Subject: RE: draft-ietf-opes-protocol-reqs-01

From: <[email-masked]>
Date: Wed, 19 Jun 2002 12:03:30 -0400

Hi,
I had a few questions/comments about the OPES Callout protocol draft which you submitted yesterday evening!

>  A callout transaction is defined as a message exchange between an
>  OPES processor and a callout server consisting of a callout request
>  and a callout response.  Both, the callout request as well as the
>  callout response, MAY each consist of one or more protocol messages,
>  i.e.  a series of protocol messages.

What did you mean when you referred to one or more "protocol" messages? Are you implying that multiple "OCP" messages can be packaged in each request or response? What is the justification for possibly packaging multiple protocol messages in a single callout request or response? Except if you feel that this might cause a great increase in overhead! If not, why not restrict each request and response to have only one protocol message (as is usually done in other request-response protocols).

>   Callout transactions are always initiated by a callout request from
>   an OPES processor and typically terminated by a callout response from
>   a callout server.  The OPES callout protocol MUST, however, also
>   allow either endpoint of a callout transaction to terminate a callout
>   transaction prematurely, i.e.  before a callout request or response
>   has been completely received by the corresponding endpoint. ...
>   
>   A premature termination of a callout transaction is required to
>   support OPES services which may terminate even before they have
>   processed the entire application message.  Content analysis services,
>   for example, may be able to classify a Web object after having
>   processed just the first few bytes of a Web object.

Why do you call this termination of the callout service "premature"? Isnt the fact that the content analysis task, for example, has outputted a result re. what the content is the expected result of the callout task and the normal completion of the same? So, I dont see why the example you have referred to is a case of premature termination of the callout transaction. Please clarify.

Regards,
-Srinivas
 
> -----Original Message-----
> From: ext Andre Beck [mailto:[email-masked]]
> Sent: Tuesday, June 18, 2002 6:47 PM
> To: [email-masked]
> Cc: [email-masked]; Marshall Rose; Markus Hofmann
> Subject: draft-ietf-opes-protocol-reqs-01
> 
> 
> Hi,
> 
> Please publish the attached OPES WG draft as
> "draft-ietf-opes-protocol-reqs-01".
> 
>

---

From: Andre Beck <[email-masked]>
Date: Wed, 19 Jun 2002 13:20:10 -0500

Hi Srinivas,

Thanks for your comments.

[email-masked] wrote:
  >> callout response, MAY each consist of one or more protocol
  >> messages, i.e.  a series of protocol messages.
  >
  > What did you mean when you referred to one or more "protocol"
  > messages? Are you implying that multiple "OCP" messages can be
  > packaged in each request or response? What is the justification for
  > possibly packaging multiple protocol messages in a single callout
  > request or response? Except if you feel that this might cause a great
  > increase in overhead! If not, why not restrict each request and
  > response to have only one protocol message (as is usually done in
  > other request-response protocols).

Section 3.13 of the draft talks about the need for application message
segmentation, i.e. an OPES processor may have to forward an application
message to a callout server in a series of fragments. If this is the
case, then the OCP may choose to encapsulate application message
fragments into separate OCP messages (which would all be part of the
same OCP request). The same applies to OCP responses. So I don't think
we should restrict each OCP request and response to only one OCP message.

  >>  an OPES processor and typically terminated by a callout response
  >> from a callout server.  The OPES callout protocol MUST, however,
  >> also allow either endpoint of a callout transaction to terminate a
  >> callout transaction prematurely, i.e.  before a callout request or
  >> response has been completely received by the corresponding
  >> endpoint. ...
  >>
  >> processed the entire application message.  Content analysis
  >> services, for example, may be able to classify a Web object after
  >> having processed just the first few bytes of a Web object.
  >
  >
  > Why do you call this termination of the callout service "premature"?
  > Isnt the fact that the content analysis task, for example, has
  > outputted a result re. what the content is the expected result of the
  > callout task and the normal completion of the same? So, I dont see
  > why the example you have referred to is a case of premature
  > termination of the callout transaction. Please clarify.

I see your point, but we did not mean to imply that a "premature
termination" represents an error condition of any kind. It's simply
something that occurs when an OPES processor terminates a callout
transaction before the completion of a callout request. This usually
happens when an OPES service terminates before the entire OCP request
was sent. As you pointed out, this may be the normal operation of the
OPES service. If the term "premature termination" is confusing, then
maybe we should call it something else. Any suggestions?

Thanks,
Andre