NOT send
Content-Length in such a response unless its field-value equals the
decimal number of octets that would have been sent in the payload
body of a response if the same request had used the GET method.
A server MAY send a Content-Length header field in a 304 (Not
Modified) response to a conditional GET request (Section 4.1 of
[Part4]); a server MUST NOT send Content-Length in such a response
unless its field-value equals the decimal number of octets that would
have been sent in the payload body of a 200 (OK) response to the same
request.
A server MUST NOT send a Content-Length header field in any response
with a status code of 1xx (Informational) or 204 (No Content). A
server SHOULD NOT send a Content-Length header field in any 2xx
(Successful) response to a CONNECT request (Section 4.3.6 of
[Part2]).
Aside from the cases defined above, in the absence of Transfer-
Encoding, an origin server SHOULD send a Content-Length header field
when the payload body size is known prior to sending the complete
header block. This will allow downstream recipients to measure
transfer progress, know when a received message is complete, and
potentially reuse the connection for additional requests.
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Any Content-Length field value greater than or equal to zero is
valid. Since there is no predefined limit to the length of a
payload, recipients SHOULD anticipate potentially large decimal
numerals and prevent parsing errors due to integer conversion
overflows (Section 8.3).
If a message is received that has multiple Content-Length header
fields with field-values consisting of the same decimal value, or a
single Content-Length header field with a field value containing a
list of identical decimal values (e.g., "Content-Length: 42, 42"),
indicating that duplicate Content-Length header fields have been
generated or combined by an upstream message processor, then the
recipient MUST either reject the message as invalid or replace the
duplicated field-values with a single valid Content-Length field
containing that decimal value prior to determining the message body
length.
Note: HTTP's use of Content-Length for message framing differs
significantly from the same field's use in MIME, where it is an
optional field used only within the "message/external-body" media-
type.
3.3.3. Message Body Length
The length of a message body is determined by one of the following
(in order of precedence):
1. Any response to a HEAD request and any response with a 1xx
(Informational), 204 (No Content), or 304 (Not Modified) status
code is always terminated by the first empty line after the
header fields, regardless of the header fields present in the
message, and thus cannot contain a message body.
2. Any 2xx (Successful) response to a CONNECT request implies that
the connection will become a tunnel immediately after the empty
line that concludes the header fields. A client MUST ignore any
Content-Length or Transfer-Encoding header fields received in
such a message.
3. If a Transfer-Encoding header field is present and the chunked
transfer coding (Section 4.1) is the final encoding, the message
body length is determined by reading and decoding the chunked
data until the transfer coding indicates the data is complete.
If a Transfer-Encoding header field is present in a response and
the chunked transfer coding is not the final encoding, the
message body length is determined by reading the connection until
it is closed by the server. If a Transfer-Encoding header field
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is present in a request and the chunked transfer coding is not
the final encoding, the message body length cannot be determined
reliably; the server MUST respond with the 400 (Bad Request)
status code and then close the connection.
If a message is received with both a Transfer-Encoding and a
Content-Length header field, the Transfer-Encoding overrides the
Content-Length. Such a message might indicate an attempt to
perform request or response smuggling (bypass of security-related
checks on message routing or content) and thus ought to be
handled as an error. A sender MUST remove the received Content-
Length field prior to forwarding such a message downstream.
4. If a message is received without Transfer-Encoding and with
either multiple Content-Length header fields having differing
field-values or a single Content-Length header field having an
invalid value, then the message framing is invalid and MUST be
treated as an error to prevent request or response smuggling. If
this is a request message, the server MUST respond with a 400
(Bad Request) status code and then close the connection. If this
is a response message received by a proxy, the proxy MUST discard
the received response, send a 502 (Bad Gateway) status code as
its downstream response, and then close the connection. If this
is a response message received by a user agent, it MUST be
treated as an error by discarding the message and closing the
connection.
5. If a valid Content-Length header field is present without
Transfer-Encoding, its decimal value defines the expected message
body length in octets. If the sender closes the connection or
the recipient times out before the indicated number of octets are
received, the recipient MUST consider the message to be
incomplete and close the connection.
6. If this is a request message and none of the above are true, then
the message body length is zero (no message body is present).
7. Otherwise, this is a response message without a declared message
body length, so the message body length is determined by the
number of octets received prior to the server closing the
connection.
Since there is no way to distinguish a successfully completed, close-
delimited message from a partially-received message interrupted by
network failure, a server SHOULD use encoding or length-delimited
messages whenever possible. The close-delimiting feature exists
primarily for backwards compatibility with HTTP/1.0.
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A server MAY reject a request that contains a message body but not a
Content-Length by responding with 411 (Length Required).
Unless a transfer coding other than chunked has been applied, a
client that sends a request containing a message body SHOULD use a
valid Content-Length header field if the message body length is known
in advance, rather than the chunked transfer coding, since some
existing services respond to chunked with a 411 (Length Required)
status code even though they understand the chunked transfer coding.
This is typically because such services are implemented via a gateway
that requires a content-length in advance of being called and the
server is unable or unwilling to buffer the entire request before
processing.
A user agent that sends a request containing a message body MUST send
a valid Content-Length header field if it does not know the server
will handle HTTP/1.1 (or later) requests; such knowledge can be in
the form of specific user configuration or by remembering the version
of a prior received response.
If the final response to the last request on a connection has been
completely received and there remains additional data to read, a user
agent MAY discard the remaining data or attempt to determine if that
data belongs as part of the prior response body, which might be the
case if the prior message's Content-Length value is incorrect. A
client MUST NOT process, cache, or forward such extra data as a
separate response, since such behavior would be vulnerable to cache
poisoning.
3.4. Handling Incomplete Messages
A server that receives an incomplete request message, usually due to
a canceled request or a triggered time-out exception, MAY send an
error response prior to closing the connection.
A client that receives an incomplete response message, which can
occur when a connection is closed prematurely or when decoding a
supposedly chunked transfer coding fails, MUST record the message as
incomplete. Cache requirements for incomplete responses are defined
in Section 3 of [Part6].
If a response terminates in the middle of the header block (before
the empty line is received) and the status code might rely on header
fields to convey the full meaning of the response, then the client
cannot assume that meaning has been conveyed; the client might need
to repeat the request in order to determine what action to take next.
A message body that uses the chunked transfer coding is incomplete if
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the zero-sized chunk that terminates the encoding has not been
received. A message that uses a valid Content-Length is incomplete
if the size of the message body received (in octets) is less than the
value given by Content-Length. A response that has neither chunked
transfer coding nor Content-Length is terminated by closure of the
connection, and thus is considered complete regardless of the number
of message body octets received, provided that the header block was
received intact.
3.5. Message Parsing Robustness
Older HTTP/1.0 user agent implementations might send an extra CRLF
after a POST request as a lame workaround for some early server
applications that failed to read message body content that was not
terminated by a line-ending. An HTTP/1.1 user agent MUST NOT preface
or follow a request with an extra CRLF. If terminating the request
message body with a line-ending is desired, then the user agent MUST
count the terminating CRLF octets as part of the message body length.
In the interest of robustness, servers SHOULD ignore at least one
empty line received where a request-line is expected. In other
words, if a server is reading the protocol stream at the beginning of
a message and receives a CRLF first, the server SHOULD ignore the
CRLF.
Although the line terminator for the start-line and header fields is
the sequence CRLF, recipients MAY recognize a single LF as a line
terminator and ignore any preceding CR.
Although the request-line and status-line grammar rules require that
each of the component elements be separated by a single SP octet,
recipients MAY instead parse on whitespace-delimited word boundaries
and, aside from the CRLF terminator, treat any form of whitespace as
the SP separator while ignoring preceding or trailing whitespace;
such whitespace includes one or more of the following octets: SP,
HTAB, VT (%x0B), FF (%x0C), or bare CR.
When a server listening only for HTTP request messages, or processing
what appears from the start-line to be an HTTP request message,
receives a sequence of octets that does not match the HTTP-message
grammar aside from the robustness exceptions listed above, the server
SHOULD respond with a 400 (Bad Request) response.
4. Transfer Codings
Transfer coding names are used to indicate an encoding transformation
that has been, can be, or might need to be applied to a payload body
in order to ensure "safe transport" through the network. This
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differs from a content coding in that the transfer coding is a
property of the message rather than a property of the representation
that is being transferred.
transfer-coding = "chunked" ; Section 4.1
/ "compress" ; Section 4.2.1
/ "deflate" ; Section 4.2.2
/ "gzip" ; Section 4.2.3
/ transfer-extension
transfer-extension = token *( OWS ";" OWS transfer-parameter )
Parameters are in the form of attribute/value pairs.
transfer-parameter = attribute BWS "=" BWS value
attribute = token
value = word
All transfer-coding names are case-insensitive and ought to be
registered within the HTTP Transfer Coding registry, as defined in
Section 7.4. They are used in the TE (Section 4.3) and Transfer-
Encoding (Section 3.3.1) header fields.
4.1. Chunked Transfer Coding
The chunked transfer coding modifies the body of a message in order
to transfer it as a series of chunks, each with its own size
indicator, followed by an OPTIONAL trailer containing header fields.
This allows dynamically generated content to be transferred along
with the information necessary for the recipient to verify that it
has received the full message.
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chunked-body = *chunk
last-chunk
trailer-part
CRLF
chunk = chunk-size [ chunk-ext ] CRLF
chunk-data CRLF
chunk-size = 1*HEXDIG
last-chunk = 1*("0") [ chunk-ext ] CRLF
chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] )
chunk-ext-name = token
chunk-ext-val = token / quoted-str-nf
chunk-data = 1*OCTET ; a sequence of chunk-size octets
trailer-part = *( header-field CRLF )
quoted-str-nf = DQUOTE *( qdtext-nf / quoted-pair ) DQUOTE
; like quoted-string, but disallowing line folding
qdtext-nf = HTAB / SP / %x21 / %x23-5B / %x5D-7E / obs-text
Chunk extensions within the chunked transfer coding are deprecated.
Senders SHOULD NOT send chunk-ext. Definition of new chunk
extensions is discouraged.
The chunk-size field is a string of hex digits indicating the size of
the chunk-data in octets. The chunked transfer coding is complete
when a chunk with a chunk-size of zero is received, possibly followed
by a trailer, and finally terminated by an empty line.
