HTTP response
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... client, usually with modified messages. The adapted messages may be
either HTTP requests or HTTP responses. Though transformations may
be possible on other non-HTTP content, they are beyond the scope of
...
... the response message for use in answering subsequent requests.
The rules for determining the cachability of HTTP responses are
defined in Section 13 of [4]. Even if a resource is cachable,
...
... As described earlier, ICAP focuses on modification of HTTP requests
(Section 3.1), and modification of HTTP responses (Section 3.2).
...
... further modification.
2) Send back an HTTP response to the request. This is used to
provide information useful to the user in case of an error (e.g.,
"you sent a request to view a page you are not allowed to see").
...
... In the "response modification" (respmod) mode, an ICAP client sends
an HTTP response to an ICAP server. (The response sent by the ICAP
client typically has been generated by an origin server.) The ICAP
...
... method is intended for post-processing
performed on an HTTP response before it is delivered to a client.
Examples include formatting HTML ...
... header is allowed in ICAP requests, following the
same semantics as the corresponding HTTP response headers (Section
6.2 of [4 ...
... unexpectedly arrives during the preview process. This is a
particularly useful optimization if a header-only HTTP response
arrives at the ICAP client (i.e., zero bytes of body); only a single
...
...
For example, consider an ICAP client that has just received HTTP
response headers from an origin server and initiates an ICAP RESPMOD
transaction ...
... HTTP request to an ICAP server. The ICAP server returns a modified
version of the request, an HTTP response, or (if the client indicates
it supports 204 responses) an indication that no modification is
...
... HTTP error response. Note that Request
Modification requests may only be satisfied with HTTP responses in
cases when the HTTP response is an error (e.g., 403 Forbidden).
...
... Modification requests may only be satisfied with HTTP responses in
cases when the HTTP response is an error (e.g., 403 Forbidden).
The first line of the response message ...
... method, described in Section 3.2, an ICAP client sends an
origin server's HTTP response to an ICAP server, and (if available)
the original client request that caused that response. Similar to
...
... Request Modification method, the response from the ICAP server can be
an adapted HTTP response, an error, or a 204 response code indicating
that no adaptation is required.
...
... encapsulation described in Section 4.4, the header and body of
the HTTP response to be modified MUST be included in the ICAP body.
If available, the header of the original client request ...
... response body, or
- An HTTP response 204 indicating that the ICAP client's request
requires no adaptation.
...
... clients, just as any
other surrogate might cache HTTP responses. Similar to HTTP, ICAP
clients ...
... HTTP caching
directives located in the encapsulated HTTP response (NOT in the ICAP
header section). Consequently, the ICAP client ...
... headers in case of REQMOD, and in the
encapsulated HTTP response in case of RESPMOD.
In cases where an ICAP server returns a modified version ...