Http headers
Overview
HTTP 헤더 관련 내용 정리
Header list
원문은 이곳<ref>http://en.wikipedia.org/wiki/List_of_HTTP_header_fields</ref>에서 확인할 수 있다.
Cache-Control
전송되는 내용을 캐싱해 줄 것을 요청한다.
The Cache-Control general-header field is used to specify directives for caching mechanisms in both requests and responses. Caching directives are unidirectional, meaning that a given directive in a request is not implying that the same directive is to be given in the response.
Syntax
Cache request directives
Cache-Control: max-age=<seconds> Cache-Control: max-stale[=<seconds>] Cache-Control: min-fresh=<seconds> Cache-Control: no-cache Cache-Control: no-store Cache-Control: no-transform Cache-Control: only-if-cached
Cache response directives
Cache-Control: must-revalidate Cache-Control: no-cache Cache-Control: no-store Cache-Control: no-transform Cache-Control: public Cache-Control: private Cache-Control: proxy-revalidate Cache-Control: max-age=<seconds> Cache-Control: s-maxage=<seconds>
Extension Cache-Control directives Extension Cache-Control directives are not part of the core HTTP caching standards document. Be sure to check the compatibility table for their support.
Cache-Control: immutable Cache-Control: stale-while-revalidate=<seconds> Cache-Control: stale-if-error=<seconds>
Directives
Cacheability =
public
- Indicates that the reponse may be cached by any cache, even if the response would normally be non-cacheable(e.g. if the response does not contain a max-age directive or the Expires header).
Request field
원문은 이곳<ref>http://www.w3.org/Protocols/HTTP/HTRQ_Headers.html</ref>에서 확인할 수 있다.
Accept
This field contains a semicolon-separated list of representation schemes ( Content-Type metainformation values) which will be accepted in the response to this request.
The set given may of course vary from request to request from the same user.
This field may be wrapped onto several lines according to RCFC822, and also more than one occurence of the field is allowed with the signifiance being the same as if all the entries has been in one field. The format of each entry in the list is (/ meaning "or")
<field> = Accept: <entry> *[ , <entry> ]
<entry> = <content type> *[ ; <param> ]
<param> = <attr> = <float>
<attr> = q / mxs / mxb
<float> = <ANSI-C floating point text represntation>
See the appendix on the negotiation algorithm as a function and penalty model. Note that a semicolon has a higher precedence than a comma in this syntax, to conform to MIME use.
If no Accept: field is present, then it is assumed that text/plain and text/html are accepted. Example
Accept: text/plain, text/html
Accept: text/x-dvi; q=.8; mxb=100000; mxt=5.0, text/x-c
Wildcards
In order to save time, and also allow clients to receive content types of which they may not be aware, an asterisk "*" may be used in place of either the second half of the content-type value, or both halves. This only applies to the Accept: filed, and not to the content-type field of course. Example
Accept: *.*, q=0.1
Accept: audio/*, q=0.2
Accept: audio/basic q=1
may be interpreted as "if you have basic audio, send it; otherwise send me some other audio, or failing that, just give me what you've got." Type parameters
Parameters on the content type are extremely useful for describing resolutions, colour depths, etc. They will allow a client to specify in the Accept: field the resolution of its device. This may allow the server to economise greatly on transmission time by reducing the resultion of an image, for example, and enable a more appropriate custom-designed black and white image to be selected rathther than giving the client a color image to convert into monochrome.
These parameters are to be specified when types are registered.. @@ TBS.
Sugestions include the following. Please feed back any references to existing improved abreviations for these:
dpi
dots per inch: pixels per inch [cm?!]
pxmax
maximum width in pixels (image or video)
pymax
maximum height in pixels
bits
bits per sample (sound) or pixels (graphics)
mchrome
greyscale or black and white (no value)
sps
samples (sound) or frames (video) per second
length
total size of object in bytes [bits?]
Accept-Encoding:
Similar to Accept, but lists the Content-Encoding types which are acceptable in the response.
<field> = Accept-Encoding: <entry> *[ , <entry> ]
<entry> = <content transfer encoding> *[ , <param> ]
Example
Accept-Encoding: x-compress; x-zip
Accept-Language
Similar to Accept, but lists the Language values which are preferable in the response. A response in an unspecifies language is not illegal. See also: Language .
Language coding TBS. (ISO standard xxxx.)
Authorization
If this line is present it contains authorization information. The format is To Be Specified (TBS). The format of this field is in extensible form. The first word is a specification of the authorisation system in use.
Basic
Specification for current one implemented by AL Sep 1993. PGP/PEM Encryption
People at NCSA are designing a PGP/PEM based protection system.