4.1.1. Trailer
A trailer allows the sender to include additional fields at the end
of a chunked message in order to supply metadata that might be
dynamically generated while the message body is sent, such as a
message integrity check, digital signature, or post-processing
status. The trailer MUST NOT contain fields that need to be known
before a recipient processes the body, such as Transfer-Encoding,
Content-Length, and Trailer.
When a message includes a message body encoded with the chunked
transfer coding and the sender desires to send metadata in the form
of trailer fields at the end of the message, the sender SHOULD send a
Trailer header field before the message body to indicate which fields
will be present in the trailers. This allows the recipient to
prepare for receipt of that metadata before it starts processing the
body, which is useful if the message is being streamed and the
recipient wishes to confirm an integrity check on the fly.
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Trailer = 1#field-name
If no Trailer header field is present, the sender of a chunked
message body SHOULD send an empty trailer.
A server MUST send an empty trailer with the chunked transfer coding
unless at least one of the following is true:
1. the request included a TE header field that indicates "trailers"
is acceptable in the transfer coding of the response, as
described in Section 4.3; or,
2. the trailer fields consist entirely of optional metadata and the
recipient could use the message (in a manner acceptable to the
server where the field originated) without receiving that
metadata. In other words, the server that generated the header
field is willing to accept the possibility that the trailer
fields might be silently discarded along the path to the client.
The above requirement prevents the need for an infinite buffer when a
message is being received by an HTTP/1.1 (or later) proxy and
forwarded to an HTTP/1.0 recipient.
4.1.2. Decoding chunked
A process for decoding the chunked transfer coding can be represented
in pseudo-code as:
length := 0
read chunk-size, chunk-ext (if any) and CRLF
while (chunk-size > 0) {
read chunk-data and CRLF
append chunk-data to decoded-body
length := length + chunk-size
read chunk-size and CRLF
}
read header-field
while (header-field not empty) {
append header-field to existing header fields
read header-field
}
Content-Length := length
Remove "chunked" from Transfer-Encoding
Remove Trailer from existing header fields
All recipients MUST be able to receive and decode the chunked
transfer coding and MUST ignore chunk-ext extensions they do not
understand.
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4.2. Compression Codings
The codings defined below can be used to compress the payload of a
message.
4.2.1. Compress Coding
The "compress" format is produced by the common UNIX file compression
program "compress". This format is an adaptive Lempel-Ziv-Welch
coding (LZW). Recipients SHOULD consider "x-compress" to be
equivalent to "compress".
4.2.2. Deflate Coding
The "deflate" format is defined as the "deflate" compression
mechanism (described in [RFC1951]) used inside the "zlib" data format
([RFC1950]).
Note: Some incorrect implementations send the "deflate" compressed
data without the zlib wrapper.
4.2.3. Gzip Coding
The "gzip" format is produced by the file compression program "gzip"
(GNU zip), as described in [RFC1952]. This format is a Lempel-Ziv
coding (LZ77) with a 32 bit CRC. Recipients SHOULD consider "x-gzip"
to be equivalent to "gzip".
4.3. TE
The "TE" header field in a request indicates what transfer codings,
besides chunked, the client is willing to accept in response, and
whether or not the client is willing to accept trailer fields in a
chunked transfer coding.
The TE field-value consists of a comma-separated list of transfer
coding names, each allowing for optional parameters (as described in
Section 4), and/or the keyword "trailers". Clients MUST NOT send the
chunked transfer coding name in TE; chunked is always acceptable for
HTTP/1.1 recipients.
TE = #t-codings
t-codings = "trailers" / ( transfer-coding [ t-ranking ] )
t-ranking = OWS ";" OWS "q=" rank
rank = ( "0" [ "." 0*3DIGIT ] )
/ ( "1" [ "." 0*3("0") ] )
Three examples of TE use are below.
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TE: deflate
TE:
TE: trailers, deflate;q=0.5
The presence of the keyword "trailers" indicates that the client is
willing to accept trailer fields in a chunked transfer coding, as
defined in Section 4.1, on behalf of itself and any downstream
clients. For chained requests, this implies that either: (a) all
downstream clients are willing to accept trailer fields in the
forwarded response; or, (b) the client will attempt to buffer the
response on behalf of downstream recipients. Note that HTTP/1.1 does
not define any means to limit the size of a chunked response such
that a client can be assured of buffering the entire response.
When multiple transfer codings are acceptable, the client MAY rank
the codings by preference using a case-insensitive "q" parameter
(similar to the qvalues used in content negotiation fields, Section
5.3.1 of [Part2]). The rank value is a real number in the range 0
through 1, where 0.001 is the least preferred and 1 is the most
preferred; a value of 0 means "not acceptable".
If the TE field-value is empty or if no TE field is present, the only
acceptable transfer coding is chunked. A message with no transfer
coding is always acceptable.
Since the TE header field only applies to the immediate connection, a
sender of TE MUST also send a "TE" connection option within the
Connection header field (Section 6.1) in order to prevent the TE
field from being forwarded by intermediaries that do not support its
semantics.
5. Message Routing
HTTP request message routing is determined by each client based on
the target resource, the client's proxy configuration, and
establishment or reuse of an inbound connection. The corresponding
response routing follows the same connection chain back to the
client.
5.1. Identifying a Target Resource
HTTP is used in a wide variety of applications, ranging from general-
purpose computers to home appliances. In some cases, communication
options are hard-coded in a client's configuration. However, most
HTTP clients rely on the same resource identification mechanism and
configuration techniques as general-purpose Web browsers.
HTTP communication is initiated by a user agent for some purpose.
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The purpose is a combination of request semantics, which are defined
in [Part2], and a target resource upon which to apply those
semantics. A URI reference (Section 2.7) is typically used as an
identifier for the "target resource", which a user agent would
resolve to its absolute form in order to obtain the "target URI".
The target URI excludes the reference's fragment identifier
component, if any, since fragment identifiers are reserved for
client-side processing ([RFC3986], Section 3.5).
5.2. Connecting Inbound
Once the target URI is determined, a client needs to decide whether a
network request is necessary to accomplish the desired semantics and,
if so, where that request is to be directed.
If the client has a response cache and the request semantics can be
satisfied by a cache ([Part6]), then the request is usually directed
to the cache first.
If the request is not satisfied by a cache, then a typical client
will check its configuration to determine whether a proxy is to be
used to satisfy the request. Proxy configuration is implementation-
dependent, but is often based on URI prefix matching, selective
authority matching, or both, and the proxy itself is usually
identified by an "http" or "https" URI. If a proxy is applicable,
the client connects inbound by establishing (or reusing) a connection
to that proxy.
If no proxy is applicable, a typical client will invoke a handler
routine, usually specific to the target URI's scheme, to connect
directly to an authority for the target resource. How that is
accomplished is dependent on the target URI scheme and defined by its
associated specification, similar to how this specification defines
origin server access for resolution of the "http" (Section 2.7.1) and
"https" (Section 2.7.2) schemes.
HTTP requirements regarding connection management are defined in
Section 6.
5.3. Request Target
Once an inbound connection is obtained, the client sends an HTTP
request message (Section 3) with a request-target derived from the
target URI. There are four distinct formats for the request-target,
depending on both the method being requested and whether the request
is to a proxy.
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request-target = origin-form
/ absolute-form
/ authority-form
/ asterisk-form
origin-form = absolute-path [ "?" query ]
absolute-form = absolute-URI
authority-form = authority
asterisk-form = "*"
origin-form
The most common form of request-target is the origin-form. When
making a request directly to an origin server, other than a CONNECT
or server-wide OPTIONS request (as detailed below), a client MUST
send only the absolute path and query components of the target URI as
the request-target. If the target URI's path component is empty,
then the client MUST send "/" as the path within the origin-form of
request-target. A Host header field is also sent, as defined in
Section 5.4, containing the target URI's authority component
(excluding any userinfo).
For example, a client wishing to retrieve a representation of the
resource identified as
http://www.example.org/where?q=now
directly from the origin server would open (or reuse) a TCP
connection to port 80 of the host "www.example.org" and send the
lines:
GET /where?q=now HTTP/1.1
Host: www.example.org
followed by the remainder of the request message.
absolute-form
When making a request to a proxy, other than a CONNECT or server-wide
OPTIONS request (as detailed below), a client MUST send the target
URI in absolute-form as the request-target. The proxy is requested
to either service that request from a valid cache, if possible, or
make the same request on the client's behalf to either the next
inbound proxy server or directly to the origin server indicated by
the request-target. Requirements on such "forwarding" of messages
are defined in Section 5.7.
An example absolute-form of request-line would be:
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GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
To allow for transition to the absolute-form for all requests in some
future version of HTTP, HTTP/1.1 servers MUST accept the absolute-
form in requests, even though HTTP/1.1 clients will only send them in
requests to proxies.
authority-form
The authority-form of request-target is only used for CONNECT
requests (Section 4.3.6 of [Part2]). When making a CONNECT request
to establish a tunnel through one or more proxies, a client MUST send
only the target URI's authority component (excluding any userinfo) as
the request-target. For example,
CONNECT www.example.com:80 HTTP/1.1
asterisk-form
The asterisk-form of request-target is only used for a server-wide
OPTIONS request (Section 4.3.7 of [Part2]). When a client wishes to
request OPTIONS for the server as a whole, as opposed to a specific
named resource of that server, the client MUST send only "*" (%x2A)
as the request-target. For example,
OPTIONS * HTTP/1.1
If a proxy receives an OPTIONS request with an absolute-form of
request-target in which the URI has an empty path and no query
component, then the last proxy on the request chain MUST send a
request-target of "*" when it forwards the request to the indicated
origin server.
For example, the request
OPTIONS http://www.example.org:8001 HTTP/1.1
would be forwarded by the final proxy as
OPTIONS * HTTP/1.1
Host: www.example.org:8001
after connecting to port 8001 of host "www.example.org".
5.4. Host
The "Host" header field in a request provides the host and port
information from the target URI, enabling the origin server to
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distinguish among resources while servicing requests for multiple
host names on a single IP address. Since the Host field-value is
critical information for handling a request, it SHOULD be sent as the
first header field following the request-line.
Host = uri-host [ ":" port ] ; Section 2.7.1
A client MUST send a Host header field in all HTTP/1.1 request
messages. If the target URI includes an authority component, then
the Host field-value MUST be identical to that authority component
after excluding any userinfo (Section 2.7.1). If the authority
component is missing or undefined for the target URI, then the Host
header field MUST be sent with an empty field-value.
