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ICAP Interface Support
that potential charging-based redirections (i.e. Advice of Charge, Top Up page, etc.) will not interfere with the decisions
taken by the application server.
Functions of the ACF include:
Retrieval of subscriber policies based on the subscriber identity passed in the ICAP message
Determining the appropriate action (permit, deny, redirect) to take for the type of content based on subscriber
profile
Communication of the action (permit, deny, or redirect) decision for the URL back to the ACS module
Failure Action on Retransmitted Packets
ICAP rating is enabled for retransmitted packet when default ICAP failure action was taken on an ICAP request for that
flow. ICAP default failure action is taken on the pending ICAP request for a connection when the connection needs to
be reset and there is no other redundant connection available. For example, in the ICAP request timeout and ICAP
connection timeout scenarios. In these cases the retransmitted packet in the uplink direction is sent for ICAP rating
again.
In case of WAP CO, uplink retransmitted packet for the WAP transactions for which ICAP failure action was taken will
be sent for ICAP rating. WSP header of the retransmitted packet is not parsed by the WSP analyzer. The URL received
in the previous packet for that transaction is used for ICAP rating. If failure action was taken on multiple WTP
transactions for the same flow (case: WTP concatenated GET request) then uplink retransmitted packet for each of the
transaction is sent for rating again.
In case of HTTP, uplink retransmitted packets for the HTTP flow on which ICAP failure action is taken is sent for ICAP
rating. The URL present in the current secondary session (last uplink request) is used for ICAP rating. However, if there
were multiple outstanding ICAP request for the same flow (pipelined request) then for the retransmitted packet the URL
that will be sent for rating will be that of the last GET request.
Retransmission in various cases of failure-action taken on re-transmitted packets when the ICAP response is not
received for the original request and the retransmitted request comes in:
WSP CO:
Permit: The uplink packet is sent for ICAP rating and depending on the ICAP response the WTP
Content Insert: The retransmitted packet is not sent for ICAP rating.
Redirect: The retransmitted packet is not sent for ICAP rating.
Discard: The uplink packet is sent for ICAP rating and depending on the ICAP response the WTP
Terminate flow: The uplink packet is sent for ICAP rating and depending on the ICAP response the
HTTP:
Permit: The uplink packet is sent for ICAP rating and depending on the ICAP response the last HTTP
transaction is allowed/blocked. It is possible that the WAP gateway sends the response for the
permitted GET request. Hence, there is a race condition and the subscriber may be able to view the
web page even thought the rating was redirect or content insert.
transaction is allowed/blocked.
WTP transaction is allowed or blocked. The WAP gateway may send an Abort transaction for this
GET request if the WSP disconnect packet sent while terminating the flow is received by the WAP
gateway.
GET request. It is possible that the HTTP server sends the response for the permitted GET request.
Hence there is a race condition and the subscriber may be able to view the web page even thought the
rating was redirect or content insert.
Cisco ASR 5x00 Packet Data Network Gateway Administration Guide ▄
ICAP Interface Support Overview ▀
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