User/Password scheme
Authorization: user fred:mypassword
The scheme name is "user". The second word is a user name (typically derived from a USER environment variable or prompted for), with an optional password separated by a colon (as in the URL syntax for FTP). Without a password, this povides very low level security. With the password, it provides a low-level security as used by unmodified FTP, Telnet, etc. Kerberos
Authorization: kerberos kerberosauthenticationsparameters
The format of the kerberosauthenticationsparameters is to be specified. ChargeTo:
This line if present contains account information for the costs of the application of the method requested. The format is TBS. The format of this field must be in extensible form. The first word starts with a specification of the namespace in which the account is . (This is similar to extensible URL definition.) No namespaces are currently defined. Namespaces will be registered with the registration authority .
The format of the rest of the line is a function of the charging system, but it is recommended that this include a maximum cost whose payment is authorized by the client for this transaction, and a cost unit.
If-Modified-Since: date
This request header is used with GET method to make it conditional: if the requested document has not changed since the time specified in this field the document will not be sent, but instead a Not Modified 304 reply.
Format of this field is the same as for Date:.
Cache-Control
전송되는 내용을 캐싱해 줄 것을 요청한다.
The Cache-Control general-header field is used to specify directives for caching mechanisms in both requests and responses. Caching directives are unidirectional, meaning that a given directive in a request is not implying that the same directive is to be given in the response.
Example
Cache-Control: max-age=<seconds> Cache-Control: max-stale[=<seconds>] Cache-Control: min-fresh=<seconds> Cache-Control: no-cache Cache-Control: no-store Cache-Control: no-transform Cache-Control: only-if-cached
Connection
Control options for the current connection and list of hop-by-hop request fields.
Connection: keep-alive Connection: Upgrade
From
In Internet mail format, this gives the name of the requesting user. This field may be used for logging purposes and an insecure form of access protection. The interpretation of this field is that the request is being performed on behalf of the person given, who accepts responsability for the method performed.
The Internet mail address in this field does not have to correspond to the internet host which issued the request. (For example, when a request is passed through a gateway, then the original issuer's address should be used).
The mail address should, if possible, be a valid mail address, whether or not it is in fact an internet mail address or the internet mail representation of an address on some other mail system.
Host
호스트의 이름과 URI의 PORT 번호를 지정한다. 클라이언트는 HTTP 1.1 에 반드시 이 정보를 공급해야 하는데, 이는 여러 개의 호스트명이 갖는 애매한 URL을 쉽게 구분하는데 도움이 된다. 서버의 도메인 이름(가상 호스팅을 위한..)과 TCP 포트 번호를 지정한다. HTTP/1.1 부터는 반드시 설정해야 한다.
Host: en.wikipedia.org:80 Host: en.wikipedia.org
Referer
This optional header field allows the client to specify, for the server's benefit, the address ( URI ) of the document (or element within the document) from which the URI in the request was obtained.
This allows a server to generate lists of back-links to documents, for interest, logging, etc. It allows bad links to be traced for maintenance.
If a partial URI is given, then it should be parsed relative to the URI of the object of the request. Example:
Referer: http://www.w3.org/hypertext/DataSources/Overview.html
Pragma
Syntax is the same as for other multiple-value fields in HTTP, like the Accept: field, namely, a comma-separated list of entries, for which the optional parameters are separated by semicolons.
Pragma directives should be understood by servers to which they are relevant, e.g. a proxy server; currently only one pragma is defined:
no-cache
When present the proxy should not return a document from the cache even though it has not expired, but it should always request the document from the actual server.
Pragmas should be passed through by proxies even though they might have significance to the proxy itself. This is necessary in cases when the request has to go through many proxies, and the pragma should affect all of them.
Transfer-Encoding
전송 인코딩 방식을 정의한다.
chunked Transfer in a series of chunks [RFC7230] Section 4.1 compress UNIX "compress" data format [Welch, T., "A Technique for High Performance Data Compression", IEEE Computer 17(6), June 1984.] [RFC7230] Section 4.2.1 deflate "deflate" compressed data ([RFC1951]) inside the "zlib" data format ([RFC1950]) [RFC7230] Section 4.2.2 gzip GZIP file format [RFC1952] [RFC7230] Section 4.2.3 identity (withdrawn in errata to [RFC2616]) [RFC2616] Section 3.6 x-compress Deprecated (alias for compress) [RFC7230] Section 4.2.1 x-gzip Deprecated (alias for gzip) [RFC7230] Section 4.2.3
User-Agent
The user agent string of the user agent
This line if present gives the software program used by the original client. This is for statistical purposes and the tracing of protocol violations. It should be included. The first white space delimited word must be the software product name, with an optional slash and version designator. Other products which form part of the user agent may be put as separate words.
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20100101 Firefox/21.0
References
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