For example, a GET request to the origin server for
<http://www.example.org/pub/WWW/> would begin with:
GET /pub/WWW/ HTTP/1.1
Host: www.example.org
The Host header field MUST be sent in an HTTP/1.1 request even if the
request-target is in the absolute-form, since this allows the Host
information to be forwarded through ancient HTTP/1.0 proxies that
might not have implemented Host.
When a proxy receives a request with an absolute-form of request-
target, the proxy MUST ignore the received Host header field (if any)
and instead replace it with the host information of the request-
target. If the proxy forwards the request, it MUST generate a new
Host field-value based on the received request-target rather than
forward the received Host field-value.
Since the Host header field acts as an application-level routing
mechanism, it is a frequent target for malware seeking to poison a
shared cache or redirect a request to an unintended server. An
interception proxy is particularly vulnerable if it relies on the
Host field-value for redirecting requests to internal servers, or for
use as a cache key in a shared cache, without first verifying that
the intercepted connection is targeting a valid IP address for that
host.
A server MUST respond with a 400 (Bad Request) status code to any
HTTP/1.1 request message that lacks a Host header field and to any
request message that contains more than one Host header field or a
Host header field with an invalid field-value.
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5.5. Effective Request URI
A server that receives an HTTP request message MUST reconstruct the
user agent's original target URI, based on the pieces of information
learned from the request-target, Host header field, and connection
context, in order to identify the intended target resource and
properly service the request. The URI derived from this
reconstruction process is referred to as the "effective request URI".
For a user agent, the effective request URI is the target URI.
If the request-target is in absolute-form, then the effective request
URI is the same as the request-target. Otherwise, the effective
request URI is constructed as follows.
If the request is received over a TLS-secured TCP connection, then
the effective request URI's scheme is "https"; otherwise, the scheme
is "http".
If the request-target is in authority-form, then the effective
request URI's authority component is the same as the request-target.
Otherwise, if a Host header field is supplied with a non-empty field-
value, then the authority component is the same as the Host field-
value. Otherwise, the authority component is the concatenation of
the default host name configured for the server, a colon (":"), and
the connection's incoming TCP port number in decimal form.
If the request-target is in authority-form or asterisk-form, then the
effective request URI's combined path and query component is empty.
Otherwise, the combined path and query component is the same as the
request-target.
The components of the effective request URI, once determined as
above, can be combined into absolute-URI form by concatenating the
scheme, "://", authority, and combined path and query component.
Example 1: the following message received over an insecure TCP
connection
GET /pub/WWW/TheProject.html HTTP/1.1
Host: www.example.org:8080
has an effective request URI of
http://www.example.org:8080/pub/WWW/TheProject.html
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Example 2: the following message received over a TLS-secured TCP
connection
OPTIONS * HTTP/1.1
Host: www.example.org
has an effective request URI of
https://www.example.org
An origin server that does not allow resources to differ by requested
host MAY ignore the Host field-value and instead replace it with a
configured server name when constructing the effective request URI.
Recipients of an HTTP/1.0 request that lacks a Host header field MAY
attempt to use heuristics (e.g., examination of the URI path for
something unique to a particular host) in order to guess the
effective request URI's authority component.
5.6. Associating a Response to a Request
HTTP does not include a request identifier for associating a given
request message with its corresponding one or more response messages.
Hence, it relies on the order of response arrival to correspond
exactly to the order in which requests are made on the same
connection. More than one response message per request only occurs
when one or more informational responses (1xx, see Section 6.2 of
[Part2]) precede a final response to the same request.
A client that has more than one outstanding request on a connection
MUST maintain a list of outstanding requests in the order sent and
MUST associate each received response message on that connection to
the highest ordered request that has not yet received a final (non-
1xx) response.
5.7. Message Forwarding
As described in Section 2.3, intermediaries can serve a variety of
roles in the processing of HTTP requests and responses. Some
intermediaries are used to improve performance or availability.
Others are used for access control or to filter content. Since an
HTTP stream has characteristics similar to a pipe-and-filter
architecture, there are no inherent limits to the extent an
intermediary can enhance (or interfere) with either direction of the
stream.
Intermediaries that forward a message MUST implement the Connection
header field, as specified in Section 6.1, to exclude fields that are
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only intended for the incoming connection.
In order to avoid request loops, a proxy that forwards requests to
other proxies MUST be able to recognize and exclude all of its own
server names, including any aliases, local variations, or literal IP
addresses.
5.7.1. Via
The "Via" header field MUST be sent by a proxy or gateway in
forwarded messages to indicate the intermediate protocols and
recipients between the user agent and the server on requests, and
between the origin server and the client on responses. It is
analogous to the "Received" field used by email systems (Section
3.6.7 of [RFC5322]). Via is used in HTTP for tracking message
forwards, avoiding request loops, and identifying the protocol
capabilities of all senders along the request/response chain.
Via = 1#( received-protocol RWS received-by
[ RWS comment ] )
received-protocol = [ protocol-name "/" ] protocol-version
; see Section 6.7
received-by = ( uri-host [ ":" port ] ) / pseudonym
pseudonym = token
The received-protocol indicates the protocol version of the message
received by the server or client along each segment of the request/
response chain. The received-protocol version is appended to the Via
field value when the message is forwarded so that information about
the protocol capabilities of upstream applications remains visible to
all recipients.
The protocol-name is excluded if and only if it would be "HTTP". The
received-by field is normally the host and optional port number of a
recipient server or client that subsequently forwarded the message.
However, if the real host is considered to be sensitive information,
it MAY be replaced by a pseudonym. If the port is not given, it MAY
be assumed to be the default port of the received-protocol.
Multiple Via field values represent each proxy or gateway that has
forwarded the message. Each recipient MUST append its information
such that the end result is ordered according to the sequence of
forwarding applications.
Comments MAY be used in the Via header field to identify the software
of each recipient, analogous to the User-Agent and Server header
fields. However, all comments in the Via field are optional and MAY
be removed by any recipient prior to forwarding the message.
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For example, a request message could be sent from an HTTP/1.0 user
agent to an internal proxy code-named "fred", which uses HTTP/1.1 to
forward the request to a public proxy at p.example.net, which
completes the request by forwarding it to the origin server at
www.example.com. The request received by www.example.com would then
have the following Via header field:
Via: 1.0 fred, 1.1 p.example.net (Apache/1.1)
A proxy or gateway used as a portal through a network firewall SHOULD
NOT forward the names and ports of hosts within the firewall region
unless it is explicitly enabled to do so. If not enabled, the
received-by host of any host behind the firewall SHOULD be replaced
by an appropriate pseudonym for that host.
A proxy or gateway MAY combine an ordered subsequence of Via header
field entries into a single such entry if the entries have identical
received-protocol values. For example,
Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
could be collapsed to
Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
Senders SHOULD NOT combine multiple entries unless they are all under
the same organizational control and the hosts have already been
replaced by pseudonyms. Senders MUST NOT combine entries that have
different received-protocol values.
5.7.2. Transformations
Some intermediaries include features for transforming messages and
their payloads. A transforming proxy might, for example, convert
between image formats in order to save cache space or to reduce the
amount of traffic on a slow link. However, operational problems
might occur when these transformations are applied to payloads
intended for critical applications, such as medical imaging or
scientific data analysis, particularly when integrity checks or
digital signatures are used to ensure that the payload received is
identical to the original.
If a proxy receives a request-target with a host name that is not a
fully qualified domain name, it MAY add its own domain to the host
name it received when forwarding the request. A proxy MUST NOT
change the host name if it is a fully qualified domain name.
A proxy MUST NOT modify the "absolute-path" and "query" parts of the
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received request-target when forwarding it to the next inbound
server, except as noted above to replace an empty path with "/" or
"*".
A proxy MUST NOT modify header fields that provide information about
the end points of the communication chain, the resource state, or the
selected representation. A proxy MAY change the message body through
application or removal of a transfer coding (Section 4).
A non-transforming proxy MUST preserve the message payload (Section
3.3 of [Part2]). A transforming proxy MUST preserve the payload of a
message that contains the no-transform cache-control directive.
A transforming proxy MAY transform the payload of a message that does
not contain the no-transform cache-control directive; if the payload
is transformed, the transforming proxy MUST add a Warning 214
(Transformation applied) header field if one does not already appear
in the message (see Section 7.5 of [Part6]).
6. Connection Management
HTTP messaging is independent of the underlying transport or session-
layer connection protocol(s). HTTP only presumes a reliable
transport with in-order delivery of requests and the corresponding
in-order delivery of responses. The mapping of HTTP request and
response structures onto the data units of an underlying transport
protocol is outside the scope of this specification.
As described in Section 5.2, the specific connection protocols to be
used for an HTTP interaction are determined by client configuration
and the target URI. For example, the "http" URI scheme
(Section 2.7.1) indicates a default connection of TCP over IP, with a
default TCP port of 80, but the client might be configured to use a
proxy via some other connection, port, or protocol.
HTTP implementations are expected to engage in connection management,
which includes maintaining the state of current connections,
establishing a new connection or reusing an existing connection,
processing messages received on a connection, detecting connection
failures, and closing each connection. Most clients maintain
multiple connections in parallel, including more than one connection
per server endpoint. Most servers are designed to maintain thousands
of concurrent connections, while controlling request queues to enable
fair use and detect denial of service attacks.
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6.1. Connection
The "Connection" header field allows the sender to indicate desired
control options for the current connection. In order to avoid
confusing downstream recipients, a proxy or gateway MUST remove or
replace any received connection options before forwarding the
message.
When a header field aside from Connection is used to supply control
information for or about the current connection, the sender MUST list
the corresponding field-name within the "Connection" header field. A
proxy or gateway MUST parse a received Connection header field before
a message is forwarded and, for each connection-option in this field,
remove any header field(s) from the message with the same name as the
connection-option, and then remove the Connection header field itself
(or replace it with the intermediary's own connection options for the
forwarded message).
Hence, the Connection header field provides a declarative way of
distinguishing header fields that are only intended for the immediate
recipient ("hop-by-hop") from those fields that are intended for all
recipients on the chain ("end-to-end"), enabling the message to be
self-descriptive and allowing future connection-specific extensions
to be deployed without fear that they will be blindly forwarded by
older intermediaries.
