What Http Request Header Is Used to Denote What Uri Linked to the Resource Being Requested?
1992
HTTP Asking fields
These header lines are sent by the customer in a HTTP protocol transaction. All lines are RFC822 format headers. The list of headers is terminated by an empty line.
-
From -
Accept -
Accept-Encoding -
Accept-Language -
User-Agent -
Referer -
Authority -
Charge-To -
If-Modified-Since -
Pragma
From:
In Internet mail service format, this gives the name of the requesting user. This field may be used for logging purposes and an insecure class 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 post address in this field does not have to correspond to the internet host which issued the request. (For instance, when a request is passed through a gateway, so the original issuer's address should be used).
The mail accost should, if possible, be a valid mail accost, whether or non information technology is in fact an cyberspace post address or the internet mail representation of an address on some other postal service system.
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 ready given may of grade vary from asking to request from the same user.
This field may be wrapped onto several lines co-ordinate to RCFC822, and besides more than 1 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>
Encounter the appendix on the negotiation algorithm as a function and penalty model. Notation that a semicolon has a higher precedence than a comma in this syntax, to suit to MIME use.
If no Accept: field is present, then it is assumed that text/patently and text/html are accepted.
Example
Accept: text/plainly, text/html Accept: text/ten-dvi; q=.8; mxb=100000; mxt=5.0, text/x-c
Wildcards
In lodge to save time, and also allow clients to receive content types of which they may not be aware, an asterisk "*" may exist used in place of either the second half of the content-type value, or both halves. This but applies to the Accept: filed, and not to the content-blazon field of course.
Instance
Accept: *.*, q=0.ane Accept: sound/*, q=0.2 Take: audio/basic q=1
may exist interpreted as "if you have bones audio, send it; otherwise send me some other audio, or failing that, just give me what you lot've got."
Type parameters
Parameters on the content type are extremely useful for describing resolutions, colour depths, etc. They will let a customer to specify in the Accept: field the resolution of its device. This may allow the server to economise greatly on transmission fourth dimension 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 epitome to catechumen into monochrome.
These parameters are to exist 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 (audio) or pixels (graphics)
- mchrome
- greyscale or blackness and white (no value)
- sps
- samples (audio) or frames (video) per second
- length
- total size of object in bytes [bits?]
Accept-Encoding:
Similar to Have, but lists the Content-Encoding types which are acceptable in the response.
<field> = Accept-Encoding: <entry> *[ , <entry> ] <entry> = <content transfer encoding> *[ , <param> ]
Example
Take-Encoding: x-compress; x-zip
Accept-Language:
Like to Accept, simply lists the Linguistic communication values which are preferable in the response. A response in an unspecifies language is not illegal. Run across also: Language .
Language coding TBS. (ISO standard xxxx.)
User-Agent:
This line if present gives the software programme used by the original client. This is for statistical purposes and the tracing of protocol violations. It should be included. The start white infinite delimited word must be the software production name, with an optional slash and version designator. Other products which grade part of the user amanuensis may be put equally separate words.
<field> = User-Agent: <product>+ <product> = <give-and-take> [/<version>] <version> = <word>
Example:
User-Amanuensis: LII-Cello/1.0 libwww/two.5
Referer:
This optional header field allows the customer to specify, for the server's benefit, the address ( URI ) of the document (or chemical element within the document) from which the URI in the request was obtained.
This allows a server to generate lists of dorsum-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.
Instance:
Referer: http://www.w3.org/hypertext/DataSources/Overview.html
Authorization:
If this line is present it contains potency data. The format is To Be Specified (TBS). The format of this field is in extensible form. The first discussion is a specification of the say-so system in apply.
Basic
Specification for electric current one implemented by AL Sep 1993.
PGP/PEM Encryption
People at NCSA are designing a PGP/PEM based protection system.
User/Password scheme
Potency: user fred:mypassword
The scheme proper noun is "user". The second discussion is a user proper name (typically derived from a USER surroundings 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, information technology provides a low-level security as used past 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 course. The showtime 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 balance of the line is a role of the charging system, only information technology is recommended that this include a maximum toll whose payment is authorized by the customer for this transaction, and a cost unit.
If-Modified-Since: date
This request header is used with GET method to make it provisional: if the requested certificate has not changed since the time specified in this field the document will non be sent, but instead a Non Modified 304 reply.
Format of this field is the same equally for Date:.
Pragma:
Syntax is the aforementioned as for other multiple-value fields in HTTP, similar the Accept: field, namely, a comma-separated listing of entries, for which the optional parameters are separated by semicolons.
Pragma directives should be understood by servers to which they are relevant, e.one thousand. a proxy server; currently but 1 pragma is divers:
-
no-enshroud - When present the proxy should non return a document from the cache even though it has not expired, but it should always request the certificate from the bodily server.
Pragmas should be passed through by proxies fifty-fifty though they might accept significance to the proxy itself. This is necessary in cases when the asking has to go through many proxies, and the pragma should affect all of them.
Terminal modified: May three, 1994
Source: https://www.w3.org/Protocols/HTTP/HTRQ_Headers.html
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