Wccp question, please help

Question

I'm writing for a design problem regarding ACNS deployment, I
wish You could help me.
We are an italian organization implementing ACNS Network for our e-learning platform.
We'd like to configure transparent caching using wccp v.2, the typical
deployment for our branch sites is represented in the attached image.
At our typical branch site we have an access router connected to
Intranet, the outside interface of a pix and the CE all on the same
subnet while web clients are on the inside interface of the pix (on
another subnet of course). Client behind the pix access the Intranet
via NAT Overloading.
The access router (Cisco c2621-XM IOS 12.1(3)T) is configured to
intercept http traffic (web-cache service), all the http get are
coming from the ip address of the pix outside interface. All these
HTTP sessions are initiated behind the firewall of course.
This http request are then redirected by the wccp enabled router to
the CE (using GRE), the CE (ACNS 5.2) then serves this request getting
the content from the origin server (cache-miss example) and serving it
to the client using the source IP address of the origin server and
source port 80.
My question is: will this work with the pix firewall (515E 6.3(3))?
In other words the pix will see the returning HTTP traffic from the CE
to the client on its outside interface as if it would came frome the origin server?
Will this traffic have the ip
address and port of the origin server and all the
protocol info (sequence number etc. etc) to match the xlate entry in
the NAT table of the pix for the egress HTTP GET generated by the
client? Will this traffic from the CE get back to the client trough
the pix?
IMHO this could work only if the CE hijacks the TCP session started by
the client requesting the content to the origin server (the CE has all
the info it needs to do that).
Is this what actually happens? Do i miss some points?
I do hope that the CE won't try to start a new TCP connection from
outside the firewall to serve the client !!!
If this scenario won't work have You any suggestion? The type of
traffic that the CE returns to the client it doesn't seem to be very
well described on the Cisco Systems documentation concerning ACNS.
Thank You very much

Answer 1

Ruben,
This will work properly. Using WCCP, the TCP connection setup will be redirected to the Content Engine (CE). The CE will handle communication with the origin server separately. The client (and the PIX for that matter), don't really have any idea they are talking to the CE instead of the origin server.
~Zach