Re: OPES Status Update, Drafts, ICAP

Hi all,


   The following are the few points about the ICAP protocol
   we would like to share.


1. A single client request-response flow could include both reqmod and
   respmod modifications. This could be explicitly mentioned in the
draft.
   An example could be the decompression service.
   ( This service is mentioned in the 4 point)

2. One concern over the request modification.

   Icap client sends  the client request to icap server. The icap server
   could sent an adapted request , an HTTP error message
   indicating the client request is prohibited or ICAP error msg.

    The icap server sends ICAP error msg due to an error in ICAP
    semantics such as ICAP request is not correct or service not
available.
    In this case , the icap client can either forward the original
    request without any modification to OS or send an error msg to 
    client stating that the service could not be provided.

    It would be useful if the draft says how to handle this scenario.


3. The draft is not posing any prerequisite to the tools used to provide
   the actual services. Based on the protocol , it seems to be valid to
   have few prerequisite on the service tools.

   1. The tool has to be run in non-interactive mode. GUI interface is
      not needed.

   2. The tool should be started by cli. Allows to pass command line
      arguments.

   3. In the simplest form, each instance of the tool serves only one
      request.Considering the overhead due to the size of the tool and 
      time to load and make it ready , it would be fine to make a single
      instance of the tool to serve multiple requests either
      sequentially or parallely. I am not sure how far this is
achievable.


4. It could be possible to make use of the ICAP protocol for real
   bandwidth savings.This is possible by providing a service 
   called decompression.

   For example, consider a scenario.
   The client makes a request to html page in OS. Due to ICAP ,a request 
   with  a url which points to the compressed copy of the html page is
   sent to OS. This is done in REQMOD mode.

   OS sends back the compressed data. The compressed data is sent to
   ICAP server which can decompress and send the data in the format 
   requested by the end-user. This is done in RESPMOD mode.

   Thus the bandwidth needed to transfer the html page is reduced to the
   level of compression.

   If this service is considered as a valid one, then this service could
   be mentioned in the draft.


Regards
Arumugam

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