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Header Fields
Cache-Control
Connection
Date
Pragma
Trailer
Transfer-Encoding
Upgrade
Via
Warning
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Cache-Control
Specifies directives that must be obeyed by all caching mechanisms along the request/response chain.
Example:
Cache-Control: private
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Note:
Many web servers incorrectly set this header to be no-cache or private
so that their dynamic pages are not cached. However, this may also be set for images, making it
so that non-changing images are not cached as well.
CacheRight,
DynaCache, and
XCache are some products
that can help you with your cache control policies.
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Connection
Specifies options that are desired for the particular connection and must not be communicated by proxies over further connections.
Example:
Connection: close
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Date
Date and time at which the message was originated.
Example:
Date: Mon, 5 Aug 2002 19:43:31 GMT
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Note:
The Date field is important for caches. It is supposed to represent the best
available approximation of the date and time of message generation.
CacheRight,
DynaCache, and
XCache are some products
that can help you with your cache control policies.
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Pragma
Used to include implementation-specific directives that might (optionally) apply to
any recipient along the request/response chain.
Example:
Pragma: no-cache
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Note:
Because the meaning of "Pragma: no-cache as a response header field is not actually
specified, it does not provide a reliable replacement for "Cache-Control: no-cache" in a response.
CacheRight,
DynaCache, and
XCache are some products
that can help you with your cache control policies.
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Trailer
Indicates that the given set of header fields is present in the trailer of a message encoded with chunked transfer-coding.
Example:
Trailer: Content-Length
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Note:
The Trailer header field MUST NOT include the following header fields:
Transfer-Encoding,
Content-Length,
Trailer
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Transfer-Encoding
Indicates what (if any) type of transformation has been applied to the message body in order
to safely transfer it between the sender and the recipient. This differs from the Content-Encoding
in that the transfer-coding is a property of the message, not of the entity.
Example:
Transfer-Encoding: chunked
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Note:
Many older HTTP/1.0 applications do not understand the Transfer-Encoding header.
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Upgrade
Used by a client to specify what additional communication protocols it supports and would like to
use if the server finds it appropriate to switch protocols. The server uses the Upgrade header
to indicate which protocol(s) are being switched.
Example:
Upgrade: HTTP/2.0, SHTTP/1.3, IRC/6.9, RTA/x11
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Via
Used by gateways and proxies 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.
Example:
Via: 1.0 fred, 1.1 nowhere.com (Apache/1.1)
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Warning
Carries additional information about the status or transformation of a message which
might not be reflected in the message.
Example:
Warning: 10 Response is stale
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