Subject: ICAP header questions

From: Yimin Chen <[email-masked]>
Date: Tue, 18 Mar 2003 17:17:10 -0800 (PST)

Hi,

I am studying the ICAP protocol spec (Dec 2002
version), and have some
questions on section 4.3.2 to 4.3.4, which talk about
the ICAP request 
and response headers. I would really appreciate if
someone could shed light on them.

Original text in specification:
----------------------------------------------------------------
A response-specific header is allowed in ICAP
requests, following the
same semantics as the corresponding HTTP response
headers (Section 6.2
of [4]). This is:

Server (see Section 14.38 of [4])

In addition to HTTP-like headers, there is also a
request header 
unique
to ICAP defined:

ISTag (see Section 4.7)
------------------------------------------------------------------
Question:
1) Is it a typo and it is supposed to be "A
response-specific header 
is allowed in ICAP *responses*"?

2) Is "Server" the only HTTP-like ICAP response header
in ICAP 
protocol besides the ICAP-specific "Encapsulated"? 

3) If 2) is true, then what header is ICAP server
supposed to use if 
an ICAP client sends a request with "Authorization"
ICAP header? I 
don't see a corresponding response header for that in
the 
specification. Since 

Original text in specification:
-------------------------------------------------------------------
A number of request-specific headers are allowed in
ICAP requests,
following the same semantics as the corresponding HTTP
*request 
headers*
(Section 5.3 of [4]). These are:

Authorization
Allow (see Section 4.6)
From (see Section 14.22 of [4])
Host (REQUIRED in ICAP as it is in HTTP/1.1)
Referer (see Section 14.36 of [4])
User-Agent

In addition to HTTP-like headers, there are also
request headers 
unique
to ICAP defined:

Preview (see Section 4.5)
--------------------------------------------------------------------
Question:
1) So these are all the ICAP request headers? Section
4.4 mentioned 
that "Proxy-Authenticate and Proxy-Authorization
headers must be 
forwarded to the ICAP server in the ICAP header
section (not 
encapsulated message). What ICAP header should be
used? I can't find 
a match in the listed headers in the original text
cited.

2) Allow is not a request-specific header, but a
entity-header.

I would appreciate it if any of you could clarify for
me.

Thanks!
Yimin

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