The Connection header field's value has the following grammar:
Connection = 1#connection-option
connection-option = token
Connection options are case-insensitive.
A sender MUST NOT send a connection option corresponding to a header
field that is intended for all recipients of the payload. For
example, Cache-Control is never appropriate as a connection option
(Section 7.2 of [Part6]).
The connection options do not have to correspond to a header field
present in the message, since a connection-specific header field
might not be needed if there are no parameters associated with that
connection option. Recipients that trigger certain connection
behavior based on the presence of connection options MUST do so based
on the presence of the connection-option rather than only the
presence of the optional header field. In other words, if the
connection option is received as a header field but not indicated
within the Connection field-value, then the recipient MUST ignore the
connection-specific header field because it has likely been forwarded
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by an intermediary that is only partially conformant.
When defining new connection options, specifications ought to
carefully consider existing deployed header fields and ensure that
the new connection option does not share the same name as an
unrelated header field that might already be deployed. Defining a
new connection option essentially reserves that potential field-name
for carrying additional information related to the connection option,
since it would be unwise for senders to use that field-name for
anything else.
The "close" connection option is defined for a sender to signal that
this connection will be closed after completion of the response. For
example,
Connection: close
in either the request or the response header fields indicates that
the connection MUST be closed after the current request/response is
complete (Section 6.6).
A client that does not support persistent connections MUST send the
"close" connection option in every request message.
A server that does not support persistent connections MUST send the
"close" connection option in every response message that does not
have a 1xx (Informational) status code.
6.2. Establishment
It is beyond the scope of this specification to describe how
connections are established via various transport or session-layer
protocols. Each connection applies to only one transport link.
6.3. Persistence
HTTP/1.1 defaults to the use of "persistent connections", allowing
multiple requests and responses to be carried over a single
connection. The "close" connection-option is used to signal that a
connection will not persist after the current request/response. HTTP
implementations SHOULD support persistent connections.
A recipient determines whether a connection is persistent or not
based on the most recently received message's protocol version and
Connection header field (if any):
o If the close connection option is present, the connection will not
persist after the current response; else,
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o If the received protocol is HTTP/1.1 (or later), the connection
will persist after the current response; else,
o If the received protocol is HTTP/1.0, the "keep-alive" connection
option is present, the recipient is not a proxy, and the recipient
wishes to honor the HTTP/1.0 "keep-alive" mechanism, the
connection will persist after the current response; otherwise,
o The connection will close after the current response.
A server MAY assume that an HTTP/1.1 client intends to maintain a
persistent connection until a close connection option is received in
a request.
A client MAY reuse a persistent connection until it sends or receives
a close connection option or receives an HTTP/1.0 response without a
"keep-alive" connection option.
In order to remain persistent, all messages on a connection MUST have
a self-defined message length (i.e., one not defined by closure of
the connection), as described in Section 3.3. A server MUST read the
entire request message body or close the connection after sending its
response, since otherwise the remaining data on a persistent
connection would be misinterpreted as the next request. Likewise, a
client MUST read the entire response message body if it intends to
reuse the same connection for a subsequent request.
A proxy server MUST NOT maintain a persistent connection with an
HTTP/1.0 client (see Section 19.7.1 of [RFC2068] for information and
discussion of the problems with the Keep-Alive header field
implemented by many HTTP/1.0 clients).
Clients and servers SHOULD NOT assume that a persistent connection is
maintained for HTTP versions less than 1.1 unless it is explicitly
signaled. See Appendix A.1.2 for more information on backward
compatibility with HTTP/1.0 clients.
6.3.1. Retrying Requests
Connections can be closed at any time, with or without intention.
Implementations ought to anticipate the need to recover from
asynchronous close events.
When an inbound connection is closed prematurely, a client MAY open a
new connection and automatically retransmit an aborted sequence of
requests if all of those requests have idempotent methods (Section
4.2.2 of [Part2]). A proxy MUST NOT automatically retry non-
idempotent requests.
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A user agent MUST NOT automatically retry a request with a non-
idempotent method unless it has some means to know that the request
semantics are actually idempotent, regardless of the method, or some
means to detect that the original request was never applied. For
example, a user agent that knows (through design or configuration)
that a POST request to a given resource is safe can repeat that
request automatically. Likewise, a user agent designed specifically
to operate on a version control repository might be able to recover
from partial failure conditions by checking the target resource
revision(s) after a failed connection, reverting or fixing any
changes that were partially applied, and then automatically retrying
the requests that failed.
An automatic retry SHOULD NOT be repeated if it fails.
6.3.2. Pipelining
A client that supports persistent connections MAY "pipeline" its
requests (i.e., send multiple requests without waiting for each
response). A server MAY process a sequence of pipelined requests in
parallel if they all have safe methods (Section 4.2.1 of [Part2]),
but MUST send the corresponding responses in the same order that the
requests were received.
A client that pipelines requests MUST be prepared to retry those
requests if the connection closes before it receives all of the
corresponding responses. A client that assumes a persistent
connection and pipelines immediately after connection establishment
MUST NOT pipeline on a retry connection until it knows the connection
is persistent.
Idempotent methods (Section 4.2.2 of [Part2]) are significant to
pipelining because they can be automatically retried after a
connection failure. A user agent SHOULD NOT pipeline requests after
a non-idempotent method until the final response status code for that
method has been received, unless the user agent has a means to detect
and recover from partial failure conditions involving the pipelined
sequence.
An intermediary that receives pipelined requests MAY pipeline those
requests when forwarding them inbound, since it can rely on the
outbound user agent(s) to determine what requests can be safely
pipelined. If the inbound connection fails before receiving a
response, the pipelining intermediary MAY attempt to retry a sequence
of requests that have yet to receive a response if the requests all
have idempotent methods; otherwise, the pipelining intermediary
SHOULD forward any received responses and then close the
corresponding outbound connection(s) so that the outbound user
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agent(s) can recover accordingly.
6.4. Concurrency
Clients SHOULD limit the number of simultaneous connections that they
maintain to a given server.
Previous revisions of HTTP gave a specific number of connections as a
ceiling, but this was found to be impractical for many applications.
As a result, this specification does not mandate a particular maximum
number of connections, but instead encourages clients to be
conservative when opening multiple connections.
Multiple connections are typically used to avoid the "head-of-line
blocking" problem, wherein a request that takes significant server-
side processing and/or has a large payload blocks subsequent requests
on the same connection. However, each connection consumes server
resources. Furthermore, using multiple connections can cause
undesirable side effects in congested networks.
Note that servers might reject traffic that they deem abusive,
including an excessive number of connections from a client.
6.5. Failures and Time-outs
Servers will usually have some time-out value beyond which they will
no longer maintain an inactive connection. Proxy servers might make
this a higher value since it is likely that the client will be making
more connections through the same server. The use of persistent
connections places no requirements on the length (or existence) of
this time-out for either the client or the server.
When a client or server wishes to time-out it SHOULD issue a graceful
close on the transport connection. Clients and servers SHOULD both
constantly watch for the other side of the transport close, and
respond to it as appropriate. If a client or server does not detect
the other side's close promptly it could cause unnecessary resource
drain on the network.
A client, server, or proxy MAY close the transport connection at any
time. For example, a client might have started to send a new request
at the same time that the server has decided to close the "idle"
connection. From the server's point of view, the connection is being
closed while it was idle, but from the client's point of view, a
request is in progress.
Servers SHOULD maintain persistent connections and allow the
underlying transport's flow control mechanisms to resolve temporary
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overloads, rather than terminate connections with the expectation
that clients will retry. The latter technique can exacerbate network
congestion.
A client sending a message body SHOULD monitor the network connection
for an error status code while it is transmitting the request. If
the client sees an error status code, it SHOULD immediately cease
transmitting the body and close the connection.
6.6. Tear-down
The Connection header field (Section 6.1) provides a "close"
connection option that a sender SHOULD send when it wishes to close
the connection after the current request/response pair.
A client that sends a close connection option MUST NOT send further
requests on that connection (after the one containing close) and MUST
close the connection after reading the final response message
corresponding to this request.
A server that receives a close connection option MUST initiate a
lingering close (see below) of the connection after it sends the
final response to the request that contained close. The server
SHOULD send a close connection option in its final response on that
connection. The server MUST NOT process any further requests
received on that connection.
A server that sends a close connection option MUST initiate a
lingering close of the connection after it sends the response
containing close. The server MUST NOT process any further requests
received on that connection.
A client that receives a close connection option MUST cease sending
requests on that connection and close the connection after reading
the response message containing the close; if additional pipelined
requests had been sent on the connection, the client SHOULD assume
that they will not be processed by the server.
If a server performs an immediate close of a TCP connection, there is
a significant risk that the client will not be able to read the last
HTTP response. If the server receives additional data from the
client on a fully-closed connection, such as another request that was
sent by the client before receiving the server's response, the
server's TCP stack will send a reset packet to the client;
unfortunately, the reset packet might erase the client's
unacknowledged input buffers before they can be read and interpreted
by the client's HTTP parser.
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To avoid the TCP reset problem, a server can perform a lingering
close on a connection by closing only the write side of the read/
write connection (a half-close) and continuing to read from the
connection until the connection is closed by the client or the server
is reasonably certain that its own TCP stack has received the
client's acknowledgement of the packet(s) containing the server's
last response. It is then safe for the server to fully close the
connection.
It is unknown whether the reset problem is exclusive to TCP or might
also be found in other transport connection protocols.
6.7. Upgrade
The "Upgrade" header field is intended to provide a simple mechanism
for transitioning from HTTP/1.1 to some other protocol on the same
connection. A client MAY send a list of protocols in the Upgrade
header field of a request to invite the server to switch to one or
more of those protocols before sending the final response. A server
MUST send an Upgrade header field in 101 (Switching Protocols)
responses to indicate which protocol(s) are being switched to, and
MUST send it in 426 (Upgrade Required) responses to indicate
acceptable protocols. A server MAY send an Upgrade header field in
any other response to indicate that they might be willing to upgrade
to one of the specified protocols for a future request.
Upgrade = 1#protocol
protocol = protocol-name ["/" protocol-version]
protocol-name = token
protocol-version = token
For example,
Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11
Upgrade eases the difficult transition between incompatible protocols
by allowing the client to initiate a request in the more commonly
supported protocol while indicating to the server that it would like
to use a "better" protocol if available (where "better" is determined
by the server, possibly according to the nature of the request method
or target resource).
