HP 5500 EI Series Configuration Manual page 217

• 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 CPE monitoring, the
main ACS switch all CPEs in the area to the backup ACS.
Figure 64 Example of CWMP message interaction
The following steps show how CWMP works:
1. Establish a TCP connection.
2. Intialize 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, 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
standby ACS.
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