This is a good point that I have had some discussion. What about
information to/from any "side" service (cache, iCAP, ...) are
these 2/3 or different points? What do others think?
At 03:45 PM 5/4/2001 +0530, Rajnish Pandey wrote:
Hi Markus,
Is OPES is going to have a system, in which certain services will be
provided
at fixed processing points. Example : Virus scanning ay point 3.
According to IRML, point 3 is considered, only when object couldn't be
served
from cache. Let us assume a case .
There are two clients C1 and C2.
C2 has given a rule that says : If User-Agent = Nokia
Execute Service1.
Assume C1 asks for object www.foo.com and an entry is made for this
object
in cache. Now, C2 asks for the same object. Since the object is present in
cache, it will be served from cache. In order to make sure that rule
specified
by C2 should be verified, it is necessary to put rule given by C2 at point 4.
But in this case, processing of service2 wouldn't be cached.So, if C2
makes
one more request for the same object, service1 would be executed once again.
Suggestion : We can put such rules at point 3. And rules at point 3
should
be always considered, irrespective of object coming from origin server or
cache.
This would help us in taking advantage of cache.
Thanks
Rajnish
Beck, Hofmann Expires August 2001 [Page 6]
Internet Draft IRML February 2001
The "processing-point" attribute specifies at which of the four
points in figure 1 the rule engine on the intermediary must process
a rule. The four "processing-points" are derived from the Extensible
Proxy Services Framework as described in [2] and only apply to
caching proxies. Implementation architectures for other
intermediaries might define different or additional "processing-
points".
..................................................
Point 2: Proxy Request
The requested Web object cannot be served from the cache and
the origin server is about to be contacted for the HTTP
resource.
...........................................
Depending on the service type, rules may be processed and services
may be executed at any of the four points outlined in figure 1. A
virus scanning service for instance could be executed at point 3 in
figure 1 in order to scan all Web objects for viruses before they
can be stored in the cache. A URL-based request filtering service on
the other hand should be executed at point 1 and an ad insertion
service will probably be executed at point 4.
Michael W. Condry
Director, Network Edge Technology