Upgrade cannot be used to insist on a protocol change; its acceptance
and use by the server is optional. The capabilities and nature of
the application-level communication after the protocol change is
entirely dependent upon the new protocol chosen, although the first
action after changing the protocol MUST be a response to the initial
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HTTP request that contained the Upgrade header field.
For example, if the Upgrade header field is received in a GET request
and the server decides to switch protocols, then it first responds
with a 101 (Switching Protocols) message in HTTP/1.1 and then
immediately follows that with the new protocol's equivalent of a
response to a GET on the target resource. This allows a connection
to be upgraded to protocols with the same semantics as HTTP without
the latency cost of an additional round-trip. A server MUST NOT
switch protocols unless the received message semantics can be honored
by the new protocol; an OPTIONS request can be honored by any
protocol.
When Upgrade is sent, a sender MUST also send a Connection header
field (Section 6.1) that contains the "upgrade" connection option, in
order to prevent Upgrade from being accidentally forwarded by
intermediaries that might not implement the listed protocols. A
server MUST ignore an Upgrade header field that is received in an
HTTP/1.0 request.
The Upgrade header field only applies to switching application-level
protocols on the existing connection; it cannot be used to switch to
a protocol on a different connection. For that purpose, it is more
appropriate to use a 3xx (Redirection) response (Section 6.4 of
[Part2]).
This specification only defines the protocol name "HTTP" for use by
the family of Hypertext Transfer Protocols, as defined by the HTTP
version rules of Section 2.6 and future updates to this
specification. Additional tokens ought to be registered with IANA
using the registration procedure defined in Section 7.6.
7. IANA Considerations
7.1. Header Field Registration
HTTP header fields are registered within the Message Header Field
Registry [BCP90] maintained by IANA at <http://www.iana.org/
assignments/message-headers/message-header-index.html>.
This document defines the following HTTP header fields, so their
associated registry entries shall be updated according to the
permanent registrations below:
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+-------------------+----------+----------+---------------+
| Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+---------------+
| Connection | http | standard | Section 6.1 |
| Content-Length | http | standard | Section 3.3.2 |
| Host | http | standard | Section 5.4 |
| TE | http | standard | Section 4.3 |
| Trailer | http | standard | Section 4.1.1 |
| Transfer-Encoding | http | standard | Section 3.3.1 |
| Upgrade | http | standard | Section 6.7 |
| Via | http | standard | Section 5.7.1 |
+-------------------+----------+----------+---------------+
Furthermore, the header field-name "Close" shall be registered as
"reserved", since using that name as an HTTP header field might
conflict with the "close" connection option of the "Connection"
header field (Section 6.1).
+-------------------+----------+----------+-------------+
| Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+-------------+
| Close | http | reserved | Section 7.1 |
+-------------------+----------+----------+-------------+
The change controller is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force".
7.2. URI Scheme Registration
IANA maintains the registry of URI Schemes [BCP115] at
<http://www.iana.org/assignments/uri-schemes.html>.
This document defines the following URI schemes, so their associated
registry entries shall be updated according to the permanent
registrations below:
+------------+------------------------------------+---------------+
| URI Scheme | Description | Reference |
+------------+------------------------------------+---------------+
| http | Hypertext Transfer Protocol | Section 2.7.1 |
| https | Hypertext Transfer Protocol Secure | Section 2.7.2 |
+------------+------------------------------------+---------------+
7.3. Internet Media Type Registration
This document serves as the specification for the Internet media
types "message/http" and "application/http". The following is to be
registered with IANA (see [BCP13]).
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7.3.1. Internet Media Type message/http
The message/http type can be used to enclose a single HTTP request or
response message, provided that it obeys the MIME restrictions for
all "message" types regarding line length and encodings.
Type name: message
Subtype name: http
Required parameters: none
Optional parameters: version, msgtype
version: The HTTP-version number of the enclosed message (e.g.,
"1.1"). If not present, the version can be determined from the
first line of the body.
msgtype: The message type -- "request" or "response". If not
present, the type can be determined from the first line of the
body.
Encoding considerations: only "7bit", "8bit", or "binary" are
permitted
Security considerations: none
Interoperability considerations: none
Published specification: This specification (see Section 7.3.1).
Applications that use this media type:
Additional information:
Magic number(s): none
File extension(s): none
Macintosh file type code(s): none
Person and email address to contact for further information: See
Authors Section.
Intended usage: COMMON
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Restrictions on usage: none
Author/Change controller: IESG
7.3.2. Internet Media Type application/http
The application/http type can be used to enclose a pipeline of one or
more HTTP request or response messages (not intermixed).
Type name: application
Subtype name: http
Required parameters: none
Optional parameters: version, msgtype
version: The HTTP-version number of the enclosed messages (e.g.,
"1.1"). If not present, the version can be determined from the
first line of the body.
msgtype: The message type -- "request" or "response". If not
present, the type can be determined from the first line of the
body.
Encoding considerations: HTTP messages enclosed by this type are in
"binary" format; use of an appropriate Content-Transfer-Encoding
is required when transmitted via E-mail.
Security considerations: none
Interoperability considerations: none
Published specification: This specification (see Section 7.3.2).
Applications that use this media type:
Additional information:
Magic number(s): none
File extension(s): none
Macintosh file type code(s): none
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Person and email address to contact for further information: See
Authors Section.
Intended usage: COMMON
Restrictions on usage: none
Author/Change controller: IESG
7.4. Transfer Coding Registry
The HTTP Transfer Coding Registry defines the name space for transfer
coding names.
Registrations MUST include the following fields:
o Name
o Description
o Pointer to specification text
Names of transfer codings MUST NOT overlap with names of content
codings (Section 3.1.2.1 of [Part2]) unless the encoding
transformation is identical, as is the case for the compression
codings defined in Section 4.2.
Values to be added to this name space require IETF Review (see
Section 4.1 of [RFC5226]), and MUST conform to the purpose of
transfer coding defined in this section. Use of program names for
the identification of encoding formats is not desirable and is
discouraged for future encodings.
The registry itself is maintained at
<http://www.iana.org/assignments/http-parameters>.
7.5. Transfer Coding Registration
The HTTP Transfer Coding Registry shall be updated with the
registrations below:
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+----------+----------------------------------------+---------------+
| Name | Description | Reference |
+----------+----------------------------------------+---------------+
| chunked | Transfer in a series of chunks | Section 4.1 |
| compress | UNIX "compress" program method | Section 4.2.1 |
| deflate | "deflate" compression mechanism | Section 4.2.2 |
| | ([RFC1951]) used inside the "zlib" | |
| | data format ([RFC1950]) | |
| gzip | Same as GNU zip [RFC1952] | Section 4.2.3 |
+----------+----------------------------------------+---------------+
7.6. Upgrade Token Registry
The HTTP Upgrade Token Registry defines the name space for protocol-
name tokens used to identify protocols in the Upgrade header field.
Each registered protocol name is associated with contact information
and an optional set of specifications that details how the connection
will be processed after it has been upgraded.
Registrations happen on a "First Come First Served" basis (see
Section 4.1 of [RFC5226]) and are subject to the following rules:
1. A protocol-name token, once registered, stays registered forever.
2. The registration MUST name a responsible party for the
registration.
3. The registration MUST name a point of contact.
4. The registration MAY name a set of specifications associated with
that token. Such specifications need not be publicly available.
5. The registration SHOULD name a set of expected "protocol-version"
tokens associated with that token at the time of registration.
6. The responsible party MAY change the registration at any time.
The IANA will keep a record of all such changes, and make them
available upon request.
7. The IESG MAY reassign responsibility for a protocol token. This
will normally only be used in the case when a responsible party
cannot be contacted.
This registration procedure for HTTP Upgrade Tokens replaces that
previously defined in Section 7.2 of [RFC2817].
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7.7. Upgrade Token Registration
The HTTP Upgrade Token Registry shall be updated with the
registration below:
+-------+----------------------+----------------------+-------------+
| Value | Description | Expected Version | Reference |
| | | Tokens | |
+-------+----------------------+----------------------+-------------+
| HTTP | Hypertext Transfer | any DIGIT.DIGIT | Section 2.6 |
| | Protocol | (e.g, "2.0") | |
+-------+----------------------+----------------------+-------------+
The responsible party is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force".
8. Security Considerations
This section is meant to inform developers, information providers,
and users of known security concerns relevant to HTTP/1.1 message
syntax, parsing, and routing.
8.1. DNS-related Attacks
HTTP clients rely heavily on the Domain Name Service (DNS), and are
thus generally prone to security attacks based on the deliberate
misassociation of IP addresses and DNS names not protected by DNSSEC.
Clients need to be cautious in assuming the validity of an IP number/
DNS name association unless the response is protected by DNSSEC
([RFC4033]).
8.2. Intermediaries and Caching
By their very nature, HTTP intermediaries are men-in-the-middle, and
represent an opportunity for man-in-the-middle attacks. Compromise
of the systems on which the intermediaries run can result in serious
security and privacy problems. Intermediaries have access to
security-related information, personal information about individual
users and organizations, and proprietary information belonging to
users and content providers. A compromised intermediary, or an
intermediary implemented or configured without regard to security and
privacy considerations, might be used in the commission of a wide
range of potential attacks.
Intermediaries that contain a shared cache are especially vulnerable
to cache poisoning attacks.
Implementers need to consider the privacy and security implications
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of their design and coding decisions, and of the configuration
options they provide to operators (especially the default
configuration).
Users need to be aware that intermediaries are no more trustworthy
than the people who run them; HTTP itself cannot solve this problem.
8.3. Buffer Overflows
Because HTTP uses mostly textual, character-delimited fields,
attackers can overflow buffers in implementations, and/or perform a
Denial of Service against implementations that accept fields with
unlimited lengths.
To promote interoperability, this specification makes specific
recommendations for minimum size limits on request-line
(Section 3.1.1) and blocks of header fields (Section 3.2). These are
minimum recommendations, chosen to be supportable even by
implementations with limited resources; it is expected that most
implementations will choose substantially higher limits.
This specification also provides a way for servers to reject messages
that have request-targets that are too long (Section 6.5.12 of
[Part2]) or request entities that are too large (Section 6.5 of
[Part2]).
