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RE: Shortcuts

2003-04-11 03:35:59
Alex,

yes I agree with your assement.
This case is beyond OCP.(although in theory u can still use OCP but the
question is why?)

Should we call it distributed OPES processor (where performance does not
count)

abbie


-----Original Message-----
From: Alex Rousskov [mailto:rousskov(_at_)measurement-factory(_dot_)com] 
Sent: Friday, April 11, 2003 12:03 AM
To: ietf-openproxy(_at_)imc(_dot_)org
Subject: Re: Shortcuts



On Thu, 10 Apr 2003, The Purple Streak, Hilarie Orman wrote:

I had a returned thought on the issue of whether or not data had to 
complete the loop between the OPES processor and the 
callout server. 
If the proxied protocol is a store-and-forward type, like 
SMTP, then 
it seems that the callout server might, quite properly, send 
transformed messages directly to an application endpoint 
(SMTP server) 
without going back through the OPES processor.

If this is proper, should we document it.  If it is 
improper, can we 
say why?

Excellent question!

If a callout server accepts application message and then just 
forwards an adapted version elsewhere, it is not (should not 
be) a callout server. It is an OPES processor! Thus, it is 
absolutely proper to do that as long as the entity in 
question does not pretend to be a callout server and obeys 
all processor requirements.

Here is what you get in that case:

 -- (SMTP) --> OPES         --> (SMTP) --> OPES        --> (SMTP)
               processor 1                 processor 2

Which is perfectly fine and is obviously beyond OCP scope 
(OCP is not involved here).

If, for some unnatural reason, the same thing is implemented 
using OCP, it may still be OPES-legal as long as both OPES 
agents know what they are doing:

                                          callout server
 -- (SMTP) --> OPES         --> (OCP) --> _and_ OPES     --> (SMTP)
               processor 1                processor 2

Essentially, "adaptation service" here means "I took care of 
it, forget it". This is OK as long as processors cooperate. 
Note that the callout server would be required to respond 
with that "I took care of it" application message to its OPES 
processor 1 (that application message/response will probably 
have no payload though, just metadata). No need to documented 
this convoluted case, IMO.

A somewhat similar but more realistic example with an "I took 
care of it" response would be a "black hole" service (e.g., a 
SPAM filter):

 -- (SMTP) --> OPES         --> (OCP) --> callout
               processor 1                server

The latter might be worth documenting in an "SMTP adaptation 
using OPES" draft.

HTH,

Alex.



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