ietf-openproxy
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Re: OPES protocol, pre-draft

2003-03-17 05:49:24

Markus,

        We probably need a "sticky" [copied] flag meaning "I am going
to have a copy of every byte from now on, until further notice". This
way the callout server can remove itself from the loop earlier.

Thanks,

Alex.


On Sun, 16 Mar 2003, Markus Hofmann wrote:


Please apologize my late reply, but this just came to mind when
catching-up with all the emails after coming back from vacation and
reading through them for a second time on the plane...


Martin Stecher wrote:
Example 2:
Callout server analyzes beginning of application message and detects
that it is not interested in this app. message:

A. Traditional approach, ICAP/1.0 like with multiple preview
    0. C: Start of app. message 1
    1. C: Here is preview chunk 1
    2.                                S: Need another preview chunk
    3. C: Here is preview chunk 2
    4.                                S: Not interested (204 resp.)
    5. C: Start of app. message 2

B. Proposed OPES protocol
    0. C: Start of app. message 1
    1. C: Chunk 1 of data             S: Start of app. message 1
    2. C: Chunk 2 of data
    3. C: Chunk 3 of data             S: Not interested
    4. C: Chunk 4 of data
    5. C: Start of app. message 2

In this case B sent more data and data chunks 3 and 4 will be ignored
by the callout server.

This might be obvious, but please allow me to add the following for
clarification only... Chunks 3 and 4 can only be ignored (i.e.
discarded) by the callout server if the OPES processor has sent them
with the [copied] flag set in the respective <data-have amid offset
size [copied]> message(s). If the [copied] flag was not set, the
callout server must not ignore chunk 3 and 4, but simply copy/send
them back to the OPES processor. Obviously, this can be done without
further processing (i.e. servicing), but they still need to be sent
back, since the OPES processor might no longer have a copy of these
chunks. Note, that this is true even if chunks 1 and 2 were sent with
the [copied] flag set.

Thanks,
   Markus