Recipients SHOULD carefully limit the extent to which they read other
fields, including (but not limited to) request methods, response
status phrases, header field-names, and body chunks, so as to avoid
denial of service attacks without impeding interoperability.
8.4. Message Integrity
HTTP does not define a specific mechanism for ensuring message
integrity, instead relying on the error-detection ability of
underlying transport protocols and the use of length or chunk-
delimited framing to detect completeness. Additional integrity
mechanisms, such as hash functions or digital signatures applied to
the content, can be selectively added to messages via extensible
metadata header fields. Historically, the lack of a single integrity
mechanism has been justified by the informal nature of most HTTP
communication. However, the prevalence of HTTP as an information
access mechanism has resulted in its increasing use within
environments where verification of message integrity is crucial.
User agents are encouraged to implement configurable means for
detecting and reporting failures of message integrity such that those
means can be enabled within environments for which integrity is
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necessary. For example, a browser being used to view medical history
or drug interaction information needs to indicate to the user when
such information is detected by the protocol to be incomplete,
expired, or corrupted during transfer. Such mechanisms might be
selectively enabled via user agent extensions or the presence of
message integrity metadata in a response. At a minimum, user agents
ought to provide some indication that allows a user to distinguish
between a complete and incomplete response message (Section 3.4) when
such verification is desired.
8.5. Server Log Information
A server is in the position to save personal data about a user's
requests over time, which might identify their reading patterns or
subjects of interest. In particular, log information gathered at an
intermediary often contains a history of user agent interaction,
across a multitude of sites, that can be traced to individual users.
HTTP log information is confidential in nature; its handling is often
constrained by laws and regulations. Log information needs to be
securely stored and appropriate guidelines followed for its analysis.
Anonymization of personal information within individual entries
helps, but is generally not sufficient to prevent real log traces
from being re-identified based on correlation with other access
characteristics. As such, access traces that are keyed to a specific
client should not be published even if the key is pseudonymous.
To minimize the risk of theft or accidental publication, log
information should be purged of personally identifiable information,
including user identifiers, IP addresses, and user-provided query
parameters, as soon as that information is no longer necessary to
support operational needs for security, auditing, or fraud control.
9. Acknowledgments
This edition of HTTP/1.1 builds on the many contributions that went
into RFC 1945, RFC 2068, RFC 2145, and RFC 2616, including
substantial contributions made by the previous authors, editors, and
working group chairs: Tim Berners-Lee, Ari Luotonen, Roy T. Fielding,
Henrik Frystyk Nielsen, Jim Gettys, Jeffrey C. Mogul, Larry Masinter,
and Paul J. Leach. Mark Nottingham oversaw this effort as working
group chair.
Since 1999, the following contributors have helped improve the HTTP
specification by reporting bugs, asking smart questions, drafting or
reviewing text, and evaluating open issues:
Adam Barth, Adam Roach, Addison Phillips, Adrian Chadd, Adrien W. de
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Croy, Alan Ford, Alan Ruttenberg, Albert Lunde, Alek Storm, Alex
Rousskov, Alexandre Morgaut, Alexey Melnikov, Alisha Smith, Amichai
Rothman, Amit Klein, Amos Jeffries, Andreas Maier, Andreas Petersson,
Anil Sharma, Anne van Kesteren, Anthony Bryan, Asbjorn Ulsberg, Ashok
Kumar, Balachander Krishnamurthy, Barry Leiba, Ben Laurie, Benjamin
Niven-Jenkins, Bil Corry, Bill Burke, Bjoern Hoehrmann, Bob
Scheifler, Boris Zbarsky, Brett Slatkin, Brian Kell, Brian McBarron,
Brian Pane, Brian Smith, Bryce Nesbitt, Cameron Heavon-Jones, Carl
Kugler, Carsten Bormann, Charles Fry, Chris Newman, Chris Weber,
Cyrus Daboo, Dale Robert Anderson, Dan Wing, Dan Winship, Daniel
Stenberg, Darrel Miller, Dave Cridland, Dave Crocker, Dave Kristol,
David Booth, David Singer, David W. Morris, Diwakar Shetty, Dmitry
Kurochkin, Drummond Reed, Duane Wessels, Duncan Cragg, Edward Lee,
Eliot Lear, Eran Hammer-Lahav, Eric D. Williams, Eric J. Bowman, Eric
Lawrence, Eric Rescorla, Erik Aronesty, Evan Prodromou, Florian
Weimer, Frank Ellermann, Fred Bohle, Gabriel Montenegro, Geoffrey
Sneddon, Gervase Markham, Grahame Grieve, Greg Wilkins, Harald Tveit
Alvestrand, Harry Halpin, Helge Hess, Henrik Nordstrom, Henry S.
Thompson, Henry Story, Herbert van de Sompel, Howard Melman, Hugo
Haas, Ian Fette, Ian Hickson, Ido Safruti, Ilya Grigorik, Ingo
Struck, J. Ross Nicoll, James H. Manger, James Lacey, James M. Snell,
Jamie Lokier, Jan Algermissen, Jeff Hodges (who came up with the term
'effective Request-URI'), Jeff Walden, Jeroen de Borst, Jim Luther,
Joe D. Williams, Joe Gregorio, Joe Orton, John C. Klensin, John C.
Mallery, John Cowan, John Kemp, John Panzer, John Schneider, John
Stracke, John Sullivan, Jonas Sicking, Jonathan A. Rees, Jonathan
Billington, Jonathan Moore, Jonathan Rees, Jonathan Silvera, Jordi
Ros, Joris Dobbelsteen, Josh Cohen, Julien Pierre, Jungshik Shin,
Justin Chapweske, Justin Erenkrantz, Justin James, Kalvinder Singh,
Karl Dubost, Keith Hoffman, Keith Moore, Ken Murchison, Koen Holtman,
Konstantin Voronkov, Kris Zyp, Lisa Dusseault, Maciej Stachowiak,
Marc Schneider, Marc Slemko, Mark Baker, Mark Pauley, Mark Watson,
Markus Isomaki, Markus Lanthaler, Martin J. Duerst, Martin Musatov,
Martin Nilsson, Martin Thomson, Matt Lynch, Matthew Cox, Max Clark,
Michael Burrows, Michael Hausenblas, Mike Amundsen, Mike Belshe, Mike
Kelly, Mike Schinkel, Miles Sabin, Murray S. Kucherawy, Mykyta
Yevstifeyev, Nathan Rixham, Nicholas Shanks, Nico Williams, Nicolas
Alvarez, Nicolas Mailhot, Noah Slater, Pablo Castro, Pat Hayes,
Patrick R. McManus, Patrik Faltstrom, Paul E. Jones, Paul Hoffman,
Paul Marquess, Peter Lepeska, Peter Saint-Andre, Peter Watkins, Phil
Archer, Philippe Mougin, Phillip Hallam-Baker, Poul-Henning Kamp,
Preethi Natarajan, Rajeev Bector, Ray Polk, Reto Bachmann-Gmuer,
Richard Cyganiak, Robert Brewer, Robert Collins, Robert O'Callahan,
Robert Olofsson, Robert Sayre, Robert Siemer, Robert de Wilde,
Roberto Javier Godoy, Roberto Peon, Roland Zink, Ronny Widjaja, S.
Mike Dierken, Salvatore Loreto, Sam Johnston, Sam Ruby, Scott
Lawrence (who maintained the original issues list), Sean B. Palmer,
Shane McCarron, Stefan Eissing, Stefan Tilkov, Stefanos Harhalakis,
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Stephane Bortzmeyer, Stephen Farrell, Stephen Ludin, Stuart Williams,
Subbu Allamaraju, Subramanian Moonesamy, Sylvain Hellegouarch, Tapan
Divekar, Tatsuya Hayashi, Ted Hardie, Thomas Broyer, Thomas Fossati,
Thomas Nordin, Thomas Roessler, Tim Bray, Tim Morgan, Tim Olsen,
Tobias Oberstein, Tom Zhou, Travis Snoozy, Tyler Close, Vincent
Murphy, Wenbo Zhu, Werner Baumann, Wilbur Streett, Wilfredo Sanchez
Vega, William A. Rowe Jr., William Chan, Willy Tarreau, Xiaoshu Wang,
Yaron Goland, Yngve Nysaeter Pettersen, Yoav Nir, Yogesh Bang, Yutaka
Oiwa, Yves Lafon (long-time member of the editor team), Zed A. Shaw,
and Zhong Yu.
See Section 16 of [RFC2616] for additional acknowledgements from
prior revisions.
10. References
10.1. Normative References
[Part2] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
Transfer Protocol (HTTP/1.1): Semantics and Content",
draft-ietf-httpbis-p2-semantics-22 (work in progress),
February 2013.
[Part4] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
Transfer Protocol (HTTP/1.1): Conditional Requests",
draft-ietf-httpbis-p4-conditional-22 (work in
progress), February 2013.
[Part5] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed.,
"Hypertext Transfer Protocol (HTTP/1.1): Range
Requests", draft-ietf-httpbis-p5-range-22 (work in
progress), February 2013.
[Part6] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching",
draft-ietf-httpbis-p6-cache-22 (work in progress),
February 2013.
[Part7] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext
Transfer Protocol (HTTP/1.1): Authentication",
draft-ietf-httpbis-p7-auth-22 (work in progress),
February 2013.
[RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data
Format Specification version 3.3", RFC 1950, May 1996.
[RFC1951] Deutsch, P., "DEFLATE Compressed Data Format
Specification version 1.3", RFC 1951, May 1996.
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[RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and
G. Randers-Pehrson, "GZIP file format specification
version 4.3", RFC 1952, May 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter,
"Uniform Resource Identifier (URI): Generic Syntax",
STD 66, RFC 3986, January 2005.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for
Syntax Specifications: ABNF", STD 68, RFC 5234,
January 2008.
[USASCII] American National Standards Institute, "Coded Character
Set -- 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986.
10.2. Informative References
[BCP115] Hansen, T., Hardie, T., and L. Masinter, "Guidelines
and Registration Procedures for New URI Schemes",
BCP 115, RFC 4395, February 2006.
[BCP13] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, January 2013.
[BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90,
RFC 3864, September 2004.
[ISO-8859-1] International Organization for Standardization,
"Information technology -- 8-bit single-byte coded
graphic character sets -- Part 1: Latin alphabet No.
