HP VPN Firewall Appliances System Management and Maintenance Configuration Guide

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• Download—The ACS requires a CPE to download a specific file from the specified URL, ensuring
upgrading of CPE software and auto download of the vendor configuration file.
• Upload—The ACS requires a CPE to upload a specific file to the specified location.
• Reboot—The ACS remotely reboots the CPE when the CPE encounters a failure or completes a
software upgrade.
How CWMP works
The following example illustrates how CWMP works. Suppose there are two ACSs in an area: main and
backup. The main ACS must restart for a system upgrade. To ensure a continuous monitoring of the CPE,
the main ACS redirects all CPEs in the area to the backup ACS.
Figure 112 CWMP message interaction procedure
The following steps show how CWMP works:
1. Establish a TCP connection.
2. Initialize SSL and establish a security connection.
3. The CPE sends an Inform request message to initiate a CWMP connection. The Inform message
carries the reason for sending this message in the Eventcode field. In this example, the reason is "6
CONNECTION REQUEST," indicating that the ACS requires the CPE to establish a connection.
4. If the CPE passes the authentication of the ACS, the ACS returns an Inform response, and the
connection is established.
5. Upon receiving the Inform response, the CPE sends an empty message, if it has no other requests.
The CPE does this in order to comply with the request/reply interaction model of HTTP/HTTPS, in
which CWMP messages are conveyed.
6. The ACS queries the value of the ACS URL set on the CPE.
7. The CPE replies to the ACS with the obtained value of the ACS URL.
8. The ACS finds that its local URL value is the same as the value of the ACS URL on the CPE. Therefore,
the ACS sends a Set request to the CPE to modify the ACS URL value of the CPE to the URL of the
backup ACS.