Subject: RE: no-transform & Warning

From: "Yang, Lily L" <[email-masked]>
Date: Tue, 16 Apr 2002 09:14:43 -0700

> -----Original Message-----
> From: Markus Hofmann [mailto:[email-masked]]
> Sent: Tuesday, April 16, 2002 7:43 AM
> To: Mark Nottingham
> Cc: [email-masked]; [email-masked]
> Subject: Re: no-transform & Warning
> 
> 
> 
> Mark Nottingham wrote:
> 
> > These mechanisms are required in order to be 
> HTTP-compliant; therefore, 
> > I'd say they should be part of the ICAP server's HTTP stack.
> 
> Hm, this assumes that the payload (i.e. the content-path protocol) is 
> NOT transparent to the OPES/Callout protocol, i.e. the OPES/Callout 
> protocol needs to have knowledge about the sematics of the 
> encapsulated application protocol (HTTP in this case).

I thought this has been the case. The callout protocol is going to transport
and transform the encapsulated application protocol data stream, and hence
has to understand the interaction with that application protocol.

> 
> Do we want to make this assumption? Comments?
> 
> -Markus
>

---

From: Markus Hofmann <[email-masked]>
Date: Tue, 16 Apr 2002 13:49:27 -0400

> has to understand the interaction with that application protocol.

The callout protocol does transport the application messages, but the 
callout protocol itself does *not* transform them. As such, it is not 
required to understand the application protocol - indeed, protocol 
layering rather suggests that the (underlying) callout protocol does 
not make any assumptions about the (above) application protocol (just 
as it is assumed that TCP does not understand the higher-layer payload 
it transports).

There might be good reasons for us to consider characteristics of the 
encapsulated application protocol, I'm just wondering where to draw 
the line...

-Markus