1", ISO/IEC 8859-1:1998, 1998.
[Kri2001] Kristol, D., "HTTP Cookies: Standards, Privacy, and
Politics", ACM Transactions on Internet Technology Vol.
1, #2, November 2001,
<http://arxiv.org/abs/cs.SE/0105018>.
[RFC1919] Chatel, M., "Classical versus Transparent IP Proxies",
RFC 1919, March 1996.
[RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen,
"Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945,
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May 1996.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet
Mail Extensions (MIME) Part One: Format of Internet
Message Bodies", RFC 2045, November 1996.
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail
Extensions) Part Three: Message Header Extensions for
Non-ASCII Text", RFC 2047, November 1996.
[RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and
T. Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2068, January 1997.
[RFC2145] Mogul, J., Fielding, R., Gettys, J., and H. Nielsen,
"Use and Interpretation of HTTP Version Numbers",
RFC 2145, May 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2817] Khare, R. and S. Lawrence, "Upgrading to TLS Within
HTTP/1.1", RFC 2817, May 2000.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3040] Cooper, I., Melve, I., and G. Tomlinson, "Internet Web
Replication and Caching Taxonomy", RFC 3040,
January 2001.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
[RFC4559] Jaganathan, K., Zhu, L., and J. Brezak, "SPNEGO-based
Kerberos and NTLM HTTP Authentication in Microsoft
Windows", RFC 4559, June 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing
an IANA Considerations Section in RFCs", BCP 26,
RFC 5226, May 2008.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer
Security (TLS) Protocol Version 1.2", RFC 5246,
August 2008.
[RFC5322] Resnick, P., "Internet Message Format", RFC 5322,
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October 2008.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
April 2011.
Appendix A. HTTP Version History
HTTP has been in use by the World-Wide Web global information
initiative since 1990. The first version of HTTP, later referred to
as HTTP/0.9, was a simple protocol for hypertext data transfer across
the Internet with only a single request method (GET) and no metadata.
HTTP/1.0, as defined by [RFC1945], added a range of request methods
and MIME-like messaging that could include metadata about the data
transferred and modifiers on the request/response semantics.
However, HTTP/1.0 did not sufficiently take into consideration the
effects of hierarchical proxies, caching, the need for persistent
connections, or name-based virtual hosts. The proliferation of
incompletely-implemented applications calling themselves "HTTP/1.0"
further necessitated a protocol version change in order for two
communicating applications to determine each other's true
capabilities.
HTTP/1.1 remains compatible with HTTP/1.0 by including more stringent
requirements that enable reliable implementations, adding only those
new features that will either be safely ignored by an HTTP/1.0
recipient or only sent when communicating with a party advertising
conformance with HTTP/1.1.
It is beyond the scope of a protocol specification to mandate
conformance with previous versions. HTTP/1.1 was deliberately
designed, however, to make supporting previous versions easy. We
would expect a general-purpose HTTP/1.1 server to understand any
valid request in the format of HTTP/1.0 and respond appropriately
with an HTTP/1.1 message that only uses features understood (or
safely ignored) by HTTP/1.0 clients. Likewise, we would expect an
HTTP/1.1 client to understand any valid HTTP/1.0 response.
Since HTTP/0.9 did not support header fields in a request, there is
no mechanism for it to support name-based virtual hosts (selection of
resource by inspection of the Host header field). Any server that
implements name-based virtual hosts ought to disable support for
HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact,
badly constructed HTTP/1.x requests wherein a buggy client failed to
properly encode linear whitespace found in a URI reference and placed
in the request-target.
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A.1. Changes from HTTP/1.0
This section summarizes major differences between versions HTTP/1.0
and HTTP/1.1.
A.1.1. Multi-homed Web Servers
The requirements that clients and servers support the Host header
field (Section 5.4), report an error if it is missing from an
HTTP/1.1 request, and accept absolute URIs (Section 5.3) are among
the most important changes defined by HTTP/1.1.
Older HTTP/1.0 clients assumed a one-to-one relationship of IP
addresses and servers; there was no other established mechanism for
distinguishing the intended server of a request than the IP address
to which that request was directed. The Host header field was
introduced during the development of HTTP/1.1 and, though it was
quickly implemented by most HTTP/1.0 browsers, additional
requirements were placed on all HTTP/1.1 requests in order to ensure
complete adoption. At the time of this writing, most HTTP-based
services are dependent upon the Host header field for targeting
requests.
A.1.2. Keep-Alive Connections
In HTTP/1.0, each connection is established by the client prior to
the request and closed by the server after sending the response.
However, some implementations implement the explicitly negotiated
("Keep-Alive") version of persistent connections described in Section
19.7.1 of [RFC2068].
Some clients and servers might wish to be compatible with these
previous approaches to persistent connections, by explicitly
negotiating for them with a "Connection: keep-alive" request header
field. However, some experimental implementations of HTTP/1.0
persistent connections are faulty; for example, if an HTTP/1.0 proxy
server doesn't understand Connection, it will erroneously forward
that header field to the next inbound server, which would result in a
hung connection.
One attempted solution was the introduction of a Proxy-Connection
header field, targeted specifically at proxies. In practice, this
was also unworkable, because proxies are often deployed in multiple
layers, bringing about the same problem discussed above.
As a result, clients are encouraged not to send the Proxy-Connection
header field in any requests.
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Clients are also encouraged to consider the use of Connection: keep-
alive in requests carefully; while they can enable persistent
connections with HTTP/1.0 servers, clients using them need will need
to monitor the connection for "hung" requests (which indicate that
the client ought stop sending the header field), and this mechanism
ought not be used by clients at all when a proxy is being used.
A.1.3. Introduction of Transfer-Encoding
HTTP/1.1 introduces the Transfer-Encoding header field
(Section 3.3.1). Transfer codings need to be decoded prior to
forwarding an HTTP message over a MIME-compliant protocol.
A.2. Changes from RFC 2616
HTTP's approach to error handling has been explained. (Section 2.5)
The expectation to support HTTP/0.9 requests has been removed.
The term "Effective Request URI" has been introduced. (Section 5.5)
HTTP messages can be (and often are) buffered by implementations;
despite it sometimes being available as a stream, HTTP is
fundamentally a message-oriented protocol. (Section 3)
Minimum supported sizes for various protocol elements have been
suggested, to improve interoperability.
Header fields that span multiple lines ("line folding") are
deprecated. (Section 3.2.4)
The HTTP-version ABNF production has been clarified to be case-
sensitive. Additionally, version numbers has been restricted to
single digits, due to the fact that implementations are known to
handle multi-digit version numbers incorrectly. (Section 2.6)
The HTTPS URI scheme is now defined by this specification;
previously, it was done in Section 2.4 of [RFC2818]. (Section 2.7.2)
The HTTPS URI scheme implies end-to-end security. (Section 2.7.2)
Userinfo (i.e., username and password) are now disallowed in HTTP and
HTTPS URIs, because of security issues related to their transmission
on the wire. (Section 2.7.1)
Invalid whitespace around field-names is now required to be rejected,
because accepting it represents a security vulnerability.
(Section 3.2)
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The ABNF productions defining header fields now only list the field
value. (Section 3.2)
Rules about implicit linear whitespace between certain grammar
productions have been removed; now whitespace is only allowed where
specifically defined in the ABNF. (Section 3.2.3)
The NUL octet is no longer allowed in comment and quoted-string text,
and handling of backslash-escaping in them has been clarified.
(Section 3.2.6)
The quoted-pair rule no longer allows escaping control characters
other than HTAB. (Section 3.2.6)
Non-ASCII content in header fields and the reason phrase has been
obsoleted and made opaque (the TEXT rule was removed).
(Section 3.2.6)
Bogus "Content-Length" header fields are now required to be handled
as errors by recipients. (Section 3.3.2)
The "identity" transfer coding token has been removed. (Sections 3.3
and 4)
The algorithm for determining the message body length has been
clarified to indicate all of the special cases (e.g., driven by
methods or status codes) that affect it, and that new protocol
elements cannot define such special cases. (Section 3.3.3)
"multipart/byteranges" is no longer a way of determining message body
length detection. (Section 3.3.3)
CONNECT is a new, special case in determining message body length.
(Section 3.3.3)
Chunk length does not include the count of the octets in the chunk
header and trailer. (Section 4.1)
Use of chunk extensions is deprecated, and line folding in them is
disallowed. (Section 4.1)
The segment + query components of RFC3986 have been used to define
the request-target, instead of abs_path from RFC 1808. (Section 5.3)
The asterisk form of the request-target is only allowed in the
OPTIONS method. (Section 5.3)
Exactly when "close" connection options have to be sent has been
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clarified. (Section 6.1)
"hop-by-hop" header fields are required to appear in the Connection
header field; just because they're defined as hop-by-hop in this
specification doesn't exempt them. (Section 6.1)
The limit of two connections per server has been removed.
(Section 6.3)
An idempotent sequence of requests is no longer required to be
retried. (Section 6.3)
The requirement to retry requests under certain circumstances when
the server prematurely closes the connection has been removed.
(Section 6.3)
Some extraneous requirements about when servers are allowed to close
connections prematurely have been removed. (Section 6.3)
The semantics of the Upgrade header field is now defined in responses
other than 101 (this was incorporated from [RFC2817]). (Section 6.7)
Registration of Transfer Codings now requires IETF Review
(Section 7.4)
The meaning of the "deflate" content coding has been clarified.
(Section 4.2.2)
This specification now defines the Upgrade Token Registry, previously
defined in Section 7.2 of [RFC2817]. (Section 7.6)
Empty list elements in list productions (e.g., a list header
containing ", ,") have been deprecated. (Appendix B)
Issues with the Keep-Alive and Proxy-Connection headers in requests
are pointed out, with use of the latter being discouraged altogether.
(Appendix A.1.2)
Appendix B. ABNF list extension: #rule
A #rule extension to the ABNF rules of [RFC5234] is used to improve
readability in the definitions of some header field values.
A construct "#" is defined, similar to "*", for defining comma-
delimited lists of elements. The full form is "<n>#<m>element"
indicating at least <n> and at most <m> elements, each separated by a
single comma (",") and optional whitespace (OWS).
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Thus,
1#element => element *( OWS "," OWS element )
and:
#element => [ 1#element ]
and for n >= 1 and m > 1:
<n>#<m>element => element <n-1>*<m-1>( OWS "," OWS element )
For compatibility with legacy list rules, recipients SHOULD accept
empty list elements. In other words, consumers would follow the list
productions:
#element => [ ( "," / element ) *( OWS "," [ OWS element ] ) ]
1#element => *( "," OWS ) element *( OWS "," [ OWS element ] )
Note that empty elements do not contribute to the count of elements
present, though.
For example, given these ABNF productions:
example-list = 1#example-list-elmt
example-list-elmt = token ; see Section 3.2.6
Then these are valid values for example-list (not including the
double quotes, which are present for delimitation only):
"foo,bar"
"foo ,bar,"
"foo , ,bar,charlie "
But these values would be invalid, as at least one non-empty element
is required:
""
","
", ,"
Appendix C shows the collected ABNF, with the list rules expanded as
explained above.
Appendix C. Collected ABNF
BWS = OWS
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Connection = *( "," OWS ) connection-option *( OWS "," [ OWS
connection-option ] )
Content-Length = 1*DIGIT
HTTP-message = start-line *( header-field CRLF ) CRLF [ message-body
]
HTTP-name = %x48.54.54.50 ; HTTP
HTTP-version = HTTP-name "/" DIGIT "." DIGIT
Host = uri-host [ ":" port ]
OWS = *( SP / HTAB )
RWS = 1*( SP / HTAB )
TE = [ ( "," / t-codings ) *( OWS "," [ OWS t-codings ] ) ]
Trailer = *( "," OWS ) field-name *( OWS "," [ OWS field-name ] )
Transfer-Encoding = *( "," OWS ) transfer-coding *( OWS "," [ OWS
transfer-coding ] )
URI-reference = <URI-reference, defined in [RFC3986], Section 4.1>
Upgrade = *( "," OWS ) protocol *( OWS "," [ OWS protocol ] )
Via = *( "," OWS ) ( received-protocol RWS received-by [ RWS comment
] ) *( OWS "," [ OWS ( received-protocol RWS received-by [ RWS
comment ] ) ] )
absolute-URI = <absolute-URI, defined in [RFC3986], Section 4.3>
absolute-form = absolute-URI
absolute-path = 1*( "/" segment )
asterisk-form = "*"
attribute = token
authority = <authority, defined in [RFC3986], Section 3.2>
authority-form = authority
chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
chunk-data = 1*OCTET
chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] )
chunk-ext-name = token
chunk-ext-val = token / quoted-str-nf
chunk-size = 1*HEXDIG
chunked-body = *chunk last-chunk trailer-part CRLF
comment = "(" *( ctext / quoted-cpair / comment ) ")"
connection-option = token
ctext = HTAB / SP / %x21-27 ; '!'-'''
/ %x2A-5B ; '*'-'['
/ %x5D-7E ; ']'-'~'
/ obs-text
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field-content = *( HTAB / SP / VCHAR / obs-text )
field-name = token
field-value = *( field-content / obs-fold )
header-field = field-name ":" OWS field-value BWS
http-URI = "http://" authority path-abempty [ "?" query ]
https-URI = "https://" authority path-abempty [ "?" query ]
last-chunk = 1*"0" [ chunk-ext ] CRLF
message-body = *OCTET
method = token
obs-fold = CRLF ( SP / HTAB )
obs-text = %x80-FF
origin-form = absolute-path [ "?" query ]
partial-URI = relative-part [ "?" query ]
path-abempty = <path-abempty, defined in [RFC3986], Section 3.3>
port = <port, defined in [RFC3986], Section 3.2.3>
protocol = protocol-name [ "/" protocol-version ]
protocol-name = token
protocol-version = token
pseudonym = token
qdtext = HTAB / SP / "!" / %x23-5B ; '#'-'['
/ %x5D-7E ; ']'-'~'
/ obs-text
qdtext-nf = HTAB / SP / "!" / %x23-5B ; '#'-'['
/ %x5D-7E ; ']'-'~'
/ obs-text
query = <query, defined in [RFC3986], Section 3.4>
quoted-cpair = "\" ( HTAB / SP / VCHAR / obs-text )
quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text )
quoted-str-nf = DQUOTE *( qdtext-nf / quoted-pair ) DQUOTE
quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
rank = ( "0" [ "." *3DIGIT ] ) / ( "1" [ "." *3"0" ] )
reason-phrase = *( HTAB / SP / VCHAR / obs-text )
received-by = ( uri-host [ ":" port ] ) / pseudonym
received-protocol = [ protocol-name "/" ] protocol-version
relative-part = <relative-part, defined in [RFC3986], Section 4.2>
request-line = method SP request-target SP HTTP-version CRLF
request-target = origin-form / absolute-form / authority-form /
asterisk-form
segment = <segment, defined in [RFC3986], Section 3.3>
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special = "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "\" /
DQUOTE / "/" / "[" / "]" / "?" / "=" / "{" / "}"
start-line = request-line / status-line
status-code = 3DIGIT
status-line = HTTP-version SP status-code SP reason-phrase CRLF
t-codings = "trailers" / ( transfer-coding [ t-ranking ] )
t-ranking = OWS ";" OWS "q=" rank
tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /
"^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
token = 1*tchar
trailer-part = *( header-field CRLF )
transfer-coding = "chunked" / "compress" / "deflate" / "gzip" /
transfer-extension
transfer-extension = token *( OWS ";" OWS transfer-parameter )
transfer-parameter = attribute BWS "=" BWS value
uri-host = <host, defined in [RFC3986], Section 3.2.2>
value = word
word = token / quoted-string
Appendix D. Change Log (to be removed by RFC Editor before publication)
D.1. Since RFC 2616
Changes up to the first Working Group Last Call draft are summarized
in <http://trac.tools.ietf.org/html/
draft-ietf-httpbis-p1-messaging-21#appendix-D>.
D.2. Since draft-ietf-httpbis-p1-messaging-21
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/128>: "Cite HTTPS
URI scheme definition" (the spec now includes the HTTPs scheme
definition and thus updates RFC 2818)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/389>: "mention of
'proxies' in section about caches"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/390>: "use of ABNF
terms from RFC 3986"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/392>: "editorial
improvements to message length definition"
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o <http://tools.ietf.org/wg/httpbis/trac/ticket/395>: "Connection
header field MUST vs SHOULD"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/396>: "editorial
improvements to persistent connections section"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/397>: "URI
normalization vs empty path"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/408>: "p1 feedback"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/409>: "is parsing
OBS-FOLD mandatory?"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/410>: "HTTPS and
Shared Caching"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/411>: "Requirements
for recipients of ws between start-line and first header field"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/412>: "SP and HT
when being tolerant"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/414>: "Message
Parsing Strictness"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/415>: "'Render'"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/418>: "No-Transform"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/419>: "p2 editorial
feedback"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/420>: "Content-
Length SHOULD be sent"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/431>: "origin-form
does not allow path starting with "//""
o <http://tools.ietf.org/wg/httpbis/trac/ticket/433>: "ambiguity in
part 1 example"
Index
A
absolute-form (of request-target) 40
accelerator 10
application/http Media Type 58
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asterisk-form (of request-target) 41
authority-form (of request-target) 41
B
browser 7
C
cache 11
cacheable 12
captive portal 11
chunked (Coding Format) 27, 30, 34
client 7
close 48, 53
compress (Coding Format) 37
connection 7
Connection header field 48, 53
Content-Length header field 28
D
deflate (Coding Format) 37
downstream 9
E
effective request URI 43
G
gateway 10
Grammar
absolute-form 40
absolute-path 16
absolute-URI 16
ALPHA 6
asterisk-form 40
attribute 34
authority 16
authority-form 40
BWS 24
chunk 35
chunk-data 35
chunk-ext 35
chunk-ext-name 35
chunk-ext-val 35
chunk-size 35
chunked-body 35
comment 26
Connection 48
connection-option 48
Content-Length 29
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CR 6
CRLF 6
ctext 26
CTL 6
date2 34
date3 34
DIGIT 6
DQUOTE 6
field-content 22
field-name 22
field-value 22
header-field 22
HEXDIG 6
Host 42
HTAB 6
HTTP-message 19
HTTP-name 13
http-URI 16
HTTP-version 13
https-URI 18
last-chunk 35
LF 6
message-body 26
method 20
obs-fold 22
obs-text 26
OCTET 6
origin-form 40
OWS 24
partial-URI 16
port 16
protocol-name 45
protocol-version 45
pseudonym 45
qdtext 26
qdtext-nf 35
query 16
quoted-cpair 26
quoted-pair 26
quoted-str-nf 35
quoted-string 26
rank 37
reason-phrase 21
received-by 45
received-protocol 45
request-line 20
request-target 40
RWS 24
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segment 16
SP 6
special 25
start-line 20
status-code 21
status-line 21
t-codings 37
t-ranking 37
tchar 25
TE 37
token 25
Trailer 35
trailer-part 35
transfer-coding 34
Transfer-Encoding 27
transfer-extension 34
transfer-parameter 34
Upgrade 54
uri-host 16
URI-reference 16
value 34
VCHAR 6
Via 45
word 25
gzip (Coding Format) 37
H
header field 19
header section 19
headers 19
Host header field 41
http URI scheme 16
https URI scheme 17
I
inbound 9
interception proxy 11
intermediary 9
M
Media Type
application/http 58
message/http 57
message 7
message/http Media Type 57
method 20
N
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non-transforming proxy 10
O
origin server 7
origin-form (of request-target) 40
outbound 9
P
proxy 10
R
recipient 7
request 7
request-target 20
resource 15
response 7
reverse proxy 10
S
sender 7
server 7
spider 7
T
target resource 38
target URI 38
TE header field 37
Trailer header field 35
Transfer-Encoding header field 27
transforming proxy 10
transparent proxy 11
tunnel 11
U
Upgrade header field 54
upstream 9
URI scheme
http 16
https 17
user agent 7
V
Via header field 45
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Authors' Addresses
Roy T. Fielding (editor)
Adobe Systems Incorporated
345 Park Ave
San Jose, CA 95110
USA
EMail: fielding@gbiv.com
URI: http://roy.gbiv.com/
Julian F. Reschke (editor)
greenbytes GmbH
Hafenweg 16
Muenster, NW 48155
Germany
EMail: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/
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